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Larry Stouse and Charles Marr

Master Gardeners are volunteers who assist local cooperative extension horticulture and related program efforts by receiving training and conducting educational activities and projects. Participants generally receive training and volunteer within a 1-year period. The emphasis has shifted to longer retention of trained, experienced Master Gardeners. There are several advantages in retaining volunteers. Volunteers with established knowledge who “know the ropes” serve as spokespersons for the program to recruit additional volunteers and as mentors for new class members. Since 1980, Master Gardeners in Johnson County, Ran., have served the 300,000 population base of the southwestern Kansas City suburban area through the county extension horticulture program. About 35% of the members of the first classes are still active volunteer participants after 10 years. Retention is encouraged by emphasizing that volunteer time is an opportunity for continued learning, rather than a “payback” for training received. An advisory board and committee structure encourages “ownership” of the program, and an advanced training program is offered to retained volunteers. Developing ideas for quality volunteer activities is continuously stressed. As new volunteers start the program, their abilities and skills in nonhorticultural areas that may be useful are assessed, such as woodworking, photography, speaking, leadership, and art. Applicants are screened to limit class size to 20 to 25 participants.

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I.E. Yates and Darrell Sparks

Stored pollen from pecan [Carya illinoensis (Wangenh.) C. Koch] was analyzed for in vitro germination, fertilization efficiency, final fruit set, and characteristics of mature fruits. We demonstrate pecan pollen can be stored for several years and set fruit. Pollen stored for 1, 2, and 3 years at -80C and 1 year at -196C retained the capacity for fertilization. Pollen stored at -196C was more viable than pollen stored at -80C, with no significant correlation between length of storage at -80C, as judged by fruit abortions during the second drop. Final fruit set was not affected by pollen storage conditions, except for pollen collected in a season of drought. Fruit set is a more reliable indicator of pollen viability than in vitro germination. With two minor exceptions, fruits produced with stored pollen were similar to those developing after pollination with fresh pollen.

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Warren E. Shafer, Gregory Clarke, Robert Fritts Jr., and Derek Woolard

ReTain™ is an organic, water-soluble formulation that contains 15% (w/w) of aminoethoxy-vinylglycine (AVG). AVG, a naturally occurring plant growth regulator, competitively inhibits ACC (1-aminocyclopropane-1-carboxylic acid) synthase, the enzyme responsible for the conversion of S-adenosylmethionine (SAM) to ACC, the immediate precursor of ethylene in plants. ReTain has been under commercial development for the past 6 years, which includes U.S. EPA-approved Experimental Use Permit (EUP) programs in 1995 (Shafer et al., 1996, Proc 23rd Annu. PGRSA Mtg., p. 233–234) and 1996. Under the 1996 EUP, ReTain was tested on nearly 4000 acres of apples in 18 states. When used according to label directions (i.e., 50 g AVG/acre applied 4 weeks before anticipated harvest) with a nonionic surfactant, ReTain effectively reduced preharvest drop and generally resulted in fruit of higher quality than untreated (control) or naphthaleneacetic acid (NAA) -treated fruit. ReTain can delay fruit maturity (as indexed by starch conversion) by ≈7 to 10 days. ReTain-treated fruit were typically firmer (by 0.5 to 1.0 lb), produced significantly less ethylene, and maintained notably greater firmness through storage. The incidence and severity of watercore in `Delicious' was significantly reduced by ReTain, as was the frequency of fruit cracking in `Fuji' and `Gala' in several trials. Based on this benefit profile, ReTain can be an effective harvest management tool for apple growers. U.S. EPA approval for the commercial registration of ReTain is anticipated prior to the 1997 use season.

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M. Clayton, W.V. Biasi, S.M. Southwick, and E.J. Mitcham

ReTain™, a commercial derivative of aminoethoxyvinylglycine, was applied as a single application at 124 g·ha-1 a.i. to `Bartlett' pear (Pyrus communis L.) trees 28, 21, 14, or 7 days prior to initial commercial harvest and at 62 g·ha-1 a.i. in combination with naphthaleneacetic acid (NAA) at 92 g·ha-1 a.i. 14 days prior to initial commercial harvest. Maturity and quality of treated fruits at harvest and following storage were compared with those of nontreated pears in 1996 and 1997. Ethylene production by mature green pears at harvest was not significantly affected by ReTain™ treatments, although softening, loss of chlorophyll, and starch clearance were usually inhibited by the 14- or 7-day treatment. ReTain™ suppressed ethylene production, softening and loss of chlorophyll in ripening pears and mature green pears cold-stored for 4 months, although loss of chlorophyll did not differ in the cold-stored fruit in 1997. ReTain™ had little effect on softening during a ripening period of 6 days after 4 months of cold storage. Application at 14 or 7 days prior to initial harvest appeared most effective, often with little difference between the two timings, and the 28- or 21-day treatment or combined ReTain™ and NAA treatment were seldom more effective. ReTain™ applied 14 or 7 days before initial harvest delayed fruit maturation by 4-10 days depending on the maturity index. The maturity or ripeness of pears from the combined ReTain™ and NAA, NAA only, and control treatments was often similar or differed only slightly. Premature ripening, prevalent in 1997, was dramatically suppressed in fruit treated with ReTain™. Ripening of both ReTain™- and non-ReTain™-treated fruit with ethylene reduced premature ripening by ≈50%.

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K.C. Taylor

For peach fruit to withstand the rather vigorous postharvest handling during the packing and shipping process, growers pick them fairly early when they are very firm. Yet they soften very quickly, giving them a shelf life of generally 5–15 days. It may be desirable to allow fruit to remain on the tree longer, allowing them to increase in size, while improving in flavor and color. The fact that aminoethoxyvinyl glycine (AVG), ReTain™, interferes with ethylene synthesis was borne out by findings that AVG applications prior to harvest delayed ripening, increased fruit removal force in apple, and reduced preharvest drop. Seven-day preharvest application of 50 g AVG/100 gal to two peach varieties increased firmness from 12% to 54% and moved 7% of the harvest to a date 3–7 days after AVG treatment. The additional time to peak harvest may indicate that the fruit can hang on the tree for a longer period, allowing additional time for fruit expansion. Preliminary indications are that only a 2% to 4% size increase can be achieved. However, this appears to be enough to move 5% to 7% of the fruit into the next ring size.

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Desmond R. Layne, Zhengwang Jiang, and James W. Rushing

Replicated trials were conducted in Summers 1998 and 1999 at two commercial orchards (A and B) to determine the influence of a metalized, high density polyethylene reflective film (SonocoRF) and aminoethoxyvinylglycine (ReTain), on fruit red skin coloration and maturity of `Gala' apples (Malus sylvestris var. domestica). There were four experimental treatments: 1) nontreated control; 2) reflective film (RF); 3) ReTain; and 4) RF + ReTain. RF was applied 4 weeks before anticipated start of harvest by laying a 5-ft-wide (150-cm) strip on each side of the tree row in the row middle. ReTain was applied 4 weeks before harvest at the commercial rate in one orchard and at 60% of the commercial rate in a second test. ReTain delayed fruit maturity. Fruit from RF trees had a significantly greater percent surface red color than fruit from trees not treated with RF. Fruit from RF + ReTain were significantly redder and had higher soluble solids concentration (SSC) than fruit from trees treated with ReTain alone. There were no differences in size, fruit firmness or starch content between fruit from RF and RF + Retain. RF appears to be a method to increase red skin coloration in `Gala' apples treated with ReTain without adversely impacting maturity.

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Chris B. Watkins, Randolph M. Beaudry, Terence L. Robinson, and Alan N. Lakso

ReTain™, a commercial plant growth regulator containing aminoethoxyvinylglycine, an inhibitor of ethylene production, was applied 4 weeks before normal harvest to `Jonagold' trees and the effects on fruit maturity and quality at harvest, and quality after air and controlled atmosphere storage was investigated. When fruit were harvested from 3 to 6 weeks after treatment, fruit ripening was inhibited as indicated by lower internal ethylene concentrations, delayed starch hydrolysis, and lower levels of skin greasiness. A number of factors indicated that other aspects of fruit metabolism were affected by the compound. Treated fruit were softer than nontreated fruit at the first harvest, and the benefits of ReTain on firmness appeared only at the later harvests. Also, at each harvest date, average fruit weight of ReTain-treated fruit was lower than nontreated fruit. We have investigated the possibility the ReTain and/or the accompanying surfactant, Silwet, inhibited leaf photosynthesis, thereby leading to altered carbon metabolism. Trees were unsprayed, or sprayed with surfactant, and ReTain plus surfactant. No treatment effects on photosynthesis were detected. However, leaf photosynthesis rates were generally low and quite variable. Measurements of fruit diameter confirmed that the increase in fruit volume following treatment was ≈2% less on the ReTain plus surfactant-treated fruit than nontreated fruit. The increase in fruit volume for the Silwet treatment was ≈1.5% less than in untreated fruit. The data indicates a rapid change in fruit volume as fruit changed in color. Inhibition of ethylene by ReTain may be an important factor influencing fruit size.

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Bob Ebel, Bobby Boozer, and Jim Pitts

This experiment was conducted to determine peach harvest delay, quality, and storage life by ReTain. ReTain was applied to `Loring' at 50 ppm at 17, 14, 12, 10, or 7 days before harvest (n = 4). Fruit were harvested based on conversion of ground color to yellow over five dates at 3- to 4-day intervals in July. Fruit were segregated into five size classes, counted, and weighed. Ten fruit were randomly selected from the 2.5-in. size class, and fruit quality was measured at harvest and after 5 days at 20 °C. Some fruit were stored for 5 days at 4 °C, removed from storage, and fruit quality measured 4 h after removal. Harvest date was not affected by ReTain. Firmness was higher for fruit held at 5 days in cold storage with earlier treatment application but not at harvest or after 5 days at room temperature, although the trend at harvest was similar to the 5-day storage data. Soluble solids were not affected at harvest, after storage or after 5 days at room temperature. Red blush was slightly less at harvest and after 5 days in cold storage with earlier application rates, but differences disappeared after 5 days at room temperature. Yellow color was higher with earlier application date after 5 days of cold storage but not at harvest or after 5 days at room temperature. These results indicate that ReTain may have some utility for improving peach firmness at harvest, but there was no benefit of harvest delay at the rates applied in this study.

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Wlodzimierz Ptasznik and Anwar A. Khan

The effects of various drying conditions on seed quality and performance of matriconditioned `Bush Blue Lake 47' snap bean (Phaseolus vulgaris L.) seeds were studied. An exponential model based on the Page equation provided a good fit (R2 = 0.9) to changes in moisture content during drying. Drying matriconditioned seeds with high initial moisture content (47.2%) for 5 to 6 hours at 35C, 30% to 35% relative humidity, and 0.7 to 1.4 m·s-1 air velocity (v) retained, and in some cases augmented, the benefits derived from conditioning. Matriconditioning greatly reduced electrolyte leakage (34.3 vs. 94.7 μS·cm-1·g-1 for nontreated seeds); drying to 15% moisture content at 0.7 or 1.4 m·s-1 v moderately increased the leakage rate (59.1 to 60.9 vs. 34.3 μS·cm-1·g-1), while drying at 0.02 m·s-1 v (ambient) increased the rate to that of nontreated seeds. The leakage rate remained low (43.6 to 50.8 μS·cm-1·g-1) in matriconditioned seeds dried to 22% moisture content at all air velocities. In growth-chamber studies, rapidly drying matriconditioned seeds to 15% moisture content at 1.4 m·s-1 v improved the emergence percentage over that of nontreated seeds, increased the shoot fresh and dry weight over that of nontreated and nondried matriconditioned seeds, and increased the shoot fresh weight over that of seeds dried at 0.02 or 0.7 m·s-1 v. Drying matriconditioned seeds to 15% moisture content at 0.7 m·s-1 v improved plant fresh weight over that produced by nontreated seeds. Rapid drying to 22% moisture content at 1.4 or 0.7 m·s-1 v improved only shoot fresh weight over that of nontreated seeds. In a 1992 field planting, percent emergence of matriconditioned seeds dried at 0.7 or 1.4 m·s-1 v was similar to that of nondried matriconditioned seeds and higher than that of nontreated seeds. No significant differences were noted in plant yield among the treatments.

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Desmond R. Layne, Zhengwang Jiang, and James W. Rushing

Replicated trials were conducted in summers of 1998 and 1999 at two commercial orchards (A and B) to determine the influence of a metalized, high-density polyethylene reflective film (SonocoRF, Sonoco Products Co., Hartsville, S.C.) and ReTain (Abbott Laboratories, Inc., N. Chicago, Ill.), on fruit red skin color and maturity of `Gala' apples. There were four experimental treatments: i) Control; ii) Reflective Film (RF); iii) ReTain; and iv) RF + ReTain. RF was laid 4 weeks before anticipated first pick date by laying a 5-ft-wide strip of plastic on either side of the tree row in the middle. ReTain was applied 4 weeks before harvest at the commercial rate in one orchard (A) and at 60% the commercial rate in the other orchard (B). At harvest, two 50-fruit samples were picked from each of four replicate blocks per treatment. All fruit were sized and visually sorted for color (1 = 0% to 25%, 2 = 26% to 50%, 3 = 51% to 75%, and 4 = 76% to 100% red surface, respectively). A 10-fruit subsample was selected following color sorting and evaluated for puncture pressure, soluble solids concentration (SSC) and starch hydrolysis. ReTain delayed maturity and reduced preharvest drop of `Gala'. Fruit from RF trees had a significantly greater percent red surface than fruit from trees not treated with RF. Fruit from RF + ReTain were significantly redder and had higher SSC than fruits from trees treated with ReTain alone. There were no differences in size, puncture pressure or starch hydrolysis between RF and RF + ReTain. RF appears to be a means to ensure greater redness in `Gala' treated with ReTain in South Carolina.