Cultural, morphological and pathogenic variability of Phytophthora colocasiae isolate from taro in Cameroon

Abstract

There exist 124 species of Phytophthora worldwide that cause serious diseases in natural ecosystems. These species have been identified using molecular methods. This study was conducted to determine the cultural, morphological and pathogenic variability of isolates of P. colocasiae processed from cultivars of Taro from Cameroon.The study was conducted in three agroecological regions, namely, Yaoundé, Bambui and Ekona where the disease was prevalent. Morphology showed that the mycelia were circular on all the isolates, in the three study zones. Mycelia colours ranged from white to cotton white. The colours of the culture media, after inoculation and mycelia growth, were the same. There was a significant difference (P<0.05) in mycelial growth among the isolate; with the longest of 5.5 cm in V6 juice agar media. Spore morphology was either spherical or ovoid in all the Taro isolates, in all culture media, except water medium. All four isolates were pathogenic to the four cultivars of Taro, causing lesions on leaves on inoculation. The most virulent fungi isolates were L1 (dark green petiole with small leaves) and L2 (red petiole with small leaves), which caused the largest lesion (>10 mm) in Taro cultivars during 14 days of inoculation.