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R.E. Myers, D.E. Deyton, and C.E. Sams

Spurs of `Starkspur Delicious' trees were dipped in 0, 3, 6, 9 or 12% petroleum oil (dormant oil) or soybean oil emulsions on 26 January 1993. The spurs were cooled at 3C/hr until -9C or kept at 21C. After treatment, the flower buds on spurs were forced at 20C for 11 days and then dissected. The cambium and xylem of the spurs and the interior of the flower buds were rated for damage as indicated by browning. The experiment was repeated at the silver tip stage of buds (early March) except that treated spurs were exposed to 20C, -6C, or -9C. Neither the oil treatments nor low temperature exposure caused visual damage to flower buds or cambium in January. However, the oil treatments damaged flower buds at the silver tip stage (March). Neither petroleum or soybean oil caused visible damage to the xylem or cambium of the spurs.

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R. E. Myers, D. E. Deyton, and C. E. Sams

`Redhaven' peach trees at the Knoxville Experiment Station were sprayed to runoff on 3 February 1993 with single applications of 0, 2.5, 5.0, 10.0, or 15.0% (v/v) degummed soybean oil with 0.6% Latron AG 44M emulsifier. Treatments were arranged in a randomized complete block design with 6 single tree replications. The internal CO2 concentration of treated twigs was elevated the first day and continued to be significantly higher than the control through the fifth day following treatment. Respiration rates of soybean oil treated buds-twigs were lower than the control for the first eight days after treatment. Flower bud and bloom development were delayed by treatment of trees with 5.0 to 15.0% soybean oil. Treatment with 5.0% oil delayed bloom approximately 4 days. The greatest delay (approximately 6 days) occurred after treatment with 10.0 or 15.0% oil. Yield was reduced and fruit size increased as the concentration of soybean oil was increased. Optimum fruit size was achieved with the 5.0% soybean oil treatment.

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R.E. Myers, D.E. Deyton, and C.E Sams

Dormant `Georgia Belle' peach [Prunus persica (L.) Batsch.] trees were sprayed in early February 1992 with single applications of 0%, 2.5%, 5.0%, 10.0%, or 20.0% (v/v) crude soybean oil. `Redhaven' trees were sprayed in February 1993 with single applications of 0%, 2.5%, 5.0%, 10.0%, or15% degummed soybean oil. Additional treatments of two applications of 2.5% or 5.0% oil were included each year. Both crude and degummed soybean oil treatments interfered with escape of respiratory CO2 from shoots and increased internal CO2 concentrations in shoots for up to 8 days compared to untreated trees. Respiration rates, relative to controls, were decreased for 8 days following treatment, indicating a feedback inhibition of respiration by the elevated CO2. Thus, an internal controlled atmosphere condition was created. Ethylene evolution was elevated for 28 days after treatment. Flower bud development was delayed by treating trees with 5% crude or degummed soybean oil. Trees treated with 10% crude or degummed soybean oil bloomed 6 days later than untreated trees. Repeated sprays of one half concentration delayed bloom an additional four days in 1992, but < 1 day in 1993 compared to a single spray of the same total concentration. Application of soybean oil caused bud damage and reduced flower bud density (number of flower buds/cm branch length) at anthesis. In a trial comparing petroleum oil and degummed soybean oil, yields of trees treated with 6% or 9% soybean oil were 17% greater than the untreated trees and 29%more than petroleum treated trees. These results suggest that applying soybean oil delays date of peach bloom and may be used as a bloom thinner.

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E.W. Stover, M. Myers, R.M. Sonoda, and Z. Guo

Stylar-end russetting (SER) is a cosmetic defect of Florida citrus fruit most frequently associated with navel orange. SER is evident as spots or streaks of corky tissue that often form a network of intersecting lines. Occurrence of SER is reported to vary widely from year to year, but some orchards have a history of severe SER, with fruit culled annually for this defect. Growers report that SER is typically first evident in August. The cause of SER has not been determined. Reports of yeast-like fungi inducing russet in pome fruit suggest that similar organisms may be implicated in SER. Yeast-like fungi were isolated on acid PDA from navel oranges in an orchard with frequent severe SER. Strains were selected with a wide range of colony morphology, but were not identified taxonomically. These strains, and strains of Aureobasidium pullulans and Rhodotorula glutinis that caused russetting in pome fruit, were grown in liquid suspension and sprayed on navel orange trees with three repeated applications during July and Aug. 1998. No increase in SER was observed on strain-inoculated trees compared to controls. Two broad-spectrum fungicides were sprayed on other navel orange trees to further explore the possibility that fungi may be involved in SER. GA (gibberellic acid) was also applied in this experiment because it can reduce russetting in apples. All applications were made five times at 3-week intervals in June through Sept 1998. SER was assessed in fruit harvested late Sept. 1998. The proportion of fruit with less than 10% of the surface exhibiting SER was 51% for controls, increased to 69% where myclobutanil was applied at 74 mg a.i./L and increased further to 93% where manganese ethylenebisdithiocarbamate was applied at 1775 mg a.i./L. GA did not significantly influence SER.

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D.E. Deyton, C.E. Sams, J.C. Cummins, R.E. Myers, and M.A. Halcomb

Hand-defoliation of field-grown `Golden Delicious' apple and `Bradford' pear nursery trees before autumn digging is a major production cost. One-year-old field-grown trees were sprayed to runoff on 18 Oct. 1994 with; 1) 1% FeEDTA, 2) 1% CuEDTA, 3) 1% ZnEDTA, 4) 100 ppm Harvade, 5) 50 ppm Dropp, 6) 500 ppm Folex, or 7) 2.5% EDTA or 8) leaves were removed by hand or 9) leaves left on trees (control). Treatments were arranged in a randomized complete-block design, with three trees/plot and four replications. Leaves on each tree were counted before treatment and 7, 14, 21, 28, and 35 days after treatment (DAT). One tree per plot was dug, stored until February and grown the following summer. Nontreated apple and pear trees had 13% and 38% defoliation, respectively, 35 DAT. CuEDTA treated apple trees had 62% and 93% defoliation 7 and 14 DAT, respectively. Pear trees treated with Cu had 18% and 100% defoliation 7 and 14 DAT, respectively. Treatment with FeEDTA resulted in 96% defoliation of pear within 7 DAT but only 57% defoliation of apple 35 DAT. ZnEDTA, Harvade, Folex, or Dropp did not significantly promote defoliation. Copper-treated apple trees had less budbreak than nontreated trees but similar budbreak as hand-defoliated trees. None of the treatments influenced budbreak of pear. None of the treatments affected the cumulative dry weight of trees at the end of the next growing season.

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C.A. Strausbaugh, J.R. Myers, R.L. Forster, and P.E. McClean

Resistance to bean common mosaic virus (BCMV) strain NY15 (Zaumeyer) and bean common mosaic necrosis virus (BCMNV) strain NL-3 (Drijfhout) was assessed in 98 F5:6 recombinant inbred lines (RILs) derived from a cross between pinto bean (Phaseolus vulgaris L.) cultivars `Olathe' and `Sierra'. `Olathe' has bc-u and bc-12 whereas `Sierra' has no known resistance genes. The differentiation of resistant and susceptible lines was based on visual symptoms, virus titer, and top dry weight. Forty-seven RILs were moderately resistant to NL-3, while 51 RILs were susceptible. This segregation fits a 1 susceptible: 1 resistant ratio characteristic of a single gene. Sixty-nine RILs were susceptible to NY15, while 29 RILs were resistant, which fits a 3 susceptible: 1 resistant ratio characteristic of a two-gene model. Moderate resistance to NL-3 was conferred by bc-12 with or without bc-u present. Bulked segregant and two point linkage analysis identified randomly amplified polymorphic DNA (RAPD) markers linked in coupling to the Bc-1 and Bc-u alleles. The OH141100 RAPD marker was 4.5 cM from the Bc-1 locus. The OC161000 RAPD marker was linked at a distance of 10.9 cM from the Bc-u locus. Multipoint analysis, using segregation data for bc-12, bc-u, and the two markers, estimated the distance between the Bc-1 and Bc-u loci as 22.8 cM.

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Adrienne E. Kleintop, James R. Myers, Dimas Echeverria, Henry J. Thompson, and Mark A. Brick

Phytochemicals such as phenolic compounds in snap bean (Phaseolus vulgaris) have potential human health benefits. The objectives of this research were to determine the variation in total phenolic content (TPC) measured as gallic acid equivalents (GAEs)—expressed on a fresh weight (FW) basis throughout this study—among a diverse collection of both indeterminate climbing (pole) and determinate (bush) bean cultivars (n = 149) using the Folin–Ciocalteu assay. We also evaluated associations between TPC and phenotypic traits and estimated genotype by environment (G × E) interactions in a subset of the cultivars. The TPC had greater than a 4-fold difference among cultivars and ranged from 0.29 to 1.31 mg·g−1 GAE (mean = 0.49 mg·g−1 GAE). Cultivars were classified into categories of high (≥1.00 mg·g−1 GAE), intermediate (>0.64 to <1.00 mg·g−1 GAE), and low (<0.55 mg·g−1 GAE) TPC. Eighty-four percent, 10%, and 6% of the cultivars fell into the low, intermediate, and high categories, respectively. The pole type cultivars had higher TPC (mean = 0.86 mg·g−1 GAE) when compared with the bush cultivars (mean = 0.47 mg·g−1 GAE). Correlations were observed between TPC and both flower and pod pigmentation. G × E interactions did not occur among pole type cultivars for TPC during 2 years of production, but a significant G × E interaction was observed among bush cultivars. The results demonstrate a wide diversity in snap bean cultivars for TPC, and the pole beans averaged higher TPC than bush bean cultivars. This information should be useful to identify high TPC snap bean cultivars.

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Kevin E. McPhee, Robert S. Zemetra, Jack Brown, and James R. Myers

Common bean (Phaseolus vulgaris L.) is a nutritionally complete food, but contains antinutritional compounds that reduce digestibility. One group of compounds includes the raffinose family oligosaccharides (RFOs) (raffinose, stachyose, and verbascose), which are partly responsible for flatulence after beans are eaten. RFOs stabilize cell membranes during seed desiccation and when the seed rehydrates during germination. While low levels of RFOs are desirable nutritionally, high levels may enhance germination and emergence, particularly in cold, wet soils. Eight landraces selected for high and low sucrose, raffinose, and stachyose content, were crossed in a diallel mating design to investigate genetic control of the RFOs. Derivatized soluble sugars were measured using gas-liquid chromatography. Fructose, sucrose, raffinose, and stachyose were detected. In the F1, fructose varied from 0.1 to 2.5 mg·g-1 dry weight (DW), sucrose from 17.2 to 56.5 mg·g-1 DW, raffinose from 0.1 to 4.1 mg·g-1 DW, and stachyose ranged from 7.6 to 43.7 mg·g-1 DW. Griffing's analysis estimates of general combining ability were on average, 16.5 times larger than specific combining ability for all the RFOs, indicating that additive genetic variance was most important. Significant reciprocal differences were detected in the F1 and F2, but not in the F3. RFO accumulation was partially dominant as indicated by Hayman's analysis. Narrow sense heritability averaged over F2 and F3 generations for sucrose, raffinose, stachyose, total sugar, and total oligosaccharides were 0.22, 0.54, 0.44, 0.17, and 0.27, respectively. Moderate heritabilities indicate that manipulation of RFO accumulation in this set of bean lines would probably need to be done on a progeny row basis with replication.