Abstract
Apple scab resistance genes, HcrVf1 and
HcrVf2, were isolated including their native promoter,
coding and terminator sequences. Two fragment lengths
(short and long) of the native gene promoters and the
strong apple rubisco gene promoter (PMdRbc) were used for
both HcrVf genes to test their effect on expression and
phenotype. The scab susceptible cultivar ‘Gala’ was used
for plant transformations and after selection of transformants,
they were micrografted onto apple seedling rootstocks
for scab disease tests. Apple transformants were also
tested for HcrVf expression by quantitative RT-PCR (qRTPCR).
For HcrVf1 the long native promoter gave significantly
higher expression that the short one; in case of
HcrVf2 the difference between the two was not significant.
The apple rubisco gene promoter proved to give the highest
expression of both HcrVf1 and HcrVf2. The top four
expanding leaves were used initially for inoculation with
monoconidial isolate EU-B05 which belongs to race 1 of
V. inaequalis. Later six other V. inaequalis isolates were
used to study the resistance spectra of the individual HcrVf
genes. The scab disease assays showed that HcrVf1 did not
give resistance against any of the isolates tested regardless
of the expression level. The HcrVf2 gene appeared to be
the only functional gene for resistance against Vf avirulent
isolates of V. inaequalis. HcrVf2 did not provide any
resistance to Vf virulent strains, even not in case of overexpression.
In conclusion, transformants carrying the
apple-derived HcrVf2 gene in a cisgenic as well as in an
intragenic configuration were able to reach scab resistance
levels comparable to the Vf resistant control cultivar
obtained by classical breeding, cv. ‘Santana’.
Original language | English |
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Pages (from-to) | 579-591 |
Journal | Plant Molecular Biology |
Volume | 75 |
Issue number | 6 |
DOIs | |
Publication status | Published - 2011 |
Keywords
- receptor-like genes
- real-time pcr
- venturia-inaequalis
- vf gene
- plants
- sequences
- agrobacterium
- promoters
- linkage
- cluster