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- Author or Editor: Gregory Reighard x
An Asian pear variety trial consisting of 13 cultivars replicated 12 times was planted in 1989 near Columbia, S.C. For 6 years, cultivars were evaluated for commercial fruit production. The Chinese types `Ya Li' and `Shin Li' bloomed earliest (early March), whereas Japanese types such as `Twentieth Century' and `Choju' bloomed 10 to 12 days later. The largest trees were `Ya Li', `Shinsei', and `Shin Li', and the smallest were `Shinko', `Shinsui', and `Twentieth Century'. All cultivars on P. betulaefolia rootstock had suckers, with `Chojuro' and `Shinko' trees having the fewest. `Kosui' and `Shinsui' defoliated first each fall. Average fruit yields in kg/tree were largest for `Ya Li', `Shinsui', `Shin Li', and `Twentieth Century'. Fruit size was large (>200 g) for the Chinese types such as `Ya Li', `Shin Li', and `Daisu Li', but small (<100 g) and non-commercial for `Twentieth Century'. Fruit maturity dates were consistent year to year, with `Choju' and `Shinsui' ripening first (early July) and the Chinese types ripening last (mid-August). Low return bloom (i.e., alternate bearing) was observed after a heavy crop year. Winter injury, as evidenced by bark cracking on the southwest side of the trunk, was severe in 1993–1994. However, `Ya Li' suffered no cold damage. Fireblight was first observed in the 1992, and increased in 1993 and 1994. `Choju', `Shinseiki', and `Kosui' were the most-susceptible cultivars, while `Ya Li', `Shinsui', and `Shinko' were the most tolerant.
A `Redglobe' peach orchard budded to 22 rootstock cultivars was planted in 198X on a Lakeland sand near Columbia, SC. Six of the 22 cultivars were also used as interstems on Nemaguard. The rootstocks tested were Lovell, Halford, Nemaguard, Bailey, Tennessee Natural, Tzim Pee Tao, Rutgers Redleaf, Higama, Rubira, Montclar, GF 305, Juseito, Myran, Ishtara, S.2729. St. Julian A, Citation, Marianna 2624, GF 557, GF 677, (S×R 185)6 and `Redglobe' own-rooted. Trees on Marianna 2624 grew poorly and eventually died from incompatibility. Plum hybrid rootstocks St. Julian A. Ishtara and Myran were susceptible to Pseudomonas syringae. Some peach X almond (S×R 185)6 trees died from unknown causes. Tzim Pee Tao was the only rootstock to delay bloom significantly later (1.5 days) than Lovell. All Nemaguard interstem combinations and Tzim Pee Tao had significantly more-rootstock suckers. Nemaguard, Myran and Higama trees were 25 to 43% larger in TCSA than Lovell. Ishtara trees were only 61% of Lovell in TCSA. St. Julian A and Citation trees were small, weak and unproductive. The highest yielding rootstocks were Nemaguard (Myran interstem), GF 305, Nemaguard (Ishtara interstem), Montclar and Rubira which averaged 69, 65, 64, 62 and 60 kg/tree, respectively in years 4 through 6.
`Juneprince' peach was budded to Ta Tao 24 peach interstems on virus-free Lovell rootstock in June 1990. Trees were planted December 1990 in a fumigated Lakeland sand near Columbia, SC. The experimental design was a randomized complete block with 9 replicates each having 6 treatments plus a control. Four treatments were 20 and 40 cm interstem segments of Ta Tao 24 with and without an interstem branch. Two other treatments were 40 cm Ta Tao 24 interstems with no branches but receiving a single November spray of either 200 ppm ethephon or water. The control was `Juneprince' on Lovell rootstock. After 3 years, control trees were significantly larger in TCSA (cm2) than all treatment trees. Full bloom date was not significantly different among the 6 treatments, hut was significantly later (7 days) than the control trees. In March 1993, cold temperatures killed all open flowers on control trees. Fruit yields in 1993 were significantly higher in interstem trees (10.2 kg/tree) compared to the control trees (6.8 kg/tree). Fruit maturity date did not differ among treatments, hut was significantly later (10 days) than the control trees. `Juneprince' on Ta Tao 24 interstems were smaller in TCSA and had delayed bloom and fruit maturity. Ta Tao 24 interstem length presence of branches, and ethephon application did not enhance the differences observed in this study.
The growth regulator BAS 111-06W was applied twice each spring for 3 years to 5-year-old 'Loring' trees. First year treatments were foliar sprays (1 or 2 g a.i.), trunk paints (2 or 4 g a.i.), and soil shank injections (2 or 4 g a.i.). Foliar treated trees developed severe leaf shotholing or bacteriosis. Shank treatments were the most effective in controlling shoot growth. Thus, second and third year treatments consisted only of the shank applications. Both the 2 and 4 g rates were equally effective in reducing shoot elongation 10-34% annually. Treated trees bloomed 1-2 days earlier and had shorter bloom periods than the controls. Flower bud density and flower number were greater on treated trees. Fruit yields were not affected. Treated trees required less summer and corrective winter pruning, but had more short shoots to thin out.
Eight rootstock cultivars of peach (Prunus persica) were grown for 3 months in a greenhouse and evaluated for vigor by measuring root hydraulic conductivity and recording stem caliper, shoot and root dry weights, and root lengths. These data were compared with tree diameter data from 3rd leaf `Redglobe' orchard trees budded on the same rootstock cultivars. The objective was to determine if rootstock seedling growth could be used as a predictor of scion vigor in the field. Correlations between orchard tree diameters and the stem calipers (r = 0.87), whole plant dry weights (r = 0.91), and root dry weights (r = 0.89) of greenhouse rootstock were statistically significant (P < 0.05), but not significant was the correlation between root length (r = 0.76) and tree diameter. Root hydraulic conductivity as measured with a pressure-induced water flux system at 0.4 MPa of pressure and calculated on both a root length and a root dry weight basis was inversely correlated with both the greenhouse and field data. This suggested that root hydraulic conductivity was a function of a pressure-mediated mechanism that was independent of root membrane permeability and xylem conductance.
New foreign rootstocks for peaches [Prunus persica (L.) Batsch] are now being introduced into the United States through commercial nurseries for future sales to stone fruit growers. Almost all of these rootstocks are complex Prunus L. hybrids that are propagated vegetatively. Past experience with foreign Prunus rootstocks has shown that extensive testing is critical to avoid potential problems in commercial situations due to nonadaptation of some rootstocks to North American climatic and edaphic conditions. In addition, putative resistance of introduced rootstocks to common soil diseases and other pathogens has not always carried over to orchard sites in the United States. To ensure widespread horticultural testing of new rootstocks, the NC-140 regional research group continues to serve as an unbiased tester in many different geographic and production areas of the United States and Canada.
Peach [Prunus persica (L.) Batsch (Peach Group)] trees bloom in response to chilling and postrest heat accumulation. The peach cultivar Coronet exposed to a graft-transmissible, infectious agent known as peach latent mosaic viroid (PLMVd) blooms at a different time than noninoculated trees of the same cultivar. To determine if chilling requirements differed between trees inoculated with PLMVd and noninoculated controls, fruiting shoots collected from the orchard and artificially chilled containerized trees were forced in a greenhouse. Additional artificially chilled containerized trees were forced under constant temperatures in growth chambers to determine if postrest heat accumulation requirements differed. There was no difference in the chilling requirement of the fruiting shoots collected from the field although the shoots exposed to PLMVd had a delayed response and fewer responded to greenhouse forcing conditions. The containerized trees also showed no differences in chilling requirements during winter 1999 or 2000. Trees inoculated with PLMVd had a significant delay in bloom. Growth chamber data revealed a significantly higher base temperature for heat accumulation in the PLMVd inoculated trees.
Twenty-six peach and six plum cultivars budded to 20–50 cm Ta Tao five or twenty-four interstems on Lovell rootstock were observed in four trials at two locations in South Carolina. The locations were in the Piedmont near Clemson and the Sandhills near Pontiac, S.C. The objective of growing peach cultivars on interstems was to delay scion phenology to reduce risk from late spring freezes. Data from these trials were collected from 1989 to 1996. Average bloom delay for peach cultivars on interstems was significant each year from 1991 through 1996 and ranged from 5 to 9 days later than the noninterstem controls. Bloom of plum cultivars on interstems was not significantly affected. Interstem peach trees had significantly smaller trunk cross-sectional areas and averaged from 32% smaller in 3-year-old trees to 35% in 7-year-old trees. Interstem trees also had fewer lateral vegetative budbreaks (i.e., blind wood). Fruit maturity was significantly delayed on most peach cultivars on interstems. Fruit of early cultivars (90 days past bloom) ripened 2–4 days later on interstems. Likewise, mid-season cultivars ripened 5–6 days later and late season cultivars (>130 days past bloom) 3-4 days later. Fruit size was smaller on interstem trees when trees were either inadequately thinned or drought-stressed.
`Redhaven' peach trees were planted on a nonfumigated peach tree short life (PTSL) site in Pontiac, S.C. The experimental design was a split plot with 12 replicates. Preplant subplot treatments were 0, 3, and 6 kg of hydrated lime mixed with 1.9 cubic meters of native soil (Lakeland sand) per planting hole. Main plot treatments consisted of mixing in the planting holes 0 or 5 liters of soil taken from a nearby orchard site that had shown “suppressive” tendencies towards ring nematode reproduction. Hydrated lime treatments increased soil pH by 0.6 to 1.4 units. Boron deficiency occurred in the 6-kg plots. Hydrated lime did not significantly reduce PTSL as 88%, 79%, and 92% of the trees in the 0-, 3-, and 6-kg plots, respectively, died from PTSL by the fifth year. No differences in survival were found between the nonsuppressive and suppressive soil treatments, as both had 86% tree death from PTSL. No trends in ring nematode populations were found among treatments.
Trees of `Redhaven' peach [Prunus persica (L.) Batsch] budded to `Lovell', `Bailey', and `Nemaguard' rootstocks were grown with bahiagrass or cultivated orchard middles. Terminal shoots were collected once a month through the dormant season. `Redhaven' on `Lovell' had significantly higher levels of sucrose, sorbitol, total soluble sugars, starch and total non-structural carbohydrates than `Redhaven' on `Nemaguard'. However, there were no significant differences in any carbohydrate fraction between `Redhaven' on `Bailey' and the other rootstocks. Orchard floor management system had no significant effect on carbohydrate levels.