Abstract
Grapevine (Vitis vinifera ssp. vinifera) is a major fruit crop with high economic importance. Due to its susceptibility towards fungal and oomycete pathogens such as Erysiphe necator and Plasmopara viticola, the causal agents of powdery and downy mildew (PM and DM, respectively), grapevine growers annually face a major challenge in coping with shortfalls of yield caused by these diseases. Here we report the confirmation of a genetic resource for grapevine resistance breeding against PM. During the delimitation process of Ren3 on chromosome 15 from the cultivar ‘Regent’, a second resistance-encoding region on chromosome 15 termed Ren9 was characterized. It mediates a trailing necrosis associated with the appressoria of E. necator and restricts pathogen growth. In this study, we confirm this QTL in a related mapping population of ‘Regent’ × ‘Cabernet Sauvignon’. The data show that this locus is located at the upper arm of chromosome 15 between markers GF15-58 (0.15 Mb) and GF15-53 (4 Mb). The efficiency of the resistance against one of the prominent European PM isolates (EU-B) is demonstrated. Based on fine-mapping and literature knowledge we propose two possible regions of interest and supply molecular markers to follow both regions in marker-assisted selection.
Highlights
The era of accelerated plant breeding started with the emergence of marker-assisted selection (MAS)
On ‘Regent’ the larger portion of germinated spores were accompanied by papilla formation (Figure 3C, ~30%). These results indicate that Ren3/Ren9 is capable of restricting the growth of the GF.En-01 isolate
For all R-loci combinations a significant reduction in hyphal growth compared to the susceptible controls could be observed at both four and six dpi (Figure 5). These results indicate that both resistance loci by themselves are capable to detect the EU-B powdery mildew (PM) isolate and inhibit its growth
Summary
The era of accelerated plant breeding started with the emergence of marker-assisted selection (MAS). To achieve effective plant protection for the highly PM and DM susceptible V. vinifera cultivars, fungicides such as the sulphur and copper compounds or other synthetic protectants have to be applied, depending on the environmental conditions, up to 12 times during the growing season [8] This makes viticulture one of the highest agricultural consumers of fungicides [9]. A reduced fungicide application may allow the other ascomycete diseases BR and AN to develop Resistance research on these pathogens is strongly required for breeders to identify new loci for MAS to solve this potentially upcoming problem [6]. For the two individuals carrying Ren, the median score was shifted to a score of two at the last date (Figure 1, 16-4)
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