Regions of Chromosome 2A of Bread Wheat (Triticum aestivum L.) Associated with Variation in Physiological and Agronomical Traits under Contrasting Water Regimes.

Understanding the genetic architecture of drought tolerance is of great importance for overcoming the negative impact of drought on wheat yield. Earlier, we discovered the critical role of chromosome 2A for the drought-tolerant status of wheat spring cultivar Saratovskaya 29. A set of 92 single-chromosome recombinant double haploid (SCRDH) lines were obtained in the genetic background of Saratovskaya 29. The lines carry fragments of chromosome 2A from the drought-sensitive cultivar Yanetzkis Probat. The SCRDH lines were used to identify regions on chromosome 2A associated with the manifestation of physiological and agronomical traits under distinct water supply, and to identify candidate genes that may be associated with adaptive gene networks in wheat. Genotyping was done with Illumina Infinium 15k wheat array using 590 SNP markers with 146 markers being polymorphic. In four identified regions of chromosome 2A, 53 out of 58 QTLs associated with physiological and agronomic traits under contrasting water supply were mapped. Thirty-nine candidate genes were identified, of which 18 were transcription factors. The region 73.8-78.1 cM included the largest number of QTLs and candidate genes. The variation in SNPs associated with agronomical and physiological traits revealed among the SCRDH lines may provide useful information for drought related marker-assisted breeding.

Quantitative characteristics of pubescence in wheat (Triticum aestivum L.) are associated with photosynthetic parameters under conditions of normal and limited water supply.

MAIN CONCLUSION: Density and length of leaf pubescence are important factors of diversity in the response to water deficiency among wheat genotypes. Many studies evidence an important protective value of leaf hairiness in plants, especially under the conditions of drought, thermal loads and increased solar radiation. However, the physiological and adaptive roles of such traits in cereals, including cultivated plants, have not been sufficiently studied to date. The aim of this work was to study the association of morphological characteristics of leaves with parameters of gas exchange and chlorophyll fluorescence in wheat lines carrying a genetically different leaf hairiness. Isogenic and inter-varietal substitution wheat lines were used, carrying various combinations of dominant and recessive alleles of the known genes. A quantitative assessment of the pubescence was carried out in contrasting watering conditions to establish the physiological role of this trait in adaptation to drought. With the help of a portable system for studying the gas exchange and chlorophyll fluorescence, ten parameters of photosynthesis were studied, as well as morphological features of leaves and shoot biomass. It was found that gas exchange parameters are inversely proportional to the density and length of trichomes. In drought conditions, the trichome density increased and the length of trichomes decreased under the observed decrease in the level of gas exchange. A similar dependence was observed for the level of non-photochemical quenching of chlorophyll fluorescence. Under optimal conditions, the poorly haired cultivars exhibited a higher biomass than the densely haired. However, under water deficiency they significantly reduced the biomass and showed a low value of the tolerance index.

Extraction of quantitative characteristics describing wheat leaf pubescence with a novel image-processing technique.

Leaf pubescence (hairiness) in wheat plays an important biological role in adaptation to the environment. However, this trait has always been methodologically difficult to phenotype. An important step forward has been taken with the use of computer technologies. Computer analysis of a photomicrograph of a transverse fold line of a leaf is proposed for quantitative evaluation of wheat leaf pubescence. The image-processing algorithm is implemented in the LHDetect2 software program accessible as a Web service at http://wheatdb.org/lhdetect2 . The results demonstrate that the proposed method is rapid, adequately assesses leaf pubescence density and the length distribution of trichomes and the data obtained using this method are significantly correlated with the density of trichomes on the leaf surface. Thus, the proposed method is efficient for high-throughput analysis of leaf pubescence morphology in cereal genetic collections and mapping populations.