Forty eight cultivars and seedlings of plum involving the species Prunus americana, P. auqustifolia, P. cerasifiera, P. munsoniana, P. salicina, P. simoni, and P. triflora were evaluated for the presence of xylem limiting bacteria (Xyllela fastidiosa) and tree longevity. Plum leaf scald (PLS) ratings, based on the percent of scalded leaves in the tree were correlated with the concentrations of bacteria in the twigs and leaf petioles. Observations of symptoms of PLS and monitoring of progeny from interspecific crosses, cultivars, and seedlings indicate that resistance to the PLS organism is present in the Auburn material and heritable. Uniform infection of seedlings was made by double budding of one year whips with buds from infected trees. Resistance to PLS has been incorporated into horticultural types and seedlings are currently being evaluated for possible release for commercial and home use.
J.D. Norton, G.E. Boyhan, and B.R. Abrahams
J. D. Norton, G. E. Boyhan, and B. R. Abrahams
Plum production in the Southeastern United States is limited because cultivars are susceptible to bacterial canker (Pseudomonas syringae), bacterial fruit and leaf spot (Xanthomonas pruni), black knot (Apisporina morbosa) and plum leaf scald (Xylella fastidiosa). Evaluation of four new cultivars developed by the Alabama Agricultural Experiment Station indicated that AU-Rubrum, AU-Rosa and AU -Cherry were resistant to all the diseases listed, and AU-Amber was resistant to all excapt A. morbosa. Disease ratings were made on trees in six experimental plantings in Alabama, in Georgia test plantings and in grower trials.
J.D. Norton, G.E. Boyhan, and B.R. Abrahams
Disease is a major factor limiting production of watermelons in Alabama. Gummy stem blight, anthracnose, and Fusarium wilt are three of the most serious diseases, causing reduced yields of melons in certain fields in Alabama. Although satisfactory control of gummy stem blight and anthracnose may be accomplished with the proper application of organic fungicides during normal weather conditions, no control measure is effective during periods of high humidity and high rainfall. The discovery that certain plant introductions were resistant to gummy stem blight and race 2 anthracnose led to development of multiple disease resistant breeding lines that produce high yields of excellent quality fruit. This research resulted in the 1991 release of AU-Golden Producer and Au-Sweet Scarlet varieties that are resistant to gummy stem blight, Fusarium wilt, and anthracnose (Colletotrichum laginarium race 2). Both melons are superior to current varieties of their type in yield, quality, and disease resistance.
G.E. Boyhan, J.D. Norton, B.R. Abraham, and J.A. Pitts
G.E. Boyhan, B.R. Abrahams, J.D. Norton, and Hongwen Huang
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.
J. D. Norton, C. E. Boyhan, Hongwen Huang, and B. R. Abrahams
On March 13-15, 1993 Alabama and much of the eastern United States experienced an unusually severe winter storm. This afforded the evaluation of plum cultivar production under cold stress. The highest yielding variety that bloomed before the storm was Bruce 12-4 with 28 kg/tree. Bruce 12-4 is noted for blooming over an extended period of time and producing very heavy yields. The average yield of the top five performers that bloomed after the storm was 51 kg/tree. The lowest temperature recorded at the test site, Shorter, AL was -5C.
J.D. Norton, G.E. Boyhan, D.A. Smith, and B.R. Abrahams
G.E. Boyhan, J.D. Norton, B.R. Abrahams, and H.H. Wen
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.