MANAGEMENT OF POTATO LATE BLIGHT (Phytopthora infestans) USING ARBUSCULAR MYCORRHIZAL FUNGI

Abstract

Potato (Solanum tuberosum) is a key food as well as cash crop in the highlands of Kenya, and is extensively produced by small-scale farmers. It is the second most significant food crop in Kenya after maize employing over 2.5 million persons. It plays a key role in Kenyan food security and contributes to alleviation of poverty. The potato sector is plagued by many problems, among them potato blight whose management still poses a great challenge, particularly among small-scale farmers in the Kenyan highlands. About 30 – 60% of the potato crop is lost to the late blight yearly in Kenya. Because of development of more virulent and fungicide-resistant strains and the poor ability of resource-strained farmers to control late blight, the optimum management of the disease in Kenya is likely to be achieved through biological control and in this case, by use of abuscular mycorrhiza fungi. Potato tubers were planted in the greenhouse and the effectiveness of arbuscular mycorrhizal fungi, Glomus intraradices and Glomus mosseae in conferring resistance to Phytopthora infestans and in promoting growth and yield was tested. Some plants were inoculated with the isolates of arbuscular mycorrhiza fungi while others were not inoculated to serve as controls. All the plants were then inoculated with P. infestans thirty days after planting. The effects of the mycorrhizal treatments on the pathogen progression were evaluated throughout the season. The mixture of Glomus mosseae and Glomus intraradices recorded the highest mean weight of the tubers per plant (103.20±5.56g), with the control recording the lowest (63.20±5.17g). There was a significant difference between the control and all the treatments (p>0.05). In terms of number of tubers, G. mosseae showed the highest mean (7.60±0.60). The number of tubers in all the treatments were significantly higher than those of the control (p>0.05). This study demonstrated that inoculation of potato plants with abuscular mycorrhiza fungi confers significant degree of reduction in severity of potato blight. Arbuscular mycorrhizal fungi inoculation in potato plants was also found to significantly promote growth and increase potato yield. Glomus mosseae showed the highest reduction of potato blight severity while control had the least. This research study indicated that inoculation of potato plants with abuscular mycorrhiza fungi conferred some degree of resistance to potato blight, promoted growth and increased yield. Further investigation under field conditions and using mixtures of different abuscular mycorrhiza fungi isolates needs to be carried out.