Exploiting cucurbitaceous species as rootstocks for management of Fusarium wilt (Fusarium oxysporum) in bitter gourd

Abstract

Bitter gourd is affected by various kinds of pathogens, of which Fusarium wilt Fusarium oxysporum plays a vital role. The present investigation focuses on the role of defense related enzymes which impart resistance against Fusarium wilt. A total of ten cucurbitaceous rootstocks and two bitter gourd scions were screened against Fusarium wilt pathogen under in vitro. Results on screening against Fusarium wilt revealed that Citrullus colocynthis, Cucumis metuliferus and Cucurbita moschata exhibited no symptom and manifested as resistant to Fusarium wilt and the least percent incidence of 21.62, 37.44 and 48.90 was observed in Luffa cylindrica followed by Momordica charantia var. muricata rootstock (23.58, 42.18 and 50.34) at 30, 45 and 60 days after inoculation. Seedlings of aforementioned species were harvested at 0, 7, 14, 21, 28 and 35 days after challenge inoculation and assayed for defense related enzymes activity. Significant increases in the activities of peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) activity was observed in resistant rootstocks viz., C. colocynthis, C. metuliferus and C.moschata followed by moderately resistant rootstocks viz., M. charantia var. muricata and L. cylindrica. Native page analysis of both PO and PPO isozymes was carried out for the time course and examined. Isozyme analysis revealed that unique PO and PPO isozymes were induced in aforementioned resistant rootstocks. From this study point out that the cucurbitaceous species viz., kumatikai (C. colocynthis), African horned cucumber (C. metuliferus) and pumpkin (C. moschata) with high or moderate levels of these biochemical constituents suffered less for Fusarium wilt pathogen and these rootstocks served as the best rootstocks for grafting with bitter gourd scions followed by mithipakal(M. charantia var. muricata) and sponge gourd (L. cylindrica).