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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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Graft incompatibility of 3 chestnut Castanea spp. was studied. Nine American chestnut C. crenata Sieb. & Zucc and 15 Chinese chestnut C. mollissima Bl. cultivars used as scions were tested on rootstocks of Chinese chestnut. Interspecific grafts with 7 of 9 American chestnut selections had satisfactory graft compatibility on Chinese chestnut rootstocks (70%-100%), so did 6 of 8 Japanese chestnuts. Twelve and 10 out of 15 Chinese cultivars had high graft compatibility on Chinese chestnut rootstocks. Three Chinese cultivars with less than 50% success were probably due to very diverse genetic variation within one cultivar group of Chinese chestnuts. Spring grafts always had higher percent success rates than fall grafts. Graft incompatibility was not found to be related to the cambial isoperoxidase banding patterns in the present study.

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