Evaluation of Phytophthora colocasiae resistance in Taro (Colocasia esculenta) using leaf disc bioassay

Abstract

Taro leaf blight disease is the most destructive disease affecting taro production worldwide. Identifying resistant genotypes is the most practical means for managing the disease. In this regard, eleven taro genotypes were screened for taro leaf blight disease resistance with four isolates of P. colocasiae (Pc7, Pc12, Pc25 and Pc35) using leaf disc assay. Leaf discs of each genotype was inoculated with approximately 1 x 10⁴ zoospores of the P. colocasiae isolates which were arranged in Completely Randomised Design (CRD) with three replications in a factorial experiment. Results of the study showed varied reactions of taro genotypes to the isolates tested. Significant differences (P<0.05) in lesions size was recorded among the genotypes irrespective of isolate used. Similarly, significant genotype-isolate interactions were observed. Taro genotypes BL/SM/134 and BL/SM/10 inhibited growth of all P. colocasiae isolates. They recorded mean lesion sizes of 16.6 and 17.3 mm compared to 59.9 mm recorded for local genotype (control) at 5-days-post-inoculation. The local landrace (check) genotype was susceptible to all P. colocasiae isolates whilst 2 and 7 taro genotypes were categorized as reistant resistant and moderately resistant. It is recommended that the identified resistant genotypes (BL/SM/134 and BL/SM/10) be screened further under natural infestation to confirm results.

Keywords: Disease management , Ghana, lesion size, resistance, taro leaf blight