Variation in chromosome number of hybrid seedlings between 'Tosa-Buntan' and 'Suisho-Buntan' pummelo (Citrus grandis [L.] osb.)

To breed pummelo (Citrus grandis [L.] Osb.) varieies with a few seeds, a fe male parent 'Tosa-Buntan' and a male parent 'Suisho-Buntan' were crossed; t he seed weight and the chromosome number of the progenies were determined f rom 1996 to 1998 inclusive. The weight of full developed seeds peaked betwe en 301mg to 330mg. Those which weighed less than 30mg were considered to be unfertilized ovules. About 20% of partially developed seeds weighed betwee n 31 to 180mg. Embryos rescued from seeds, weighing between 61 and 180mg, g erminated better under embryo culture than when sown in plug trays. Hence, embryo culture is an effective means of obtaining seedlings from these poor ly developed seeds. Furthermore, about 15% of them were not diploid. Chromo some counts of 128 embryo cultured seedlings derived from seeds weighing be tween 61 and 180 mg revealed that there were 109 diploids, eight triploids, three tetraploid, and eight aneuploids. The aneuploids had chromosome numb ers of 2n = 17, 19, and 28.