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`Coronet' peach on Lovell rootstock was planted near Clemson, S.C., in Dec. 1995 in 4 rows (= reps) 6.1 meters apart with trees 2.2 meters apart in-row. Trees were trained to a Kearney-V. In the 2nd leaf (Aug. 1997), `Ta Tao 5' buds were grafted to half (= 6-tree plot) the trees in each row. These trees received 2 `Ta Tao 5' chip buds infected with Peach Latent Mosaic Viroid (PLMVd) per scaffold at ≈0.75 to 1.15 m above ground. Dot blot hybridization confirmed that the chip buds successfully (100%) inoculated the treated trees, whereas the controls tested negative. Data collected in 2003 included bloom date, tree size, dormant and summer pruning times, fruit maturity date, fruit yield, mean fruit weight, skin color, soluble solids, flesh firmness, titratable acidity, and pH. Flowering and fruit maturity were delayed by ≈4 days in PLMVd-inoculated (PI) trees. PI trees produced larger fruit, but yield was 23% less than that of non-inoculated trees. Both fruit size and yield had been larger in PI trees in previous years. There were no differences in yield efficiency in 2003, but PI trees were 26% smaller in trunk cross-sectional area and 9% shorter. PI trees took 34% and 23% less time to dormant and summer prune, respectively and had 34% and 28% less wood removed by dormant and summer pruning, respectively than control trees. PLMVd increased fruit firmness, and PLMVd fruit lost firmness at a much slower rate. PLMVd did not significantly affect skin color, but PLMVD fruit were slightly less red. Soluble solid levels were higher in PLMVd fruit than control fruit during the first harvest, but were lower by the last harvest. Acidity was significantly higher and the soluble solids to acidity ratio significantly lower in PLMVd fruit. Control fruit had a slightly higher pH.
Poor peach seed germination can be a problem for commercial tree fruit nurseries. Even standard rootstocks such as Lovell and Nemaguard do not always have high germination rates. New seed-propagated rootstocks under development, such as Guardian peach rootstock, often are selected for their field traits, with nursery characteristics being of secondary importance. Guardian rootstock is derived from bulked open-pollinated seed from a number of F1 seedling selections. Germination of Guardian bulked seed has been poor. Four pre-stratification cold treatments were given to four 100-seed lots each of Lovell, Nemaguard, and 10 Guardian selections prior to planting each year (1994 to 1998) in a Cecil sandy loam at Musser Fruit Research Center near Clemson, S.C. Treatments included taking dry, refrigerated seed that were harvested in August and soaking 100-seed seedlots in 1500 mL perlite and 400 mL distilled water for 0 (no soaking), 2, 4, 6, and 8 weeks at 6 °C before sowing (typically early November). All treatments consisted of 25 seeds per replicate (4 reps/year) per rootstock or selection and were sowed the same day. The experiment was analyzed as a blocked split plot design with duration of stratification the whole-plot and seedlot the sub-plot. Number of emerged seedlings were counted weekly starting in January of each year. There were significant differences between stratification treatments, seedlots and years. The 6-week pre-stratification had the highest germination over 5 years and like the 8-week treatment advanced the average germination date by 20 to 30 days. Nemaguard (65%), Lovell (64%), and Guardian 3-17-7 (60%) had the best germination percent across all treatments and years, with SL2891 (42%) slightly less. All other selections averaged less than 25%. Year-to-year variation was large, indicating strong environmental influences on seed germination despite the pre-stratification treatments.
A field planting of 18 selections and 10 named cultivars of pawpaw (Asimina triloba) was established in November 1996 near Clemson, S.C., as part of the Pawpaw Regional Variety Trial coordinated by Kentucky State University. Trees were planted at 2.0 × 5.5 m spacing with drip irrigation and straw mulch in a randomized complete block design consisting of 8 single-tree replications. Data collected through 2005 included tree survival, total tree yield, and yield and average weight of fruit weighing >150 g. Since the start of the trial, 3 selections, 1-7-1, 11-5 and 8-58 have been named and released as `Shenandoah', `Susquehanna' and `Rappahannock', respectively. The highest yielding cultivars were `Shenandoah', `Rappahannock', and `PA-Golden'. The cultivars with the largest percentage of large fruit were `Shenandoah' and `Susquehanna'. `Middletown', `Mitchell', `Rappahannock', `Taytwo', `Wells' and `Wilson' produced the largest percentage of small fruit (<150 g). After 9 years, 66% of the original trees (i.e., scions) were alive. `Rappahannock', `PA-Golden', `Sunflower' and `Wilson' had either one or zero trees die, whereas `Middleton' and `Wells' had only 2 trees alive. Among the selections, 2-54, 9-58, 11-13, 1-68, 3-11, and 8–20 had either 88% or 100% survival. The highest yielding selections were 10-35, 1-7-2, 1-68, and 2-10, and 1-7-2, 2-10, 4-2, and 5-5 produced the highest percent of large fruit. Fruit quality characters such as aroma, flavor, aftertaste and texture were not quantified or evaluated.
Winter cover crops (wheat or rye and crimson clover) in combination with three levels of nitrogen fertilizer (0, 60, 120 kg/ha) were evaluated as to their influence on bean and tomato production (fruit yield, disease and insect injury on fruit) over a three year period (1991-1993). A split plot design was used with the cover crop as the main treatment and nitrogen rate as the split treatment. Results indicate that total marketable and cull yields for bean increased significantly in 1992 but decreased again in 1993. Tomato yields were significantly greater in 1991 than in 1992 and 1993 for both early and total marketable yields while early cull yield increased each year and total cull yield was highest in 1993. Cover crop had an effect on non-marketable tomato fruit. There was a higher incidence of cracked and insect damaged tomato fruit in association with clover or fallow treatment. Marketable yields responded in a quadratic manner while the number of cull fruit increased linearly for both bean and tomato as nitrogen rate increased. The incidence of diseased bean pods increased linearly as nitrogen rate increased. Catfaced tomato fruit responded in a quadratic manner and cracked tomato fruit increased linearly as nitrogen increased. Results from the three year evaluation do not indicate an influence of cover crop on marketable yields of bean and tomato.
Rye and crimson clover as winter cover crops and red clover as a companion crop were evaluated in sweet corn and bell pepper production systems in South Carolina. Winter cover crops were planted in fall and incorporated into the soil 3 weeks prior to planting vegetable crops. Red clover was overseeded with the vegetable crops. There were no significant differences among treatments for corn yield. Marketable number and weight of bell peppers were significantly higher in both winter cover crops compared to red clover and fallow (control) treatments. Number of cull peppers (smaller peppers than USDA grades) were lower in both cover crops compared to other treatments. Lack of response in red clover compared to the fallow treatment may be due to the lower emergence of red clover when used as a companion crop with bell pepper. Marketable bell pepper yield was higher in the late harvest compared to the early harvest in all the treatments.
Pest management is of primary importance to the vegetable industry in our nation. In recent years producers have undergone much scrutiny concerning their pest control strategies, which often include the use of chemical pesticides. Due to the detrimental effects of many fumigants, growers are being forced to incorporate more environmentally sound agricultural practices while still producing a healthy, marketable commodity. The effects of three different fumigants and reflective mulches on plant growth and development were studied in field-grown, staked tomatoes. Methyl bromide, Telone II, or Telone C-17 were used in fumigation of plots. The establishment of mulch color was done via applications of exterior enamel paint, white or red in color, to the surface of black polyethylene mulch. With the exception of total marketable yields, no interactions existed between mulch color and fumigant. Red mulch and Telone II treatments resulted in the highest total marketable yield. Telone II application increased early marketable yield. White mulch color increased preharvest yield and black mulch color decreased early marketable yield. Low initial populations of nematodes may be the cause for lack of response due to fumigation.
Winter cover crops (wheat and crimson clover) in combination with three levels of nitrogen fertilizer (0, 6, 120 kg/ha) were evaluated as to their influence on bean and tomato production (fruit yield, disease and insect on fruit, and nutrient content of fruit and plants). The influence of cover crop and fertilizer on nitrogen distribution in the soil profile was determined for each treatment. A split plot design was used with the cover crop as the main treatment and nitrogen rate as the split treatment. Soil cores were taken in the spring before planting and at the termination of harvest each year. Results indicate that cover crop had an effect on non-marketable bean fruit, but did not affect marketable fruit harvested for both bean and tomato. Cracked and insect damaged tomato fruit was greatest in fallow and wheat treatment, and culls of bean fruit was greatest in the clover treatment. Cover crop treatment had no affect on overall tomato and bean plant nutrient content. Wheat and clover cover crop treatment reduced the amount of nitrate leaching in the soil profile as compared to the fallow. These results suggest that wheat and clover can be used effectively as cover crops to reduce nitrate leaching without affecting bean and tomato fruit yield.
Pest control-related problems jeopardize the advancement of our nation's vegetable industry. Because of the adverse effects of many fumigants. the grower is increasingly pressured to utilize sustainable. environmentally sound agricultural practices yet still maintain a marketable, blemish-free product.
The effects of wavelength selective mulches and three different fumigants on overall plant development and nematode control were studied in field grown, staked tomatoes. Plots were fumigated with methyl bromide. Telone II, or Telone C17. Within rows, mulch color was established by application of either white or red exterior enamel paint to the black plastic surface of polyethylene mulch. Reflective light from each mulch color was measured using a LiCor 1800 Spectroradiometer. Temperature below the mulch surface was monitored with a datalogger.
Prior to the first marketable harvest, plants grown on white mulch produced greater fruit weight and total dry weight than plants grown on black or red mulch. Total marketable yields, however. were not significantly different between the three mulches. Early and marketable yields from fumigated plots did not differ from control treatments. The lack of response due to fumigation may have been due to low initial nematode populations in the field.