Drought tolerance in andean and mesoamerican genotypes of the common bean.

Author: Ombaka, Joseph

Supervisors: Paul M.; Mary W. K. and Narla R. D.

Dry bean (Phaseolus vulgaris L.) is a popular legume sensitive to water stress especially during reproductive development phase. Adaptation to drought stress is therefore an increasingly important trait in production of dry beans crop. Climate change has caused a low water resource, abandoned farming land, frequent crop failure and food insecurity, and the emerging strong market preferences in Africa drives research to adapt to changing conditions. The objective of this study was to select bean lines tolerant to drought stress through on-station evaluation, on-farm variety selection and to determine physiological traits associated with drought tolerance. Two hundred and sixty three (263) genetically diverse genotypes composed of 155 large seeded, and 108 small seeded grain types sourced from International Center for Tropical Agricultural (CIAT) core collections, regional and national breeding programs, the Gene Bank of Kenya farmer varieties and landraces were screened for drought adaptation at Kabete Field Station at University of Nairobi. The large seeded beans were further classified into red mottled with 81 genotypes, red kidney with 49 genotypes and speckled sugar beans with 25 genotypes. The small-seeded beans comprised of small red, navy beans and carioca, pinto and purple with 36 genotypes in each market class. The experimental design was split-plot with three replicates. The germplasm was screened under drought stress nursery with water stress as main treatment (irrigated and rain-fed) while season and genotypes as sub-plots. Each plot consisted of two 3m rows. Spacing was 50cm between rows and 10cm between plants. Both trial treatments were irrigated up to flowering stage to ensure uniform crop stand. Rain-fed plots depended on rain water, while irrigated plots received three supplemental sprinkler irrigations depending on visual appearance of the plants.