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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING GRAPE ROOTSTOCK AND SCION PEST AND DISEASE RESISTANCE
2010 Annual Report


1a.Objectives (from AD-416)
1. Develop improved genetic systems for functional genomics research of grape pest and disease resistance. 2. Characterize the genetic, genomic, proteomic, and other aspects of the interaction of grapevines and fungal and oomycete pathogens to identify the key determinants of resistance, tolerance, and susceptibility. 3. Improve grapevine rootstocks through identification, development, deployment, and enhancement of resistance to pests and diseases.


1b.Approach (from AD-416)
Develop a grapevine system with reduced juvenile period for rapid candidate gene evaluation of disease and pest resistance. Optimize and evaluate the utility of a newly created dwarf grapevine system for investigating interactions between grapevines and key pests and pathogens. Determine race-specificity of powdery mildew resistance in Vitis species. Develop molecular markers associated with resistance to grape powdery mildew. Characterize the relationship between biochemical changes in the berry-powdery mildew interface and developmentally-regulated resistance to powdery mildew on grape berries. Enhance non-race-specific resistance in Vitis vinifera to powdery mildew and/or downy mildew via knock-out of susceptibility loci. Characterize the genetic control of resistance to Meloidogyne species (root-knot nematodes) in grapevine. Develop molecular markers associated with resistance to root-knot nematodes. Develop grape rootstocks with enhanced resistance to root-knot nematodes. Evaluate the ability of rootstocks to mitigate symptoms of Pierce’s disease in grapevine rootstocks. Develop autotetraploid selections with reduced vigor induction and evaluate their pest resistance.


3.Progress Report
To develop new cultivars with disease resistance to powdery mildew and downy mildew, we germinated 3000 seeds from 13 independent hybridizations for evaluation of disease resistance.We analyzed the genome of the powdery mildew pathogen and identified genes required for virulence and sporulation. Functional analysis of these genes enables the development of novel disease management strategies that target the weaknesses of the pathogen.

We identified eleven easily propagated, nematode resistant rootstock selections that can provide an alternative to methyl bromide fumigation. In order to identify these candidate rootstocks, we tested the propagation ability of 190 selections and 176 selections showed that they are easily propagated. 80 selections were retested to confirm nematode resistance in replicated trials.

An optimized hairy-root induction system was established and will be used as a high through-put system for evaluating nematode resistance genes in grape, overcoming limitations of the conventional rootstock breeding. We characterized the responses of 14 grape species to the inoculation of 3 Agrobacterium strains and observed that plant genotypes and inoculation sites significantly impacted the success hairy root induction.

In order to develop a small, rapid cycling, and easily transformed grapevine variety, we introduced several plant-growth related into grapevines to see how these genes might affect plant architecture and growth cycle. We observed that these genes had significant impact on plant heights, branching and other growth traits. This knowledge will help us design a better strategy for creating a new grapevine variety for functional genomics research.

Grapevine seedlings often do not flower until after several seasons. We showed inheritance of precocious flowering of interspecific hybrid populations of grapevine seedlings. The hybrid grapevine seedlings flowered precociously within four months; they did not receive chilling hours or dormancy, typically required for regular flowering in mature grapevines. We have now shown multiple generations of inheritance of precocious flowering. Seedlings of crosses of select precocious and continuously reblooming parents to rootstock and wine grape varieties show precocious flowering, indicating broad application of this source of precocious flowering in developing model grapevine varieties for research.

To identify the genetic control of resistance against aggressive root-knot nematodes, the allelism of a putative new allele for resistance inherited from Vitis cordifolia was tested to determine its relationship to the N allele. Based on progeny testing, the novel allele from V. cordifolia is not allelic to the N allele. The independent assortment of resistance alleles indicates that the N allele and the V. cordifolia allele represent forms of different genes. The V. cordifolia allele provides protection to a broader range of nematodes than does the N allele and is deployed in resistant rootstock selections. Determination of the non-allelic nature of the N and the V. cordifolia allele will facilitate breeding improved rootstocks and gene pyramiding to enhance resistance durability


4.Accomplishments
1. Accelerating introduction of powdery mildew resistant table, raisin, and wine grape cultivars through marker assisted selection. New cultivars with powdery mildew resistance are desired by grape growers, but durability of this resistance is critical due to the cost of vineyard establishment and the necessary longevity of grapevines. ARS Researchers at Geneva, New York successfully documented that some resistances in breeding programs could be overcome quickly by common pathogen isolates and communicated a need for breeders to pyramid multiple resistance genes in new cultivars. We are applying molecular markers to track these resistance genes and further the development of varieties with multiple resistance gene durability. Further, we identified a source of powdery mildew resistance that prevents the pathogen penetration and appears to be durable by itself. We are using molecular markers to track the introgression of this resistance gene into high quality raisin, table, and wine grapes. Varieties bred with broad spectrum powdery mildew resistance would save growers between $100 to 400 per acre per year in pesticide costs and reduce direct and indirect effects of pesticide application. 301 2 B 2006 301 2 C 2006 301 3 B 2006 301 3 C 2006 303 3 A 2006


Last Modified: 12/19/2014
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