Response of winter and spring barley genotypes to biotic and abiotic stresses in Kenya

Mixed response to net blotch disease, drought and aluminium toxicity in barley under different growing regions is one of the key problems leading to low average yield of barley in Kenya. The study aimed at determining whether spring and winter barley genotypes grown in Kenya would respond differently to the three stresses and establish a baseline for subsequent studies. A total of 16 spring and 16 winter genotypes were screened. Aluminium screening was done using 148 µM Al and 0 µM Al treatments in a completely randomized design (CRD) in laboratory and screenhouse. Data on relative net root growth, percent response, hematoxylin stain intensity, apical root length were collected. Drought screening was conducted under 20% and 80% field capacities alongside the membrane stability index (MSI) using EC meter. Data on MSI, height, tillers, heading, maturity, and 1000 seed weight were recorded. Net blotch screening was done in three sites identified as hot-spots for natural inoculation and confirmed in a screenhouse experiment. Field experiments were planted in a randomized complete block design while screenhouse in a CRD. Disease severity was assessed on a 0-9 scale. Significant differences were noted (p < 0.001) among the genotypes in their response to drought, net blotch and aluminium toxicity. Malt 1, HKBL 1663-3, Grace and Aliciana exhibited tolerance to the three stresses but other genotypes expressed mixed reactions to the same stresses. Mixed responses could mean that phenotypic expression of tolerance, resistance or susceptibility to stress is dependent on other external factors other than genetic make-up. In conclusion, winter and spring barley respond differently to biotic and abiotic stresses but the mechanism of response is dependent on other external factors.