[Show abstract][Hide abstract] ABSTRACT: Following the release of 'Guardian' (BY520-9) peach rootstock in 1993, nurseries experienced significant problems with seed germination when fall-planted directly into the nursery. Rooted cuttings were proposed as a possible alternative. 'Cresthaven' peach trees budded onto 'Nemaguard' seedlings, 'Guardian' cuttings and seedlings, and 'Lovell' cuttings and seedlings were established in 1997 in a high density orchard and trained to a 2-arm open center system. Through 2003, trees on 'Nemaguard' seedlings displayed the highest vigor when measured as trunk cross-sectional area (TCSA). Trees on 'Lovell' seedlings displayed the smallest TCSA. There was no significant difference in the TCSA observed in trees propagated on 'Guardian' cuttings vs. 'Guardian' seedlings. Through three harvest seasons, trees on 'Guardian' cuttings produced the largest cumulative yield but were not significantly different from that observed on 'Guardian' or 'Lovell' seedlings. Trees on 'Lovell' cuttings had the smallest cumulative yield. Trees on 'Lovell' seedlings displayed significantly higher cumulative yield efficiency than all other rootstock treatments. Trees on 'Nemaguard' seedlings displayed significantly lower cumulative yield efficiency than all other rootstock treatments except 'Lovell' cuttings. There was no significant difference in the cumulative yield efficiency of trees on 'Guardian' cuttings and those on 'Guardian' seedlings. There appears to be no clear horticultural advantage or disadvantage to the use of 'Guardian' cuttings over 'Guardian' seedlings at this time.
[Show abstract][Hide abstract] ABSTRACT: Abstract: A new and distinct variety of peach tree which has a winter chilling requirement of approximately 400 chill units (cu). The tree is of large size, with a highly vigorous spreading growth habit; and has showy pink flowers. Glands are small and reniform in shape and isolated to the basal portions of leaves. This tree, which has been denominated 'Gulfprince' is a regular bearer of heavy crops of early mid-season fruit which are large for its ripening season. Fruit are very firm, yellow, non-melting flesh which are clingstone. Fruit are uniform, attractive, substantially symmetrical shape, and have an attractive 45 to 55% solid red skin. The fruit ripens 10 to 14 days after 'June Gold' in early June at Attapulgus, Ga.
[Show abstract][Hide abstract] ABSTRACT: Data were collected in early ripening peach [Prunus persica (L.) Batsch] varieties trained to a vase system to determine if a relationship exists between fruit weight and shoot diameter. The experiment was conducted with 3 varieties at Gainesville, FL with detailed pruning and with 3 other varieties at Atapulgus, GA with minimum pruning. All the varieties were similar in fruit development period (FDP) and fruit size. The largest shoot diameter was generally found in the upper canopy in all varieties. There was no correlation between shoot diameter and fruit weight for 'TropicBeauty', 'TropicSnow' and 'UF2000' at Gainesville under detailed pruning. There was a significant (p = 0.01) correlation for 'Flordacrest' in the lower (r = 0.53) canopy and for 'White Robin' in both the upper (r = 0.38) and lower (r = 0.40) canopy at Attapulgus, GA under minimal pruning. In these situations, large stems were associated with large fruit. 'Delta', grown at Attapulgus with minimal pruning, showed no correlation between shoot diameter and fruit weight, probably because it is male sterile and produced large fruit due to a reduced crop load.
[Show abstract][Hide abstract] ABSTRACT: Previous work has suggested that peach scion cultivar exerts a significant influence on incidence of peach tree short life (PTSL) in trees budded onto Nemaguard and Flordaguard seedling peach rootstocks. If this influence is consistent across a range of rootstocks then the influence of scion cultivar might offer a new tool for the management of PTSL. Growers could minimize losses on those sites most prone to PTSL by using the least susceptible scion/rootstock combinations. In this trial trees of ‘Agua 6-4,’ ‘Springcrest,’ ‘Redglobe,’ ‘Redhaven’ and ‘Cresthaven’ budded onto Guardian (BY520-9), Lovell, Nemaguard and Siberian C peach seedling rootstocks were planted on a site with a known history of PTSL. After 6 years, 31% of test trees had succumbed to PTSL and 18% to other causes. Both scion and rootstock exerted a profound influence on incidence of PTSL (P<0.0001). Mean effects of scion cultivar ranged from 10 to 49% PTSL mortality. Mean effects of rootstock treatment ranged from 10 to 85% PTSL mortality. However, a significant scion x rootstock interaction was also present (P<0.05). This appeared to be largely the result of anomalously low or high PTSL incidence observed in 2 scion/rootstock combinations. These results suggest that some caution should be used in extrapolating the rootstock treatment effects determined in a typical PTSL trial budded with a single scion cultivar to their influence beneath other untested scion cultivars.
[Show abstract][Hide abstract] ABSTRACT: Guardian peach rootstock was evaluated for susceptibility to Meloidogyne incognita race 3 (Georgia-peach isolate) and M. javanica in the greenhouse. Both commercial Guardian seed sources produced plants that were poor hosts of M. incognita and M. javanica. Reproduction as measured by number of egg masses and eggs per plant, eggs per egg mass, and eggs per gram of root were a better measure of host resistance than number of root galls per plant. Penetration, development, and reproduction of M. incognita in Guardian (resistant) and Lovell (susceptible) peach were also studied in the greenhouse. Differences in susceptibility were not attributed to differential penetration by the infectivestage juveniles (J2) or the number of root galls per plant. Results indicated that M. incognita J2 penetrated Guardian roots and formed galls, but that the majority of the nematodes failed to mature and reproduce.
Journal of nematology 10/1999; 31(3):334-40. · 0.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Advanced lines of 'Guardian' (i.e., SL2891 and SC 3-17-7) and 'Lovell' peach rootstocks were evaluated for their susceptibility and growth response to Meloidogyne incognita (GA-peach isolate) and M. javanica (NC-tobacco isolate) 23 months after inoculation in field microplots. Results indicate that there was a significant interaction between nematode and rootstock for above-ground tree growth. Growth suppression, as measured by trunk diameter and fresh shoot weight of SC 3-17-7 was greater (P<0.05) in the presence of M. javanica as compared to the presence of M. incognita or to the uninoculated plots. 'Guardian' line SL2891 growth was not affected by either nematode when compared to the uninoculated plots. Tree growth of 'Lovell' was suppressed by both M. incognita and M. javanica when compared to the uninoculated plots. Below-ground growth suppression, as measured by dry root weight, was greater in 'Lovell' than in either SC 3-17-7 or SL2891 regardless of nematode species. No difference in dry root weight was detected between the two 'Guardian' lines. Root galling occurred on all rootstocks tested with either M. incognita or M. javanica. Root galling was more abundant on 'Lovell', intermediate on SL2891 and least abundant on SC 3-17-7. Similar results were also detected for number of eggs per gram dry root weight regardless of nematode species. In another microplot study, M. floridensis and M. incognita did not suppress tree growth of SC 3-17-7, 'Nemaguard', or 'Flordaguard' rootstocks as compared to the uninoculated control. Meloidogyne floridensis reproduced on all 3 rootstocks, with greatest number of eggs per gram dry root being produced on 'Guardian' and 'Nemaguard'.
[Show abstract][Hide abstract] ABSTRACT: Recently observed hybrid populations of peach [Prunus persica (L.) Batsch] provide evidence for the presence of a single gene controlling full red skin color. The fruit of seedling populations of 'UFQueen x 'Springbaby, 'UFQueen x 'Springprince, FL93-12C x 'Springprince, FL92-22C x BY79P1945, and AP98-18 o.p. were rated for percent red skin color at full maturity. At this stage of development, "full red" phenotypes display red color over the entire surface of the fruit, including the stem cavity and portions of the fruit shaded by leaves or stems. Both crosses with 'UFQueen yielded populations displaying a 1:1 segregation ration for partial red : full red. All other crosses produced populations that did not deviate significantly from a 3:1 segregation ratio. These data are consistent with the hypothesis that the "full red" phenotype is a single gene recessive trait. We propose the gene symbols of fr and Fr for the recessive full red and dominant partial red (wild-type) alleles, respectively. None of the progeny of this cross had 100% red skin color (Table 1) and the mean red skin color was about halfway between that of the two parents (Fig. 1A). The data from all other populations pro-vid ed evidence for qualitative gene action. The 'UFQueen x 'Spring Baby and 'UFQueen x 'Springprincepopulations yield ed phenotypic segregation ratios typical of those observed for a test cross and did not deviate significantly from a 1:1 ratio (Table 1). The hybrid origin of these progeny was con firmed by the pres-ence of the peach phenotype, since progeny originating from self-pol li na tion of 'UFQueen would be nectarines. The observed segregation ratios for FL93-12C x 'Springprince, FL92-22C x BY79P1945, and AP98-18 o.p. seedling populations were typ i cal of those expected for a F 2 segregating population and did not deviate significantly from a 3:1 (partial red : full red) phenotypic segregation ratio. The phenotypic dis tri bu tions for the partial red progeny from 'UFQueen x 'Spring Baby (Fig. 1B) and FL92-22C x BY79P1945 (Fig. 1C) indicate that quantitative segregation for percent skin color is also occurring in these populations. These data also appear to indicate that the ho-mozygous full-red genotype may be mask ing the expression of the quantitative red gen o types similar to the recessive epistasis ob served in conjunction with the white flower (W) locus of peach (Lammerts, 1945). These data are consistent with the hy-poth e sis that the "full red" phenotype is a single gene recessive trait. We propose that the recessive allele controlling full red skin de vel op ment is present in the homozygous state in 'UFQueenand that 'Spring Baby, 'Spring-prince, FL93-12C, FL92-22C, BY79P1945, and AP98-18 are heterozygous. Selections FL95-1NW and FL94-5NW are evidently both homozygous for the dominant allele. We propose the gene symbols of fr and Fr for the recessive full red and dominant partial red (wild-type) alleles, respectively. This trait should prove useful in breeding fresh market peach and nectarine cultivars, as red blush development in the full red phe no -types is profoundly accelerated providing very high percent red blush at the "shipping ripe" stage, i.e., as ground color starts to change from green to yellow. Full red color de vel op ment is achieved in many seedlings before any shift in ground color is observed.
[Show abstract][Hide abstract] ABSTRACT: Six commonly known peach rootstocks (i.e., Flordaguard, Guardian, Halford, Lovell, Nemaguard, and Okinawa) were evaluated for their susceptibility to Meloidogyne mayaguensis in the greenhouse. All rootstocks were rated as either nonhosts (highly resistant) or poor hosts (resistant) of M. mayaguensis. Lovell generally supported greater numbers of M. mayaguensis eggs per plant and eggs per gram of dry root, whereas no nematode reproduction was noted on Flordaguard rootstock (nonhost). Root galling occurred on all six rootstocks. However, reproduction as measured by number of egg masses, eggs per plant, and eggs per gram of dry root was a better measure of host resistance than number of root galls per plant.
[Show abstract][Hide abstract] ABSTRACT: A 3-way cooperative project between the USDA and the Universities of Georgia and Florida was designed to devel op new early ripening fresh-market peach and nectarine variet ies for the lower coastal plain of the Southeastern United States. This industry requires varieties in the 400-650 chill hour range in combination with handling characteristics suitable for long distance shipping. Since 1990, over 4000 seedlings have been evaluated resulting in nearly 70 peach and nectarine se lections, which include both yellow and white-fleshed types. Some selections may be adapted to other areas with similar dormancy requirements and growing conditions. Selections from other breeding programs are also under evaluation. 'Sun-splash', released in 1993 as a result of this cooperative effort, is an attractive, early season, 400 chill hour nectarine. Recent ly, this program has emphasized the use of non-melting flesh parents for the purpose of improving fruit quality, handling and shelf-life. most commercial production in this region is located in south Georgia, which produces ca. 10% of the state's annual peach crop. However, given suitable varieties, there is a potential production zone stretching from North Carolina south along the Atlantic coast and west along the Gulf coast into Texas. In the primary moderate-chill production area centered around Brooks County in south Georgia, winter chilling over the last 35 years has averaged slightly more than 800 hours an nually (accumulated hours below 7C through Feb. 15th), but over that time span chilling has ranged widely from a low of 422 hours in the winter of 1973-74 to a high of 1160 hours in 1980-81. Over the last 10 years, winter chilling has averaged only slightly more than 700 hours (Table 1). Spring frosts in this area have always been a threat to peach production. Very few varieties are adapted to this climate, and the industry cur rently relies on a few varieties "spun-off' from breeding pro grams located in distinctly different climates. This cooperative program is the first to specifically target the needs of the southeastern moderate chill area. Program aims are to produce a series of peach and nectar ine varieties with chilling requirements ranging from 400 to 650 hours, but primarily in the 500-550 hour range, which will provide sequential ripening from early-May to mid-June. These varieties must have superior handling qualities to with stand the rigors of long-distance shipping to markets in the northern United States. High levels of resistance to bacterial spot (Xanthomonas campestris pv. pruni [Smith] Dye) are also necessary in this production area.
[Show abstract][Hide abstract] ABSTRACT: 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 x FL84-18C, FL90-50CN x FL92-2C, FL90-48C x FL91-12, FL91-8 x FL88-6, and open-pollinated or selfed populations from unselected seedlings of 'Contender' x PI65977 ('Giallo di Padova') and 'Mexico Selection' x '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.
[Show abstract][Hide abstract] ABSTRACT: Two F1 hybrid Prunus rootstocks, K62-68 and P101-41, developed from a cross of 'Lovell' [susceptible to both Meloidogyne incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood] and 'Nemared' (resistant to both root-knot nematode species), were selfed to produce two F2 seedling populations. Vegetative propagation by herbaceous stem cuttings was used to produce four or eight self-rooted plants of each F2 seedling for treatment replications. Eggs of M. incognita and M. javanica were inoculated into the potted media where plants were transplanted, and plants were harvested and roots examined for signs and symptoms associated with root-knot nematode infection approximately equal to 120 days later. Segregation ratios in both F2 families suggested that resistance to M. incognita in 'Nemared' is controlled by two dominant genes (Mi and Mij) and that to M. javanica by a single dominant gene (Mij). Thus, Mij conveys resistance to both M. incognita and M. javanica.
[Show abstract][Hide abstract] ABSTRACT: Large field plantings are often difficult to label and to plant randomly. A DOS computer program was developed in SAS and BASIC to randomize lists of experimental factors and print sorted paper labels to apply to trees or plants. Tagged trees can be resorted readily by block or row to speed planting. The computer lists are useful for plot verification and subsequent data collection, especially if data are collected and inputted directly to a computer. Copies of the programs are available from W.R. Joyner if a formatted diskette and self-addressed mailer are supplied. Breeding and cultivar testing often require field or greenhouse experiments with many varieties or genotypes as treatments, arranged in blocks either singly or in multiple-plant plots. The logistics of labeling and planting can be difficult. To minimize the difficulty, we have developed a computer program in SAS (SAS Institute, 1985) and BASIC program-ming languages (Waite et al., 1990) that ran-domizes the appropriate factors (i.e., row and plot numbers, treatment names, and color codes) and produces a sorted file that can be printed on paper labels (Fig. 1). As an example, we used each program to describe a planting consisting of three randomized complete blocks of four varieties each, to be planted in two rows each with six single-tree plots. These experimental factors should be adjusted as needed for a particular design. Slight program modifications can be made for completely randomized, split plot, or multiple-plant plot configurations. In SAS (Fig. 2), a treatment list is inputted (Fig. 2A), and merged with a list of random numbers (IDX). The RANUNI function re-turns a random number between 0 and 1. By sorting on appropriate identification variables and the random variable using PROC SORT (Fig. 2B), a randomized layout for the testis created. Plot and row values are generated in order (Fig. 2C). Then these values are merged with the randomized layout list (Fig. 2D) that is saved to a map file (plot.map) for use in data collection and displayed on the screen for verification. The map is resorted by variety name (Fig. 2E), and then outputted (Fig. 2F) as a DOS print file (labels.prt) in a format suit-able for printing labels. This program will work even if the block consists of rows and parts of rows. For multiple-plant plots, either use one tag per plot bundle or increment the Received for publication 22 Mar. 1993. Accepted for publication 25 Aug. 1993. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.