Article ID: UTD-136
Male sterility is defined as the loss of pollen fertility, and it represents a plant reproductive isolation symptom, along with self-incompatibility. It plays an important role in the efficient production of F1-hybrid seeds, which results in affordable seed prices for farmers. Male sterile cultivated strawberry Fragaria × ananassa Duch. plants were found in an F1 population and reciprocal backcrossed populations derived from a cross between ‘Fukuoka S6’ and ‘Kaorino’. Male sterile plants were clearly distinguished from male fertile plants in those populations based on the anther color. The pollen of the male sterile plants was a lighter yellow color and not maturely shaped compared with pollen of male fertile plants. Genotyping was performed using EST-SSR markers in the three populations. Quantitative trait locus analyses for pollen fertility were conducted independently using three kinds of populations, and this revealed that male sterility was controlled by three independent chromosomal regions in these populations, which corresponded to chromosome 4 in the wild strawberry (Fragaria vesca) genome. One region was derived from ‘Fukuoka S6’ and the other two regions from ‘Kaorino’. The segregation patterns of fertile and sterile plants in each population clearly supported the three gene theory of male sterility in cultivated strawberries. The accumulation of recessive alleles at the three regions led to male sterility, and the existence of a dominant allele in at least one region resulted in fertile pollen. Male sterile plants were also found in two self-pollenated populations derived from ‘Fukuoka S6’ and ‘Kaorino’, and the effects of the three regions were validated. The adaptability levels of the three genes with different genetic backgrounds were also evaluated using core collection cultivars and selected lines derived using recurrent selection. We also detected flanking DNA markers for the three regions associated with male sterility. The use of these markers, which are in the vicinity of quantitative trait loci and responsible for male-sterility, could increase the efficiency of producing seed-propagated strawberry F1-hybrids.
