Gummy stem blight (GSB), caused by Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), is a destructive foliar disease of watermelon in areas with hot and humid climates. The wild watermelon germplasm PI 189225 is a known source of resistance to GSB. The identification and use of molecular markers linked to resistance genes in the wild-type germplasm will speed up the introgression of GSB resistance into new watermelon varieties. An F2 segregating population was obtained from a cross between the resistant wild watermelon genotype PI 189225 and the susceptible genotype K3. The F2-derived F3 families were inoculated with a single isolate of S. cucurbitacearum (JS002) from Jiangsu Academy of Agricultural Sciences. The results of the genetic analysis demonstrated that GSB resistance in PI 189225 was controlled by a major quantitative trait locus (QTL), temporarily designated Qgsb8.1. Based on the results of bulk sergeant analysis and sequencing, one associated region spanning 5.7 Mb (10,358,659 to 16,101,517) on chromosome 8 was identified as responsible for the resistance to GSB using the Δ(single-nucleotide polymorphism [SNP]-index) method. The result of a QTL linkage analysis with Kompetitive allele-specific PCR (KASP) SNP markers further mapped the GSB resistance locus between the SNP markers KASP_JS9383 and KASP_JS9168 in a region of 571.27 kb on chromosome 8. According to the watermelon gene annotation database, the region contains approximately 19 annotated genes and, of these 19 genes, 2 are disease resistance gene analogs: Cla001017 (coiled-coil nucleotide-binding site leucine-rich repeat resistance protein) and Cla001019 (pathogenesis related). Reverse-transcription quantitative PCR demonstrated that the expression of the two genes changed following S. cucurbitacearum infection, suggesting that they play important roles in GSB resistance in watermelon. This result will facilitate fine mapping and cloning of the Qgsb8.1 locus, and the linked markers will further provide a useful tool for marker-assisted selection of this locus in watermelon breeding programs.
Bottle gourd [Lagenaria siceraria (Molina) Standley] has been used exclusively as rootstocks for Cucurbit crops. Haploid technique increases the selection e ciency for developing resistant bottle gourd varieties. This work focused on haploid induction in bottle gourd through in situ parthenogenesis by pollination with gamma-irradiated pollen. Pollination were carried out for six genotypes of bottle gourd with 50, 75, 100, 125 and 150 Gray (Gy) doses of gamma rays. Production of in vitro haploid plants was in uenced by irradiation dose, genotype and embyo stage. Seeds at 17 to 21 days after pollination was found to be optimum for embryo rescue. Pollination with irradiated pollen at 100 to 125 Gy was effective for haploid induction. The ploidy level of the 11 parthenogenetic plantlets was con rmed by ow cytometry and 36.3% haploid and 9% triploid plantlets were obtained. This work provides valuable germplasm resources for bottle gourd genetic analysis and breeding programs.
Bottle gourd [Lagenaria siceraria (Molina) Standley] has been used exclusively as rootstocks for Cucurbit crops. Haploid technique increases the selection efficiency for developing resistant bottle gourd varieties. This work focused on haploid induction in bottle gourd through in situ parthenogenesis by pollination with gamma-irradiated pollen. Pollination were carried out for six genotypes of bottle gourd with 50, 75, 100, 125 and 150 Gray (Gy) doses of gamma rays. Production of in vitro haploid plants was influenced by irradiation dose, genotype and embyo stage. Seeds at 17 to 21 days after pollination was found to be optimum for embryo rescue. Pollination with irradiated pollen at 100 to 125 Gy was effective for haploid induction. The ploidy level of the 11 parthenogenetic plantlets was confirmed by flow cytometry and 36.3% haploid and 9% triploid plantlets were obtained. This work provides valuable germplasm resources for bottle gourd genetic analysis and breeding programs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.