DIVERSITY OF ELITE KENYAN BREAD WHEAT MUTANT LINES IN STEM RUST (Puccinia graminis f. sp. tritici) RESISTANCE

Abstract

Stem rust caused by Puccinia graminis f. sp. tritici is a major constraint to wheat production in Kenya. The re-emergence of a new fungal race Ug99 and its variants have caused devastating losses to wheat production since the disease overcome many resistant genes that were used against stem rust and most commercial wheat varieties grown in Kenya are now susceptible to stem rust. Breeding for rust resistance is the best mechanism to manage this disease as it’s economical, durable and environmentally friendly. The objective of this study was to determine the diversity in stem rust resistance and yield potential of selected elite bread wheat mutant lines. The study was divided into three experiments. The first experiment was to determine yield potential of the selected elite mutant lines in comparison to their parent varieties. The study found that two mutant lines SP-26 of Kwale (SP-K) and SP-21 of Njoro II (SP-N) gave significantly (P≤0.05) higher grain yield of 4.04 t/ha and 4.34 t/ha respectively. Their parent varieties SP-K and SP-N gave 1.91 t/ha and 2.92 t/ha respectively. The other mutant lines gave grain yield of between 0.89 t/ha – 2.32 t/ha. The commercial checks gave grain yield of between 0.69 t/ha – 2.27 t/ha. The second experiment was to determine the genetic diversity of the wheat genotypes using morphological characteristics and molecular markers. The study found out that wheat genotypes showed variations for morphological characteristics, being separated mostly by grain yield per spike, days to maturity, 1000 seed weight and number of tillers per plant. The SSR markers used in this study grouped the genotypes into two major clusters with four sub clusters with mutant lines clustering with their respective parents. The third experiment was to evaluate the diversity of stem rust resistance in the elite mutant lines in comparison with their parent varieties and commercial checks in the green house and field conditions. Ten polymorphic SSR markers were used and the genotypes exhibited different reactions to stem rust. Significant (P≤0.05) genotypic, location and seasonal effects were recorded in the field. The genotypes evaluated had high genetic diversity regarding their response to stem rust. From the genotypes evaluated, the most resistant genotypes were SP-21 and SP-26. The study added to the pool of knowledge through identifications of high yielding stem rust resistant genotypes that can be recommended to farmers for growing as new varieties.