Middle-East Journal of Scientific Research 4 (3): 190-196, 2009 ISSN 1990-9233 © IDOSI Publications, 2009 Corresponding Author: Raj K umar Niroula, Biotechnology Unit, N.A.R.C, Khumaltar, Lalitpur, Nepal 190 Monitoring of Meiotic Behaviour in Intergenomic Rice Hybrids Produced Between Nepalese Cultivated Rice O. sativa (AA) and O. officinalis (CC) Raj Kumar Niroula Biotechnology Unit, N.A.R.C, Khumaltar, Lalitpur, Nepal Abstract: Cytogenetics of intergenomic rice hybrids produced between cultivated rice, (O. sativa cv. Manshara and Kalo Jhinuwa) and Nepalese wild species, O. officinalis (2n = 24, CC) was investigated at different stages of meiotic divisions. At pachytene stage of meiosis, more than 50% cells showed complete pairing. Cytological analysis at diakinesis, metaphase I (MI), anaphase I (AI) and telophase I (TI) however, revealed that lacking of pairing between species chromosomes. At diakinesis and MI, almost all hybrid pollen mother cells (PMCs) had 24 univalents (I) resulted into marked reduction in chiasma frequency/PMC in comparison to their respective parents. The chiasmata/hybrid PMC was ranged from 1.33±1.06–2.57±2.20. The frequency of bridges, laggards and bridges + laggards was very high in AI and TI. Manshara x O. officinalis hybrid PMCs showed normal segregation in few of the cells (1.09%). All the hybrid plants showed 100% sterility for both pollen and spikelet. The present study suggest that pairing between chromosome was partially normal and most of the abnormalities associated with later stages are due to desynapsis rather than lack of homology between A and C genomes. Key words: Bivalent %Bridges %Chiasmata %Laggards %Oryza offcinalis %PMCs %Pachytene INTRODUCTION species is urgently needed to prevent the vulnerability Rice (Oryza sativa L.) is, an improtant world's food diversification desired in the breeding germplasm and crops, taxonomically classified under the family Poaceae subsequent gene introgression using wild species, (gramineae), sub-family Oryzodeae and tribe Oryzae. however, ultimately depends upon the extent of Oryzae tribe includes 12 genera. Under the genus Oryza crossability and chromosome pairing and subsequent there are 24 spcecies that represent ten distinct genomes recombination. and three levels of gene pool [1]. Of them only O. sativa O. officinalis, one of the most important secondary and O. glaberrima are in cultivation and remaining gene pools of cultivated rice, is threatening species to 22 species are available in wild forms. Nepal also Nepal and possesses wide range of economic traits endowed with wild species like O. rufipogon, O. nivara, including resistant to brown plant hopper and O. officnalis and O. granulata. Most of the wild whitebacked plant hopper and shade tolerance [4]. germplasm, in particular, contain an essentially untapped Several earlier studied conducted elsewhere revealed reservoir of agriculturally important genes. Genetic that chromosome pairing between cultivated rice and variability for some of the essential agronomic traits such O. officinalis from other geographical region was largely as resistance to biotic and abiotic stresses is limited in abnormal with frequently 20-24 univalents/cell [5, 6]. cultivated rice germplasm [2]. Moreover, continuous Large amount of irregularities and limited chromosome changes in insect biotypes and disease races are a pairing at diakinesis and MI stages have also been continuing threat to increase rice production. Following reported in intergenomic hybrids between O. sativa and the plant breeding aided with genomics and molecular other wild species having genomes other than AA [2]. cytogentic techniques to date more than dozen of But, the chromosome relationship between O. sativa and economic genes have been successfully introduced into O. officinalis of Nepal origin is still unknown. Therefore, popular varieties of rice from different wild species [3]. from the utilization point of view, the present study was Further diversification of current rice gene pool using wild carried out to elucidate the background information on to various biotic and abiotic factors. The extent of