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Synthetic hexaploid wheat and their advanced derivatives (SYN-DERs) are promising sources for introducing novel genetic diversity to develop climate-resilient cultivars. In a series of field and laboratory experiments, we measured biochemical, physiological and agronomic traits in a diversity panel of SYN-DERs evaluated under well-watered (WW) and water-limited (WL) conditions. Analysis of variance revealed significant differences among genotypes, treatments and their interaction for all agronomic and physiological traits. Grain yield (GY) was reduced by 62.75% under WL, with a reduction of 38.10% in grains per spike (GS) and 19.42% in 1000-grain weight (TGW). In a Pearson’s coefficient correlation, GY was significantly correlated with GS, number of tillers per plant and TGW in both conditions. Path coefficient analysis showed that TGW and GS made the highest contribution to GY in WW and WL conditions, respectively. The traits examined in this experiment explained 59.6% and 63.01% of the variation in GY under WL and WW conditions, respectively; TGW, canopy temperature at spike and superoxide dismutase were major determinants of GY under WL conditions. The major flowering-time determinant gene Ppd-D1 was fixed in the diversity panel, with presence of the photoperiod-insensitive allele (Ppd-D1a) in 99% accessions. Wild-type alleles at Rht-B1 and Rht-D1, and presence of the rye translocation (1B.1R), favoured GY under WL conditions. Continuous variation for the important traits indicated the potential use of genome-wide association studies to identify favourable alleles for drought adaptation in the SYN-DERs. This study showed sufficient genetic variation in the SYN-DERs diversity panel to improve yields during droughts because of better adaptability than bread wheat.

Adaptation of wheat (Triticum aestivum L.) to high temperature could be improved by introgressions from wild relatives. The response of 137 D genome synthetic hexaploid wheats (SHWs) to high temperature was evaluated to determine their potential for wheat improvement. Field experiments were conducted in two temperature scenarios (normal sowing time [NOR] and late sowing time to expose the plants to heat stress [HS]) for 2 yr at three locations to assess the effect of terminal high temperature on yield‐related traits. High temperature stress overall led to a 46.9% reduction in grain yield and significant reductions of 25.2% in days to heading, 26.6% in plant height, 16.1% in grain number per square meter, and 18.3% in thousand grain weight. In ridge regression analysis, agronomic traits explained 8.74 to 35.2% of the variation in grain yield in the HS treatments with an average of 30.47%. In NOR treatments, agronomic traits explained 8.85 to 45.5% of the variation in grain yield, with an average of 34.5%. Days to heading was negatively correlated with grain yield in the heat‐stressed environments but did not explain significant variation in grain yield in optimal environments. Thousand‐grain weight explained the highest variation in grain yield in all environments, followed by grain number per square meter. The top ten highest grain‐yielding SHWs in the HS treatment were also tolerant to heat stress, with a heat susceptibility index ranging from 0.33 to 0.40. These SHWs could be a promising source to introduce yield‐related traits to develop high‐yielding wheat cultivars for heat‐stressed environments.

No abstract

Root systems play an important role in crop performance particularly under rain fed conditions. Root architecture is key in determining the ability of crops to extract water at various soil depths. In many rain fed production regions, opportunities to improve yield through changes in management practices are limited. Thus, genetic solutions to improve yield under water limitation are required. We postulate that in drought-prone environments, genotypes with greater yield and yield stability can be developed by breeding for genotypes with favorable root systems. We studied wheat root architecture late in the developmental cycle. Narrow and deep root systems may help wheat to extract more water at depth late in the season and give an advantage to yield and yield stability where crops rely on stored moisture deep in the soil. To improve yield stability in rain fed regions, an effective phenotypic method is needed. However, studying root traits in mature field-grown crops is extremely challenging. A PVC tube method was developed and has been used to identify genotypic differences in root architecture late in crop development. Identification of root traits to improve deep water uptake late in crop development and the development of phenotypic methods to identify genetic sources of such traits will assist breeders to improve yield and yield stability in water-limited environments.