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The wild relatives of crops represent a rich reservoir of genes for introducing resilience to climate change into cultivated crops. To introgress genes from Sinapis alba, a wild relative of Brassicaceae, into Brassica juncea, a cultivated member of this family, we initially produced somatic hybrids between the two species and then produced a large number of backcross populations involving the two somatic hybrids (H1 and H2) with Brassica juncea. BC1 progeny were morphologically very similar. However, when they were challenge inoculated with a highly virulent Alternaria brassicae (ITCC No. 2542) culture under in vivo and in vitro conditions in two growing seasons, they showed wide variations in their disease reaction. Of the 40 BC1 lines tested in one season, 36 showed a resistant reaction. BC1F2 progenies derived from these resistant BC1 plants also showed resistance to Alternaria brassicae, indicating stable inheritance of the resistant phenotype. However, BC1F2 progenies showed a wide variation in morphological traits, including plant height, basal branching, leaf thickness, trichome density on leaves and stem. BC1 plants were examined by genomic in-situ hybridization (GISH) to determine their chromosome constitution. All five plants were found to possess 12 strong hybridization signals upon hybridization with a FITC-labeled S. alba-specific probe. GISH studies on BC1F2 plants indicated localized signals in addition to 12 full chromosome hybridization signals, suggesting alien introgressions into B. juncea that requires further validation. The BC2 generation was found to possess half of the haploid set of alien chromosomes. The BC1F2 and BC2 generations were further screened against A. Brassiceae and found to be resistant/tolerant. [ABSTRACT FROM AUTHOR]

Cymbopogon, commonly known as lemon grass, is one of the most important aromatic grasses having therapeutic and medicinal values. FISH signals on somatic chromosome spreads off Cymbopogon species indicated the localization of 45S rDNA on the terminal region of short arms of a chromosome pair. A considerable interspecific variation in the intensity of 45S rDNA hybridization signals was observed in the cultivars of Cymbopogon winterianus and Cymbopogon flexuosus. Furthermore, in all the varieties of C. winterianus namely Bio-13, Manjari and Medini, a differential distribution of 45S rDNA was observed in a heterologous pair of chromosomes 1. The development of C. winterianus var. Manjari through gamma radiation may be responsible for breakage of fragile rDNA site from one of the chromosomes of this heterologous chromosome pair. While, in other two varieties of C. winterianus (Bio-13 and Medini), this variability may be because of evolutionary speciation due to natural cross among two species of Cymbopogon which was fixed through clonal propagation. However, in both the situations these changes were fixed by vegetative method of propagation which is general mode of reproduction in the case of C. winterianus. [ABSTRACT FROM AUTHOR]