Mutation based approaches for functional genomics and trait development in vegetatively propagated plants

Natural and induced mutations represent powerful tools for validating gene function and generating novel crop traits. The reverse-genetic strategy known as TILLING has been applied to a large number of seed propagated plants. Genetic bottlenecks exist, however, for vegetatively propagated species where meiosis rarely, if ever, occurs. We have used triploid banana as a model for obligate vegetatively propagated plants to evaluate the induction, heritability, density and spectrum of induced mutations. A high density of heterozygous SNP mutations were recovered in EMS mutagenized banana, as expected for a triploid species. Analysis of mutation inheritance has provided insights into diplontic selection of meristematic cells after mutagenesis. We also observed a high rate of morphological variation that is greater than expected based on gene function predictions of induced and natural heterozygous polymorphisms found in the genome. In parallel, an Ecotilling platform has been developed for the efficient recovery of nucleotide polymorphisms in diploid and polyploid accessions of the genus Musa (banana and plantain). A core germplasm collection has also been evaluated for response to drought conditions. Similar work is being carried out for facultative vegetatively propagated crops such as cassava where chemical and physical mutagens have been used to develop TILLING populations. To establish an efficient Ecotilling platform for Jatropha curcas, a sample pooling strategy was employed to capture rare nucleotide variation. The collective research suggests that efficient strategies for mutation induction, reverse-genetics and germplasm characterization can be developed for a range of clonally propagated plants.