Effect of Variety Tolerance, Soil Amendment and Biological Control Agents in the Management of Bacterial Wilt (Ralstonia Solanacearum) of Potato (Solanum Tuberosum L.) Under Field Condition in Chencha, Southern Ethiopia
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Date
2019-06-06
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Addis Ababa University
Abstract
Potato (solanum tuberosum L.) is an important food security crop which provides higher carbohydrate per unit area within a short period of time than the major cereals wheat and reice. Its production in Ethiopia is increasing rapidly, as it is grown by more than a million small holder farmers as a food and a cash crop. However, potato yield is low due to many factors among which diseases and insect pests are among the most limiting factors to the production of potato. Bacterial wilt caused by Ralstonia solanacearum is the second most important disease next to late blight. The pathogen is soil born and transmitted by seed, irrigation water and contaminated tools making its management a complex issue that require an integrated approach. Three separate experiments were carried out during 2015 and 2016 short rainy seasons under natural infestation condition on farmers’ fields at Chencha, Southern Ethiopia. The aim of the first experiment was to screen bacterial wilt tolerant potato genotypes and better yield. In the second experiment, soil amendments compost and manure at the rate of 20 t/ha, lime, and recommended fertilizer (110 kg of N/ha and 96 kg of P2O5/ha) and their combinations were studied to identify effective soil amendments which reduce the effect of the disease, improve yield and the soil condition. Thirdly, different biocontrol agents which were found effective in previous laboratory and greenhouse studies were tested for their efficacy on the disease development and improvement of yield. All experiments were laid in RCBD with four replications. Data on disease, yield and yield components were collected and subjected to analysis using SAS 9.3 and minitab softwares. The response of potato genotypes to the wilt disease varied significantly (p < 0.05) under natural infestation condition. The genotypes Cruza, Shangai, and CIP clone CIP-392661.18 showed lower DSI and AUDPC combined with a higher marketable yield. The local variety Sula also showed a better performance in terms of disease tolerance and yield which calls for further molecular study. Soil amendements showed better disease control than the control treatment though there was no significant differences between the organic fertilization and their iv
combinations except for lime only treatment. The biological control agents also generally improved crop performance and delayed the onset of the disease. Treatments also significantly differed in terms of DSI, AUDPC and tuber yield. The lowest AUDPC value (738) and highest tuber yield (34.8 t ha-1) was obtained from Neem gold @ 0.25 ton ha-1. However, Neem gold @ 0.1 ton ha-1 showed the highest AUDPC (1565) followed by arbuscular mycorrhizal fungui (AMF) and control, which achieved intermediate and the lowest AUDPC (1545 and 1500, respectively). The lowest yield (28 t ha-1) and the highest percentage of infected tubers (25.3 %) was recorded from the control plot. From these results, it can be recommended that the use of an integrated approach including tolerant varieties, application of soil amendment and biocontrol agents can improve potato productivity and lower the effect of bacterial wilt in the study area although in the presence of pathogen in the soil. This approach can be recommended as a better alternative to current practices as it is user-friendly and environmentally safe. However, the availability and cost of biocontrol agents and soil amendments should be taken in to consideration when making recommendations outside the study area.
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Keywords
Ralstonia Solanasearum, Integrated Management, Natural Infestation, Biocontrol Agents, Soil Amendment