Botrytis cinerea infects many crops including potato and tomato. Major genes
for complete resistance to B. cinerea are not known, but a few quantitative
trait loci (QTL) have been described in tomato. Previous studies have also
proven that the loss of function of particular susceptibility (S) genes may
provide resistance to B. cinerea in Arabidopsis.

Kaile Sun Wageningen University & Research used RNAi to silence the
orthologs of Arabidopsis S genes DND1, DMR6, DMR1 and PMR4 in potato and the
DND1 ortholog in tomato. The DND1-silenced potato and tomato plants showed
significantly reduced B. cinerea leaf lesions as compared to control plants.
Reduced lesions were also observed on the leaves of DMR6-silenced potato
plants but only at 3 days after inoculation.

On the other hand, the DMR1 and PMR4-silenced potato transformants were
still susceptible to B. cinerea as the control plants. Microscopic analysis
in DND1-silenced potato and tomato leaves revealed that a significantly
lower number of B. cinerea conidia remained attached to the leaf surface of
the DND1-silenced potato and tomato plants. Moreover, the growth of the
hyphae was also hindered.

Silencing of DND1 led to reduced susceptibility to Botrytis, which was found
to be related to the impediment of conidial germination and attachment as
well as hyphae growth. These provide new insights regarding the use of S
genes in resistance breeding.



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