Random chloroplast segregation and mitochondrial genome recombination in somatic hybrid plants of Diplotaxis catholica+Brassica juncea

Detailed molecular analysis of the somatic hybrid plants of Diplotaxis catholica+B. juncea indicated random chloroplast segregation. One of the five hybrid plants analyzed derived its chloroplasts from D. catholica and two hybrids had chloroplasts of B. juncea origin. Two hybrid plants maintained mixed population of chloroplasts. The mitochondrial (mt) genomes of the fusion partners had undergone recombinations. Occurrence of fragments specific to both the parents in HindIII digestion followed by atp 9 probing, as in hybrid DJ5, provided evidence for intergenomic mitochondrial recombination between D. catholica and B. juncea. Similar mt genome organization in two hybrids (DJ3 and DJ6) suggested that intergenomic recombination may be preferred at specific sites. Hybrid DJ1 had about 70% similarity to D. catholica in mt genome organization. mt genomes of hybrids DJ2, 3, 5, and 6 differed from B. juncea by 14.3-28%. The significance of these novel mt genome organizations in developing novel male sterility systems is discussed.