Evaluation of Advanced Kenyan Barley (Hordeum vulgare L.) Genotypes for Resistance to Stem Rust (Puccinia graminis Pers:.Pers. f.sp tritici Eriks. & E. Henn.) Race Ttksk and Its Variants

Stem rust caused by Puccinia graminis Pers:.Pers. f.sp tritici affects all the aerial parts of wheat and barley plants leading to yield losses. The objective of this study was to determine the level of resistance in advanced Kenyan barley lines to stem rust race TTKSK and its variants. The greenhouse and field experiments were laid in complete block design and randomized complete block design respectively with all experiments replicated three times. The experiments were conducted at Kenya Agricultural and Livestock Research Organization- Njoro. In the greenhouse experiment, forty genotypes were sown in perforated plastic pots and when the seedlings attained two-leaf stage, stem rust isolate collected from wheat variety, KS Mwamba was used to inoculate the genotypes. In the field, forty genotypes were sown in a one meter twin rows of each genotype were planted and all agronomic practices implement except management of stem rust disease. Infection types (IT) on the seedlings were observed and data collected following a scale described by Stakman et al. 1962. Disease severity data was collected according to modified Cobbs scale and then subjected to Area Under Disease Progress Curve (AUDPC). All genotypes showed immunity to moderate resistance at seedling level ranging from 0 to 2+. Adult plant reactions to race TTKSK and its variants ranged from an overlap of moderately resistant (MR) to susceptible (S). In all genotypes AUDPC ranged from 225.83 to 887.92 for under this study and the Coefficient of Infection ranged from 13 to 47. High levels of slow rusting were observed in only 12.5% of the genotypes tested while 10% of the genotypes had low levels. 77.5% of the genotypes had moderate levels of slow rusting. The genotypes with high levels of slow rusting can be advanced for release as varieties or be included in barley breeding.