Naturally occurring broad-spectrum powdery mildew resistance in a central American tomato accession is caused by loss of Mlo function

作者：Bai Yuling^*; Pavan Stefano; Zheng Zheng; Zappel Nana F; Reinstaedler Anja; Lotti Concetta; De Giovanni Claudio; Ricciardi Luigi; Lindhout Pim; Visser Richard; Theres Klaus; Panstruga Ralph

来源：Molecular Plant-Microbe Interactions, 2008, 21(1): 30-39.

DOI：10.1094/MPMI-21-1-0030

• comparative genetics
• co-orthologs
• introgression lines
• pleiotropic effects

The resistant cherry tomato (Solanum lycopersicum var. cerasiforme) line LC-95, derived from an accession collected in Ecuador, harbors a natural allele (ol-2) that confers broad-spectrum and recessively inherited resistance to powdery mildew (Oidium neolycopersici). As both the genetic and phytopathological characteristics of ol-2-mediated resistance are reminiscent of powdery mildew immunity conferred by loss-of-function mlo alleles in barley and Arabidopsis, we initiated a candidate-gene approach to clone Ol-2. A tomato Allo gene (SlMlo1) with high sequence-relatedness to barley Mlo and Arabidopsis AtMLO2 mapped to the chromosomal region harboring the Ol-2 locus. Complementation experiments using transgenic tomato lines as well as virus-induced gene silencing assays suggested that loss of SlMlo1 function is responsible for powdery mildew resistance conferred by ol-2. In progeny of a cross between a resistant line bearing ol-2 and the susceptible tomato cultivar Moneymaker, a 19-bp deletion disrupting the SlMlo1 coding region cosegregated with resistance. This polymorphism results in a frameshift and, thus, a truncated nonfunctional SlMlo1 protein. Our findings reveal the second example of a natural mlo mutant that possibly arose post-domestication, suggesting that natural mlo alleles might be evolutionarily short-lived due to fitness costs related to loss of mlo function.

• 出版日期2008-1