High embryo sac fertility and diversity of abnormal embryo sacs detected in autotetraploid indica/japonica hybrids in rice by whole-mount eosin B-staining confocal laser scanning microscopy

An eosin B staining procedure for use with confocal microscopy (WE-CLSM) was used to examine the mature embryo sacs in 24 typical autotetraploid (2n = 4x = 48) indica/japonica hybrids and to compare with their original diploid (2n = 2x = 24) indica/japonica hybrids in rice. Four of the 24 hybrids showed > 80% embryo sac fertility, and 13 hybrids over 70%. The average embryo sac fertility of the 24 autotetraploid indica/japonica hybrids was 68.08%, which was 17.33% higher than that in diploid hybrids. When compared with the diploid hybrids, 79.17% of the autotetraploid hybrids had higher embryo sac fertility. A diversity of abnormal embryo sacs occurred in autotetraploid indica/japonica hybrids. Embryo sac abnormalities were similar for both autotetraploid and diploid hybrid, but their frequencies were different. Some novel abnormal types were found in autotetraploid hybrids, such as enlarged egg apparatus. The embryo sac fertilities and frequencies of various abnormalities in autotetraploid hybrids varied with parental genotype and environment. The average seed set of the autotetraploid hybrids were higher than their diploid hybrids in different growing seasons.