Introgression of chromosomal segments conferring early heading date from wheat diploid progenitor, Aegilops tauschii Coss., into Japanese elite wheat cultivars

Image facilitated assessment of intra-spike variation in grain size in wheat under high temperature and drought stress

In wheat (Triticum aestivum L.), the grain size varies according to position within the spike. Exposure to drought and high temperature stress during grain development in wheat reduces grain size, and this reduction also varies across the length of the spike. We developed the phenomics approach involving image-based tools to assess the intra-spike variation in grain size. The grains were arranged corresponding to the spikelet position and the camera of smart phone was used to acquire 333 images. The open-source software ImageJ was used to analyze features of each grain and the image-derived parameters were used to calculate intra-spike variation as standard deviation (ISVAD). The effect of genotype and environment were highly significant on the ISVAD of grain area. Sunstar and Raj 4079 contrasted in the ISVAD of grain area under late sown environment, and RNA sequencing of the spike was done at 25 days after anthesis. The genes for carbohydrate transport and stress response were upregulated in Sunstar as compared to Raj 4079, suggesting that these play a role in intra-spike assimilate distribution. The phenomics method developed may be useful for grain phenotyping and identifying germplasm with low intra-spike variation in grain size for their further validation as parental material in breeding.

Grain yield and correlated traits of bread wheat lines: Implications for yield improvement

Global wheat yields are suffering due to differences in regional climatic conditions and soil fertility. Plant breeders are continuously working to improve the yield per unit area of wheat crop through selecting superior lines as parents. The screening and field evaluation of available lines allow the selection of superior ones and subsequently improved varieties. Therefore, heritable distinctions among 33 bread wheat lines for yield and related attributes were assessed under field conditions. The experiment included thirty lines and three check varieties. Data relating to different plant characteristics was collected at maturity. Significant differences were recorded for yield and related traits of tested wheat lines and check varieties. Wheat lines V6, V12 and V20 proved better with reduced number of days to reach anthesis and other desirable traits compared to check varieties. Days to start heading had strong correlation with spike length and number of spikelets spike-1. Flag leaf area had positive relationship with peduncle length and yield related traits. The 1000-garin weight and grain yield were also correlated with each other. It is concluded that V6, V10 and V20 proved better for all studied traits than the rest of the lines. Therefore, these lines could be used in wheat breeding program as parents to improve yield.

RNA-Seq-based DNA marker analysis of the genetics and molecular evolution of Triticeae species

The release of high-quality chromosome-level genome sequences of members of the Triticeae tribe has greatly facilitated genetic and genomic analyses of important crops such as wheat (Triticum aestivum) and barley (Hordeum vulgare). Due to the large diploid genome size of Triticeae plants (ca. 5 Gbp), transcript analysis is an important method for identifying genetic and genomic differences among Triticeae species. In this review, we summarize our results of RNA-Seq analyses of diploid wheat accessions belonging to the genera Aegilops and Triticum. We also describe studies of the molecular relationships among these accessions and provide insight into the evolution of common hexaploid wheat. DNA markers based on polymorphisms within species can be used to map loci of interest. Even though the genome sequence of diploid Aegilops tauschii, the D-genome donor of common wheat, has been released, the diploid barley genome continues to provide key information about the physical structures of diploid wheat genomes. We describe how a series of RNA-Seq analyses of wheat relatives has helped uncover the structural and evolutionary features of genomic and genetic systems in wild and cultivated Triticeae species.

Image-Based, Organ-Level Plant Phenotyping for Wheat Improvement

Wheat was one of the first grain crops domesticated by humans and remains among the major contributors to the global calorie and protein budget. The rapidly expanding world population demands further enhancement of yield and performance of wheat. Phenotypic information has historically been instrumental in wheat breeding for improved traits. In the last two decades, a steadily growing collection of tools and imaging software have given us the ability to quantify shoot, root, and seed traits with progressively increasing accuracy and throughput. This review discusses challenges and advancements in image analysis platforms for wheat phenotyping at the organ level. Perspectives on how these collective phenotypes can inform basic research on understanding wheat physiology and breeding for wheat improvement are also provided.