Location: Southern Horticultural Research
Project Number: 6062-21000-010-11-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 30, 2018
End Date: Sep 30, 2020
1) Examine the response of different Vaccinium species accessions to high soil pH and develop low-cost high throughput phenotyping protocol to screen germplasm for tolerance to high soil pH. 2) Measure the population of Xylella (X.) fastidiosa in stem internode of 98 accessions of muscadine and bunch grapes using the double antibody sandwich enzyme-linked immunosorbent assay (ELISA) and examine the correlation between the disease symptoms and the population of X. fastidiosa.
(i) About 166 accessions of highbush blueberry (Vaccinium (V.) corymbosum L. 2n=4X=48), three accessions of each of V. darrowii (2n = 2x = 24), V. tenellum Aiton (2n = 2x = 24), V. myrsinites Lam. (2n = 4x = 48), V. arboreum (2n = 2x = 24), V. elliottii (2n = 2x = 24), V. stamineum (2n = 2x = 24), V. pallidum (2n = 2x = 24), and V. virgatum (2n = 6x = 72) will be tested in alkaline soil with pH of 7.5 at Mississippi State University, Starkville, Mississippi, and in soil with pH of 5 at Poplarville, Mississippi. Shoot and root fresh weight, and tissue nutrient concentrations (mg nutrient/g tissue) of Fe and Mn will be taken for each accession. In addition, change in chlorophyll content for each accession will be monitored using GreenSeekerTM handheld crop sensor. The significance of accessions will be examined using analysis of variance (ANOVA) in SAS (SAS Institute, Cary, North Carolina, USA). Tolerance will be defined as the ability of a genotype to produce non-significant reduction in chlorophyll content, Fe and Mn concentrations, shoot and root fresh weight when grown under optimum and high soil pH. Trait(s) found to be associated with high pH tolerance will be used as breeding tools to select for high pH tolerance. (ii) The two resistant cultivars ‘Southern Home’, and ‘Noble’, the two tolerant cultivars ‘Carlos’ and ‘Pride’, and 94 muscadine and bunch grapes accessions will be utilized to in this study. Potted plants of each of these accessions will be inoculated with Xylella (X.) fastidiosa (Krivanek et al. 2005) and maintained at the growth chamber. Twelve weeks post-inoculation, samples will be collected from the stem internode of inoculated and non-inoculated plants to verify the infection with X. fastidiosa. In addition, samples from the 42 cultivars and 18 breeding selections planted in three replicates at McNeill research farm, McNeill, Mississppi, (Stringer et al. 2008) will be collected from late summer from PD-positive plants. PCR and enzyme-linked immunosorbent assay (ELISA) will be used to verify the infection with X. fastidiosa as previously described by Krivanek et al. (2005). Cane maturation index (CMI) (0 to 6 scale) will be used to discriminate between resistant and susceptible accessions (Krivanek et al. 2005). Logistic regression analysis and correlation coefficient values will be used to examine the relationship between CMI score and the mean concentration of X. fastidiosa (Krivanek and Walker 2005)