Abstract
Bacterial wilt (BW) caused by Ralstonia solanacearum is responsible for substantial losses in cultivated potato (Solanum tuberosum) crops worldwide. Resistance genes have been identified in wild species; however, introduction of these through classical breeding has achieved only partial resistance, which has been linked to poor agronomic performance. The Arabidopsis thaliana (At) pattern recognition receptor elongation factor-Tu (EF-Tu) receptor (EFR) recognizes the bacterial pathogen-associated molecular pattern EF-Tu (and its derived peptide elf18) to confer anti-bacterial immunity. Previous work has shown that transfer of AtEFR into tomato confers increased resistance to R. solanacearum. Here, we evaluated whether the transgenic expression of AtEFR would similarly increase BW resistance in a commercial potato line (INIA Iporá), as well as in a breeding potato line (09509.6) in which quantitative resistance has been introgressed from the wild potato relative Solanum commersonii. Resistance to R. solanacearum was evaluated by damaged root inoculation under controlled conditions. Both INIA Iporá and 09509.6 potato lines expressing AtEFR showed greater resistance to R. solanacearum, with no detectable bacteria in tubers evaluated by multiplex-PCR and plate counting. Notably, AtEFR expression and the introgression of quantitative resistance from S. commersonii had a significant additive effect in 09509.6-AtEFR lines. These results show that the combination of heterologous expression of AtEFR with quantitative resistance introgressed from wild relatives is a promising strategy to develop BW resistance in potato.
Highlights
Bacterial wilt (BW) caused by Ralstonia solanacearum is considered as one of the most destructive bacterial diseases of plants (Mansfield et al, 2012)
We evaluated the effect of AtEFR gene expression in a commercial potato line (INIA Iporá) and in an interspecific breeding line (09509.6), into which quantitative resistance to BW from the wild relative S. commersonii has been introgressed
The effect of the expression of AtEFR in potato on BW resistance was evaluated in two different genetic backgrounds: a commercial susceptible variety Institute for Agricultural Research (INIA) Iporá and a breeding clone 09509.6 that has partial BW resistance
Summary
Bacterial wilt (BW) caused by Ralstonia solanacearum is considered as one of the most destructive bacterial diseases of plants (Mansfield et al, 2012). R. solanacearum is able to persist in soil, weed, plant debris, rhizospheres, and alternate hosts. R. solanacearum generally enters through wounded roots or natural openings and it infects the intercellular space of the root cortex and vascular parenchyma. It can invade xylem vessels and disseminate to the stem and leaves, where bacterial cell density can reach up to 109 cfu·g−1 of host tissue (Yao and Allen, 2006; Álvarez et al, 2010). A cell density-dependent (i.e., quorum sensing) conversion occurs from a motile phenotype to a non-motile virulent phenotype, adapted to a plant parasitic lifestyle (Tans-Kesrten et al, 2004)
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