High temperature (>30 °C) at the time of grain filling is one of the major causes of yield reduction in wheat in many parts of the world, especially in tropical countries. To identify quantitative trait loci (QTL) for heat tolerance under terminal heat stress, a set of 148 recombinant inbred lines was developed by crossing a heat-tolerant hexaploid wheat (Triticum aestivum L.) cultivar (NW1014) and a heat-susceptible (HUW468) cultivar. The F(5), F(6), and F(7) generations were evaluated in two different sowing dates under field conditions for 2 years. Using the trait values from controlled and stressed trials, four different traits (1) heat susceptibility index (HSI) of thousand grain weight (HSITGW); (2) HSI of grain fill duration (HSIGFD); (3) HSI of grain yield (HSIYLD); and (4) canopy temperature depression (CTD) were used to determine heat tolerance. Days to maturity was also investigated. A linkage map comprising 160 simple sequence repeat markers was prepared covering the whole genome of wheat. Using composite interval mapping, significant genomic regions on 2B, 7B and 7D were found to be associated with heat tolerance. Of these, two (2B and 7B) were co-localized QTL and explained more than 15 % phenotypic variation for HSITGW, HSIGFD and CTD. In pooled analysis over three trials, QTL explained phenotypic variation ranging from 9.78 to 20.34 %. No QTL × trial interaction was detected for the identified QTL. The three major QTL obtained can be used in marker-assisted selection for heat stress in wheat.

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Pigeonpea [Cajanus cajan (L.) Millsp.] is a waterlogging-sensitive legume crop. We studied the effect of waterlogging stress on hydrogen peroxide (H 2 O 2 ) content, lipid peroxidation and antioxidant enzyme activities in two pigeonpea genotypes viz., ICPL-84023 (waterlogging resistant) and MAL-18 (waterlogging susceptible). In a pot experiment, waterlogging stress was imposed for 6 days at early vegetative stage (20 days after sowing). Waterlogging treatment significantly increased hydrogen peroxide accumulation and lipid peroxidation, which indicated the extent of oxidative injury posed by stress conditions. Enzyme activities of peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and polyphenol oxidase (PPO) increased in pigeonpea roots as a consequence of waterlogged conditions, and all the enzyme activities were significantly higher in waterlogged ICPL-84023 than in MAL-18. POX activity was the maximum immediately after imposing stress, therefore, it was suggested to be involved in early scavenging of H 2 O 2 , while rest of the enzymes (CAT, APX, SOD and PPO) were more important in late responses to waterlogging. Present study revealed that H 2 O 2 content is directly related to lipid peroxidation leading to oxidative damage during waterlogging in pigeonpea. Higher antioxidant potential in ICPL-84023 as evidenced by enhanced POX, CAT, APX, SOD and PPO activities increased capacity for reactive oxygen species (ROS) scavenging and indicated relationship between waterlogging resistance and antioxidant defense system in pigeonpea.

Bread wheat (Triticum aestivum L.) environments in West Asia, North Africa, and Mediterranean Europe are highly variable in terms of moisture, temperature, and biotic stresses. The present study attempted to divide this region into relatively uniform subregions by cluster analysis, to reduce the large magnitude of genotype (G) ✕ environment (E) interaction. Grain yield data of 21 to wheat lines in 2 yr were analyzed by a hierarchical agglomerative program with the correlation coefficient as a distance measure and average linkage as the clustering strategy. The large and significant entry ✕ trial interaction detected in the region implied that breeding for wide adaptability for this region would be difficult. Based on differential yield responses of the wheat lines, the cluster analysis showed the differences between the irrigated/high‐rainfall (IHR) and rainfed low‐rainfall (RLR) sites. Besides moisture supply, winter temperature of the sites appeared to be another determinant of the clusters. The IHR clusters consisted of sites with milder temperature than sites in the RLR clusters. The presence or absence of diseases also influenced the delineation of the clusters, but photoperiod of the sites did not appear to have a large influence. The greater variability in RLR sites relative to IHR sites indicated that breeding for RLR environments would be more difficult. We conclude that different breeding strategies should be followed within IHR and RLR environments.

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