Evaluation of wheat (triticum aestivum l.) genotypes for resistance to leaf rust (puccinia triticina eriks) in Kenya

Abstract

Leaf rust (Puccinia triticina) of wheat (Triticum aestivum L.) is one of the major foliar diseases contributing to yield losses in wheat worldwide. Objectives of this study were: (i) to determine genotypic variation among Kenyan wheat genotypes against leaf rust at adult plant stage (ii) to determine genotypic variation among Kenyan wheat genotypes against leaf rust at seedling stage (iii) to determine leaf rust virulence in Kenya using leaf rust differential sets. Three experiments were conducted at Kenya Agricultural and Livestock Research Organization (KALRO) in Njoro. In the first experiment, 144 wheat genotypes were evaluated for response to infection at adult stage in the field. The experiment was conducted in the field in 12 12 partially balanced lattice design to evaluate wheat genotypes for leaf rust infection and agronomic traits for two seasons. In the second experiment, the same genotypes were evaluated for resistance to leaf rust at seedling stage in the greenhouse. Genotypes sown in the greenhouse were inoculated with urediniospores after seedlings had attained growth stage 12. In the third experiment, 91 leaf rust differential lines were used for leaf rust virulence analysis in the greenhouse. Fifty-six percent of the screened genotypes in the greenhouse exhibited resistance (IT‟s of “;”, “1”, “2” or combinations) and the rest 44 % genotypes showed susceptible reaction. Genotypes K. Tai, K. Korongo, Fletcher, Verder, R1244 exhibited both seedling and adult plant resistance during season one and two. Considering the adult plant disease response and yield potential, genotypes R1301 and R1305 showed lowest leaf rust infection and highest grain yield. Mean grain yield ranged from 0.06 to 6.81 tonnes ha-1. Significant (p ≤ 0.001) variations were noted among the seasons, genotypes tested over seasons and the interaction between genotype season for plant height, a thousand kernel weight, and harvest index. There were significant (p ≤ 0.01) effects due to seasons and genotypes for spike length, days to maturity, AUDPC and grain filling period, biomass, yield, respectively. Effects due to seasons were significant (p ≤ 0.05) for hectoliter weight and AUDPC of stem rust infection. Resistant genotypes identified can therefore be utilized in Kenyan wheat breeding programmes for improvement of yield and leaf rust resistance with emphasis on adult plant resistance. Results of virulence analysis revealed varied disease infection types ranging from „0‟to „3+‟. Leaf rust genes namely; Lr1, Lr2a, Lr2b, Lr2c, Lr3, Lr3a, Lr3bg, Lr3ka, Lr9, Lr10, Lr11, Lr12, Lr13, Lr14, Lr15, Lr16, Lr17, Lr18, Lr19, Lr20, Lr21, Lr22a, Lr23, Lr24, Lr25, Lr26, Lr28, Lr29, Lr30, Lr27+Lr31, Lr32, Lr34, Lr35, Lr36 and LrB were resistant to Kenyan leaf rust races. These leaf rust genes could be valuable sources of resistance to leaf rust.