NEW RESISTANCE GENES TOWARD FUSARIUM OXYSPORUM F. SP. MELONIS FOUND IN MELO L. SUBSP. MELO CONV. ADZHUR.

F. CICCARESE, O. LONGO, I. GARUCCIO, A. BOTTALICO, D. SCHIAVONE

Department of Biology and Plant Pathology, University of Bari, Via G. Amendola 165/a, 70126 Bari (Italy) – [email protected]

Resistance gene, Fusarium oxysporum f. sp. melonis, , local germplasm, molecular biology

Carosello [Cucumis melo L. subsp. melo conv. adzhur (Pang.) Grebensch] is considered as a relict of , selected for the consumption of unripe fruits. Southern Italy represents an area of diversification for C. melo and particularly in carosello is characterized by large genetic variability, with many populations and ecotypes selected by single horticulturists looking after their preservation. Populations of unripe occurring in Italy have different names with regard to the cultivation area and fruit morphology. In this work, by using molecular biology techniques, for the first time it has been possible to distinguish genotypes of carosello and melon from genotypes of different cucurbit species (cucumber, , squash, pumpkin and bottle gourd). The results of this research give a new contribution to the real botanical position of carosello, up to now only based upon the different chromosome complement. Restriction patterns obtained by the Cfo I enzyme pointed out a close similarity of ecotypes of carosello with cultivars of melon. In Apulia the cultivation of carosello is seriously affected by Fusarium-wilt caused by the race 0 of Fusarium oxysporum f. sp. melonis that represents a factor limiting the extension of carosello cultivation in Apulia and in other southern regions (Ciccarese et al., 2000). The wide and diversified availability of local germplasm of carosello represents a source of genetic variability useful to identify resistances to Fusarium-wilt. Screening of local ecotypes of carosello toward the race 0 of Fusarium oxysporum f. sp. melonis pointed out a large variability of reaction toward the disease and especially the ecotypes BA1-7 (‘’ typology) and LE3-1 (‘spuredda’ typology) were resistant. Previous studies about inheritance analysis of resistance identified in the BA1-7 ecotype assessed the occurrence of a dominant gene called Fox-1 (Longo et al., 2002). In studies dealing with inheritance of resistance of the ecotype LE3-1, all plants of the F1 progeny, obtained by crossing the susceptible parent and the resistant one, were resistant; in screenings on the F2 progeny, 131 plants were evaluated as resistant, while serious disease symptoms were recorded on 44 plants. The progeny obtained by backcross with the susceptible parent segregated 81 resistant plants and 94 susceptible plants; all the plants obtained by backcross with the resistant parent appeared healthy. The results obtained from inheritance studies clearly showed that resistance found in the LE3-1 ecotype is conferred by a single dominant gene designed as Fox-1A. In order to assess if Fox-1 and Fox-1A are the same genes as the well known resistance gene of melon called Fom-1, allelism tests were carried out. In the F2 progeny obtained by the hybrid Fom-1XFox-1 and in the F2 progeny obtained by the hybrid Fom-1XFox-1A, segregation ratios pointed out that these factors are not allelic. In fact, the chi-square test suggested that they are independent (taking as hypothesis 15 resistant plants : 1 susceptible plant). The F2 progeny obtained by the hybrid Fox-1XFox-1A, instead, has proved to be resistant to the race 0 of Fusarium oxysporum f. sp. melonis. The absence of segregation in this F2 showed that Fox-1 and Fox-1A are the same genes.