Breeding for disease resistance in wheat in Uganda
2000
Wagoire, W.W. (Kalengyere Research Station, Kabale (Uganda))
Yellow and stem rust (caused by Puccinia striiformis and P. graminis, respectively) and Septoria leaf blotches (caused by Septoria spp.) are among 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 losses due to yellow rust was carried out at Kalengyere, a hot spot for yellow rust. The performance of FIS and F2S derived from a complete 8 x 8 diallel of bread wheat lines was evaluated in fungicide-treated and untreated plots in 1995 and for the F2S in 1996. The fungicide treatment controlled yellow rust and Septoria leaf blotches. A yield loss of83% was attributed to all foliar diseases, averaged over the F IS and F2S during the test period. A yield loss of 25% was attributed specifically to yellow rust. The importance of stem rust emphasized during the 1998A season when 457 and 280 lines, comprising the PCYR/LR nursery and the 9thHigh Rainfall Wheat Screening Nursery (HRWSN) respectively, were screened at Kalengyere Research Station. During this season, stem rust of wheat was the most important disease. A total of 33 and 21 lines were selected from the PCYR/LR and 9th HRWSN, respectively, and had infection scores ranging from 'T' to '5MS' for stem rust. During the same season, a breakdown of Sr31 was detected. During testing of these selections in the following season, 1999A, when the prevalent disease was yellow rust, 80% of the selections had a yellow rust reaction range of 'TR' to '20MS'. These results indicate that screening for field disease resistance over seasons can be a useful tool for the identification and development of genotypes with resistance to a wide range of diseases.
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