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  • Author or Editor: J.D. Norton x
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Abstract

Resistance of muskmelon (Cucumis melo L.) to low levels of pickleworm (Diaphania nitidalis [Stoll]) was heritable whether expressed as percent damaged fruit or number of punctures per damaged fruit.

Open Access

The genetic diversity within and between geographic populations of the American chestnut tree was evaluated with allozyme and RAPD markers. Winter dormant or mature shoot buds from American chestnut trees collected in Alabama, Georgia, North Carolina, Virginia, Pennsylvania, Ohio, Michigan, and Connecticut were used for isozyme assays. Genetic diversity statistics calculated for 20 isozyme loci indicated that the highest level of heterozygosity was detected in the Alabama and Connecticut populations, the lowest level in the Great Smoky Mountain populations. RAPD analyses were conducted on American chestnut plant material. The best results were obtained with seed tissue. Seed from New York, Virginia, and Pennsylvania populations and buds from Alabama and Georgia populations were evaluated for RAPD markers scattered throughout the chestnut genome.

Free access

Abstract

A high level of resistance to the cowpea strain of bean yellow mosaic virus (BYMV-CS) in southern pea, Vigna sinensis, was found in P.I. 297562. Its mode of inheritance was determined in crosses with 3 susceptible cvs.: Knuckle Purple Hull, Mississippi Silver, Princess Anne, and an Alabama breeding line, Ala. 562.3-1-2.

Results of virus inoculation tests of F1, F2 and backcross populations showed that resistance in P.I. 297562 was governed by a single recessive gene pair. The high level of resistance of P.I. 297562 should prove valuable for breeding and development of resistant cultivars.

Open Access

The dwarfing characteristics of St. Julien and Pixy rootstocks, measured by shoot growth, were evident with `AU-Amber' and `AU-Producer' plum (Prunus salicina Lindl.) scions. Dwarfing did not occur with `AU-Rubrum'. Trunk cross-sectional area (TCA) was reduced with `AU-Amber', `AU-Producer', and `AU-Rubrum' scions on St. Julien and Pixy rootstocks. After 3 years, tree survival was 94% for Lovell; 89%, Halford; 57%, Nemaguard; 75%, Nemared; 83%, St. Julien; and 47%, Pixy. Tree survivability was significantly lower on Nemaguard and Pixy rootstocks than on Lovell and Halford. Multiple regression of total shoot growth, TCA, and survivability against foliar nutrient content resulted in the following significant equations: 0.460Mg - 0.210Mn, 0.236B - 0.487Mn, and 0.359N + 0.398Ca - 0.267P - 0.360Fe for each, respectively. Growth, survivability, and foliar nutrient content are significantly affected by rootstock in plum production.

Free access

The dwarfing characteristics of St. Julien and Pixy rootstocks as measured by shoot growth and trunk cross-sectional area (TCSA) was evident. Tree survival was significantly reduced after 3 years on Nemaguard and Pixy rootstocks. None of the elements measured by foliar nutrient analysis were below the minimum for plums; however, significant multiple regression equations for total shoot growth, TCSA, and survivability were evident with R 2 of ≈0.30 in all three cases.

Free access

Plum leaf scald (PLS) caused by the organism Xylella fastidiosa is one of the most serious diseases of plum. After X. fastidiosa was identified as the causal agent for PLS, a feral source (Starcher no. 1) was used extensively in the breeding program. Microscopic (phase contrast) examinations of vacuum extracts and petiole squashes and later ELISA were used to determine PLS infection and later were correlated with a rating index for PLS and tree longevity. Cultivars, species, and their progeny, including Prunus americana, P. angustifolia, P. cerasifera, P. munsoniana, P. salicina, P. simoni, P. bullata, and P. triflora were evaluated. Observations indicate that resistance is heritable and controlled by recessive genes. ELISA and visual observation indicated that an Auburn Univ. seedling (CD 122) was free from this disease.

Free access

Naturally infected plum leaves were collected during Aug. and Sept. 1994 to evaluated for the presence of Xylella fastidiosa, the causal agent of plum leaf scald (PLS). Leaves were from trees at least 4 years old in variety trials at four locations in Alabama. ELISA tests for X. fastidiosa were used to determine the presence of the organism in infected trees. The symptoms also were evaluated with a rating index for PLS. Some plum cultivars (i.e., `AU-Producer', `Morris', `Explorer', and `AU-Cherry') showed high tolerance to PLS. Both ELISA tests and visual observation indicated that an Auburn Univ. seedling (CD-l 22) was free from this disease. PLS infection was lower in North Alabama compared to Central Alabama.

Free access

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.

Free access

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.

Free access

Abstract

Watermelons Plant Introductions (PI) 189225, PI 271775, PI 271778, and PI 299379 were resistant to a population of Colletotrichum langenarium (Pass.) Ell. & Halst. in 3 states. Entries PI 203551, PI 270550, and PI 271779 were resistant in some field and greenhouse tests.

Open Access