Taro Leaf Blight (Phytophthora colocasiae) Disease Pathogenicity on Selected Taro (Colocasiae esculenta) Accessions in Maseno, Kenya

摘要

Taro (Colocasia esculenta) is an important staple crop for small-scale farmers in Asia, Pacific, Americas and Africa. Taro corms and leaves are sources of important nutrients such as calcium, phosphorus, iron, vitamin C, thiamine, riboflavin and niacin. Its cultivation is under threat from many diseases. Taro leaf blight (TLB), a major threat to taro production is caused by the fungus Phytophthora colocasiae Racib. Its control has relied on the use of fungicides which are too expensive for the majority of farmers. The study on virulence of various strains of TLB isolates in Western Kenya has been unknown but is a necessary inclusion in the management of the disease. This study aimed at evaluating the incidence and severity of TLB-disease on inoculated accessions with a view of determining the variability of the isolates’ virulence and the accessions’ TLB disease incidence and severity. Eight taro accession from Kenya and eight from Pacific-Caribbean were inoculated using four TLB strains (21R1, 21R2, 3R1 and 3R2) in greenhouse condition. A Complete Randomized Design was used with each accession replicated three times. The data included: the total number of leaves, leaf area, incidence and severity of the disease. The data obtained was analyzed using ANOVA at 95% confidence level to determine TLB disease incidence and severity. Analysis of Variance and the means declared significant were separated by the least significant difference at 5%. The two categories of isolates caused TLB disease lesions, on inoculated leaves. However, higher incidence and severity were caused by isolates 21R1 and 21R2 than isolates 3R1 and 3R2. On inoculation with 3R1 pathogen isolate, 39.01% and 88.18% incidence were recorded on Pacific-Caribbean and Kenyan taro respectively. On inoculation with pathogen isolate 21R1 a % incidence of 47.22% and 88.18% was recorded on Pacific-Caribbean and Kenyan taro respectively. The control did not show significant disease incidence in all taro accessions. The mean TLB disease incidence for the Pacific-Caribbean accessions was 20.08% and that of Kenya was 59.04%. The lowest TLB disease incidence among the Kenyan taro of 34.4% was recorded from KNY/KAK/16 of Kakamega. The highest incidence among the Pacific-Caribbean of 32.48% was obtained from CE/IND/01 of Indonesia. Similar results were obtained with disease severity. Higher disease tolerance was realized among the Pacific-Caribbean accessions. The knowledge obtained from this research would help in the development of taro cultivars with improved resistance to taro leaf blight pathogen. This will increase taro production in Kakamega county of Kenya.