Evaluation of Taro Leaf Blight (Phytophthora Colocasiae) Disease Incidence, Severity, Environmental Effects And Relationship Between Resistance And Agronomic Traits of Selected Taro (Colocasiae Esculenta) Accessions in Western Kenya.

Abstract

Taro (Colocasiae esculenta L. Schott) popularly known as ‘nduma’ is an aquatic plant grown for its edible leaves and corms. It is mainly cultivated in Western and Central Kenya but its production is constrained majorly by Phytophthora colocasiae, a taro leaf blight (TLB) disease. The disease causes destruction of leaf and corm. Knowledge pertaining to taro association with the disease incidence, severity, index, Rainfall, R.H, temperature, interrelationship between agronomic traits and disease resistance of Kenyan and Pacific – Caribbean taro accessions remain unknown in Western Kenya. The study was conducted at MMUST University farm, Maseno university laboratory and greenhouse to determine disease incidence, severity, index, resistance and agronomic traits of Pacific - Caribbean and Kenyan taro both in-vivo and in-vitro. Field experiments were arranged in a C.R.D and replicated five times while the control experiments in the greenhouse were blocked. Disease incidence was obtained by calculating the percentage number of leaves infected per accession. Severity was derived from a subjective score scale of 1-9 adopted from Simongo et al. (2016). Effect of R.H, rainfall and temperature was determined based on disease incidence, severity and index vis a vis the meteorological data obtained from Kakamega weather station. Number of leaves, suckers, plant height and leaf surface area represented the agronomic traits. Relationship between agronomic traits and disease resistance was determined by correlation and dendogram analyses. Analysis of variance was used and significant means separated by the L.S.D at 5% significance level. Disease incidence ranged between 17.71% - 29.86%, severity 33.2% - 53.5% and index 0.71 - 1.54 for Pacific - Caribbean and Kenyan taro respectively. The peak rainfall amounts of 174 and 223.9 mm, maximum temperature of 28.6°C and R.H range of 56 - 66% yielded the highest incidence, severity and index. Disease resistance ranged between 58.27% - 89.73% for Kenyan and Pacific – Caribbean taro respectively with BL/SM/128 portraying the highest resistance of 89.73% while KNY/ELD/75 had the highest resistance (84.34%) among the Kenyan taro accessions. Disease incidence and severity negatively correlated with number of leaves and corm weight. Plant height was not affected by disease infection. BL/SM/120 had the highest mean number of leaves (8.1) and KNY/KSM/20 had the lowest (4.6). The identified tolerant taro accessions could be suggested for future breeding. Further evaluations should be done on the identified taro under diverse environments and screening with more virulent TLB isolates to aid in understanding disease pattern. These would guide in ascertaining the right planting time to prevent disease epidemic and to develop accessions with improved resistance and productivity.