Genetic Engineering of the Self-Incompatibility Mechanism in 'Elstar' Apple Leads to Distinct Levels of Self-Fertility

The apple cultivar 'Elstar' (S-RNase genotype S3S5) was transformed with TDNA constructs containing the S3-RNase cDNA in anti-sense orientation. The resultant transgenic lines were screened for their ability to set fruit following selfpollination under controlled greenhouse conditions and results compared to previous work on lines containing a full length sense S3-cDNA T-DNA construct. Detailed molecular and physiological analysis identified 12 lines with a stable, altered SI-phenotype. In all 12 lines complete S3 S-RNase gene silencing, and partial S5 S-RNase silencing significantly modified the self-incompatibility behaviour of the plant, leading to either intermediate or complete self-fertility. Interestingly, the intermediate self-fertile phenotype appeared to be due to a slower growth rate of 'self' pollen tubes and was only observed in a subset of lines that were generated using the 3' end of the S3-cDNA in anti-sense orientation. For as yet unknown reasons, the SI-reproductive barrier remains partially active in this subset of lines. We also demonstrated that transgenic S-silenced lines can still display fruit set in the absence of any active pollination vector. Overall, our data demonstrate that SRNase-silenced apple trees displaying a range of self-fertile phenotypes represent a powerful tool to help understand the biological implications of the removal of the GSI reproductive barrier and the possible impact of this technology on hard fruit production.

ISBN:9789066056558

Publication year:2012

BOF-keylabel:yes

IOF-keylabel:yes

Authors from:Higher Education