Intergeneric hybridization between Erucastrum canariense and Brassica rapa. Genetic relatedness between EC and A genomes

Abstract

An intergeneric hybrid between a wild species, Erucastrum canariense (2n = 18; E(C)E(C)), and a cultivated oilseed brassica species, Brassica rapa (2n = 20; AA), was synthesized through ovary culture in White's basal medium supplemented with casein hydrolysate. Morphological, cytological and DNA-based analysis helped to establish the hybrid nature of the derived plants. Hybrid plants were morphologically intermediate between the two parents and were completely male, as well as female sterile. Cytological analysis revealed the occurrence of 19 I in about 38% of the PMCs investigated. However 1-8 bivalents/PMC were also observed, indicating a significant level of homology between the two genomes. Normal chromosome pairing and pollen fertility was restored following colchiploidy. The intergeneric amphiploid developed during the investigation can be used as a bridging species for the transfer of desirable genes from E(C) to cultivated genomes (especially A and C), and for resistance to Alternaria blight and mustard aphid. Under field conditions, the E. canariense intergeneric hybrid and the amphiploid appeared to be moderately resistant to Alternaria blight and also harboured a significantly lower population of mustard aphid than the cultivated B. rapa.

Intergeneric hybridization between Erucastrum cardaminoides and two diploid crop Brassica species

“…This became apparent from the demonstration of homology between the A/C Brassica genomes with the E c genome of E. canariense (Harberd and McArthur 1980;Bhaskar et al 2002) and with the E a genome of E. abyssinicum (Harberd and McArthur 1980). To further enlarge the scope of gene introgression from Erucastrum, we synthesized two intergeneric hybrids between B. rapa/B.…”

“…The family Brassicaceae comprises a large number of wild and weedy plants which are excellent repositories of genes for many economically important traits, especially for tolerance to environmental stresses, and novel seed storage products. Therefore, the bringing together of the diverse genomes in wide crucifer hybrids (Bhaskar et al 2002;Banga et al 2003a) has not only provided an access to a range of potentially beneficial genetic or cytoplasmic variation but has also allowed the establishment of genomic affinities through study of homoeologous pairing between two sets of differentiated genomes. Many primitive species have been used for synthesizing new intergeneric hybrids/ amphiploids (Sareen et al 1992;Bhaskar et al 2002, Banga et al 2003a following hybridization with crop Brassica species.…”

“…Therefore, the bringing together of the diverse genomes in wide crucifer hybrids (Bhaskar et al 2002;Banga et al 2003a) has not only provided an access to a range of potentially beneficial genetic or cytoplasmic variation but has also allowed the establishment of genomic affinities through study of homoeologous pairing between two sets of differentiated genomes. Many primitive species have been used for synthesizing new intergeneric hybrids/ amphiploids (Sareen et al 1992;Bhaskar et al 2002, Banga et al 2003a following hybridization with crop Brassica species. A number of alloplasmic male sterility systems have also been bred by exploiting the cytoplasmic diversity available in these primitive species (Prakash 2001;Banga et al 2003b).…”

“…Amplifications were performed in a MJ Research PTC 200 thermal cycler (MJ Research, Waltham, Mass.) using the method described by Bhaskar et al (2002). The amplified products were separated by electrophoresis on a 1.5% agarose gel in 1 TBE buffer and stained with 10 ppm ethidium bromide.…”

Synthesis of intergeneric hybrids and establishment of genomic affinity between Diplotaxis catholica and crop Brassica species

“…For ovary culture, pistils were excised 2-3 days after pollination (DAP), surface sterilized with mercuric chloride (0.01%) and cultured on Murashige and Skoog's (MS) medium containing 5% sucrose, 0.8% agar and 500 mg/l of casein hydrolysate. Cultures were maintained at 25 € 2 C under a 16-h light (2,000 lux)/8-h dark cycle as described earlier (Bhaskar et al 2002). The seeds were excised aseptically, from 20 to 25 day-old cultured ovaries and cultured on the MS medium.…”