Oral or poster presentation at XII International Conference on Grapevine Breeding and Genetics, 15-20 Jul, 2018
Abstract
Salinity is a serious challenge facing viticulture, and is caused by high sodium and chloride concentrations in soils and irrigation water. Vitis vinifera is moderately sensitive to salinity, especially to chloride. Excessive chloride reduces vine water uptake, causes plant growth inhibition, leaf burn and vine death. These challenges can be minimised using chloride excluding rootstocks, but further investigations are required to uncover the genetic mechanisms contributing to this phenotype. VviALMT2 was more highly expressed in the good chloride excluder 140-Ruggeri than in the poor excluder K51-40. Gene expression analyses and in vitro functional assays were conducted to evaluate whether this candidate gene has a role in grapevine salt tolerance. Two electrode voltage clamping using Xenopus laevis oocytes expressing ALMT2 showed that it is a low affinity nitrate (NO3−) transporter which also transports Cl− and several organic acids. VviALMT2 promoter driven GFP and GUS activities in Arabidopsis roots and RT-qPCR results on grapevine root stelar and cortex fractions suggest that ALMT2 is most highly expressed in root stele, and also expressed in endodermal passage cells and cortex, which suggests that ALMT2 may have roles in anion loading from root to shoot. Expression levels of ALMT2 responded to NO3− starvation and resupply in grapevine roots; however, its expression did respond to 25 mM Cl− stress. This evidence suggested that, rather than directly excluding chloride, ALMT2 may contribute to maintaining a higher NO3−/Cl− ratio in the xylem, hence contributing to grapevine’s chloride tolerance. Further experiments will measure the phenotypes of a VviALMT2 Arabidopsis stelar over-expression line under salt stress and different NO3− treatments, and the results may help to develop genetic markers for salt tolerant grapevine breeding.
Summary
Oral or poster presentation at XII International Conference on Grapevine Breeding and Genetics, 15-20 Jul, 2018