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Agronomy
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Crop Breeding for Stress Tolerance
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Crop Breeding for Stress Tolerance

A topical collection in Agronomy (ISSN 2073-4395). This collection belongs to the section "Crop Breeding and Genetics".

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Editor

Prof. Dr. Meixue Zhou

E-Mail Website
Guest Editor
Tasmanian Institute of Agriculture, University of Tasmania, Tasmania, Australia
Interests: plant abiotic and biotic stress tolerance; grain quality; genetics and breeding; agronomic traits
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

It is our great pleasure to inform you that a Special Issue focused on “Crop Breeding for Stress Tolerance” will be published in Agronomy. This Special Issue aims to highlight a range of reviews, opinions, and research articles on:

  • Breeding for crop disease resistance;
  • Breeding for crop abiotic stress tolerance (drought, waterlogging, acid soil, salinity, sodicity, frost, heavy metal toxicity, lodging, etc.);
  • Fast-tracking development of improved wheat varieties with stress tolerance;
  • Molecular and physiological mechanisms for crop biotic and abiotic stress tolerances;
  • Development of phenotyping methodology.

Considering your expertise in the field, we would like to invite you to submit related papers to us. As an open access journal, we not only publish papers but also make them available worldwide to increase their downloads and citations.

Prof. Dr. Meixue Zhou
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Agronomy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • crop
  • abiotic stress
  • biotic stress
  • molecular mechanisms
  • stress physiology
  • breeding methodology
  • phenotyping

Published Papers (17 papers)

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2024

Jump to: 2023, 2022, 2021

14 pages, 1870 KiB  
Article
Evaluation of Cold Resistance at Seedling Stage for 70 Peanut Genotypes Based on Photosynthetic Fluorescence Characteristics
by Linmei Ye, Tao Wang, Renye Wu, Conghui Zheng, Liuqi Zhan, Jianhong Chen, Shengyao Guo and Yongkuai Chen
Agronomy 2024, 14(8), 1699; https://doi.org/10.3390/agronomy14081699 - 1 Aug 2024
Cited by 2 | Viewed by 727
Abstract
Low-temperature stress is one of the factors affecting the growth and development of peanuts. Currently, biochemical detection technologies for crop freeze damage are well established. In the context of rapid development in optical sensing technology and smart agriculture, non-destructive crop freeze damage detection [...] Read more.
Low-temperature stress is one of the factors affecting the growth and development of peanuts. Currently, biochemical detection technologies for crop freeze damage are well established. In the context of rapid development in optical sensing technology and smart agriculture, non-destructive crop freeze damage detection based on such technologies has gained increasing attention. The accurate detection, early warning, and targeted control of crop cold damage are particularly important. In this study, 70 peanut germplasm resources were collected and used for the research objectives. Indoor low-temperature seedling identification was conducted at 25 °C (the control group) and 5 °C (low-temperature stress group) for 7 days. Photosynthetic fluorescence values in leaves, as well as 13 indicators (Fo, Fm, Fv, Fv/Fm, Fv’/Fm’, ΦPSII, NPQ, qP, Rfd, Pn, Gs, Ci, and Tr), were analyzed for their responses to low-temperature stress. The results showed that under low-temperature stress, the Pn and Ci of peanut seedlings exhibited an ascending trend, while Tr and other indicators showed a decreasing trend compared to the control group. Based on the relative coefficients of resistance to low temperature for each individual indicator, a comprehensive non-destructive evaluation of cold resistance was conducted using methods such as principal component analysis, cluster analysis, and stepwise regression. Through principal component analysis, the 13 individual physiological indicators were transformed into 3 comprehensive indicators. The 70 peanut varieties were divided into 4 categories based on their resistance to low temperature: sensitive materials, moderately sensitive materials, moderately cold-tolerant materials, and cold-tolerant materials. Additionally, a mathematical model for evaluating cold resistance in peanuts was established. Full article
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17 pages, 5155 KiB  
Article
Transcriptomic Analysis of Maize Inbred Lines with Different Leaf Shapes Reveals Candidate Genes and Pathways Involved in Density Tolerance
by Shulei Guo, Yiyang Guo, Jun Zhang, Yinghui Song, Jinsheng Guo, Liangming Wei, Qianjin Zhang, Zhenhua Wang, Zanping Han, Liru Cao, Xin Zhang and Xiaomin Lu
Agronomy 2024, 14(7), 1506; https://doi.org/10.3390/agronomy14071506 - 11 Jul 2024
Viewed by 693
Abstract
Maize is an important food and feed crop. Under limited arable land area, the cultivation of high-density-tolerance crops is a key factor in promoting yield improvement. Leaf width and stalk strength are important influences on density tolerance in maize. However, no comprehensive transcriptomic [...] Read more.
Maize is an important food and feed crop. Under limited arable land area, the cultivation of high-density-tolerance crops is a key factor in promoting yield improvement. Leaf width and stalk strength are important influences on density tolerance in maize. However, no comprehensive transcriptomic analysis has focused on maize’s leaf width and stalk strength formation mechanisms. In this study, comparative transcriptomic analyses demonstrated that significant transcriptome changes occurred regarding leaf width and stalk strength of narrow-leaved and wide-leaved maize inbred lines, with a total of 5001 differentially expressed genes (DEGs) identified. Enrichment analysis showed that phenylpropanoid biosynthesis, starch and sucrose metabolism, phytohormone signaling, amino acid metabolism, and brassinosteroid biosynthesis were significantly correlated with the formation of maize leaf shape and stalk strength and that the genes in these pathways were primarily involved in cell wall formation. Weighted gene co-expression network analysis identified 2 modules significantly correlated with leaf width and stalk strength, from which 11 hub genes were further identified. The 11 leaf and stem development genes in different pathways were validated using qRT-PCR. These findings can provide a theoretical basis for the mechanism of narrow-leaf and high-strength stalk formation in high-density-tolerance maize and contribute to the proposal of a breeding strategy for yield improvement. Full article
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2023

Jump to: 2024, 2022, 2021

19 pages, 12331 KiB  
Article
Identification, Characterization, and Expression Profiling of Maize GATA Gene Family in Response to Abiotic and Biotic Stresses
by Yuchao Hu, Jingyi Huang, Li Yu, Changjin Wang, Xinwei Zhang, Xinxin Cheng, Haibing Yu and Kaijing Zhang
Agronomy 2023, 13(7), 1921; https://doi.org/10.3390/agronomy13071921 - 20 Jul 2023
Cited by 4 | Viewed by 2117
Abstract
GATA transcription factor is crucial for plant growth and development, physiological metabolism, and environmental response, which has been reported in many plants. Although the identification of maize GATA genes has been reported previously, the number of maize GATA genes was incomplete, and the [...] Read more.
GATA transcription factor is crucial for plant growth and development, physiological metabolism, and environmental response, which has been reported in many plants. Although the identification of maize GATA genes has been reported previously, the number of maize GATA genes was incomplete, and the expression patterns of maize GATA genes were not analyzed. Therefore, in this study, the GATA gene family of maize (Zea mays L.) was systematically analyzed. Forty-one GATA family genes were identified in the maize and were divided into four groups. The gene structure of each subgroup was basically consistent with that of the motif. The maize GATA genes were distributed on 10 chromosomes, including 3 and 17 pairs of tandem and segmental duplication genes, respectively. Fourteen types of cis-acting elements were identified in the promoter sequences of maize GATA family genes, involving four categories: light response, stress, hormone, and growth and development. The tissue-specific expression analysis of maize GATA family genes revealed that 4 GATA genes were highly expressed in almost all the maize tissues, and 11 GATA genes were not expressed in almost all tissues. The other maize GATA family genes showed a tissue-specific expression pattern. The results of RNA-seq reanalysis of publicly available transcriptome sequencing big data revealed that the gene ZmGATA37 was significantly down-regulated in response to abiotic stresses including high temperature, low temperature, drought, waterlogging, and salt, and significantly up-regulated in response to biotic stresses including smut disease, Maize Iranian mosaic virus infection, beet armyworm and aphid infestations. This indicated that the ZmGATA37 gene plays an important role in maize growth and development. Our findings offer new insight into the potential role of GATA transcription factors in abiotic and biotic stresses and provide a theoretical groundwork for the molecular mechanisms underlying maize adaptation to such stress. Full article
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2022

Jump to: 2024, 2023, 2021

17 pages, 2073 KiB  
Article
Winter Cereal Reactions to Common Root Rot and Crown Rot Pathogens in the Field
by Ahmed Saad, Bethany Macdonald, Anke Martin, Noel L. Knight and Cassandra Percy
Agronomy 2022, 12(10), 2571; https://doi.org/10.3390/agronomy12102571 - 19 Oct 2022
Cited by 5 | Viewed by 2344
Abstract
In Australia, Fusarium pseudograminearum and F. culmorum are the two main fungi causing crown rot, while Bipolaris sorokiniana is the causal agent of common root rot. Fusarium graminearum is typically linked with Fusarium head blight; however, it has been associated with crown rot [...] Read more.
In Australia, Fusarium pseudograminearum and F. culmorum are the two main fungi causing crown rot, while Bipolaris sorokiniana is the causal agent of common root rot. Fusarium graminearum is typically linked with Fusarium head blight; however, it has been associated with crown rot in Australia and other parts of the world. This study investigated the reactions of single cultivars of barley, bread wheat, durum wheat, oat, and triticale to inoculation with strains of F. pseudograminearum, F. culmorum, F. graminearum and B. sorokiniana in field trials across two seasons. Fusarium pseudograminearum and F. culmorum caused greater visual discolouration than F. graminearum and B. sorokiniana on both stems and sub crown internodes of all hosts. Fusarum pseudograminearum caused the greatest reduction in plant dry weight across hosts in both years. Durum wheat (cv. Hyperno) barley (cv. Grimmett), bread wheat (cv. Livingston) and triticale (cv. Endeavour) observed significantly high levels of visual discolouration on stems when inoculated with F. pseudograminearum, while oat (cv. Genie) exhibited the least visual discolouration. Despite variation in the visual discolouration, the DNA of all pathogens were detected in all cultivars. This research further highlights the complicated nature of the pathogen × strain × cultivar × environment interaction, which remains a challenge in breeding for genetic resistance. The specific infection of each fungus and the host responses in these field trials improves our understanding of disease development and its importance in cropping systems. Full article
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18 pages, 3054 KiB  
Article
Understanding the Role of Physiological and Agronomical Traits during Drought Recovery as a Determinant of Differential Drought Stress Tolerance in Barley
by Md. Hasanuzzaman, Lana Shabala, Timothy J. Brodribb, Meixue Zhou and Sergey Shabala
Agronomy 2022, 12(9), 2136; https://doi.org/10.3390/agronomy12092136 - 8 Sep 2022
Cited by 7 | Viewed by 2369
Abstract
The fast and efficient recovery could be an important trait defining the efficacy of plant drought adaptation. In this work, we aimed to develop a set of simple and appropriate physiological proxies that could be used as reliable indicators to predict plant drought [...] Read more.
The fast and efficient recovery could be an important trait defining the efficacy of plant drought adaptation. In this work, we aimed to develop a set of simple and appropriate physiological proxies that could be used as reliable indicators to predict plant drought responses and validate the role of specific physiological traits such as root length, stomata density, and residual transpiration, in the drought tolerance and recovery in barley. Eighty barley (Hordeum vulgare L.) genotypes were subjected to progressive droughting until the soil moisture level reached 10%, followed by rewatering. Plants were visually scored at the end of drought period and two weeks after rewatering. SPAD values and chlorophyll fluorescence Fv/Fm ratio were also measured, alongside with stomatal density (SD) and residual transpiration (RT). The same genotypes were germinated in paper rolls treated with 15% (w/v) of polyethylene glycol (PEG) 8000 by quantification of changes in the root growth patterns. Responses to drought stress varied among the genotypes, and drought tolerance and recovery scores were significantly correlated with each other. Changes in SPAD value, Fv/Fm ratio and root length were significantly correlated with the drought tolerance and recovery indices. Both indices correlated strongly with the SD and RT of irrigated plants, although in an unexpected direction. We have also correlated the extent of plants’ drought tolerance to their ability to grow in saline soils (a condition often termed a “physiological drought”) and found a positive association between these two traits. The fact that drought tolerant genotype also possessed higher salinity tolerance implies some common mechanisms conferring both traits. Plants having less SD and more RT under irrigated conditions showed higher drought tolerance. It is concluded that lower SD and higher RT under optimal conditions may be used as proxies for drought tolerance in barley. Full article
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14 pages, 648 KiB  
Review
Cadmium Accumulation in Cereal Crops and Tobacco: A Review
by Shineng Mei, Kaina Lin, Darron V. Williams, Yang Liu, Huaxin Dai and Fangbin Cao
Agronomy 2022, 12(8), 1952; https://doi.org/10.3390/agronomy12081952 - 18 Aug 2022
Cited by 19 | Viewed by 3179
Abstract
Cadmium (Cd) is a toxic heavy metal with no known biological function in plants and one of the most toxic substances released into the environment. Crops, such as rice, maize, wheat and tobacco are the major sources of Cd for humans. Cd toxicity [...] Read more.
Cadmium (Cd) is a toxic heavy metal with no known biological function in plants and one of the most toxic substances released into the environment. Crops, such as rice, maize, wheat and tobacco are the major sources of Cd for humans. Cd toxicity inhibits crop growth and development by affecting many central physiological and biochemical processes, and finally it affects human health via the food chain. To adapt to Cd toxicity, crops have evolved a series of detoxification mechanisms. Immediate responses include rapid changes at the transcriptional level with simultaneous changes at the physiological and metabolic levels. However, the long-term responses involve genetic modifications and epigenetic changes. During the last decade, many genes involved in Cd uptake and translocation have been identified, and many of them are transporters. To decrease the accumulation of Cd in cereal grains and tobacco leaves, a number of approaches have been proposed, including physical and chemical methods, developing and planting low accumulation genotypes using transgenic strategies or marker–trait association breeding. In this review, we describe the toxicity of Cd to crops and human body, advances in the molecular mechanisms of Cd accumulation in cereal crops and tobacco, and approaches to decrease Cd accumulation. Full article
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12 pages, 1123 KiB  
Article
Single-Nucleotide Polymorphisms in Bmy1 Intron III Alleles Conferring the Genotypic Variations in β-Amylase Activity under Drought Stress between Tibetan Wild and Cultivated Barley
by Xiaojian Wu, Wenhao Yue, Kangfeng Cai, Huan Wang, Fanrong Zeng and Junmei Wang
Agronomy 2022, 12(8), 1737; https://doi.org/10.3390/agronomy12081737 - 22 Jul 2022
Cited by 3 | Viewed by 1412
Abstract
β-amylase activity is related to the polymorphisms of Bmy1 intron III; however, no attention has been given to such relationships under environmental stresses such as drought. In this study, 73 cultivated barley genotypes and 52 Tibetan wild barley accessions were used to test [...] Read more.
β-amylase activity is related to the polymorphisms of Bmy1 intron III; however, no attention has been given to such relationships under environmental stresses such as drought. In this study, 73 cultivated barley genotypes and 52 Tibetan wild barley accessions were used to test the association between Bmy1 gene intron III polymorphisms and β-amylase activity under drought stress. Our results showed that three alleles, Bmy1.a, Bmy1.b, and Bmy1.c, existed in the examined barley genotypes. Tibetan wild barley had a higher proportion of Bmy1.b, whereas cultivated barley showed a higher proportion of Bmy1.a. Impressively, barley genotypes with Bmy1.b showed a significant increase in β-amylase activity under drought stress, compared with those with Bmy1.a or Bmy1.c, indicating that the Bmy1.b allele might provide more chances for developing barley cultivars with higher β-amylase activity under water stress than both the Bmy1.a and Bmy1.c alleles. Furthermore, the Tibetan wild barley XZ147, belonging to the Bmy1.b allele type, showed significantly higher β-amylase activity than Triumph under drought stress. This might be the result of the unique amino acid substitution M527 or the amino acid composition of R115, D165, A233, S347, and M527 of XZ147. Full article
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18 pages, 1044 KiB  
Review
Understanding R Gene Evolution in Brassica
by Fangning Zhang, Ting Xiang Neik, Tingting Wu, David Edwards and Jacqueline Batley
Agronomy 2022, 12(7), 1591; https://doi.org/10.3390/agronomy12071591 - 30 Jun 2022
Viewed by 2955
Abstract
Brassica crop diseases caused by various pathogens, including viruses, bacteria, fungi and oomycetes, have devastating effects on the plants, leading to significant yield loss. This effect is worsened by the impact of climate change and the pressure to increase cultivation worldwide to feed [...] Read more.
Brassica crop diseases caused by various pathogens, including viruses, bacteria, fungi and oomycetes, have devastating effects on the plants, leading to significant yield loss. This effect is worsened by the impact of climate change and the pressure to increase cultivation worldwide to feed the burgeoning population. As such, managing Brassica diseases has become a challenge demanding a rapid solution. In this review, we provide a detailed introduction of the plant immune system, discuss the evolutionary pattern of both dominant and recessive disease resistance (R) genes in Brassica and discuss the role of epigenetics in R gene evolution. Reviewing the current findings of how R genes evolve in Brassica spp. provides further insight for the development of creative ideas for crop improvement in relation to breeding sustainable, high quality, disease-resistant Brassica crops. Full article
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14 pages, 1917 KiB  
Article
Investigation of Two QTL Conferring Seedling Resistance to Fusarium Crown Rot in Barley on Reducing Grain Yield Loss under Field Environments
by Zhi Zheng, Jonathan Powell, Shang Gao, Cassandra Percy, Alison Kelly, Bethany Macdonald, Meixue Zhou, Philip Davies and Chunji Liu
Agronomy 2022, 12(6), 1282; https://doi.org/10.3390/agronomy12061282 - 27 May 2022
Cited by 2 | Viewed by 2138
Abstract
Fusarium crown rot (FCR) is one of the most damaging cereal diseases in semi-arid regions worldwide. Genetic studies on FCR resistance have mainly focused on disease symptoms measured by the browning of either leaf sheaths in seedlings or stems of mature plants. Two [...] Read more.
Fusarium crown rot (FCR) is one of the most damaging cereal diseases in semi-arid regions worldwide. Genetic studies on FCR resistance have mainly focused on disease symptoms measured by the browning of either leaf sheaths in seedlings or stems of mature plants. Two major QTLs conferring FCR resistance in barley, Qcsr.cpi-1H and Qcrs.cpi-4H, were previously identified in the growth room. They could explain up to 33.4 and 45.3% of phenotypic variance, respectively. This is the first study where the possible effects of FCR-resistant loci identified in the previous studies based on seedling assay are tested for their abilities to reduce grain yield loss. Near isogenic lines (NILs) and backcross (BC) lines targeting these two loci were assessed in the 2017 and 2018 crop seasons. Results from the NILs showed that the presence of a resistance allele at either the 1HL or 4HL locus reduced grain yield loss by an average of 12.0% and 10.7%, respectively. Grain yields of the top BC lines containing resistance alleles at both loci were 34.4% higher than the average of the commercial varieties under FCR inoculation. These lines will be highly valuable in breeding barley varieties with enhanced resistance to FCR. Full article
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30 pages, 1513 KiB  
Review
Genetic Improvement of Heat Stress Tolerance in Cereal Crops
by Camilla Beate Hill and Chengdao Li
Agronomy 2022, 12(5), 1205; https://doi.org/10.3390/agronomy12051205 - 17 May 2022
Cited by 15 | Viewed by 5124
Abstract
Crop heat stress is a threat to food supply, with heatwaves expected to increase in frequency and intensity globally. In addition to yield loss, heat stress dramatically reduces fertility and seed-setting rate, grain quality and weight, and seed germination and growth. Genetic variability [...] Read more.
Crop heat stress is a threat to food supply, with heatwaves expected to increase in frequency and intensity globally. In addition to yield loss, heat stress dramatically reduces fertility and seed-setting rate, grain quality and weight, and seed germination and growth. Genetic variability for heat stress tolerance can be used in breeding programs to develop tolerant genotypes. The availability of genome assemblies with high-confidence sequences for many cereal crops, including rice, maize, wheat and barley, now allows the identification of heat stress tolerance-associated genes and gene networks. This review focuses on synthesizing current advances in understanding the detrimental effects of heat stress on cereal crop production at the physiological and genetic levels. It provides an account of available genomic resources, genetic variation, candidate genes, and molecular markers for heat stress tolerance. Lastly, this review offers insight into crop genetic improvement for heat stress tolerance, including germplasm screening in glasshouse and field trials, marker-assisted selection, mapping genomic loci and identification of candidate genes, and genomic-assisted breeding. Full article
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15 pages, 3858 KiB  
Article
Ectopic Expression of Kenaf (Hibiscus cannabinus L.) HcWRKY50 Improves Plants’ Tolerance to Drought Stress and Regulates ABA Signaling in Arabidopsis
by Xiaoping Niu, Meixia Chen, Zeyuan She, Mohammad Aslam, Jianmin Qi and Yuan Qin
Agronomy 2022, 12(5), 1176; https://doi.org/10.3390/agronomy12051176 - 13 May 2022
Cited by 6 | Viewed by 5006
Abstract
Kenaf (Hibiscus cannabinus L.) is an environmentally friendly, multipurpose fiber crop suitable for osmotic stress tolerance studies. However, the mechanisms of tolerance remain largely unknown. Here, we identified a stress-responsive HcWRKY50 gene from kenaf (Hibiscus cannabinus L.) and studied its function [...] Read more.
Kenaf (Hibiscus cannabinus L.) is an environmentally friendly, multipurpose fiber crop suitable for osmotic stress tolerance studies. However, the mechanisms of tolerance remain largely unknown. Here, we identified a stress-responsive HcWRKY50 gene from kenaf (Hibiscus cannabinus L.) and studied its function and tolerance under drought stress. HcWRKY50 is a nuclear-localized protein. The overexpression of HcWRKY50 in Arabidopsis showed higher drought tolerance, exhibiting increased root length and lateral root number, and reduced stomatal density compared with the control lines. The seed germination and seedling growth of HcWRKY50 transgenic plants showed less sensitivity to ABA but they became more sensitive to ABA in their stomatal aperture. Furthermore, qRT-PCR analysis revealed that HcWRKY50 regulated ABA signaling by promoting the expression of several key ABA-responsive and stress-responsive genes such as RD29B and COR47 in transgenic lines. Taken together, this study demonstrated that the kenaf transcription factor HcWRKY50 regulates seed germination and seedling growth and improves drought stress tolerance via an ABA signaling pathway. Full article
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11 pages, 1654 KiB  
Article
Topping Inhibited Potassium Uptake via Regulating Potassium Flux and Channel Gene Expression in Tobacco
by Taibo Liang, Huaxin Dai, Waleed Amjad Khan, Yadi Guo, Xiangyu Meng, Guiyao Wang and Yanling Zhang
Agronomy 2022, 12(5), 1166; https://doi.org/10.3390/agronomy12051166 - 11 May 2022
Cited by 1 | Viewed by 2014
Abstract
Potassium (K+) is mainly absorbed by plants from the soil and is primarily transported within the plant through the xylem. Topping has been reported to cause efflux and loss of K+ in plants; however, its effect on the real-time flow [...] Read more.
Potassium (K+) is mainly absorbed by plants from the soil and is primarily transported within the plant through the xylem. Topping has been reported to cause efflux and loss of K+ in plants; however, its effect on the real-time flow rate and genotypes with varying K+ accumulation ability is still unknown. Therefore, we carried out a pot experiment containing sand culture using two tobacco cultivars EY1 (high K+ accumulating) and Y87 (low K+ accumulating). The results demonstrated the change of K+ flow direction from influx to efflux in the roots of both cultivars due to topping. The percentage ratio of K+ efflux to influx was estimated to be 18.8% in EY-1 and 157.0% in Y87, respectively. We noticed a decline in indole acetic acid (IAA) content due to topping, which activated the expression of K+ efflux channel gene NTORK1 and inhibited the expression of K+ influx channel genes NKT1 and NtKC1. Furthermore, K+ loss from the roots increased due to topping, which led to decreased K+ concentration in entire tobacco plant. Topping had a more serious impact on the K+ efflux rate and K+ loss in Y87. IAA application after topping, in turn, decreased the K+ loss in both the cultivars. We conclude that topping caused a decrease in IAA concentration and K+ losses in tobacco leaves, and these losses can be mitigated by the exogenous application of IAA. Full article
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14 pages, 1530 KiB  
Article
Comparative Transcriptional Analysis of Two Contrasting Rice Genotypes in Response to Salt Stress
by Xiaoxue Ye, Weiwei Tie, Jianlong Xu, Zehong Ding and Wei Hu
Agronomy 2022, 12(5), 1163; https://doi.org/10.3390/agronomy12051163 - 11 May 2022
Cited by 4 | Viewed by 2145
Abstract
Improving rice salt-tolerance is an effective way to deal with the increasing food demand caused by soil salinization and population growth. Nevertheless, the molecular mechanisms of rice salt-tolerance remain elusive. In this study, comparative transcriptomic analyses were performed to identify salt-tolerance genes that [...] Read more.
Improving rice salt-tolerance is an effective way to deal with the increasing food demand caused by soil salinization and population growth. Nevertheless, the molecular mechanisms of rice salt-tolerance remain elusive. In this study, comparative transcriptomic analyses were performed to identify salt-tolerance genes that were either specifically regulated or more changed in salt-tolerant cultivar FL478 relative to salt-sensitive cultivar 93-11. In total, 1423, 175, and 224 salt-tolerance genes were identified under 200 mM NaCl treatment for 6 h, 24 h, and 72 h, respectively. These genes were commonly enriched in transport and peroxidase/oxidoreductase activity across all timepoints, but specially enriched in transcription regulator activity at 6 h under salt stress. Further analysis revealed that 53 transporters, 38 transcription factors (TFs), and 23 reactive oxygen species (ROS) scavenging enzymes were involved in salt adaptation of FL478, and that overall, these salt-tolerance genes showed a faster transcriptional expression response in FL478 than in 93-11. Finally, a gene co-expression network was constructed to highlight the regulatory relationships of transporters, TFs, and ROS scavenging genes under salt-stress conditions. This work provides an overview of genome-wide transcriptional analysis of two contrasting rice genotypes in response to salt stress. These findings imply a crucial contribution of quickly transcriptional changes to salt tolerance and provide useful genes for genetic improvement of salt tolerance in rice. Full article
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8 pages, 850 KiB  
Article
Tissue-Specific Responses of Cereals to Two Fusarium Diseases and Effects of Plant Height and Drought Stress on Their Susceptibility
by Zhouyang Su, Zhi Zheng, Meixue Zhou, Sergey Shabala and Chunji Liu
Agronomy 2022, 12(5), 1108; https://doi.org/10.3390/agronomy12051108 - 2 May 2022
Cited by 3 | Viewed by 2056
Abstract
Multiple species of Fusarium can infect wheat and barley plants at various stages of development. Fusarium head blight (FHB) refers to the infection of spikes and developing kernels by these pathogens, and crown rot (FCR) infers to infection of the root, crown, and [...] Read more.
Multiple species of Fusarium can infect wheat and barley plants at various stages of development. Fusarium head blight (FHB) refers to the infection of spikes and developing kernels by these pathogens, and crown rot (FCR) infers to infection of the root, crown, and basal stem by Fusarium pathogens. Interestingly, most of the host genes conferring resistance to these two diseases are different in both wheat and barley, and plants’ susceptibility to these two diseases are oppositely affected by both plant height and reduced water availability. Available results do not support the hypothesis that reduced height genes have different effects on biotrophic and necrotrophic diseases. Rather, differences in temperature and humidity in microenvironments surrounding the infected tissues and the difference in the physical barriers originating from the difference in cell density seem to be important factors affecting the development of these two diseases. The fact that genes conferring resistance to Type I and Type II of FHB are different indicates that it could be feasible to identify and exploit genes showing resistance at the three distinct stages of FCR infection for breeding varieties with further enhanced resistance. The strong association between FCR severity and drought stress suggests that it should be possible to exploit some of the genes underlying drought tolerance in improving resistance to FCR. Full article
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15 pages, 12231 KiB  
Review
Waterlogging Stress Physiology in Barley
by James De Castro, Robert D. Hill, Claudio Stasolla and Ana Badea
Agronomy 2022, 12(4), 780; https://doi.org/10.3390/agronomy12040780 - 24 Mar 2022
Cited by 17 | Viewed by 4745
Abstract
Barley (Hordeum vulgare L.) is the most susceptible cereal species to excess moisture stress. Waterlogging-induced hypoxia causes major morphological, physiological, and metabolic changes, some of which are regulated by the action of plant growth regulators and signal molecules including nitric oxide. Recent [...] Read more.
Barley (Hordeum vulgare L.) is the most susceptible cereal species to excess moisture stress. Waterlogging-induced hypoxia causes major morphological, physiological, and metabolic changes, some of which are regulated by the action of plant growth regulators and signal molecules including nitric oxide. Recent studies have evidenced the participation of phytoglobins in attenuating hypoxic stress during conditions of excessive moisture through their ability to scavenge nitric oxide and influence the synthesis and response of growth regulators. This review will highlight major cellular changes linked to plant responses to waterlogging stress with emphasis on phytoglobins. Full article
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2021

Jump to: 2024, 2023, 2022

12 pages, 3151 KiB  
Article
Aerenchyma Formation in Adventitious Roots of Tall Fescue and Cocksfoot under Waterlogged Conditions
by Nguyen Thi Mui, Meixue Zhou, David Parsons and Rowan William Smith
Agronomy 2021, 11(12), 2487; https://doi.org/10.3390/agronomy11122487 - 8 Dec 2021
Cited by 9 | Viewed by 3559
Abstract
The formation of aerenchyma in adventitious roots is one of the most crucial adaptive traits for waterlogging tolerance in plants. Pasture grasses, like other crops, can be affected by waterlogging, and there is scope to improve tolerance through breeding. In this study, two [...] Read more.
The formation of aerenchyma in adventitious roots is one of the most crucial adaptive traits for waterlogging tolerance in plants. Pasture grasses, like other crops, can be affected by waterlogging, and there is scope to improve tolerance through breeding. In this study, two summer-active cocksfoot (Dactylis glomerata L.) cultivars, Lazuly and Porto, and two summer-active tall fescue (Lolium arundinaceum Schreb., syn. Festuca arundinacea Schreb.) cultivars, Hummer and Quantum II MaxP, were selected to investigate the effects of waterlogging on root growth and morphological change. Cultivars were subjected to four periods of waterlogging treatments (7, 14, 21 and 28 days), while comparable plants were kept under free drained control conditions. The experiment was arranged as a split–split plot design, with waterlogging treatments (waterlogged, control) considered as main plots, time periods (days of waterlogging) as subplots and cultivars as sub-subplots. Plants began to show signs of waterlogging stress 14–21 days after the onset of waterlogging treatments. There were no significant differences in shoot biomass between the waterlogged and control plants of any cultivar. However, waterlogging significantly reduced root dry matter in all cultivars, with greater reduction in cocksfoot (56%) than in tall fescue (38%). Waterlogging also led to increased adventitious root and aerenchyma formation in both species. Cocksfoot cultivars showed a greater increase in adventitious roots, while tall fescue cultivars had a greater proportion of aerenchyma. Both cultivars within each species showed similar responses to waterlogging treatments. However, an extended screening program is needed to identify whether there are varietal differences within species, which could be used to discover genes related to aerenchyma or adventitious root formation (waterlogging tolerance) for use in breeding programs. Full article
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14 pages, 1357 KiB  
Review
Improving Crop Lodging Resistance by Adjusting Plant Height and Stem Strength
by Yanan Niu, Tianxiao Chen, Chenchen Zhao and Meixue Zhou
Agronomy 2021, 11(12), 2421; https://doi.org/10.3390/agronomy11122421 - 27 Nov 2021
Cited by 30 | Viewed by 5546
Abstract
Crop height not only determines plant resistance to lodging and crowding, but also affects crop architecture, apical dominance, biomass, and mechanical harvesting. Plant height is determined by the internode elongation, regulated by genes involved in gibberellin (GA) and brassinosteroid (BR) biosynthesis or related [...] Read more.
Crop height not only determines plant resistance to lodging and crowding, but also affects crop architecture, apical dominance, biomass, and mechanical harvesting. Plant height is determined by the internode elongation, regulated by genes involved in gibberellin (GA) and brassinosteroid (BR) biosynthesis or related signaling networks. Plants’ genetic inability to synthesize or respond to GAs and BRs induce dwarfness. However, the signaling mechanisms of GAs and BRs for controlling plant height individually or collectively are still unclear. Since stem mechanically supports plant during the whole life span, components that affect stem physical strength are also important to crop lodging resistance. One of the major components is lignin, which forms stem structure, thus contributing to crop lodging resistance. In this review, we looked into the reported genes involved in lignin, GAs, and BRs biosynthesis and summarized the signaling networks centered by these genes. Then, we filled the knowledge gap by modifying plant height through interrupting normal GA and BR metabolism utilizing core gene inhibitors. Therefore, we highly endorsed the current approaches of using plant growth regulators (PRGs) to maintain an ideal plant height under lodging stress, and proposed possibilities of modifying crop culm strength against lodging as well. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Tentative review title: Genetic improvement of heat stress tolerance in cereal crops
Authors: Camilla Hill
Affiliation: Murdoch University
Abstract: Heat damage is a very common and limiting crop production constraint globally. Cereal flowering stages are very sensitive to high temperatures which can significantly decrease fertility and seed-setting rate, directly resulting in severe grain yield losses. In addition to yield loss, heat stress dramatically reduces grain quality and weight, seed germination and seedling growth. At the molecular level, heat stress leads to oxidative stress through excess production of reactive oxygen species, reduction of photosynthesis, and inhibition of starch biosynthesis. Under the current climate pattern, it is expected that high temperatures and heat shock will occur more frequently and much earlier in the future. Genetic variability for heat stress tolerance can be used in breeding programs to develop tolerant genotypes. The availability of genome assemblies with high-confidence sequences for many cereal crops including rice, maize, bread wheat and barley, now allow the identification of heat stress tolerance-associated genes and gene networks. In this review, we will report current knowledge on the detrimental effects of heat stress on cereal crop production at the physiological and molecular levels. We will further provide a summary of available genomic resources, genetic variation, candidate genes, and molecular markers for heat stress tolerance, and will discuss effective approaches for heat stress management, including germplasm screening in the glasshouse and in field trials, marker-assisted selection, mapping genomic loci and identification of candidate genes, and genomic-assisted breeding that enhance heat tolerance in cereal crops including rice, wheat and barley.

Title: Waterlogging Stress Physiology in Barley
Authors: Ana Badea
Affiliation: Plant Research International, P.O. Box 619, 6700 AP Wageningen, the Netherlands
Abstract: Barley (Hordeum vulgare) is the most susceptible cereal species to excess moisture stress. Waterlogging-induced hypoxia causes major morphological, physiological and metabolic changes some of which are regulated by the action of plant growth regulators and signal molecules including nitric oxide (NO).  Recent studies have evidenced the participation of Phytoglobins in attenuating hypoxic stress during condition of excessive moisture through their ability to scavenge NO and influence the synthesis and response of growth regulators.  This review will highlight major cellular changes linked to plant responses to waterlogging stress with emphasis on Phytoglobins.

Title: The Barley Phytoglobin 1 ameliorates plant performance to waterlogging
Authors: Ana Badea
Affiliation: Plant Research International, P.O. Box 619, 6700 AP Wageningen, the Netherlands
Abstract: Phytoglobins are ubiquitous proteins participating in a variety of stress responses, including excess moisture.  Over-expression of the barley (Hordeum vulgare) Phytoglobin 1 HvPgb1 enhanced tolerance to waterlogging.  Relative to waterlogged wild type (WT) plants, plants over-expressing HvPgb1 exhibited enhanced growth and  retention of gas exchange parameters. These effects were associated to major changes in global gene expression, as well as alterations of several morpho-physiological parameters linked to tolerance to excess moisture.  Relative to their susceptible counterparts, tolerant barley cultivars exhibited a higher expression of HvPgb1 after 20h of waterlogging, suggesting that the expression of this gene could be used as a potential tool to select for plant tolerance to excess moisture.

Title: Genome-wide association analysis of aluminium tolerance in chickpea
Authors: Yong Jia
Affiliation: Murdoch University · Western Australian State Agricultural Biotechnology Centre (SABC)
Abstract: Domesticated chickpea (Cicer arietinum L.) is one of the most important legumes with great food and nutritional values. Like many other crops, the production of chickpea can be severely limited by aluminium (Al) toxicity under acidic soils, which are prevalent in many countries. To investigate the genetic mechanism of Al resistance in chickpea, we used a collection of 212 chickpea genotypes (45 Cicer arietinum, 127 Cicer reticulatum, and 40 Cicer echinospermum) and grow them in hydroponics for 4 days with different Al concentrations. The Al tolerance was assessed by calculating the relative root growth under two Al treatments (15 µM & 30 µM Al) compared to the control (0 µM Al). Significant variations in Al tolerance was observed across the target chickpea genotypes, indicating an effective pool for genetic association analyses. Single nucleotide polymorphism (SNP) data of 190 target chickpea lines was obtained from a previous chickpea genome sequencing study. After adjusting for the subpopulation factor, genome-wide association analysis identified a QTL on chromosomes 7 which was consistently detected under both 15 µM and 30 µM Al treatments. The potential candidate gene underlying this QTL is selected and discussed. In summary, this study contributes to our understanding of the genetic mechanism of Al tolerance in chickpea. The SNP markers identified in this study may be used for future breeding program to improve Al tolerance in chickpea.

Title: Review on heavy metal
Authors: Fangbin Cao
Affiliation: Zhejiang University

Title: Recent progress in Fusarium crown rot resistance in wheat and barley
Authors: Chunji Liu
Affiliation: The Commonwealth Scientific and Industrial Research Organisation | CSIRO · Division of Plant Industry
Abstract: Fusarium crown rot (FCR), caused by various Fusarium pathogens, is a chronic disease to wheat and barley production worldwide. This disease has become more prevalent in recently years likely due to the wide adoption of minimum tillage and stubble retention. Several loci conferring FCR resistance have been reported in both species but plant height is likely responsible for the locus on 4BS in wheat and the one on 3HL in barley. Near isogenic lines (NILs) have been generated for some of these loci and evaluating effects of a given locus using NILs overcomes issues related to interaction between FCR resistance and other traits of agronomic importance. Facilitated by transcriptome analysis, markers tightly linked to a few loci have been obtained by analysing NIL-derived populations. These markers and populations form solid foundation for cloning genes underlying each of these resistance loci. Gene pyramiding has been shown to be effective in enhancing resistance to this disease in both wheat and barley. Different from Fhb1 which confers resistance to Fusarium head blight but not to FCR, Fhb7 seems to provide resistance to both Fusarium diseases. Effects of Fhb7 against different Fusarium pathogens in different environments need to be assessed and interactions between it and other resistance loci need to be evaluated.

Title: Cross-tolerances between biotic and abiotic stresses in crops
Authors: Chunji Liu
Affiliation: The Commonwealth Scientific and Industrial Research Organisation | CSIRO · Division of Plant Industry
Abstract: Crop production is constantly threatened by biotic and abiotic stresses. Enhancing crop resistance and tolerance to either of these threats genetically must be a target in all major breeding programs worldwide, and many genes conferring resistance or tolerance to a wide array of stresses have been identified. Available results indicate that some genes can confer resistance or tolerance to several different biotic and abiotic stresses and exploiting such genes would increase breeding efficiency by reducing the number of targeted loci. However, several factors must be considered when selecting such genes for use: a) the values of a gene cannot be adequately determined by the level of its expression alone; b) mapping based on segregation populations does not only suffer from limited resolution but also from the interferences of non-targeted traits; and c) deleterious effect of a gene on yield and quality. Selected studies are used to discuss these factors and possible solutions are discussed in this review.

Title: Understanding the evolution of plant disease resistance genes for crop improvement
Authors: Ting Xiang Neik; Jacqueline Batley; Tingting Wu; Fangning Zhang
Affiliation: The University of Western Australia, Perth 6009, Australia
Abstract: Brassica crop diseases caused by various pathogens, including virus, bacteria, fungi and oomycetes, have devastating effects on the plants, leading to significant yield loss. Worsened by the impact of climate change and the pressure to increase cultivation worldwide to feed the burgeoning population, managing Brassica diseases has become a challenge demanding a rapid solution. In this review, we make a detailed introduction of the plant immune system, discuss the evolutionary pattern of both dominant and recessive disease resistance (R) genes in Brassicas, and discuss the role of epigenetics in R gene evolution. Reviewing the current findings of how R genes evolve in Brassica provides further insight and develop creative ideas for crop improvement in relation to breeding sustainable, high quality, disease-resistant Brassica crops.

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