Systems favoring cross-pollination such as male sterility and female flowering type are of great importance in the development of new hybrid cultivars and their seed production. The advantages of male sterility are expressed in production of cheaper and competitive seeds. The presence of this characteristic in watermelon is not common, and in some cases, it is accompanied by negative manifestations. A collection of 150 watermelon genotypes was tested at the Maritsa Vegetable Crops Research Institute, Bulgaria, over the past nine years to search for a genetic source of male sterility. The results revealed that two mutations were found. The first mutation was in a plant of the Asar variety, which formed completely degenerated structures in the place of male and female flowers that were completely sterile. The other mutation affected male flowers, female flowers and leaf shape. Male flowers produced a small amount of pollen. Female flowers were formed but they were sterile and aborted at an early stage. The genotype can be propagated by pollination of the normal plants, which in the next generation segregate into mutant - 25%, and normal - 75%. The gene source is phenotyped according to the main characteristics of the fruits and the vegetation period. The mutation found cannot be directly used in a breeding program, but it is of interest for studying this important trait. The success of detecting flowers that are sterile depends on the number of watermelon plants, which for the conditions of the experiment amounted to a minimum of 4492 plants at a probability level of P3 – 0.95.
Velkov et al. (Thu,) studied this question.