This research was conducted to develop genic male-sterile lines of watermelon (Citrullus lanatus Matsum & Nakai) homozygous for the juvenile albino (ja) seedling marker. Male-sterile plants (msms) of the genic male-sterile line G17AB were crossed with a Dixielee plant that was heterozygous for the ja locus. Male-fertile, juvenile albino recombinants of the F2 progeny were self-pollinated, resulting in F3 progeny. The male-sterile normal green recombinants of the F2 progeny were crossed with an F1 hybrid plant with genotype MsmsJaja, and three populations (93JMSB-1, -2, and -3) were obtained from these crosses. Juvenile albino recombinants were confined to 93JMSB-1. Of the juvenile albino plants of 93JMSB-1, male-sterile plants were sib-crossed with male-fertile plants, resulting in 93JMSB-1-1. Progeny of 93JMSB-1-1 was homozygous for ja and segregated for ms in a 127 male-sterile: 128 male-fertile ratio, fitting a 1:1 ratio. The male-sterile juvenile albino plants of F3 were crossed with male-fertile juvenile albino plants of 93JMSB-1, resulting in 93JMSF3-1 and -2. Plants 93JMSF3-1 and -2 were homozygous for ja but segregated for ms at 10 male-sterile: 13 male-fertile and 15 male-sterile: 19 male-fertile for 93JMSF3-1 and 93JMSF3-2, respectively, fitting the 1:1 ratio. These three genic male-sterile lines with the ja seedling marker provide valuable germplasm for introducing ms and ja genes into diverse genetic backgrounds and for studying cross-pollination and gene flow in watermelon populations.
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