Peach tree short life (PTSL) is associated with the presence of ring nematode, Mesocriconema xenoplax, and poor orchard management practices. Finding a noncommercial field site to evaluate rootstocks for PTSL resistance is increasingly difficult. The time needed to create a PTSL test site was investigated. In 1994, a site not planted in peaches for >80 years was identified in Byron, Ga. Analysis of preplant soil samples revealed that there were no M. xenoplax on the site. One-third of the land was planted to peach and infested with 1600 ring nematodes per tree in Spring 1994 (P2) and another one-third in Spring 1995 (P1). The remaining one-third of the land received no trees or ring nematode and served as the control (F2). In Fall 1995, trees were removed from P1 and P2 plots and all treatments were replanted to peach in 1996. In 1997, tree death resulting from PTSL occurred only in P2 (7%). By 2000, PTSL tree death reached 41% in P2, 16% in P1, and 4% in F2 plots. Nematode populations were higher (P < 0.05) in P1 (649 ring nematode/100 cm3 soil) than in F2 (221 ring nematode/100 cm3 soil) plots, whereas populations in P2 (300 ring nematode/100 cm3 soil) plots did not differ from those in P1 or F2 plots. Establishing a PTSL screening site was possible 3 years after M. xenoplax introduction; PTSL development among treatments in the subsequent planting was dependent upon cumulative population exposure of trees to M. xenoplax.
A.P. Nyczepir, W.R. Okie, and T.G. Beckman
T.G. Beckman, W.R. Okie, G. Krewer, and W.B. Sherman
The purpose of this three-way cooperative project is to develop new fresh-market peach and nectarine varieties in the 400 to 650 chill hour range for the early season shipping market. Since 1990, >3000 seedlings have been evaluated, resulting in 48 selections. Additionally, several hundred selections from other programs have been evaluated. `Sunsplash', an attractive, early season, 400 chill hour nectarine, was released in 1993 as a result of this cooperative effort. A novel aspect of the program has been the use of non-melting flesh parents for the purpose of improving handling characteristics. Selections include both yellow- and white-flesh types, peaches and nectarines. Some may be adapted for use in other production areas and are available for testing under non-propagation agreement. Evaluation summaries of selections and standards will be presented.
T.G. Beckman, G.L. Reighard, A.P. Nyczepir, and W.R. Okie
Thirteen rootstocks grafted with Redhaven peach were established on a severe peach tree short-life (PTSL) site in central Georgia. Most rootstocks tested were peach seedling types: Lovell, Nemaguard, Guardian (BY520-9), BY520-8, Boone County, Bailey and two `Tennessee Natural' selections. A seedling plum rootstock, St. Julian, was also used. Clonal type rootstocks included a peach × almond hybrid, GF677; plum, GF43 and Damas 1869; and a plum hybrid, GF655-2. Trees on Guardian displayed the best survival with only 20% mortality due to PTSL, through 7 years. In contrast, 40% of trees on Lovell succumbed to PTSL. Currently, Lovell is the recommended rootstock for PTSL-prone sites. Other rootstocks ranged from 50% to 100% mortality due to PTSL. Trees on Guardian displayed significantly higher vigor through the first 4 years following planting compared to trees on Lovell. Furthermore, trees on Guardian produced significantly greater yields than those on Lovell, in all but 1 year. Rootstock effects on tree survival, vigor, bloom and harvest dates, fruit yield and size, and suckering will be discussed.
T.G. Beckman, J. Rodriguez Alcazar, W.B. Sherman, and D.J. Werner
Recently observed hybrid populations of peach [Prunus persica (L.) Batsch] provide evidence for the presence of a single gene suppressing red skin color. The fruit of seedling populations of FL90-48C and FL90-37C × FL84-18C, FL90-50CN × FL92-2C, FL90-48C × FL91-12, FL91-8 × FL88-6, and open-pollinated or selfed populations from unselected seedlings of `Contender' × PI65977 (`Giallo di Padova') and `Mexico Selection' × `Oro A' were rated for normal quantitative vs. no anthocyanin skin color at maturity. At this stage of development, anthocyaninless phenotypes displayed no red color over the entire surface of the fruit. Instead they were characterized by a bright yellow ground color that stood out visually in the seedling rows, and which was dubbed highlighter. The two crosses with FL84-18C yielded populations that approximated a 1:1 segregation ratio for quantitative red:no red skin color. All other crosses produced populations that closely approximated a 3:1 segregation ratio for quantitative red to no red. These data are consistent with the hypothesis that the highlighter phenotype is a single gene recessive trait. We propose the gene symbols of h and H for the recessive no red (highlighter) and dominant normal quantitative red (wild-type) alleles, respectively.
T.G. Beckman, W.R. Okie, A.P. Nyczepir, P.L. Pusey, and C.C. Reilly
Nearly 5000 seedling trees representing more than 100 peach [Prunus persica (L.) Batsch.] and plum (Prunus spp.) lines were planted at a 4 × 0.6-m spacing in Jan. 1983, on a site with a known history of peach tree short life (PTSL) and Armillaria root rot (ARR). Trees were arranged in a randomized complete-block with eight replicates of six trees each. Beginning in Spring 1984 and each year thereafter the cause of tree death was determined. At the end of 9 years, 50% of the trees had succumbed to PTSL and 35% had been killed by ARR apparently caused by Armillaria tabescens. Analysis of the data for trees killed by ARR showed a wide range in mortality, some peach lines appeared significantly more tolerant to ARR than others. Plum lines derived from native North American species also appeared to be a potential source of improved tolerance. We did not establish whether ARR tolerance is affected by PTSL.
W.R. Okie, T.G. Beckman, A.P. Nyczepir, G. L. Reighard, W.C. Newall Jr., and E.I. Zehr
W.R. Okie, T.G. Beckman, G.L. Reighard, W.C. Newall Jr., C.J. Graham, D.J. Werner, A.A Powell, and G. Krewer
This paper describes the climatic and cropping conditions in the major peach [Prunus persica (L.) Batsch] producing areas in the southeastern United States in 1996. The peach and nectarine crop was the smallest since 1955 due to a series of unusually cold temperatures in February, March, and April. Crop set was not strictly a function of late blooming. No variety produced a full crop across the region. Many reputedly hardy peaches cropped poorly. The only peach or nectarine varieties that produced substantial crops in multiple locations were `La Premiere', `Ruston Red', and `Contender'. Cropping ability of some breeding selections shows that peach frost tolerance may be improved further.
W.R. Okie, G.L. Reighard, T.G. Beckman, A.P. Nyczepir, C.C. Reilly, E.I. Zehr, W.C. Newall Jr., and D.W. Cain
Long-term field trials of a wide range of peach [Prunus persica (L.) Batsch] germplasm on two peach tree short-life (PTSL) sites revealed marked differences in survival among lines. Generally, cuttings and seedlings of a given line performed similarly, as did ungrafted seedlings and their counterparts grafted to a commercial cultivar. No apparent relationship existed between a line's chilling requirement and survival. B594520-9 survived best in Georgia and South Carolina, providing significantly greater longevity than Lovell, the standard rootstock for use on PTSL sites. B594520-9 is derived from root-knot-nematode-resistant parentage, and progeny of surviving seedlings have demonstrated root-knot resistance similar to Nemaguard seedlings.
B.S. Wilkins, R.C. Ebel, W.A. Dozier, J. Pitts, D.J. Eakes, D.G. Himelrick, T. Beckman, and A.P. Nyczepir
Twelve peach [Prunus persica (L.) Batsch] seedling rootstocks [Lovell, Nemaguard, Flordaguard, 14DR51, five Guardian™ (BY520-9) selections, and three BY520-8 selections] budded with `Cresthaven' were planted in 1994 and evaluated through 2000 to determine performance under commercial management practices. Mesocriconema xenoplax population densities were above the South Carolina nematicide treatment threshold of 50 nematodes/100 cm3 of soil after 1996. However, symptoms of peach tree short life (PTSL) were not observed. Tree mortality was less than 14% through 1999, with most of the dead trees exhibiting symptoms consistent with Armillaria root rot. About 13% of the surviving trees in 1999 were removed in 2000 due to symptoms of phony peach. There were no differences in tree mortality among rootstocks. Tree growth, photosynthesis, and suckering varied among rootstocks, but leaf conductance, internal CO2, and leaf transpiration did not. Foliar calcium, magnesium, iron, and phosphorus varied among rootstocks, but all were within the range considered sufficient for peach trees. Fruit yield varied among rootstocks, but yield efficiency did not, indicating that higher yield corresponded with larger trees. Bloom date did not vary among rootstocks, but harvest date was advanced as much as 2 days for some rootstocks, compared to Lovell. Fruit weight varied among rootstocks but skin color, flesh firmness, and soluble solids content were similar. All rootstocks performed satisfactorily for commercial peach production.