Culture of Embryo with a Segment of Ovary Improved Germination and Crossability of Distant Hybrids in Indica Rice

Abstract

Distant hybridization in the genus Oryza is realized as an efficient Biotechnological tool for plant breeding work to introgress useful gene/s from diverse array of wild relatives into cultivated rice. This study was carried out to improve the germination frequency of hybrid embryo to enhance the crossability between O. sativa sub spp. indica and wild species. Three cultivars of indica rice viz. IR 64, Radha 4 and IR 69618 - CMS A line (cytoplasmic male sterile A line) were pollinated with the pollen of O. latifolia, O. minuta and O. officinalis. Hybrid caryopsis containing embryos were rescued at tenth day of pollination. In vitro germination frequency of rescued embryos were compared by culturing embryo alone and embryo with a bit of ovary during 2005-06 at Biotechnology Unit, Khumaltar, Lalitpur, Nepal. Culture was maintained at 25±1°C under dark until germination and there after continuous light. In majority of the cross combinations, the germination frequencies were found to be higher when embryo excised and cultured with small portion of ovary. This technique yielded up to 100 per cent germination which were later employed to study the crossability between species. Depending upon the cultivars of O. sativa, the frequencies of crossability varied from 0.53 to 3.08 per cent with highest for Radha 4/O. minuta. A total of 38 hybrid plants were successfully produced from 88 cultured embryos isolated from 2644 pollinated florets. Inclusion of a bit of ovary along with embryo in in vitro culture was found to be an effective method not only to improve the germination frequency of hybrid embryo, but also to increase the crossability between cultivars of cultivated rice and their distant relatives. Key words: Embryo rescue; Interspecific hybrid; Oryza sativa; Wild species; O. latifolia; O. minuta; O. officinalis. DOI: 10.3126/sw.v5i5.2655 Scientific World, Vol. 5, No. 5, July 2007 46-50

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