Cucurbit Genetics Cooperative Report 10:58-59 (article 31) 1987
L. Rajamony, T. A. More, and V. S. Seshadri
Division of Vegetable Crops, Indian Agricultural Research Institute, New Delhi-110012, India
A. Varma
Division of Mycology and Plant Pathology, Indian Agricultural Research Institute, New Delhi-110012, India
A sap transmissible virus causing mild mosaic of muskmelon was identified as CGMMV (2) which is one of the few viruses with a natural host range restricted to Cucurbitaceae (1). In sub-tropical parts of India around Delhi, a strain of virus from muskmelon was isolated (3) and identified as a minor variant of CGMMV.
A project on breeding for virus resistance has been initiated at the Indian Agricultural Research Institute, New Delhi. About 152 collections of muskmelon from 10 countries comprised of 124 dessert varieties, 10 non-dessert forms and 18 wild species of Cucumis were screened against CGMMV in three stages, twice under natural field conditions (summer and rainy season of 1985) and once under artificial transmission by inoculating with a purified strain of CGMMV adopting a sap-inoculation technique (3) in an insect proof nethouse. Plants were rated on a 0-5 scale, 0 being immune/symptomless and 5 being highly susceptible.
All the dessert varieties of muskmelon tested were found susceptible to CGMMV both under natural field condition and artificial inoculation. Among the wild species, C. myriocarpus (disectifolium) Naud., C. myriocarpus (normal type) Naud., C. africanus L. f. (two collections), C. figarei Naud., C. meeusii C. Jeffrey, C. zeyheri Sond. and C. ficifolius A. Rich. were found to be resistant to CGMMV under all the screening tests.
It was observed that the two non-dessert types “phoot” (C. melo var. momordica) and “Kachri” grown mostly in north India and Cornell breeding line No. 83-273-6R (Mon. MR. 328) of Dr. H. M. Munger, Cornell University, Ithaca, U.S.A. were found to be resistant (Score = 1) to CGMMV. These three resistant genotypes are crossable with all the cultivated dessert varieties of muskmelon and could be directly used in virus resistance breeding program. It is pointed out that “phoot” and “kachri” (non-dessert forms) can possibly serve also as bridge species to transfer resistance from wild species to the cultivated ones after studying their crossability with the wild species.
Cucumis metuliferus Naud. and C. anguria var. longipes A. Meeuse showed moderate susceptibility (Score-= 3) to CGMMV. Nevertheless resistance reaction to CGMMV showed by some of the above wild species conformed to the reports from IVT (4).
Preliminary studies were conducted on the confirmation of the nature of resistance by back inoculation technique. Taking the sap of resistant genotypes 150 days after inoculation with pure isolate of CGMMV and inoculating it on the susceptible stock (uninfected) in virus free nethouse, indicated that C. figarei was immune to CGMMV while all the other resistant types, “phoot”, “kachri”, Cornell No. 83-273-6R and other Cucumis sp., were found to show symptomless carrier reaction. Further investigation is planned on this latter type of reaction.
Studies on the interspecific hybridization between CGMMV resistant wild species and cultivated forms of muskmelon indicated that C. figarei crosses with Pusa Madhuras and Monoecious-4 (cultivated forms) with 11 to 25 per cent fruit set. The F1 generation and succeeding generations will be used to evaluate the nature of resistance.
Literature Cited
- Lovisolo, O. 1980. Virus and viroid diseases of cucurbits. Acta Horticulture 88:33-82.
- Nariani, T. K., S. M. Viswanath, S. P. Raichoudhuri, and A. V. Mohanir. 1977. Studies on mosaic disease of muskmelon (Cucumis melo L.). Curr. Sci. 46(2):47-48.
- Raychaudhuri, M. and A. Varma. 1978. Mosaic disease of muskmelon caused by a minor variant of cucumber green mottle mosaic virus. Phytopathologische Zeitschirifet 93(2):120-125.
- Visser, D. L. and A.P.M. den Nijs. 1980. The Cucumis species collection at the IVT. Cucurbit Genetics Coop. Rpt. 3:68-74.