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Agronomy
Volume 8
Issue 4
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Agronomy, Volume 8, Issue 4 (April 2018) – 25 articles

Cover Story (view full-size image): Effective and validated methods to simulate drought can facilitate the screening of breeding materials. We examined the response of the wheat cultivar ‘Norin 61’ under irrigated control, drought after anthesis, and 2% or 4% potassium chlorate (KClO3) at anthesis or grain filling. Both 2% and 4% KClO3 simulated the effect of drought stress. The selection of drought-tolerant genotypes can be aided by the chlorophyll content and δ13C measurement of leaves when 2% or 4% KClO3 is used to simulate drought. View this paper
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24 pages, 754 KiB  
Review
Sensing Technologies for Precision Phenotyping in Vegetable Crops: Current Status and Future Challenges
by Pasquale Tripodi, Daniele Massa, Accursio Venezia and Teodoro Cardi
Agronomy 2018, 8(4), 57; https://doi.org/10.3390/agronomy8040057 - 22 Apr 2018
Cited by 75 | Viewed by 12379
Abstract
Increasing the ability to investigate plant functions and structure through non-invasive methods with high accuracy has become a major target in plant breeding and precision agriculture. Emerging approaches in plant phenotyping play a key role in unraveling quantitative traits responsible for growth, production, [...] Read more.
Increasing the ability to investigate plant functions and structure through non-invasive methods with high accuracy has become a major target in plant breeding and precision agriculture. Emerging approaches in plant phenotyping play a key role in unraveling quantitative traits responsible for growth, production, quality, and resistance to various stresses. Beyond fully automatic phenotyping systems, several promising technologies can help accurately characterize a wide range of plant traits at affordable costs and with high-throughput. In this review, we revisit the principles of proximal and remote sensing, describing the application of non-invasive devices for precision phenotyping applied to the protected horticulture. Potentiality and constraints of big data management and integration with “omics” disciplines will also be discussed. Full article
(This article belongs to the Special Issue Precision Phenotyping in Plant Breeding)
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15 pages, 2713 KiB  
Article
The Effect of Community-Based Soil and Water Conservation Practices on Abundance and Diversity of Soil Macroinvertebrates in the Northern Highlands of Ethiopia
by Mengistu Welemariam, Fassil Kebede, Bobe Bedadi and Emiru Birhane
Agronomy 2018, 8(4), 56; https://doi.org/10.3390/agronomy8040056 - 22 Apr 2018
Cited by 4 | Viewed by 5003
Abstract
Soil and water conservation (SWC) practices in the northern highlands of Ethiopia have important implications for land restoration and biodiversity recovery. The present study determined soil macroinvertebrate (SMI) abundance and diversity in response to spatial conditions i.e., generated by different conservation practices, soil [...] Read more.
Soil and water conservation (SWC) practices in the northern highlands of Ethiopia have important implications for land restoration and biodiversity recovery. The present study determined soil macroinvertebrate (SMI) abundance and diversity in response to spatial conditions i.e., generated by different conservation practices, soil depth, and temporal seasonality with the wet and dry season. The SWC practices considered were exclosure + terrace, exclosure alone, terraces, and non-conserved grazing lands. Each SWC measure was selected in three sites that were considered as replications due to low heterogeneity in terms of human and livestock disturbances and biophysical factors. Soil macroinvertebrates were collected using a monolith according to tropical soil biology and fertility (TSBF) method. The highest density (55%) of SMI was found in exclosures followed by terraces 26%. Non-conserved communal grazing lands account for only 19% of the total. Shannon diversity index was significantly (P < 0.05) higher (1.21) in the exclosures supported with terraces and the lowest (0.9) was observed in the non-conserved communal grazing lands. Diversity was also significantly (P < 0.05) higher (1.26) in wet than dry season (0.70). The highest (41%) Sorensen similarity index among SMI was found between exclosures with terraces and exclosures alone during the wet season. The lowest (20%) Sorensen similarity index was found between terraces alone and exclosures with terraces in dry season. Soil macroinvertebrate abundance was higher in upper (0–10 cm) than lower (10–20 and 20–30 cm) soil depth. Soil macroinvertebrate abundance was positively and strongly correlated with soil moisture (R2 = 0.85) and soil organic carbon stock (R2 = 0.95). However, it was negatively (R2 = −0.71) correlated with bulk density. Generally, the abundance and diversity of SMI increased as exclosures and communal grazing lands are supported with terraces. Full article
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10 pages, 2768 KiB  
Article
Assessment of Genetic Diversity in Opuntia spp. Portuguese Populations Using SSR Molecular Markers
by Carlos M. G. Reis, Joana Raimundo and Maria Margarida Ribeiro
Agronomy 2018, 8(4), 55; https://doi.org/10.3390/agronomy8040055 - 20 Apr 2018
Cited by 6 | Viewed by 5072
Abstract
The Opuntia spp., most likely few individuals, were introduced in the Iberian Peninsula in the beginning of the 16th century, after the discovery of America, spreading afterwards throughout the Mediterranean basin. We analysed, for the first time, the genetic diversity in a set [...] Read more.
The Opuntia spp., most likely few individuals, were introduced in the Iberian Peninsula in the beginning of the 16th century, after the discovery of America, spreading afterwards throughout the Mediterranean basin. We analysed, for the first time, the genetic diversity in a set of 19 Portuguese Opuntia spp. populations from the species O. ficus-indica, O. elata, O. dillenii and O. robusta using nuclear microsatellite (nuSSR) markers. The Italian cultivars ‘Bianca’, ‘Gialla’ and ‘Rossa’ were included in the study for comparison purposes. The nuSSR amplifications produced from five to 16 alleles, with an average of 9.2 alleles per primer pair, and average polymorphism information content of 0.71. The estimated Dice coefficient among populations varied from 0.26 to 1.0, indicating high interspecific genetic diversity but low genetic diversity at the intraspecific level. The hierarchical clustering analysis revealed four major groups that clearly separated the four Opuntia species. Among the O. ficus-indica populations, two sub-clusters were found, one including the white pulp fruits (with cv. Bianca) and the other with the orange pulp ones and including the cv. Gialla, the cv. Rossa, and one pale yellow pulp population. No genetic differences were found between the inermis form, O. ficus-indica f. ficus-indica, and the rewilded spiny one, O. ficus-indica f. amyclaea. The dendrogram indicated that the clustering pattern was unrelated to geographical origin. The results revealed a low level of genetic diversity among the Portuguese populations of O. ficus-indica. Full article
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13 pages, 2360 KiB  
Article
Chitosan Coating: A Postharvest Treatment to Delay Oxidative Stress in Loquat Fruits during Cold Storage
by Giuseppina Adiletta, Maria Silvia Pasquariello, Luigi Zampella, Francesco Mastrobuoni, Marco Scortichini and Milena Petriccione
Agronomy 2018, 8(4), 54; https://doi.org/10.3390/agronomy8040054 - 19 Apr 2018
Cited by 53 | Viewed by 6430
Abstract
Loquat is a non-climacteric fruit consumed fresh for its essential nutrients and phytochemical compounds. In this study, the effects of chitosan coating (1% w/v) on changes in the enzymatic antioxidant and membrane damage in three loquat selections (CREAFRC-S18; CREAFRC-S35 and [...] Read more.
Loquat is a non-climacteric fruit consumed fresh for its essential nutrients and phytochemical compounds. In this study, the effects of chitosan coating (1% w/v) on changes in the enzymatic antioxidant and membrane damage in three loquat selections (CREAFRC-S18; CREAFRC-S35 and CREAFRC-S36) and three loquat cultivars (Golden Nugget, Algerie and Nespolone rosso di Trabia) stored at 7 °C over 21 days were evaluated. Chitosan treatment enhanced the activities of superoxide dismutase, catalase and ascorbate peroxidase. Moreover, this treatment inhibited polyphenol oxidase and guaiacol peroxidase activities, extending the storage life of loquat. Chitosan also preserved membrane integrity by inhibiting lipoxygenase activity and malondialdehyde accumulation. Principal component analysis provided a global view of the responses of both loquat selections and cultivars to the postharvest chitosan coating and storage temperature. These findings suggest that chitosan treatment could be a valid tool for improving the activity of antioxidant enzymes, preserving the enzymatic browning of loquat fruits. Full article
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10 pages, 3171 KiB  
Article
Effect of the Slow-Release Nitrogen Fertilizer Oxamide on Ammonia Volatilization and Nitrogen Use Efficiency in Paddy Soil
by Ying Tang, Xun Li, Wenzhong Shen and Zengqiang Duan
Agronomy 2018, 8(4), 53; https://doi.org/10.3390/agronomy8040053 - 18 Apr 2018
Cited by 14 | Viewed by 6587
Abstract
The effects of a single basal fertilization with oxamide compared with those of a split application of urea on ammonia volatilization, rice yield, nitrogen (N) accumulation, and N use efficiency were investigated in a field experiment over 2 years. The study consisted of [...] Read more.
The effects of a single basal fertilization with oxamide compared with those of a split application of urea on ammonia volatilization, rice yield, nitrogen (N) accumulation, and N use efficiency were investigated in a field experiment over 2 years. The study consisted of two N fertilizers (oxamide and urea) applied at 157.5 and 225 kg N ha−1 and a no-N Control. Compared with urea, the single application of oxamide produced similar rice yields and reduced approximately 38.3% to 62.7% of the N lost through ammonia volatilization in 2013 and 2014. Oxamide applied at a rate of 225 kg N ha−1 resulted in greater aboveground accumulation of N by rice than the other treatments in both years, and oxamide fertilization resulted in the accumulation of an additional 15.2 kg N ha−1 and 15.3 kg N ha−1 compared to the amounts accumulated under the urea treatments at the same N application rates. N use efficiency was higher under oxamide than under urea treatment. In conclusion, the use of oxamide as a fertilizer can reduce N loss via ammonia volatilization, increase N use efficiency, and maintain a steady rice grain yield. Full article
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14 pages, 5558 KiB  
Article
Agronomic and Economic Benefits of Pea/Maize Intercropping Systems in Relation to N Fertilizer and Maize Density
by Caihong Yang, Zhilong Fan and Qiang Chai
Agronomy 2018, 8(4), 52; https://doi.org/10.3390/agronomy8040052 - 18 Apr 2018
Cited by 39 | Viewed by 9103
Abstract
Intercropping has been shown to increase crop yields and improve land utilization in many cases but it is unknown how the interspecies relationship is enhanced with improved crop management schemes. In this study, we investigated the effect of different maize densities and N [...] Read more.
Intercropping has been shown to increase crop yields and improve land utilization in many cases but it is unknown how the interspecies relationship is enhanced with improved crop management schemes. In this study, we investigated the effect of different maize densities and N rates on the growth, crop yields and economic benefits of pea (Pisum sativum L.)/maize (Zea mays L.) intercropping. The results indicated that total yields of pea/maize intercropping were higher than the yield of maize alone, and that pea/maize intercropping improved land use efficiency significantly compared to sole crops, the partial land equivalent ratio (LER) of maize and pea with high planting density increased from 0.98% to 9.36% compared to low planting densities during 2012 and 2013. The pea strips provided significant compensatory effects on the growing maize after the earlier-sown, shorter-seasoned pea was harvested. The crop growth rate (CGR) of the intercropped maize was 18.5% to 216.9% greater than that of sole maize after pea harvest, the leaf area index (LAI) of pea/maize intercropping was 6.9% and 45.4% greater compared with the weighted average of sole maize and sole pea in 2012 and 2013, respectively. Net returns and benefit to cost ratios of pea/maize intercropping were increased with an increase of maize planting density. A low rate of N fertilizer was coupled with increased maize plant density, allowing interspecific facilitation to be fully expressed, thus improving the land utilization rate and increasing economic benefits. Overall, our findings show that a higher density of maize and lower N application can be used to increase grain production with no adverse effects on the growth components of either pea or maize crops. It could be considered an advanced farming system for agricultural sustainable development in the oasis region of northwest China. Full article
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15 pages, 20900 KiB  
Article
Increasing Predictive Ability by Modeling Interactions between Environments, Genotype and Canopy Coverage Image Data for Soybeans
by Diego Jarquin, Reka Howard, Alencar Xavier and Sruti Das Choudhury
Agronomy 2018, 8(4), 51; https://doi.org/10.3390/agronomy8040051 - 17 Apr 2018
Cited by 20 | Viewed by 6140
Abstract
Phenomics is a new area that offers numerous opportunities for its applicability in plant breeding. One possibility is to exploit this type of information obtained from early stages of the growing season by combining it with genomic data. This opens an avenue that [...] Read more.
Phenomics is a new area that offers numerous opportunities for its applicability in plant breeding. One possibility is to exploit this type of information obtained from early stages of the growing season by combining it with genomic data. This opens an avenue that can be capitalized by improving the predictive ability of the common prediction models used for genomic prediction. Imagery (canopy coverage) data recorded between days 14–71 using two collection methods (ground information in 2013 and 2014; aerial information in 2014 and 2015) on a soybean nested association mapping population (SoyNAM) was used to calibrate the prediction models together with the inclusion of several types of interactions between canopy coverage data, environments, and genomic data. Three different scenarios were considered that breeders might face testing lines in fields: (i) incomplete field trials (CV2); (ii) newly developed lines (CV1); and (iii) predicting lines in unobserved environments (CV0). Two different traits were evaluated in this study: yield and days to maturity (DTM). Results showed improvements in the predictive ability for yield with respect to those models that solely included genomic data. These relative improvements ranged 27–123%, 27–148%, and 65–165% for CV2, CV1, and CV0, respectively. No major changes were observed for DTM. Similar improvements were observed for both traits when the reduced canopy information for days 14–33 was used to build the training-testing relationships, showing a clear advantage of using phenomics in very early stages of the growing season. Full article
(This article belongs to the Special Issue Precision Phenotyping in Plant Breeding)
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10 pages, 1716 KiB  
Article
Physiological and Biochemical Characterization of a Red Escarole Obtained from an Interspecies Crossing
by Alessandro Natalini, Giacomo Cocetta, Nazzareno Acciarri and Antonio Ferrante
Agronomy 2018, 8(4), 50; https://doi.org/10.3390/agronomy8040050 - 16 Apr 2018
Cited by 1 | Viewed by 3948
Abstract
Escarole (Cichorium endivia L.) and radicchio (Cichorium intybus L.) are two important leafy vegetables appreciated by consumers for their sensory attributes, and at the same time, they can be considered a good source of health-promoting secondary metabolites, including polyphenols, flavonoids, and [...] Read more.
Escarole (Cichorium endivia L.) and radicchio (Cichorium intybus L.) are two important leafy vegetables appreciated by consumers for their sensory attributes, and at the same time, they can be considered a good source of health-promoting secondary metabolites, including polyphenols, flavonoids, and anthocyanins. The aim of this work is the characterization of a new variety of red escarole obtained after a long-term breeding program involving the interspecies crossing between red radicchio and green escarole. Our multidisciplinary approach of investigation allowed us to study the effects of the crossing on several aspects, including the accumulation of phenolic compounds and anthocyanins, the expression pattern of some of the key genes in the phenylpropanoid pathway, and the sensory profiling of the new variety obtained. Given the results, it is possible to conclude that the new variety of red escarole presents traits deriving from both radicchio and escarole. The sensory profile and the preliminary data on yield, suggests that red escarole has interesting characteristics that could be successfully introduced into the market of leafy crops. Full article
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20 pages, 6718 KiB  
Article
Maize (Zea mays L.) Response to Secondary and Micronutrients for Profitable N, P and K Fertilizer Use in Poorly Responsive Soils
by Ruth Njoroge, Abigael N. Otinga, John R. Okalebo, Mary Pepela and Roel Merckx
Agronomy 2018, 8(4), 49; https://doi.org/10.3390/agronomy8040049 - 15 Apr 2018
Cited by 33 | Viewed by 9063
Abstract
Deficiencies of secondary and micronutrients (SMNs) are major causes of low maize yields in poorly responsive soils. This phenomenon minimizes the agronomic efficiency of N, P and K fertilizers and consequently result in a dwindling economic benefit associated with their use. Therefore, 18 [...] Read more.
Deficiencies of secondary and micronutrients (SMNs) are major causes of low maize yields in poorly responsive soils. This phenomenon minimizes the agronomic efficiency of N, P and K fertilizers and consequently result in a dwindling economic benefit associated with their use. Therefore, 18 on-farm trials were conducted in western Kenya during two cropping seasons to assess maize response to three NPK amendments; (i) N, P, K, Ca, Zn and Cu (inorganic and organic); (ii) N, P, K, Ca, Zn and Cu (inorganic) and (iii) N, P K, Zn and Cu (inorganic) and evaluate the profitability of their use compared to additions of only N, P and K fertilizers. In this set of experiments, maize response to any amendment refers to a yield increase of ≥2 t ha−1 above control and could be categorized in three clusters. Cluster 1, comprising of nine sites, maize responded to all amendments. Cluster 2, holding six sites, maize responded only to one amendment, N, P, K, Ca, Zn and Cu (inorganic). In this cluster, (2), emerging S, Mg and Cu deficiencies may still limit maize production. Cluster 3; consisting of three sites, maize responded poorly to all amendments due to relatively high soil fertility (≥17 mg P kg−1). Profitability of using NPK amendments is limited to Cluster 1 and 2 and the largest Value Cost Ratio (VCR) of 3.1 is attainable only when soil available P is below 4.72 mg kg−1. These variable responses indicate the need for developing site-specific fertilizer recommendations for improved maize production and profitability of fertilizer use in poorly responsive soils. Full article
(This article belongs to the Special Issue Fertilizer Application on Crop Yield)
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19 pages, 3525 KiB  
Review
Are Nitrogen Fertilizers Deleterious to Soil Health?
by Bijay- Singh
Agronomy 2018, 8(4), 48; https://doi.org/10.3390/agronomy8040048 - 14 Apr 2018
Cited by 166 | Viewed by 28162
Abstract
Soil is one of the most important natural resources and medium for plant growth. Anthropogenic interventions such as tillage, irrigation, and fertilizer application can affect the health of the soil. Use of fertilizer nitrogen (N) for crop production influences soil health primarily through [...] Read more.
Soil is one of the most important natural resources and medium for plant growth. Anthropogenic interventions such as tillage, irrigation, and fertilizer application can affect the health of the soil. Use of fertilizer nitrogen (N) for crop production influences soil health primarily through changes in organic matter content, microbial life, and acidity in the soil. Soil organic matter (SOM) constitutes the storehouse of soil N. Studies with 15N-labelled fertilizers show that in a cropping season, plants take more N from the soil than from the fertilizer. A large number of long-term field experiments prove that optimum fertilizer N application to crops neither resulted in loss of organic matter nor adversely affected microbial activity in the soil. Fertilizer N, when applied at or below the level at which maximum yields are achieved, resulted in the build-up of SOM and microbial biomass by promoting plant growth and increasing the amount of litter and root biomass added to soil. Only when fertilizer N was applied at rates more than the optimum, increased residual inorganic N accelerated the loss of SOM through its mineralization. Soil microbial life was also adversely affected at very high fertilizers rates. Optimum fertilizer use on agricultural crops reduces soil erosion but repeated application of high fertilizer N doses may lead to soil acidity, a negative soil health trait. Site-specific management strategies based on principles of synchronization of N demand by crops with N supply from all sources including soil and fertilizer could ensure high yields, along with maintenance of soil health. Balanced application of different nutrients and integrated nutrient management based on organic manures and mineral fertilizers also contributed to soil health maintenance and improvement. Thus, fertilizer N, when applied as per the need of the field crops in a balanced proportion with other nutrients and along with organic manures, if available with the farmer, maintains or improves soil health rather than being deleterious. Full article
(This article belongs to the Special Issue Fertilizer Application on Crop Yield)
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18 pages, 29749 KiB  
Article
Genetic Diversity of Diurnal Carbohydrate Accumulation in White Clover (Trifolium repens L.)
by Michael E. Ruckle, Lucia Bernasconi, Roland Kölliker, Samuel C. Zeeman and Bruno Studer
Agronomy 2018, 8(4), 47; https://doi.org/10.3390/agronomy8040047 - 13 Apr 2018
Cited by 8 | Viewed by 5426
Abstract
White clover (Trifolium repens L.) is one of the most important legumes for fodder production in temperate climates, particularly in intensive pasture systems. Like many other forage legumes, it lacks the energy content to maximize productivity of modern ruminant livestock breeds. White [...] Read more.
White clover (Trifolium repens L.) is one of the most important legumes for fodder production in temperate climates, particularly in intensive pasture systems. Like many other forage legumes, it lacks the energy content to maximize productivity of modern ruminant livestock breeds. White clover produces water-soluble carbohydrates and starch in its leaves as a diurnal product of photosynthesis. However, little is known about the genetically encoded variability of diel changes in carbohydrate content. We assessed the amount of glucose, fructose, sucrose, and starch in the leaves of 185 plants of a genetically diverse white clover population. Water-soluble carbohydrates only provided on average 10.6% of dry weight (DW) of the total analyzed non-structural carbohydrate (NSC) content at the end of the day (ED), while starch supplied 89.4% of the NSC content. The top 5% of individuals accumulated over 25% of their DW as starch at ED. The leaf starch content at ED showed up to a threefold difference between genotypes, with a repeatability value of 0.95. Our experiments illustrate both the physical potential of white clover to serve as a competitive energy source to meet the demand of modern ruminant livestock production and the genetic potential to improve this trait by breeding. Full article
(This article belongs to the Special Issue Photosynthetic Carbon Metabolism to Enhance Crop Productivity)
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12 pages, 18951 KiB  
Article
Molecular Cloning and Structure–Function Analysis of a Trypsin Inhibitor from Tartary Buckwheat and Its Application in Combating Phytopathogenic Fungi
by Jing-jun Ruan, Shan-jun Tian, Jun Yan, Hui Chen, Ru-hong Xu and Jian-ping Cheng
Agronomy 2018, 8(4), 46; https://doi.org/10.3390/agronomy8040046 - 12 Apr 2018
Cited by 3 | Viewed by 4350
Abstract
Host plant protease inhibitors offer resistance to proteases from invading pathogens. Trypsin inhibitors (TIs), in particular, serve as protective agents against insect and pathogen attacks. In this study, we designed a pair of degenerate primers based on highly conserved motifs at the N- [...] Read more.
Host plant protease inhibitors offer resistance to proteases from invading pathogens. Trypsin inhibitors (TIs), in particular, serve as protective agents against insect and pathogen attacks. In this study, we designed a pair of degenerate primers based on highly conserved motifs at the N- and C-termini of the TI from tartary buckwheat (Fagopyrum tataricum; Ft) to clone the central portion. Genomic walking was performed to isolate the 5′ and 3′ flanking regions of FtTI. We demonstrated the successful PCR amplification of a 644 bp portion of FtTI. The full-length DNA of FtTI contains a complete open reading frame of 264 bp, encoding 87 amino acids with a mass of approximately 9.5 kDa. The FtTI protein sequence was 49% identical and 67% similar to potato protease inhibitors. Site-directed mutagenesis identified the residues, Asp67 and Arg68, as crucial for the inhibitory activity of the FtTI. Recombinant and mutant FtTI inhibited both the hyphal growth and spore germination of Alternaria solani. The calculated 50% inhibitory concentrations of FtTI ranged from 5–100 μg mL−1 for spore germination and 1–50 μg mL−1 for fungal growth. Thus, recombinant FtTI may function in host resistance against a variety of fungal plant pathogens. Full article
(This article belongs to the Special Issue Molecular and Biotechnological Approaches for Characterization and Control of Plant Virus Disease)
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11 pages, 2461 KiB  
Article
Metabolic Profiling of Phloem Exudates as a Tool to Improve Bread-Wheat Cultivars
by S. Marisol L. Basile, Mike M. Burrell, Heather J. Walker, Jorge A. Cardozo, Chloe Steels, Felix Kallenberg, Jorge A. Tognetti, Horacio R. DallaValle and W. John Rogers
Agronomy 2018, 8(4), 45; https://doi.org/10.3390/agronomy8040045 - 10 Apr 2018
Cited by 1 | Viewed by 4249
Abstract
In a proof of concept study aimed at showing that metabolites in bread wheat (Triticum aestivum L. ssp. aestivum), phloem exudates have potential as biochemical markers for cultivar discrimination, Argentinean cultivars from three quality groups (groups 1, 2, and 3 of [...] Read more.
In a proof of concept study aimed at showing that metabolites in bread wheat (Triticum aestivum L. ssp. aestivum), phloem exudates have potential as biochemical markers for cultivar discrimination, Argentinean cultivars from three quality groups (groups 1, 2, and 3 of high, intermediate, and low quality, respectively) were grown under two nitrogen (N) availabilities and analysed for metabolic profile by electrospray ionisation mass spectrometry. Data as signal strengths of mass/charge (m/z) values binned to a resolution of 0.2 Daltons were subjected to principal component analysis and orthogonal projections to latent structures discriminant analysis. Certain bins were influential in discriminating groups taken in pairs and some were involved in separating all three groups. In high N availability, group 3 cultivars clustered away from the other cultivars, while group 1 cultivars clustered tightly together; group 2 cultivars were more scattered between group 1 and group 3 cultivars. In low N availability, the cultivars were not clustered as tightly; nonetheless, group 1 cultivars tended to cluster together and mainly separated from those of group 2. m/z values also showed potential for discrimination between N availability. In conclusion, phloem exudate metabolic profiles could provide biochemical markers for selection during breeding and for discerning the effects of N fertiliser application. Full article
(This article belongs to the Special Issue Molecular Genetics, Genomics and Biotechnology of Crop Plants Breeding)
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13 pages, 8141 KiB  
Article
Physiological Response of Wheat to Chemical Desiccants Used to Simulate Post-Anthesis Drought Stress
by Nasrein Mohamed Kamal, Yasir Serag Alnor Gorafi, Ryosuke Mega and Hisashi Tsujimoto
Agronomy 2018, 8(4), 44; https://doi.org/10.3390/agronomy8040044 - 9 Apr 2018
Cited by 6 | Viewed by 7113
Abstract
Post-anthesis drought stress is one of the main constraints on the production of wheat (Triticum aestivum L.). Because field screening for post-anthesis drought tolerance is difficult, effective and validated methods to simulate drought in order to identify sources of tolerance can facilitate [...] Read more.
Post-anthesis drought stress is one of the main constraints on the production of wheat (Triticum aestivum L.). Because field screening for post-anthesis drought tolerance is difficult, effective and validated methods to simulate drought in order to identify sources of tolerance can facilitate screening of breeding materials. Chemical desiccants are widely used to simulate post-anthesis drought stress. We aimed to identify physiological traits that respond to desiccants as they do to drought. We examined the responses of ‘Norin 61’ to six treatments in a greenhouse: irrigated control, drought after anthesis, and 2% or 4% potassium chlorate (KClO3) at anthesis (A) or grain filling (GF). We measured δ13C in leaves, aboveground fresh biomass, stomatal conductance, chlorophyll content, harvest index, and grain yield. Both 2% and 4% KClO3 at both A and GF simulated the effect of drought stress. Selection of drought-tolerant genotypes can be aided by chlorophyll content and δ13C measurement of leaves when 2% or 4% KClO3 is used to simulate drought. Full article
(This article belongs to the Special Issue Genetic Analysis of Abiotic-Stress Adaptive Traits in Wheat and Barley)
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16 pages, 8674 KiB  
Article
Assessing Olive Evapotranspiration Partitioning from Soil Water Balance and Radiometric Soil and Canopy Temperatures
by Francisco L. Santos
Agronomy 2018, 8(4), 43; https://doi.org/10.3390/agronomy8040043 - 6 Apr 2018
Cited by 6 | Viewed by 4623
Abstract
Evapotranspiration (ETc) partitioning and obtaining of FAO56 dual crop coefficient (Kc) for olive was carried out with the SIMDualKc software application for root zone and topsoil soil water balance based on the dual crop coefficients. A simplified [...] Read more.
Evapotranspiration (ETc) partitioning and obtaining of FAO56 dual crop coefficient (Kc) for olive was carried out with the SIMDualKc software application for root zone and topsoil soil water balance based on the dual crop coefficients. A simplified two source-energy balance model (STSEB), based on daily remotely sensed soil and canopy thermal infrared data and retrieval of surface fluxes, also provided information on partitioning ETc for the olive orchard. Both models were calibrated and validated with ground-based, sap flow-derived transpiration rates, and their performance was compared in partitioning ETc for incomplete cover, intensive olive grown in orchards (≤300 trees ha−1). The SIMDualKc proved adequate in partitioning ETc. The STSEB model underestimated ETc mostly by inadequately simulating soil evaporation and its contribution to the total latent heat flux. Such results suggest difficulties in using information from the STSEB algorithm for assessing ETc and dual Kc crop coefficients of intensive olive orchards with incomplete ground cover. Full article
(This article belongs to the Special Issue Sensing and Automated Systems for Improved Crop Management)
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19 pages, 6458 KiB  
Article
Assessing Field Prunus Genotypes for Drought Responsive Potential by Carbon Isotope Discrimination and Promoter Analysis
by Beatriz Bielsa, Carole Bassett, D. Michael Glenn and María José Rubio-Cabetas
Agronomy 2018, 8(4), 42; https://doi.org/10.3390/agronomy8040042 - 5 Apr 2018
Cited by 4 | Viewed by 4562
Abstract
In order to improve the effectiveness of breeding practices for Prunus rootstocks, it is essential to obtain new resistance resources, especially with regard to drought. In this study, a collection of field-grown Prunus genotypes, both wild-relative species and cultivated hybrid rootstocks, were subjected [...] Read more.
In order to improve the effectiveness of breeding practices for Prunus rootstocks, it is essential to obtain new resistance resources, especially with regard to drought. In this study, a collection of field-grown Prunus genotypes, both wild-relative species and cultivated hybrid rootstocks, were subjected to leaf ash and carbon isotope discrimination (Δ13C) analyses, which are strongly correlated to water use efficiency (WUE). Almond and peach wild relative species showed the lowest Δ13C ratios, and therefore, the highest WUE in comparison with hybrid genotypes. In addition, drought-related cis-regulatory elements (CREs) were identified in the promoter regions of the effector gene PpDhn2, and the transcription factor gene DREB2B, two genes involved in drought-response signaling pathways. The phylogenetic analysis of these regions revealed variability in the promoter region sequences of both genes. This finding provides evidence of genetic diversity between the peach- and almond-relative individuals. The results presented here can be used to select Prunus genotypes with the best drought resistance potential for breeding. Full article
(This article belongs to the Special Issue Gene Expression Regulation during Drought and Salt Stress in Crop Plants)
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26 pages, 8416 KiB  
Article
Phosphorus and Nitrogen Yield Response Models for Dynamic Bio-Economic Optimization: An Empirical Approach
by Matti Sihvonen, Kari Hyytiäinen, Elena Valkama and Eila Turtola
Agronomy 2018, 8(4), 41; https://doi.org/10.3390/agronomy8040041 - 31 Mar 2018
Cited by 6 | Viewed by 6123
Abstract
Nitrogen (N) and phosphorus (P) are both essential plant nutrients. However, their joint response to plant growth is seldom described by models. This study provides an approach for modeling the joint impact of inorganic N and P fertilization on crop production, considering the [...] Read more.
Nitrogen (N) and phosphorus (P) are both essential plant nutrients. However, their joint response to plant growth is seldom described by models. This study provides an approach for modeling the joint impact of inorganic N and P fertilization on crop production, considering the P supplied by the soil, which was approximated using the soil test P (STP). We developed yield response models for Finnish spring barley crops (Hordeum vulgare L.) for clay and coarse-textured soils by using existing extensive experimental datasets and nonlinear estimation techniques. Model selection was based on iterative elimination from a wide diversity of plausible model formulations. The Cobb−Douglas type model specification, consisting of multiplicative elements, performed well against independent validation data, suggesting that the key relationships that determine crop responses are captured by the models. The estimated models were extended to dynamic economic optimization of fertilization inputs. According to the results, a fair STP level should be maintained on both coarse-textured soils (9.9 mg L−1 a−1) and clay soils (3.9 mg L−1 a−1). For coarse soils, a higher steady-state P fertilization rate is required (21.7 kg ha−1 a−1) compared with clay soils (6.75 kg ha−1 a−1). The steady-state N fertilization rate was slightly higher for clay soils (102.4 kg ha−1 a−1) than for coarse soils (95.8 kg ha−1 a−1). This study shows that the iterative elimination of plausible functional forms is a suitable method for reducing the effects of structural uncertainty on model output and optimal fertilization decisions. Full article
(This article belongs to the Special Issue Plant Mineral Nutrition: Principles and Perspectives)
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20 pages, 1058 KiB  
Article
Generating Improved Experimental Designs with Spatially and Genetically Correlated Observations Using Mixed Models
by Lazarus K. Mramba, Gary F. Peter, Vance M. Whitaker and Salvador A. Gezan
Agronomy 2018, 8(4), 40; https://doi.org/10.3390/agronomy8040040 - 30 Mar 2018
Cited by 5 | Viewed by 5370
Abstract
The aim of this study was to generate and evaluate the efficiency of improved field experiments while simultaneously accounting for spatial correlations and different levels of genetic relatedness using a mixed models framework for orthogonal and non-orthogonal designs. Optimality criteria and a search [...] Read more.
The aim of this study was to generate and evaluate the efficiency of improved field experiments while simultaneously accounting for spatial correlations and different levels of genetic relatedness using a mixed models framework for orthogonal and non-orthogonal designs. Optimality criteria and a search algorithm were implemented to generate randomized complete block (RCB), incomplete block (IB), augmented block (AB) and unequally replicated (UR) designs. Several conditions were evaluated including size of the experiment, levels of heritability, and optimality criteria. For RCB designs with half-sib or full-sib families, the optimization procedure yielded important improvements under the presence of mild to strong spatial correlation levels and relatively low heritability values. Also, for these designs, improvements in terms of overall design efficiency (ODE%) reached values of up to 8.7%, but these gains varied depending on the evaluated conditions. In general, for all evaluated designs, higher ODE% values were achieved from genetically unrelated individuals compared to experiments with half-sib and full-sib families. As expected, accuracy of prediction of genetic values improved as levels of heritability and spatial correlations increased. This study has demonstrated that important improvements in design efficiency and prediction accuracies can be achieved by optimizing how the levels of a treatment are assigned to the experimental units. Full article
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11 pages, 5523 KiB  
Article
Barnyardgrass Root Recognition Behaviour for Rice Allelopathy
by Tingshuang Zhang, Bo Fan and Peng Wang
Agronomy 2018, 8(4), 39; https://doi.org/10.3390/agronomy8040039 - 29 Mar 2018
Cited by 8 | Viewed by 4629
Abstract
Recent studies have demonstrated that the presence of belowground neighbours induces varied morphological and biochemical responses in plants. Plant allelopathic activity is elicited by the presence of competitor seedlings or competitor root exudates. However, it is unknown whether allelopathy also influences root recognition [...] Read more.
Recent studies have demonstrated that the presence of belowground neighbours induces varied morphological and biochemical responses in plants. Plant allelopathic activity is elicited by the presence of competitor seedlings or competitor root exudates. However, it is unknown whether allelopathy also influences root recognition behaviour in weed–crop interaction. To assess barnyardgrass response to the presence of allelopathic rice roots, we conducted a greenhouse experiment of barnyardgrass–rice mixed culture, including barnyardgrass monoculture, barnyardgrass mixed with the allelopathic rice line PI312777 and barnyardgrass mixed with the nonallelopathic rice cultivar Liaojing-9. Our results showed that the presence of allelopathic rice roots enhanced root allocation and tissue density (RTD) of barnyardgrass, whereas it decreased root biomass, total root length, specific root length (SRL) and topological index (TI), compared to barnyardgrass grown in monoculture; moreover, there was a significant correlation of topological index with root foraging precision and competition. Therefore, the presence of allelopathic rice roots affected the barnyardgrass root morphology, nutrient foraging and competition, suggesting that allelopathy plays a key role in root recognition behaviour of barnyardgrass–rice competitive interaction. Full article
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17 pages, 13437 KiB  
Article
Field Screening of Waterlogging Tolerance in Spring Wheat and Spring Barley
by Tove Kristina Sundgren, Anne Kjersti Uhlen, Wendy Waalen and Morten Lillemo
Agronomy 2018, 8(4), 38; https://doi.org/10.3390/agronomy8040038 - 29 Mar 2018
Cited by 19 | Viewed by 6802
Abstract
Improved waterlogging tolerance of wheat and barley varieties may alleviate yield constraints caused by heavy or long-lasting precipitation. The waterlogging tolerance of 181 wheat and 210 barley genotypes was investigated in field trials between 2013 and 2014. A subset of wheat genotypes were [...] Read more.
Improved waterlogging tolerance of wheat and barley varieties may alleviate yield constraints caused by heavy or long-lasting precipitation. The waterlogging tolerance of 181 wheat and 210 barley genotypes was investigated in field trials between 2013 and 2014. A subset of wheat genotypes were selected for yield trials in 2015 and 2016. Our aim was to: (1) characterize the waterlogging tolerance of genotypes with importance for Norwegian wheat and barley breeding, and (2) identify which phenotypic traits that most accurately determine the waterlogging tolerance of wheat in our field trials. Waterlogging tolerance was determined by principal component analysis (PCA) where best linear unbiased predictors (BLUPs) of the traits chlorosis, relative plant height, heading delay, relative spike number, relative biomass and an overall condition score were used as input variables. Six wheat and five barley genotypes were identified as consistently more tolerant in 2013 and 2014. This included the waterlogging tolerant CIMMYT line CETA/Ae. tauschii (895). Chlorosis and the overall condition score were the traits that best explained the yield response of the genotypes selected for the yield trials. Our results show that early stress symptoms did not necessarily reflect the ability to recover post treatment. Thus, records from full crop cycles appear as fundamental when screening populations with unknown tolerance properties. Full article
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20 pages, 2120 KiB  
Article
Performance and Stability of Commercial Wheat Cultivars under Terminal Heat Stress
by Ibrahim S. Elbasyoni
Agronomy 2018, 8(4), 37; https://doi.org/10.3390/agronomy8040037 - 29 Mar 2018
Cited by 39 | Viewed by 6408
Abstract
Egypt, the fifteenth most populated country and the largest wheat importer worldwide, is vulnerable to global warming. Ten of the commercial and widely grown wheat cultivars were planted in two locations, i.e., Elbostan and Elkhazan for three successive seasons 2014/2015, 2015/2016, and 2016/2017 [...] Read more.
Egypt, the fifteenth most populated country and the largest wheat importer worldwide, is vulnerable to global warming. Ten of the commercial and widely grown wheat cultivars were planted in two locations, i.e., Elbostan and Elkhazan for three successive seasons 2014/2015, 2015/2016, and 2016/2017 under two sowing dates (recommended and late). Elbostan and Elkhazan are the two locations used in this study because they represent newly reclaimed sandy soil and the Nile delta soil (clay), respectively. A split-plot, with main plots arranged as a randomized complete block design and three replicates, was used. The overall objective of this study was to identify the ideal cultivar for recommended conditions and heat stressed conditions. The results revealed that heat stress had a significant adverse impact on all traits while it raised the prevalence and severity of leaf and stem rust which contributed to overall yield losses of about 40%. Stability measurements, the additive main effects and multiplicative interaction model (AMMI) and genotype main effect plus genotype × environment interaction (GGE), were useful to determine the ideal genotypes for recommended and late sowing conditions (heat stressed). However, inconsistency was observed among some of these measurements. Cultivar “Sids12” was stable and outperformed other tested cultivars under combined sowing dates across environments. However, cultivar “Gemmeiza9” was more stable and outperformed other cultivars across environments under the recommended sowing date. Moreover, cultivar “Gemmeiza12” was the ideal cultivar for the late sown condition. Based on our findings, importing and evaluating heat stress tolerant wheat genotypes under late sown conditions or heat stressed conditions in Egypt is required to boost heat stress tolerance in the adapted wheat cultivars. Full article
(This article belongs to the Special Issue Biotic and Abiotic Stress Responses in Crop Plants)
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9 pages, 1294 KiB  
Brief Report
Genome-Wide Identification of Insertion and Deletion Markers in Chinese Commercial Rice Cultivars, Based on Next-Generation Sequencing Data
by Kesavan Markkandan, Seung-il Yoo, Young-Chan Cho and Dong Woo Lee
Agronomy 2018, 8(4), 36; https://doi.org/10.3390/agronomy8040036 - 27 Mar 2018
Cited by 5 | Viewed by 5069
Abstract
Rice, being a staple food crop for over one-third of the world’s population, has become a potential target for many dishonest traders and stakeholders for mixing with low-grade, low-cost grains/products and poorly nutritious adulterants to make a profit with the least effort. Single-nucleotide [...] Read more.
Rice, being a staple food crop for over one-third of the world’s population, has become a potential target for many dishonest traders and stakeholders for mixing with low-grade, low-cost grains/products and poorly nutritious adulterants to make a profit with the least effort. Single-nucleotide and insertion–deletion (InDel) polymorphisms have been widely used as DNA markers, not only in plant breeding but also to identify various traits in rice. Recently, next-generation sequencing (NGS) has produced sequences that allow for genome-wide detection of these molecular markers. These polymorphisms can potentially be used to develop high-accuracy polymerase chain reaction (PCR)-based markers. PCR-based techniques are rapid and successful methods to deal with the problem of adulteration at a commercial level. Here, we report the genome-wide analysis of InDel markers of 17 commercially available Chinese cultivars. In order to achieve accurate results, all samples were sequenced at approximately 30× genome coverage using Illumina HiSeq 2500™ system. An average of 10.6 GB clean reads per sample was produced and ~96.3% of the reads could be mapped to the rice genome reference IRGSP 1.0. After a series of filtering, we selected five InDel markers for PCR validation. The results revealed that these InDel markers can be used for authentication of Korean elite cultivars from the adulterants. Full article
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8 pages, 2624 KiB  
Article
First Case of Glufosinate-Resistant Rigid Ryegrass (Lolium rigidum Gaud.) in Greece
by Ilias S. Travlos, Nikolina Cheimona, Rafael De Prado, Amit J. Jhala, Demosthenis Chachalis and Eleni Tani
Agronomy 2018, 8(4), 35; https://doi.org/10.3390/agronomy8040035 - 27 Mar 2018
Cited by 19 | Viewed by 5830
Abstract
Repeated applications of the same herbicide(s), which are characterized by the same mode of action, increase selection pressure, which in turn favours the evolution of herbicide-resistant weeds. Glufosinate is a broad-spectrum non-selective herbicide being used for weed control for many years around the [...] Read more.
Repeated applications of the same herbicide(s), which are characterized by the same mode of action, increase selection pressure, which in turn favours the evolution of herbicide-resistant weeds. Glufosinate is a broad-spectrum non-selective herbicide being used for weed control for many years around the world. Rigid ryegrass (Lolium rigidum Gaud.) is an economically important grass weed in Greece. Recent complaints by growers about control failure of rigid ryegrass with glufosinate require further investigation and have been the basis of this study. The objectives of this study were to confirm the existence of glufosinate-resistant L. rigidum in Greece and evaluate the effect of L. rigidum growth stage on glufosinate efficacy. Twenty populations of rigid ryegrass from Greece were sampled from five regions, and whole plant dose–response studies were conducted for five populations under controlled conditions with eight rates of glufosinate (0.0, 0.098, 0.187, 0.375, 0.75, 1.5, 3.0, and 6.0 kg a.i. ha−1). Glufosinate resistance was confirmed in three out of five populations with the level of resistance ranging from three-to seven-fold compared with the susceptible populations based on above-ground biomass reduction. Results also revealed that the level of glufosinate-resistance of rigid ryegrass was dependent on the growth stage at which it was applied. Full article
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22 pages, 40142 KiB  
Article
Challenges and Responses to Ongoing and Projected Climate Change for Dryland Cereal Production Systems throughout the World
by Garry J. O’Leary, Pramod K. Aggarwal, Daniel F. Calderini, David J. Connor, Peter Craufurd, Sanford D. Eigenbrode, Xue Han and Jerry L. Hatfield
Agronomy 2018, 8(4), 34; https://doi.org/10.3390/agronomy8040034 - 23 Mar 2018
Cited by 29 | Viewed by 8491
Abstract
Since the introduction of mechanized production in both developed and developing countries, crops and their management have undergone significant adaptation resulting in increased productivity. Historical yield increases in wheat have occurred across most regions of the world (20–88 kg ha−1 year−1 [...] Read more.
Since the introduction of mechanized production in both developed and developing countries, crops and their management have undergone significant adaptation resulting in increased productivity. Historical yield increases in wheat have occurred across most regions of the world (20–88 kg ha−1 year−1), but climate trends threaten to dampen or reverse these gains such that yields are expected to decrease by 5–6% despite rising atmospheric CO2 concentrations. Current and projected climatic factors are temporally and spatially variable in dryland cereal production systems throughout the world. Productivity gains in wheat in some locations have been achieved from traditional agronomic practices and breeding. Continued improvement in all cereal production regions and locations of the world requires technical advances, including closer monitoring of soils, water conservation strategies, and multiple sowing times using different crops to reduce risks. The management of disease, pests, and weeds will be an added challenge, especially in areas of higher precipitation. Excellent progress has been achieved in Asia and there is much potential in Sub-Saharan Africa. Technical solutions seem within our grasp but must be implemented in the context of variable social, economic, regulatory, and administrative constraints, providing opportunities for cross fertilization and global collaboration to meet them. Full article
(This article belongs to the Special Issue Climate Change in Agriculture: Impacts and Adaptations)
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16 pages, 1970 KiB  
Review
Relationship of Melatonin and Salicylic Acid in Biotic/Abiotic Plant Stress Responses
by Josefa Hernández-Ruiz and Marino B. Arnao
Agronomy 2018, 8(4), 33; https://doi.org/10.3390/agronomy8040033 - 22 Mar 2018
Cited by 115 | Viewed by 13487
Abstract
Melatonin (N-acetyl-5-methoxytryptamine) was discovered in plants in 1995, while salicylic acid was the name given to the active ingredient of willow in 1838. From a physiological point of view, these two molecules present in plants have never been compared, even though [...] Read more.
Melatonin (N-acetyl-5-methoxytryptamine) was discovered in plants in 1995, while salicylic acid was the name given to the active ingredient of willow in 1838. From a physiological point of view, these two molecules present in plants have never been compared, even though they have a great number of similarities, as we shall see in this work. Both molecules have biosynthesis pathways that share a common precursor and both play a relevant role in the physiology of plants, especially in aspects related to biotic and abiotic stress. They have also been described as biostimulants of photosynthetic processes and productivity enhancers in agricultural crops. We review the coincident aspects of both molecules, and propose an action model, by which the relationship between these molecules and other agents and plant hormones can be studied. Full article
(This article belongs to the Special Issue Salicylic Acid in Plant Stress Responses)
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