Screening of Iberian melon accessions for resistance to races 0, 1, 2, and 1,2 of Fusarium oxysporum f. sp melonis (Fom), causal agent of Fusarium wilt

The purpose of this paper is to report on the evaluation of melon (Cucumis melo L.) germplasm for resistance to Fom races 0, 1, 2 and 1,2 as an important step of breeding for disease control. Thirty accessions fi om Spanish seed bank collection have been tested through two inoculation methods. In the first method, all genotypes were inoculated with each race fungus suspension of about 1 x 10(4) propagules/ml. The inoculum was poured on the sterilized vermiculite substrate with 12 plants of each genotype/race at first true leaf stage. Plant pots were then placed in a green house (5-35 degrees C) and growth chamber at 15-20 degrees C (night/day). Accessions with less than 25% dead or diseased plants were selected to inoculated by a second method. In this second method seedlings grown for 10 days in sterile vermiculite were removed and their roots dipped into the same inoculum suspension for 1 hour (10 seedlings/race/accession). Then the seedlings were transferred to vermiculite substrate and placed in a growth chamber. Roots of control plants were dipped in tap water only. Final assessments of symptom severity were made after 30 days of inoculation. In addition, reisolations of the pathogen were attempted by culturing disc of stem taken from surviving plants. The results showed that a number of accessions may possess resistant genes to some of Fom four races. In the first inoculation we selected 10 accessions resistant to race 0 of Fom, 12 to race 1, 15 to race 2 and 3 to race 1,2; these selected accessions were reduced by using the second inoculation method: 6, 1, 4 and none accessions to race 0, 1, 2 and 1,2 respectively. These results were compared with Fom reisolations.