Climate change is a major threat to most of the agricultural crops grown in tropical and sub-tropical areas globally. Drought stress is one of the consequences of climate change that has a negative impact on crop growth and yield. In the past, many simulation models were proposed to predict climate change and drought occurrences, and it is extremely important to improve essential crops to meet the challenges of drought stress which limits crop productivity and production. Wheat and barley are among the most common and widely used crops due to their economic and social values. Many parts of the world depend on these two crops for food and feed, and both crops are vulnerable to drought stress. Improving drought stress tolerance is a very challenging task for wheat and barley researchers and more research is needed to better understand this stress. The progress made in understanding drought tolerance is due to advances in three main research areas: physiology, breeding, and genetic research. The physiology research focused on the physiological and biochemical metabolic pathways that plants use when exposed to drought stress. New wheat and barley genotypes having a high degree of drought tolerance are produced through breeding by making crosses from promising drought-tolerant genotypes and selecting among their progeny. Also, identifying genes contributing to drought tolerance is very important. Previous studies showed that drought tolerance is a polygenic trait and genetic constitution will help to dissect the gene network(s) controlling drought tolerance. This review explores the recent advances in these three research areas to improve drought tolerance in wheat and barley.

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Drought Stress Tolerance in Wheat and Barley: Advances in Physiology, Breeding and Genetics Research.

In recent years, with climate change, drought stress has been witnessed in many parts of the world. In many irrigated regions also, shortage of water supply allows only limited irrigation. These conditions have an adverse effect on the productivity of many crops including cereals such as wheat. Therefore, genetics of drought/water stress tolerance in different crops has become a priority area of research. This research mainly involves use of quantitative trait locus (QTL) analysis (involving both interval mapping and association mapping) for traits that are related to water-use efficiency. In this article, we briefly review the available literature on QTL analyses in wheat for traits, which respond to drought/water stress. The outlook for future research in this area and the possible approaches for utilizing the available information on genetics of drought tolerance for wheat breeding are also discussed.

https://www.mdpi.com/2073-4395/7/1/5/pdf/1

QTL Analysis for Drought Tolerance in Wheat: Present Status and Future Possibilities

A review of the available literature on genetics of yield and its component traits, tolerance to abiotic stresses and biofortification should prove useful for future research in wheat in the genomics era. The work reviewed in this article mainly covers the available information on genetics of some important quantitative traits including yield and its components, tolerance to abiotic stresses (heat, drought, salinity and pre-harvest sprouting = PHS) and biofortification (Fe/Zn and phytate contents with HarvestPlus Program) in wheat. Major emphasis is laid on the recent literature on QTL interval mapping and genome-wide association studies, giving lists of known QTL and marker-trait associations. Candidate genes for different traits and the cloned and characterized genes for yield traits along with the molecular mechanism are also described. For each trait, an account of the present status of marker-assisted selection has also been included. The details of available results have largely been presented in the form of tables; some of these tables are included as supplementary files.

Genetics of yield, abiotic stress tolerance and biofortification in wheat (Triticum aestivum L.)

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2424&context=agronomyfacpub

Genomic resources in plant breeding for sustainable agriculture.

Heat stress (HS) is one of the major abiotic stresses affecting the production and quality of wheat. Rising temperatures are particularly threatening to wheat production. A detailed overview of morpho-physio-biochemical responses of wheat to HS is critical to identify various tolerance mechanisms and their use in identifying strategies to safeguard wheat production under changing climates. The development of thermotolerant wheat cultivars using conventional or molecular breeding and transgenic approaches is promising. Over the last decade, different omics approaches have revolutionized the way plant breeders and biotechnologists investigate underlying stress tolerance mechanisms and cellular homeostasis. Therefore, developing genomics, transcriptomics, proteomics, and metabolomics data sets and a deeper understanding of HS tolerance mechanisms of different wheat cultivars are needed. The most reliable method to improve plant resilience to HS must include agronomic management strategies, such as the adoption of climate-smart cultivation practices and use of osmoprotectants and cultured soil microbes. However, looking at the complex nature of HS, the adoption of a holistic approach integrating outcomes of breeding, physiological, agronomical, and biotechnological options is required. Our review aims to provide insights concerning morpho-physiological and molecular impacts, tolerance mechanisms, and adaptation strategies of HS in wheat. This review will help scientific communities in the identification, development, and promotion of thermotolerant wheat cultivars and management strategies to minimize negative impacts of HS.

/pdf/impacts-tolerance-adaptation-and-mitigation-of-heat-stress-2x72ikwq.pdf

Impacts, Tolerance, Adaptation, and Mitigation of Heat Stress on Wheat under Changing Climates

Novel molecular breeding selection strategies were implemented in breeding programs in India for wheat improvement under drought and heat stress. Elite Indian varieties HD2733 and GW322 were targeted for improvement to abiotic stresses through marker assisted backcross breeding approach. Backcross populations were advanced to BC1/BC2 F2 after tracking QTLs for foreground selection covering traits such as canopy temperature (CT), chlorophyll content, normalized difference vegetation index (NDVI), grain filling duration (GFD), thousand kernel weight, grain yield and a range of polymorphic microsatellite markers covering entire genome (4–5 SSR markers per chromosome) being used for tracking the recurrent parent genome. Marker assisted recurrent selection (MARS) involved estimation of marker effects for several small effect/major QTLs followed by two recombination cycles. Designed intermating among selected F5 families were carried out after conducting ANOVA and AMMI analysis on multi-location yield trials and polymorphic markers among the parents in two biparental base populations (F5). Inter-family intermating among the best identified families carried out in different combinations to accumulate and recombine 4–8 QTLs per intermated progeny and confirmed in selfed homozygous lines.

/pdf/molecular-approaches-for-wheat-improvement-under-drought-and-3mtdn1wln3.pdf

Molecular approaches for wheat improvement under drought and heat stress

The present study reports the introgression of the genomic regions linked with drought tolerance traits viz., NDVI, staygreen, chlorophyll content/chlorophyll fluorescence and yield from a drought tolerant parent HI1500 in to a popular high yielding but drought susceptible wheat variety GW322 following the marker assisted backcross breeding. Background selection with 109 polymorphic SSR markers accelerated genome recovery of recurrent parent which ranged from 72.14 to 86.9% in BC1F1, 90.33 to 92.02% in BC2F1 and 91.6 to 94.95% with an average of 93.5% in BC2F2 generation. Eighteen homozygous BC2F3 progenies were found to be phenotypically superior for morpho-physiological and agronomic traits over the recurrent parent GW322.

Leena Todkar

Papers

Molecular approaches for wheat improvement under drought and heat stress

Introgression of drought tolerance QTLs through marker assisted backcross breeding in wheat (Triticum aestivum L.)