CORRECTION OF CHLOROPHYLL DEFICIENCY IN ALLOPLASMIC MALE-STERILE BRASSICA-JUNCEA THROUGH RECOMBINATION BETWEEN CHLOROPLAST GENOMES

Brassica juncea cv. Pusa Bold carrying B. oxyrrhina cytoplasm (oxy cyt oplasm) was male sterile and chlorotic under field conditions at low t emperature (Prakash & Chopra, 1990). Leaf protoplasts of the chlorotic male sterile alloplasmic line (2n = 36) were fused with hypocotyl pro toplasts of green male fertile, B. juncea cv. RLM-198 (2n = 36) using polyethylene glycol. Of the 1043 plants regenerated from 10 fusion exp eriments, 123 had 'gigas' features and were identified as presumptive fusion products. Among field-grown population, one plant was dark gree n even at low temperatures and male sterile. It possessed 72 chromosom es which formed 36 bivalents at late diakinesis of meiosis-1. This pla nt was back-crossed to B. juncea cv. Pusa Bold (the maintainer line) f or three successive generations. One male sterile, normal green BC3 pr ogeny plant with 2n = 36 was analyzed for organelle constitution. Prob ing its total DNA with the mitochondrial gene for cytochrome oxidase s ubunit I revealed that it possessed mitochondria of B. oxyrrhina. Sout hern hybridization pattern with the gene for ribulose bisphosphate car boxylase oxygenase-large subunit (rbcL) revealed that the chloroplast genome of the chlorophyll deficiency-corrected plant had characteristi cs of both B. juncea and B. oxyrrhina. The deficiency correction has b een attributed to recombination between chloroplast genomes of the two species.