Abstract:
Root-knot nematode Meloidogyne spp. And cyst nematodes Heterodera spp. Are major nematode problems in crop production, particularly under tropical weather conditions. Because of their economic importance in the country, studies were carried out on the culturing of Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949 and Heterodera zeae Koshy, Swarup & Sethi, 1971, to screen out resistance in different varieties of tomato (Lycopersicum esculentum) and of corn (Zea mays).
A number of media i.e. Murashige & Skoog, 1962; Linsmaier & Skoog, 1965, Gamborg’s B-5,1976 were tested for the development of pure cultures of M. incognita on tomato and H. zeae on corn plants, in which Linsmaier & Skoog, 1965 was found best for shoot development and Gamborg’s B-5 medium (without auxin and cytokinin) proved best for root culture. These two media were therefore used for further studies.
Eleven cultivars of tomato viz. Rutgers, Sanmarzano, Large round red, Marmande, Walter gaint, Roma VF, Marglobe, Roforto, Lyallpur selection. PARC I, PARC II and five cultivars of corn viz. Azam, Dehgan, Ehsan, HRC and Sahaheen were evaluated for resistance and life cycle studies of M. incognita and M.Javanica on tomato and Heterodera zeae on corn in vitro.
Almost all the tomato cultivars tested were found suspectible to M.incognita and M.javanica infection with varying degree of infection but PARC I was found partially resistant.
Tomato seeds were surface sterilized with 2-5% and of corn with 5-20% Nacol. Sterilized seeds were placed for germination on 1.8% water agar and incubated at 25-30 C. Egg masses of M.incognito and M.javanica, and cysts of H.zeae were surface sterilized with 0.1% mercuric chloride.Temprature ranging 25-30 C was found suitable for the growth of tomato roots and development of M. incognita and M. javanica while temperature range of 30-35 C was best for the development of H.zeae on corn roots.
Life cycle studies indicated that both the root-knot nematodes M.incognita and M. Javanica completes their life cycle within 20-25, 25-35 and 35-45 days on susceptible, moderately susceptible and partially resistant cultivars respectively at 25-28 C in vitro.
All the corn cultivars used to screed reistance against corn cyst nematode Heterodera zeae in vitro were found susceptible at various degrees to H. zeae. No cultivar was found resitant to this nematode. Studies showed that Heterodera zeae require 18-20 days to complete its life cycle from second stage juvenile to second stage juvenile on susceptible corn cultivars at 30 C in vitro.
These studies have provided basic information on the inefectivity of these pathogenic nematode on their respective host cultivars which could help in further investigation for the development of effective control measures.
