Journal of Taiwan Agricultural Research

Author:Jin-Hsing Huang*, Chaur-Tsuen Lo and Ting-Fang Hsieh

Abstract:

   A cultured leaf method was developed for disease assessment of melon powdery mildew caused by Podosphaera xanthii in this study. The detached leaves of melon (Orient sweet- Golden Light) with petiole were cultured in the transparent plastic boxes which contained nutrient solution. After incubation for 6 to 10 days, the growth of roots and vigor of leaves were better at 28-32℃ in comparison with other temperatures. When leaves were inoculated with different concentrations of conidia of P. xanthii, and then incubated at 24℃/20℃ (day/night) with a 12 hr photoperiod, percentage of lesion area increased with increasing inoculum density and incubation time. The lesion area reached 90% after 12 days at the inoculum density of 30 or 100 spore/cm². However, the lesion area was about 60% at 10 spore/cm2 after the same period of time. With this inoculation method, powdery mildews grew well at 20-24℃, but failed to grow at 8℃or 32℃. The disease development on cultured leaves of different ages was similar, but the lower leaves usually turned yellow during the inoculation period. The cultured leaf method was applicable to other cucurbit plants. With the inoculum density of 10 spore/cm2 at 24/20℃ for 12 days, the lesion area of bottle gourd (Trendy) was 42.5%, lower than those (62.5-72.5%) of  melon (Golden Light, Autumn Sweet), cucumber (Chailue No.2), pickling melon (Silver Charm) or squash (Fairy).

Key words:Melon, Powdery mildew, Podosphaera xanthii, Cultured leaf method

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