Crossability barriers in the interspecific hybridization between Oryza sativa and O. meyeriana.
Oryza meyeriana Baill (GG genome) is a precious germplasm in the tertiary gene pool of cultivated rice (AA genome), and possesses important traits such as resistance and tolerance to biotic and abiotic stress. However, interspecific crossability barrier, a critical bottleneck restricting genes transfer from O. meyeriana to cultivars has led to no hybrids through conventional reproduction. Therefore, the reasons underlying incrossability were investigated in the present report. The results showed that: (i) at 3-7 d after pollination (DAP), many hybrid embryos degenerated at the earlier globular-shaped stage, and could not develop into the later pear-shaped stage. Meanwhile, free endosperm nuclei started to degenerate at 1 DAP, and cellular endosperm could not form at 3 DAP, leading to nutrition starvation for young embryo development; (ii) at 11-13 DAP, almost all hybrid ovaries aborted. Even though 72.22% of hybrid young embryos were produced in the interspecific hybridization between O. sativa and O. meyeriana, young embryos were not able to further develop into hybrid plantlets via culturing in vitro. The main reason for the incrossability was hybrid embryo inviability, presenting as embryo development stagnation and degeneration since 3 DAP. Some possible approaches to overcome the crossability barriers in the interspecific hybridization between O. sativa and O. meyeriana are discussed.
Fu
Xue-Lin
XL
Guangdong Provincial Key Laboratory of Plant Molecular Breeding, South China Agricultural University, Guangzhou 510642, China.
Lu
Yong-Gen
YG
Liu
Xiang-Dong
XD
Li
Jin-Quan
JQ
D003433:Crosses, Genetic; D005298:Fertility; D006824:Hybridization, Genetic; D012275:Oryza / Q000196:embryology / Q000235:genetics*; D053205:Pollen Tube / Q000254:growth & development; D054817:Pollination / Q000235:genetics; D012098:Reproduction; D012639:Seeds / Q000196:embryology; D013045:Species Specificity