Development of Genic Male-sterile Watermelon Lines with Delayed-green Seedling Marker

Hybrid seed production can be facilitated by using male sterility coupled with a seedling marker. This research was initiated to combine the ms male sterility and dg delayed-green seedling marker into watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] lines. Male-sterile plants of the male-sterile line G17AB were crossed with plants of delayed-green breeding line Pale90, which has yellow cotyledons and pale-green, newly developed, true leaves. The double-recessive recombinants, male sterile and delayed green, from the F2 population were backcrossed to the male-fertile plants of G17AB. The pedigree method was used for selection in the progenies. The segregation ratios obtained from F2 and BC1F2 populations suggest that the male-sterile and delayed-green traits are inherited independently and that delayed green is inherited as a single recessive nuclear gene. Two male-sterile watermelon lines with delayed-green seedling marker have been developed. These lines will provide a convenient way to introduce male sterility and the delayed-green seedling marker into various genetic backgrounds. These two lines can be used for testing the efficiency of a new, hybrid, watermelon, seed production system.

Inheritance of two seedling characters in Sorghum almum Parodi, and cross pollination within S. almum and between S. almum and S. halepense (L) Pers.

An albino seedling character in Sorghum almum Parodi was shown to be tetrasomically inherited. Segregation ratios for a pale green seedling character were very variable, and it is probable that more than one gene is involved. With the albino seedling character as a marker gene, it was found that the average natural crossing in S. almum was approximately 54% at one location and 70% at another. The maximum natural crossing between S. almum and S. halepense (L.) Pers. was 57%, but the mean was only 20%. This may indicate that some S. almum plants exhibit a degree of genetic isolation from S. halepense when these species are grown together under natural conditions.