Phenotyping introduced bread wheat genotypes for resistance to stem rust (puccinia graminis f. sp. tritici) in Kenya

Abstract

Stem rust (Puccinia graminis f. sp. tritici) causes high yield losses in wheat (Triticum aestivum L.). Ameliorating this challenge requires a multifaceted approach, the most plausible being genetic resistance. The objective of this study was therefore to determine genotypic variation for adult and seedling resistance to stem rust, grain yield (GY) and agronomic performance. Sixty-two introduced Australian wheat genotypes and two controls, Cacuke and Kenya Robin, were planted in a field experiment over two seasons in a partially balanced lattice-square design with three replicates. Adult plant resistance (APR) was assessed based on area under disease progress curve (AUDPC), coefficient of infection (CI) and final disease severity (FDS) with genotypes scoring ≤ 300, ≤ 20 and ≤ 30, respectively, being resistant. APR was identified in seven genotypes. Effect due to genotype, season and genotype-by-season interaction was significant (p ≤ 0.05) for AUDPC, CI, FDS, GY, 1000-kernel weight (TKW) and test weight (TW). The range for GY, TKW and TW was 0.26-3.37 t ha-1, 8.9-28.3 g and 41.4-74.5 kg hL-1, respectively. In the greenhouse experiment, genotypes were inoculated with isolates TTKSK and TTKTT at the 2-leaf stage and infection types (ITs) scored after fourteen days. Eleven genotypes were identified for seedling resistance (ITs ≤ 2+) to both isolates. Genotypes Sunguard, Lancer and Gauntlet were uncovered for APR, seedling resistance, high yield performance and stability in resistance and, therefore, should be considered for inclusion in breeding programmes for resistance to stem rust and candidates for national performance trials for potential release to farmers.