Flavio Capettini

Multi-environment multi-QTL association mapping identifies disease resistance QTL in barley germplasm from Latin America.

Key messageMulti-environment multi-QTL mixed models were used in a GWAS context to identify QTL for disease resistance. The use of mega-environments aided the interpretation of environment-specific and general QTL.AbstractDiseases represent a major constraint for barley (Hordeum vulgare L.) production in Latin America. Spot blotch (caused by Cochliobolus sativus), stripe rust (caused by Puccinia striiformis f.sp. hordei) and leaf rust (caused by Puccinia hordei) are three of the most important diseases that affect the crop in the region. Since fungicide application is not an economically or environmentally sound solution, the development of durably resistant varieties is a priority for breeding programs. Therefore, new resistance sources are needed. The objective of this work was to detect genomic regions associated with field level plant resistance to spot blotch, stripe rust, and leaf rust in Latin American germplasm. Disease severities measured in multi-environment trials across the Americas and 1,096 SNPs in a population of 360 genotypes were used to identify genomic regions associated with disease resistance. Optimized experimental design and spatial modeling were used in each trial to estimate genotypic means. Genome-Wide Association Mapping (GWAS) in each environment was used to detect Quantitative Trait Loci (QTL). All significant environment-specific QTL were subsequently included in a multi-environment-multi-QTL (MEMQ) model. Geographical origin and inflorescence type were the main determinants of population structure. Spot blotch severity was low to intermediate while leaf and stripe rust severity was high in all environments. Mega-environments were defined by locations for spot blotch and leaf rust. Significant marker-trait associations for spot blotch (9 QTL), leaf (6 QTL) and stripe rust (7 QTL) and both global and environment-specific QTL were detected that will be useful for future breeding efforts.

BRS Savanna: new six-rowed malting barley cultivar for irrigated crops in the Brazilian savanna.

BRS Savanna, a cross between V. Morales x IF200113, is a spring andan early-maturing six-rowed barley, widely adapted to irrigated areas of the savanna, in Central Brazil. It presents production stability and the industrial quality, grain yield and lodging resistance are high. It is suitable for cultivation in the states of GO, MG and DF.

Genetic diversity of irrigated barley based on molecular and quantitative data and on malting quality

The objective of this work was to determine the experimental precision in the evaluation of forage turnip fresh matter weight, in scenarios formed by combinations of plot sizes and number of treatments and replicates. Data from fresh matter weight of 3,456 basic experimental units of 0.5×0.5 m (0.25 m2) were used. The scenarios (1,728) were planned and formed by the combinations of six plot sizes (0.25, 0.50, 1.00, 1.50, 2.00, and 2.25 m2), i treatments (i = 5, 6,..., 20), and r replicates (r = 3, 4,..., 20). For each scenario, 2,000 resamplings were carried out, with replacement. The average of these 2,000 estimates, in each scenario, was calculated for the least significant difference by Tukeys test, the variation index, and the experimental coefficient of variation. These statistics, in that order, are adequate to evaluate the experimental precision. To evaluate turnip fresh matter weight, in experiments in a completely randomized design with 5 to 20 treatments and five replicates, plots with the size of six basic experimental units (1.50 m2) are sufficient to identify significant differences between treatments - less than or equal to 36.88% of the overall mean -, by Tukeys test at 5% probability, in experiments in a completely randomized design with 5 to 20 treatments and five replicates.

Genome-Wide Association Mapping Identifies Disease-Resistance QTLs in Barley Germplasm from Latin America

Diseases are the main problem for barley in Latin America. Spot blotch (caused by Cochliobolus sativus), stripe rust (caused by Puccinia striiformis f. sp. hordei), and leaf rust (caused by Puccinia hordei) are three of the most important diseases that attack the crop in the region. Chemical control of those diseases is both economically and environmentally inappropriate, making the development of durable resistant varieties a priority for breeding programs. However, the availability of new resistance sources is a limiting factor. The objective of this work was to detect genomic regions associated to durable resistance to spot blotch, stripe rust, and leaf rust in Latin American germplasm. Associations between disease severities measured in several environments across the Americas and 1,536 SNPs (belonging to the barley OPA1) in a population of 360 genotypes were used to identify genomic regions associated with disease. Several models for association mapping with mixed models were compared. These models considered either the structure of the population (Q) through PCA analysis, the identity by descent through coancestry information (K), or both. Results show significant marker-trait associations for spot blotch and leaf and stripe rust. Associations are environment specific.

Genetic variability in elite barley genotypes based on the agro-morphological characteristics evaluated under irrigated system

Recently, researches have shown that the Brazilian savannah has a great potential to supply the demand for barley grains. The purpose of this study was to assess the genetic variability in 39 elite barley (Hordeum vulgare L.) genotypes based on the agro-morphological traits of a crop irrigated in the savannah system. An irrigation experiment in the design of complete randomized block with four replicates was conducted at Federal District - Brazil. The evaluated traits were: distance from the last knot to the rachis, distance from the flag leaf to rachis, spike length, number of grains by ear, flag leaf area, plant height, silking, lodging, grain yield, thousand-seed weight, protein content and grain commercial classification. After using analysis of variance the means were used to estimate the genetic dissimilarity among all genotypes pairs based on the Mahalanobis’ generalized distance. Cluster analysis using genetic distance matrix was performed having Unweighted Pair Group Method using Arithmetic Means method (UPGMA) as the criteria. Highly significant differences were found among the genotypes for all traits evaluated. The high coefficient of genetic variation indicates the possibility of having genetic gains for all traits. The traits that most contributed to the variability were the flag leaf area and silking, while the protein content and lodging were the traits that contributed the least. Based on the cluster analysis, at least three major groups of similarity were found. There was a clustering trend of two and six-rowed materials. The most divergent genotypes were PFC 2005123, Antartica-1, Nandi and FM 404.