Abstract: Abstract: 【Objective】Shatianyou (Citrus grandis Osbeck cv. Shatianyou) is a peculiar excellent pummelo cultivar in China,but it has many seeds, about 100. The aim of the experiment was to obtain different ploidy new germplasm for seedless triploid breeding by means of screening seedlings, and to analyze genome constitution of natural and artificial tetraploids by Genome in situ hybridization(GISH).【Method】Collecting randomly open-pollinated seeds, then ploidy variation seedlings were gained from them by chromosome counting; In order to analyze genome constitution of tetraploids, the labeled total gDNA of diploid as probe was hybridized to tetraploid metaphase chromosomes by GISH.【Result】5 triploids and 9 tetraploids were found from 6000 seeds. GISH analysis of tetraploids showed that there were 7 allotetraploid and 2 autotetraploid in natural tetraploids, while 4 artificial tetraploids from colchicine induction were all autotetraploid.【Conclusion】These monoembryonic polyploids would be for seedless breeding. GISH result proved existence of unreduced eggs in Citrus grandis cv. Shatianyou.

Key words: Citrus grandis cv. Shatianyou, polyploidy, Genome in situ hybridization (GISH), unreduced gamete