Prevalence of Bitter Gourd Mosaic Complex (BGMC) and Detection of Associated Viruses in Different Agro-ecological Units of Kerala

Bitter gourd mosaic complex (BGMC) is caused by multiple viruses in bitter gourd which seriously affects the crop performance and leads to complete crop loss. Bitter gourd is widely cultivated in Kerala as the market price is steady throughout the year. BGMC is the most important production constraint as most of the high yielding varieties including hybrids are severely affected by the virus complex. The study assessed the prevalence of BGMC in major bitter gourd cultivating agro-ecological units (AEUs) of Kerala and detected the viruses associated. It was found that, the disease incidence (DI) and severity in terms of Vulnerability Index (VI) of BGMC varied between AEUs as well as varieties grown. The average incidence and severity of BGMC were found to be highest i.e., 98.71 per cent and 70.2 respectively in AEU 8 with Pallichal of Thiruvananthapuram district being the highest among all locations with 100 per cent DI and 80.50 VI. Among varieties, Preethi was found to be the most susceptible with an average BGMC incidence of 99.04 per cent and severity of 65.01 per cent, whereas hybrids and local varieties were relatively tolerant. Tomato leaf curl virus (ToLCV), Papaya ring spot virus (PRSV) and Cucumber mosaic virus (CMV) were the major viruses associated with BGMC as these viruses were detected in all AEUs surveyed. Among the viruses, PRSV was found to be the most prevalent in all the AEUs and locations surveyed across Kerala (77.78 %). The viruses were detected singly as well as in combinations. Percentage of single virus infection (61.11 %) was more, followed by double virus infection (33.33 %) and triple virus infections (5.56 %). Combined infection of the viruses led to total crop failure without any flowering. Findings of the present study contribute to better understanding of prevalence of BGMC and offer information on its diversity among regions, varieties and viruses associated across different AEUs of Kerala.