Introduction of a rapid culturing technique and molecular methods for detection and race identification for𝘍𝘶𝘴𝘢𝘳𝘪𝘶𝘮 𝘰𝘹𝘺𝘴𝘱𝘰𝘳𝘶𝘮 f.sp. 𝘤𝘶𝘣𝘦𝘯𝘴𝘦 (FOC) causing the panama disease of banana

Abstract

Banana and plantain (𝘔𝘶𝘴𝘢 spp.) are among the most important fruit crops worldwide. 𝘍𝘶𝘴𝘢𝘳𝘪𝘶𝘮 wilt or panama disease, caused by 𝘍𝘶𝘴𝘢𝘳𝘪𝘶𝘮 𝘰𝘹𝘺𝘴𝘱𝘰𝘳𝘶𝘮 f. sp. 𝘤𝘶𝘣𝘦𝘯𝘴𝘦 (𝘍𝘰𝘤) is one of the most serious diseases of banana in Sri Lanka that cause a substantial economic loss. Identification of 𝘍𝘰𝘤 by presently-used culturing methods takes a longer time. Hence, a rapid culturing technique was developed for 𝘍𝘰𝘤 using pseudostem threads of symptomatic plants. A better culture medium for growth of 𝘍𝘰𝘤 was selected using Potato Dextrose Agar (PDA) and Water Agar (WA) media supplemented with 0.025 % chloramphenycole. Based on the diameter of the 𝘍𝘰𝘤 colonies on the PDA media, culturing of fresh pseudostem threads (T3) and dried pseudostem threads at 35 0C in an oven (T2) were not significantly different at α = 0.05. 𝘍𝘰𝘤 colonies appeared within significantly lower number of days in T2 and T3 compared to T1. Colonies appeared in minimum of two days in T2 and T3. In terms of the percentage of contaminants, T1 had 33.33 % contaminants while, T2 and T3 consisted of 0 % contaminants. Hence, culturing of fresh pseudostem threads and oven dried pseudostem threads on PDA medium were best for the rapid culturing of 𝘍𝘰𝘤.

PCR was identified as the rapid and reliable molecular diagnostic technique for indexing banana planting materials for panama disease. Specific primer pairs Fo-F/Fo-R and Foc-Race1-F/Foc-Race 1-R identified the presence of 𝘍. 𝘰𝘹𝘺𝘴𝘱𝘰𝘳𝘶𝘮 f. sp. 𝘤𝘶𝘣𝘦𝘯𝘴𝘦 and 𝘍𝘰𝘤 race I, respectively in infected banana planting materials.