Breeding and cultivar improvement of snap bean (Phaseolus vulgaris) for productivity and resilience under drought stress

Effective breeding and genetic improvement of beans (Phaseolus spp.) aim to harness their tremendous genetic diversity to match location-specific growing conditions and the needs of households and local markets in response to climate change. Development of improved cultivars involves evaluation of genetic resources (e.g. genotyping, phenotyping) for identification of sources of desired traits, gene discovery, and knowledge-based breeding for genetic enhancement. This paper presents the screening process as part of the developing regionally adapted snap bean cultivars for growing under water deficiency conditions. Different screening approaches have been applied, including: plant growth and yield parameters (biomass, plant height, pod and grain yield, seed germination, flower abortion); and physiological responses (chlorophyll fluorescence induction parameters). Results from field trails with Bulgarian snap bean cultivars were presented and discussion on physiological mechanisms used by plants to cope with this abiotic stress factor, as well as approaches for screening and their relation with yield in the tolerant genotypes are encompassed in the context of plant breeding methods. Two bean cultivars 'Tangra' and 'Zaria' with different water efficiency, post-drought recovering capacity and heat tolerance were identified and their incorporation into the regional industry may expand the range of conditions suitable for bean production while reducing growers' costs and risks.