Candidate resistance genes to foliar phylloxera identified at Rdv3 of hybrid grape

Authors: YIN, LU - University Of Minnesota; KARN, AVINASH - Cornell University; Cadle-Davidson, Lance; ZOU, CHENG - Cornell University; Londo, Jason; SUN, QI - Cornell University; CLARK, MATT - University Of Minnesota

Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2022
Publication Date: 2/19/2022
Citation: Yin, L., Karn, A., Cadle Davidson, L.E., Zou, C., Londo, J.P., Sun, Q., Clark, M. 2022. Candidate resistance genes to foliar phylloxera identified at Rdv3 of hybrid grape. Horticulture Research. https://doi.org/10.1093/hr/uhac027.
DOI: https://doi.org/10.1093/hr/uhac027

Interpretive Summary: Leaves of the native grape species Vitis riparia and certain cold-hardy grape varieties are particularly susceptible to the insect pest phylloxera. A previous study detected a genetic region for foliar phylloxera resistance on chromosome 14, but this region was too wide for effective marker-assisted selection for this trait. Therefore, here we used a larger grape family of 1023 progeny. In the greenhouse, we rated phylloxera severity on 188 progeny that had genetic crossovers on chromosome 14 in three experiments. DNA marker analysis in the first two experiments indicated that resistance was in a region with 158 genes that have biological functions such as flowering, oxidative stress, systemic acquired resistance, and sugar transport. The DNA markers can be used for future marker-assisted breeding. In the third experiment, we narrowed the resistance to a DNA marker that coincides with a gene involved in gallic acid synthesis, which is important in phylloxera gall formation. This may suggest that resistant vines do not respond to attempted gall formation, unlike a traditional hypersensitive resistance, but more conclusive studies are needed. This study will help grape breeders develop varieties with foliar phylloxera resistance and will help scientists to understand the genetics of resistance to gall-forming insects.

Technical Abstract: The foliage of the native grape species Vitis riparia and certain cold-hardy interspecific hybrid grapes are particularly susceptible to the insect pest phylloxera, Daktulosphaira vitifoliae Fitch. A previous study using a cold-hardy hybrid grape biparental F1 population (N~125) detected the first quantitative trait locus (QTL) for foliar resistance on chromosome 14. This region spans a 10-20 cM (~7 Mbp) region and is too wide for effective marker-assisted selection for this trait or identification of candidate genes. Therefore, we fine mapped the QTL using a larger F1 population, GE1783 (N~1023), and genome-wide rhAmpSeq haplotype markers. Through three selective phenotyping experiments replicated in the greenhouse, we screened 188 potential recombinants of GE1783 using a 0 to 7 severity rating scale among several other phylloxera severity traits. A fine mapped region spanning from 2.1 to 4.9 Mbp on chromosome 14 was identified with the rhAmpSeq marker 14_4805213 being most closely linked to this trait; this and flanking markers can be used for future marker-assisted breeding. This region contains 158 candidate genes that have annotated biological functions such as flowering, oxidative stress, systemic acquired resistance, and sugar transport. The candidate resistance gene associated with the marker 14_4805213, bifunctional 3-dehydroquinate dehydratase/shikimate dehydrogenase, plays a role in gallic acid biosynthesis which is important in phylloxera gall formation. This may suggest a non-responsiveness role underlying the resistance gene, unlike a traditional hypersensitive response, but more conclusive studies are needed. This study has implications for improvement of foliar phylloxera resistance in cold-hardy hybrid germplasm and is a starting place to understand resistance gene functions in response to gall-forming insects.