Screening for Stem Rust (Puccinia graminis f. sp Tritici, Eriks. & e. Henn.) Resistance in Mutant Barley (Hordeum vulgare l.) Lines

Stem rust is a devastating disease in barley that is caused by a fungi (Puccinia graminis f. sp tritici, Eriks. and E. Henn). The disease has been controlled for quite some time due to the presence of cultivars carrying the resistant gene Rpg1. It has been effective in controlling the various races of stem rust. This was so until the emergence of the race Ug99 from Uganda in the year 1998. This race did break all the resistant genes that were there hence the need to get new sources of resistance. In the current study, mutation breeding was used to create variation for stem rust resistance (Ug99). Seeds of barley (Nguzo variety- MO) were sent to Vienna in Austria for irradiation at the International Atomic Energy Agency at a dosage of 250 gray. The M1 seeds were multiplied in University of Eldoret experimental field. Thousand plants were randomly selected from the M1 population, two ears were harvested of each plant that were subsequently divided within two groups. One group was planted at University of Eldoret experimental field while the other group of a thousand ears were planted at KARI Njoro as M2. Each ear formed a row/line. A susceptible line of wheat was planted as a spreader and inoculated with stem rust -Ug99 in both sites. A total of 183 lines were selected from the two sites. These lines were again replanted in university of Eldoret as M3 in a RCBD design with three replicates in the field to determine adult plant resistance and in the green house in a CRD design to determine the seedling resistance. The non mutated parent, Nguzo was used as a check. The following lines did show resistance both at the seedling level and adult plant level (1, 2, 9, 21, 26, 49, 55, 58, 59, 69, 76 and 78). Mutational breeding is therefore recommended for continual screening of these lines as this race may mutate further.