Reference "Alien introgression in rice"

Reference ID

365

Title

Alien introgression in rice

Source

Plant molecular biology, 1997, vol. 35, pp. 35-47

Authors (2)

Brar-D-S

Khush-G-S

Abstract

Rice (Oryza sativa L.) productivity is affected by several biotic and abiotic
stresses. The genetic variability for some of these stresses is limited in the
cultivated rice germplasm. Moreover, changes in insect biotypes and disease
races are a continuing threat to increased rice production. There is thus an
urgent need to broaden the rice gene pool by introgressing genes for such traits
from diverse sources. The wild species of Oryza representing AA, BB, CC, BBCC,
CCDD, EE, FF, GG and HHJJ genomes are an important reservoir of useful genes.
However, low crossability and limited recombination between chromosomes of
cultivated and wild species limit the transfer of such genes. AT IRRI, a series
of hybrids and monosomic alien addition lines have been produced through embryo
rescue following hybridization between rice and several distantly related
species. Cytoplasmic male sterility and genes for resistance to grassy stunt
virus and bacterial blight have been transferred from A genome wild species into
rice. Similarly, genes for resistance to brown planthopper, bacterial blight and
blast have also been introgressed across crossability barriers from distanly
related species into rice. Some of the introgressed genes have been mapped via
linkage to molecular markers. One of the genes Xa-21 introgressed from O.
longistaminata has been cloned and physically mapped on chromosome 11 of rice
using BAC library and flourescence in-situ hybridization. RFLP analysis revealed
introgression from 11 of the 12 chromosomes of C genome species into rice.
Introgression has also been obtained from other distant genomes (EE, FF, GG)
into rice and in majority of the cases one or two RFLP markers were
introgressed. Reciprocal replacement of RFLP alleles of wild species with the
alleles of O. sativa indicates alien gene transfer through crossing over. The
rapid recovery of recurrent phenotypes in BC2 and BC3 generations from wide
crosses is an indication of limited recombination. Further cytogenetic and
molecular investigations are required to determine precisely the mechanism of
introgression of small chromosome segments from distant genomes in the face of
limited homoeologous chromosome pairing. Future research should focus on
enhancing recombination between homoeologous chromosomes. Introgression of QTL
from wild species should be attempted to increase the yield potential of rice.