Evaluation of potato (Solanum tuberosum, L.) genotypes for adaptability in Mt Elgon Region.

Potato (Solanum tuberosam L.) is among the most important crops in the world. Potato in Uganda is mainly produced in the highland areas of Kabale and Kisoro in southwestern and Bugisu and Sebei areas on the slopes of Mt Elgon in eastern part of the country. However, the yields have continuously reduced due to a lack of suitable high-yielding and disease-resistant varieties coupled with poor agronomic practices and a poor potato seed system that limits the use of the good quality seed. The purpose of this study was to; i) identify high-yielding disease-resistant potato genotypes adapted to Mt Elgon region and ii) establish the effect of staggered planting on tuber yield and its influence on incidences and severities of late blight and bacterial wilt of potato. For the first objective, eight new potato clones were evaluated alongside ten released commercial potato varieties in Buginyanya for two seasons. Based on results from the first study, ten best performing genotypes (four clones and six commercial genotypes) were selected and evaluated at two different planting dates (staggering) for two seasons in two locations. Results showed significant differences (P<0.001) in tuber size, tuber uniformity, marketable tuber yield and the total tuber yield across all genotypes. Of all the potato genotypes evaluated 392797.22(17.4t/ha) Kinigi (17.2t/ha) and Rwangume (16.7t/ha) produced significantly (P<0.001) higher tuber yield compared to the local checks Rutuku (13.9t/ha) and Cruza (10.1t/ha). rAUDPC for Late blight (LB) showed significant differences (P<0.001) among genotypes. The most resistant genotypes were Kinigi (0.013) and 399985.39 (0.025) and the most susceptible were Bumbamagara (0.413) and 396036.201 (0.318) as compared to the local check Victoria (0.185). Genotype 396036.201(0.025) and Kinigi (0.027) were the most resistant for bacterial wilt while Kachpot (0.403) and Cruza (0.456) were the most susceptible to Bacterial wilt. Total tuber yield varied significantly (P<0.001) between sites and planting dates. Buginyanya yielded (17.3t/ha) more than Kapchorwa (11.05t/ha). The first planting (17.2t/ha) performed better than the second planting (11.4t/ha) across seasons and sites. Kapchorwa was more affected with LB compared to Buginyanya with the rAUDPC of 0.17 and 0.15 respectively. Buginyanya was more affected with Bacterial wilt (BW) compared to Kapchorwa with rAUDPC of 0.155 and 0.128 respectively. The first planting (0.177) was affected with both LB and BW compared to the second planting (0.143). Based on yield and disease data the best planting period for Buginyanya during the first season should be by end of April while in Kapchorwa during the first week of April and for season 2 in both sites planting should be done in the first two weeks of October. The most suitable genotype for first planting in Buginyanya is 392797.22, Kinigi, Victoria and 398208.704 while in the second planting genotypes Kinigi, Victoria, 398208.704 and 393385.39 can be planted. In Kapchorwa first planting genotypes 392797.22, Victoria, 393079.4, and Kinigi while for second planting is genotypes Kinigi, 398208.704 and 393079.4to be planted. Generally, genotype 392797.22, Kinigi, and Rwangume were the highest yielding and disease resistant hence recommended for release as commercial varieties or as donor parents for breeding program.