A female fertile triploid loquat line produces fruits with less seed and aneuploid germplasm

Abstract

Most loquat cultivars are diploid (2n=2x=34) and produce numerous large seeds, affecting their edibility rate and processing. Therefore, breeding less seed triploid cultivars has always been a primary goal of loquat breeding. However, most triploid plants have low fertility and cannot meet commercial needs. Here, we identified a triploid line, Q24, that can set seeds normally under natural conditions. We statistically analyzed the fruit setting rate, seed number, and external quality of Q24. The fruit setting rate of Q24 was similar to that of diploid Q14. The number of seeds in Q24 was 79.40% less than that in Q14. Pollen viability analysis and hybridization experiments revealed that Q24 male gametes were sterile. Further cytological observations showed that male gamete sterility was caused by abnormal chromosome pairing during meiosis. Hybridization experiments also confirmed that Q24 female gametes were fertile. Finally, chromosome counts showed that the progeny of Q24 could produce aneuploids at a frequency of 92.52%. In conclusion, the triploid Q24 loquat is a valuable breeding resource, not only because it has less seed and fertile female gametes but also because most of its offspring are aneuploids. This study provides an optimal material for breeding the less seed loquat, and its large number of aneuploid progenies enrich the germplasm resources of loquat.