Attempts to overcome prefertilization incompatibility in interspecific and intergeneric crosses involving Oryza sativa L.

Abstract

The wild relatives of rice are a valuable source of desirable agronomic traits, but prefertilization barriers operate in crosses of Oryza sativa L. with the wild Oryza species and related genera. Pollen germination was normal in crosses with O. brachyantha, O. eichingeri, O. officinalis, and O. ridleyi and slightly inhibited in crosses with Rhynchoryza subulata. Stigmal penetration of O. brachyantha and R. subulata pollen tubes was inhibited, while O. ridleyi pollen tubes showed both incompatible and weakly compatible reactions. Pollen tubes of O. eichingeri, O. officinalis, and O. ridleyi penetrated the stigma, but growth was frequently inhibited in the style or ovary wall, particularly in O. eichingeri crosses. The effect of postpollination application of boric acid, the immunosuppressant ε-aminocaproic acid (EACA), and gibberellic acid (GA3) and of ambient temperature (29 and 35 °C) on germination and pollen tube growth was investigated. Boric acid, EACA, and GA3 inhibited germination of O. brachyantha pollen, and boric acid and EACA inhibited pollen tube growth of O. brachyantha, O. eichingeri, O. ridleyi (35 °C), and R. subulata (29 °C). Pollen tube growth in the control and GA3 treatments was similar. Temperature had no effect on pollen germination and pollen tube growth was stimulated in O. ridleyi crosses at 35 °C only. The nature of incompatibility operating in these crosses is discussed.Key words: incompatibility, pollen tube growth, fertilization, Oryza, interspecific cross, intergeneric cross.