Critical Phase of Zucchini Plant (Cucurbitapepo L.) to Zucchini Yellow Mosaic Virus (ZYMV) Infection

Zucchini Yellow Mosaic Virus (ZYMV) is one of the causes of mosaic disease in zucchini plants in Bali. Based on observations in four villages of zucchini cultivation center in BaturitiTabanan Bali area covering Pekarangan, ApitYeh, KembangMerta, and Angsri villages, the average incidence of mosaic disease was 89.74 %. Serologic detection with ELISA and molecular identification with RT-PCR in zucchini plants showing mosaic symptoms, successfully detected that ZYMV is a symptom inducer of mosaic on zucchini plants. Determination of the critical phase of zucchini plants against ZYMV infection was done through experiments in greenhouses, by mechanical inoculation of zucchini at 2 weeks, 3 weeks, 4 weeks, 5 weeks and 6 weeks after planting with inoculums source from ZYMV sap. The variables observed were incubation period, disease incidence, disease severity, endurance level and yield. The results showed that ZYMV infection in plants of different ages had an effect on the incubation period, disease incidence, disease severity, endurance level and crop yield. If ZYMV infection occurs in older zucchini plants at 5 weeks after planting, the incubation period is slow, the incidence of the disease is lower and the severity of the disease is lower than that of ZYMV infection in younger zucchini plants. Zucchini infected plants ZYMV at the age of 4 weeks after planting the incidence of the disease reached 100 % and can not produce fruit, zucchini infected ZYMV at age older than 4 weeks after planting, disease incidence reaches 50 % and still can produce fruit, with yield decrease up to 41.216 % compared with healthy zucchini plants. Zucchini plant age 4 weeks after planting, is a critical phase of ZYM infection.