Asymmetry in Somatic Hybrids for Gene Transfer, Intertribal Somatic Hybrids, Chromosome Number, Erucobrassica, Moricandiobrassica, Sirodesmin, Blackleg

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Home >> Plant Biotechnology and Genomics >> Protoplast Culture Regeneration and Somatic Hybridization >> Asymmetry in Somatic Hybrids for Gene Transfer

Asymmetry in somatic hybrids for gene transfer

As discussed above, in many somatic hybrids, the chromosome number has been found to be abnormal, often fewer than expected. For instance, in Erucobrassica about 60% plants had fewer than the expected chromosome number.

Variability was also observed in Moricandio-brassica and other hybrids. In many of these cases, chromosomes are eliminated or translocated thus facilitating limited alien gene transfer.

An important example of the use of such asymmetric hybrids in gene transfer, is the transfer of black-leg resistance to rapeseed.

The disease black-leg, caused by the fungus Phoma lingam, is world-wide problem for agricultural production of rape seed and turnip rape.

Fungal mycelia enter into stem, such that stem rots and plant dies by wilting. A toxin (Sirodesmin PI) isolated from fungus can be used to select resistant material.

To promote limited gene transfer, resistant donor lines were irradiated prior to fusion and hybridization, causing fragmentation and elimination of chromosomes, thus facilitating integration of resistance gene into the recipient line.

The fusion products were allowed to develop into colonies and then exposed to selective toxin. Caili resistant to toxin were regenerated into plants and tested for resistance. Most of these plants exhibited resistance suggesting transfer during somatic hybridization.

Transfer of Resistance of Phoma Lingam in Susceptible plants
culture of Phoma lingam		culture filtrate fractionation
	culture of hybrid cells (heterokaryons)
fusion products		this promotes transfer of limited genome
	protoplasts

recipient plant susceptible to phoma lingam		donor plant resistant to phoma lingam	resistant asymmetric hybrid plant

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