Effects of planting dates and potato (Solanum tuberosum L.) genotypes on late blight caused by Phytophthora infestans (Mont.) de Bary epidemics, growth and tuber yields in Southern Ethiopia

Abstract

The study was conducted at Chencha in Southern Ethiopia during the 2018 and 2019 main cropping years to determine the effects of planting dates and potato genotypes on late blight epidemics and yields related traits; as well as identify optimum planting date and potato genotypes which show low levels of late blight severity with high tuber yields under a natural epiphytotic environment. The treatments composed of four potato genotypes (Belete, Gudenie, Jalenie, and local check) and three planting dates (on 10th June, 10th July, and 20th August). The experiment was laid out in a split-plot design with four replications. Planting dates were assigned as the main factor, while the potato genotypes were represented as a sub-plot factor. Average late blight severities of 29.19, 35.82, and 44.70% were recorded on plants with a planting date of 20th August, 10th July, and 10th June, respectively. Foliar late blight severities of 27.31, 32.45, 38.58, and 47.95% were recorded on Belete, Gudanie, Jalenie, and local cultivar, respectively. Similarly, the relative area under disease progress curve (AUDPC) of 20.28, 24.93, and 29.31%-days were recorded on planting dates of 20th August, 10th July, and 10th June, respectively. The highest (19.37%-days) and lowest (31.32%-days) values of AUDPC were recorded from the genotypes Belete and local cultivar, respectively. Results also showed that the highest single tuber weight (87.20 g) and total tuber yield (13.40 t ha-1) were obtained from the genotype Gudenie. Regarding planting dates, the highest single tuber weight (88.91 g) was recorded from the genotypes planted on 10th June. Whereas the highest total tuber yield (15.77 t ha-1) was obtained from the genotypes planted on 20th August, which was not statistically different from the other planting dates. Overall, considering disease development, tuber yield potential, and effectiveness in disease reduction, planting of Gudenie on 20th August was relatively effective for potato late blight management as compared to other genotypes and planting dates. Therefore, this could be suggested for the study area and similar agro-ecological conditions to enhance sustainable potato production.