Quantification of genetic diversity for drought adaptation in a reference collection of common bean (Phaseolus vulgaris L.)

[摘要] English: The aims of this study were to identify sources of drought tolerance in a common bean reference collection, to improve genetic and physiological understanding of drought tolerance in different gene pools of common bean, to establish the role of rooting characteristics in improving grain yield under drought conditions, to determine the genetic structure and diversity in the reference collection using SSR marker data, and to identify simply inherited markers in close proximity to genes affecting drought tolerance. Field experiments were laid out as 11x11 Mesoamerican and 9x9 Andean lattices with three replicates under irrigated and rainfed treatments at CIAT -Palmira and Harare Research Station. Yield was significantly correlated with total shoot biomass at mid pod fill, 100-seed weight, number of pods per plant and days to maturity under both treatments at both locations. Based on geometric means and drought sensitivity indices, BAT 477, G 11721, G40 17, DOR390 (Mesoamerican) and SAB645, PVAll11, SEQ1003, SEQ1027, G 17076 and G5142 (Andean) genotypes had high and stable yields across treatments in both locations and could serve as sources of drought tolerance in common bean. Two greenhouse experiments were conducted at CIAT -Palmira using the soil cylinder system, in a randomised complete block design with three replicates. Well watered and water stressed treatments were applied in each trial. In 2009 a total of 33 Andean landraces and three Mesoamerican checks were evaluated for deep rooting and other root properties. In 2010 phenotypic differences were determined between elite genotypes in root development under water stress. A total of 40 elite Andean and Mesoamerican genotypes commonly used as parents in many breeding programmes, were evaluated. Variability of root traits under water stress was expressed either as adaptive or constitutive traits depending on genotype. It was found that deep rooting alone may not be adequate for drought tolerance in common bean, as some deep rooted genotypes had poor yields under field conditions. SSR and SNP markers were used for molecular characterisation of the reference collection to determine the population structure and identify statistically significant marker-trait associations relevant for drought tolerance in the reference collection. The reference collection is strongly structured following the geographical origins of the genotypes. TOG896943-500, TOG9l8200- 347 and TOG 910860-634 were significantly associated with 100-seed weight and total shoot biomass across locations and treatments. In conclusion, all findings in the current study need to be integrated to develop drought tolerant common bean varieties in future. Mapping studies should be extended to candidate gene analysis for the identified marker-trait associations.

[发布机构] University of the Free State