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  • Author or Editor: G.E. Boyhan x
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In an anthracnose [Colletotricum obiculare (Berk. & Mont.) Arx.] screening test of 76 plant introductions (PIs), commercial Chinese watermelons [Citrullus lanatus (Thunb.) Matsum. & Nakai], and `Crimson Sweet', PI 512385 had the highest disease resistance with a mean rating of 4.5 (1= resistant, 9 = susceptible). In a second test with PI 512385, which included material with previously reported resistance (PIs 270550,326515, 271775,271779,203551, 299379, and 189225), and `Crimson Sweet' (susceptible control), PI 512385 had significantly higher resistance than `Crimson Sweet' but was not significantly more resistant than the other PIs evaluated. PI 512385 had a mean rating of 2.2 in the second test.

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Forty eight cultivars, species, and their progeny including Prunus americana P. angustifolia, P. cerasifera P. munsoniona, P. salicina, P. simoni, and P. triflora were evaluated for resistance to Xylella fastidiosa based on percent of scalded leaves and tree longevity. Observations indicate that resistance is heritable and controlled by recessive genes. Further, X. fastidiosa transmission was evaluated in plum and peach by chip and slip budding. Transmission as measured by enzyme-linked immunoabsorbant assay indicated that chip budding resulted in a higher level of transmission over slip budding in plum but not in peach. Neither Lovell nor Nemaguard rootstock had an effect on transmission.

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Detection of Xylella fastidiosa Wells et al. by enzyme-linked immunosorbent assay indicated that plums (Prunus hybrids) had higher absorbance values than peaches [Prunus persica (L.) Batsch]. The slip-budded trees had lower readings than those that were chip budded; however, the scion × method interaction was significant. Further comparison of slip vs. chip budding indicated that the lower absorbance value of slip budding occurred in plums only; there was no difference between budding methods in peach.

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Certified organic production is challenging in the southeastern United States due to high weed, insect, and disease pressure. Maintaining and building soil organic carbon in midscale organic production systems can also be difficult due to the warm, moist conditions that promote decomposition. Focusing on cool-season cash crops paired with warm-season cover crops may help alleviate these production problems. This 3-year study (2011–13) evaluated two vegetable rotations of cool-season crops with cover crops for their productivity, disease management, and soil building potential in Watkinsville, GA. In the first rotation, cool-season cash crops included onion (Allium cepa), strawberry (Fragaria ×ananassa), and potato (Solanum tuberosum). These crops were rotated with green bean (Phaseolus vulgaris), oats/austrian winter pea (Avena sativa/Pisum sativum ssp. arvense), southernpea (Vigna unguiculata), and sunn hemp (Crotalaria juncea). In the second rotation, cool-season cash crops included onion, broccoli (Brassica oleracea Italica group), lettuce (Lactuca sativa), and carrot (Daucus carota ssp. sativus). These were rotated with millet (Urochloa ramosa), sunn hemp, egyptian wheat/iron clay pea (Sorghum sp./Vigna unguiculata), and sorghum × sudangrass (Sorghum bicolor × S. bicolor var. sudanese)/iron clay pea. Onion yields in both rotations were at least 80% of average yields in Georgia. Lettuce yields were at least double the average yields in Georgia and were comparable to national averages in the 2nd and 3rd years of the study. Strawberry yields in these rotations were lower than Georgia averages in all 3 years with a trend of lower yields over the course of the study. By contrast, potato, although lower than average yields in Georgia increased each year of the study. Broccoli yields in the first year were substantially lower than average Georgia yields, but were comparable to average yields in the 2nd year. Carrot remained less than half of average Georgia yields. Green bean were half of average Georgia yields in the 2nd year and were comparable to average yields in the 3rd year. As expected from what is observed in cool-season organic vegetable production in Georgia, disease pressure was low. Cover crops maintained soil organic carbon (C) with a small increase in active C; however, there was a net loss of potentially mineralizable nitrogen (PMN). Active C averaged across both rotations at the beginning of the study at 464 mg·kg−1 and averaged 572 mg·kg−1 at the end of the study. On the basis of this study, using cover crops can maintain soil carbon without the addition of carbon sources such as compost. Finally, longer term work needs to be done to assess soil management strategies.

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