Bread wheat expanded its habitats from a small core area of the Fertile Crescent to global environments within ~10,000 years. Genetic mechanisms of this remarkable evolutionary success are not well understood. By whole-genome sequencing of populations from 25 subspecies within genera Triticum and Aegilops, we identified composite introgression from these wild populations contributing 13%~36% of the bread wheat genome, which tremendously increased the genetic diversity of bread wheat and allowed its divergent adaptation. Meanwhile, convergent adaption to human selection showed 2-to 16-fold enrichment relative to random expectation in Triticum species despite their drastic differences in ploidy levels and growing zones, indicating the vital importance of adaptive constraints in the success of bread wheat. These results showed the genetic necessities of wheat as a global crop and provided new perspectives on leveraging adaptation success across species for crop improvement.

The architecture of wheat (Triticum aestivum) inflorescence and its complexity is among the most important agronomic traits that influence yield. For example, wheat spikes vary considerably in the number of spikelets, which are specialized reproductive branches, and the number of florets, which are spikelet branches that produce seeds. The large and repetitive nature of the three homologous and highly similar subgenomes of wheat has impeded attempts at using genetic approaches to uncover beneficial alleles that can be utilized for yield improvement. Using a population-associative transcriptomic approach, we analyzed the transcriptomes of developing spikes in 90 wheat lines comprising 74 landrace and 16 elite varieties and correlated expression with variations in spike complexity traits. In combination with coexpression network analysis, we inferred the identities of genes related to spike complexity. Importantly, further experimental studies identified regulatory genes whose expression is associated with and influences spike complexity. The associative transcriptomic approach utilized in this study allows rapid identification of the genetic basis of important agronomic traits in crops with complex genomes.Grains of cereal crops provide a major source of human diet and nutrition. Improving grain yield is a primary objective during crop domestication and a major goal of crop-breeding programs. Inflorescence (spike) architecture dictates the capacity for seed production in cereal crops, including wheat (Triticum aestivum), the world's most widely grown cereal. In the archetypal bread wheat spike, the inflorescence meristem forms a limited number of lateral spikelet meristems (SMs) per rachis node, and a single terminal SM at the distal end. Each SM is indeterminate and typically produces two to four fertile florets that produce seeds (Fig. 1A; Supplemental Fig. S1; Bonnett, 1936;Fisher, 1973). Like maize (Zea mays) and rice (Oryza sativa), wheat yield per plant largely depends on the number of florets per spike and thus spike architecture. The numbers of SMs (and rachises) and florets per spikelet are major target traits for efforts aimed at improving wheat yield. In addition, the number of SMs per rachis may be increased to increase floret number, as in rare supernumerary spikelet variations.In rice, maize, and barley (Hordeum vulgare), multiple genes regulating spike development have been identified (Sreenivasulu and Schnurbusch, 2012;Tanaka et al., 2013). However, our understanding of wheat spike development remains rudimentary at the molecular level. In wheat, increased transcription levels of Q, an AP2-like gene, was markedly associated with spike compactness, suggesting that the Q gene may be implicated in spike development (Simons et al., 2006), although its role in spike complexity remains unclear. Feng et al. (2017) underlying the genetic regulation of rare supernumerary spikelet variations. For example, wheat Photoperiod1 (Ppd1) was identified as a regulator of paired spikelet formation (Boden et al., 2...

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Allene oxide cyclase (AOC, E 5.3.99.6) is an essential enzyme in the jasmonic acid (JA) biosynthetic pathway and mediates a wide range of adaptive responses. In this report, five AOC genes (GhAOC1-GhAOC5) were cloned from upland cotton (Gossypium hirsutum L.), sequenced, and characterized. Real-time PCR analysis indicated that the transcripts of GhAOCs were abundantly expressed in roots and less in fibers, and regulated in cotton plants under methyl jasmonate (MeJA) and CuCl 2 stresses. To investigate the role of GhAOC under copper stress, transgenic Arabidopsis plants overexpressing cotton GhAOC1 under control of the Cauliflower mosaic virus 35S (CaMV 35S) promoter were generated. Compared to untransformed plants, GhAOC1-overexpressing Arabidopsis thaliana plants exhibited markedly higher survival rate, shoot fresh weight, shoot dry weight, and photosynthetic efficiency, and reduced cell membrane damage and lipid peroxidation under copper stress.This study provides the first evidence that GhAOC1 plays an important role in copper stress tolerance.

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