KALENGYERE RESEARCH STATION (NAARI)
P.O. box 722, Kabale, Uganda.
William W. Wagoire.
Yellow and stem rust and Septoria leaf boltch are amng the wide range of wheat diseases that constrain wheat production in the highlands of Uganda. Screening for resistance to these diseases relies on natural infection in the field. A study to determine the potential yield loss due to yellow rust was made at Kalengyere, a hot spot for this disease. The performance of F1s and F2s derived from a complete '8 x 8' diallel of bread wheat lines was evaluated in fungicide-treated and untreated plots in 1995-96 and for the F2s in 1996-97. The fungicide treatment controlled yellow rust and Septoria leaf blotch. A yield loss of 83 % was attributed to all foliar diseases, which was averaged over the F1s and F2s during the test period. A yield loss of 25 % was attributed specifically to yellow rust. The importance of stem rust was emphasized during the 1998-99 season when 457 and 280 lines, comprising the PCYR/LR nursery and the 9th High Rainfall Wheat Screening Nursery (HRWSN), respectively, were screened at the Kalengyere Research Station. During this season, a breakdown of Sr31 was detected. During the testing of these selections in the following season (1999-00) when the prevalent disease was yellow rust, 80 % of the selections had a yellow rust reaction in the range of trace to 20MS. These results indicate that screening for disease resistance in the field over several seasons can be a useful tool for identifing and developing genotypes with resistance to a wide range of diseases.