Inheritance of race 1.2 Fusarium wilt resistance in four melon cultivars

Abstract

The resistance to Fusarium oxysporum f.sp. melonis (Fom) race 1.2 has been studied in melons, such as the Portuguese accession 'BG-5384' and in the Japanese 'Shiro Uri Okayama', 'Kogane Nashi Makuwa', and 'C-211', since a good characterization of the resistance is necessary before its introgression into commercial varieties. These four melon accessions showed a high level of resistance to races 0, 1, and 2 of Fom, indicating that the partial resistance to the race 1.2 previously detected may not have been race specific. To determine the mode of inheritance of the resistance to Fom race 1.2, the F 1 , F 2 , BCP R , and BCP S generations from the crosses between the four resistant accessions above and 'Piel de Sapo', a Fom race 1.2 susceptible melon, were developed. They were subsequently inoculated with two Fom isolates, one from the pathotype 1.2Y and the other from the pathotype 1.2W. The area under the disease progress curve was determined for each inoculated plant, and the data were analyzed. We show that the resistance seen in these accessions is polygenically inherited with a complex genetic control because many epistatic interactions were detected. The three epistatic effects; additivity 9 additivity, dominance 9 dominance, and dominance 9 additivity are present and significant, with differing magnitudes from one cross to the next. The relatively low heritabilities, and these epistatic effects make difficult the improvement of the resistance, from these sources, through a standard selection procedure.

Cucumis melo L. Germplasm in Tunisia: Unexploited Sources of Resistance to Fusarium Wilt

“…In both cases, further characterization of the resistance and selection are needed before the resistance can be incorporated into melon breeding programs. Indeed, up to now, resistance to race 1.2 is reported to be complex, controlled by multiple recessive genes with epistatic effects, which make its management difficult [13]. Besides, Herman and Perl-Treves [16] reported that resistance to this race is controlled by two recessive genes in the breeding line BIZ, and unfortunately, the molecular markers linked to those genes were not validated.…”

“…For Fom race 1.2 inoculation experiments, disease severity in each inoculated plant was evaluated at 7, 15, 21, and 30 dpi (days post-inoculation) according to the same visual scale from 0 to 4, and the area under the disease progress curve (AUDPC) was estimated from those scores [13,15]. The AUDPC integrates both the intensity of symptoms and the time taken between inoculation and expression of symptoms.…”

“…The harmful race 1.2 has spread around the Mediterranean area and has become a problem for melon cultivation [1,6,12]; the development of genotypes with resistance not only to race 1.2 but to the other races of the pathogen represents a major objective in melon breeding programs. Resistance to race 1.2 seems to be quantitative and polygenically inherited [13][14][15]. Herman and Perl-Treves [16] reported a near-complete resistance to Fom race 1.2 in the melon breeding line BIZ, controlled by two complementary recessive genes, fom 1.2a and fom 1.2b.…”

“…Herman and Perl-Treves [16] reported a near-complete resistance to Fom race 1.2 in the melon breeding line BIZ, controlled by two complementary recessive genes, fom 1.2a and fom 1.2b. Chikh-Rouhou et al [13] reported that resistance to race 1.2 is under complex genetic control since relatively moderate broad-sense heritabilities were obtained and epistatic effects were detected.…”

Breeding melon for resistance to Fusarium wilt: recent developments

“…Segregation of the resistance response in these populations supported a model in which two complementary, recessive genes, designated fom-1,2a and fom-1,2b, are required to obtain full resistance. Recently, Chikh-Rouhou et al (2011) determined the mode of inheritance of resistance to Fom race 1,2 in lines BG-5384, Shiro Uri Okayama, Kogane Nashi Makuwa and C-211. The F 1 , F 2 , and reciprocal backcross generations from the crosses between the above four resistant accessions and 'Piel de Sapo', a Fom race 1,2 susceptible melon, were analyzed by inoculation with isolates belonging to the 1,2y and 1,2w pathotypes.…”