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  • Author or Editor: Michele Marini x
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Trunk cross-sectional area data for an NC-140 apple rootstock trial were collected in 1998. There were 18 rootstocks and 20 states, and these factors were arranged in a factorial structure; the interaction term (variety × state) was statistically significant (P < 0.05). There were 10 trees of each rootstock planted in each state, but some trees died and this created unequal numbers of observations. Historically these data would have been analyzed using PROC GLM in SAS, correctly identifying the interaction significance, and then analyzing differences for states within a rootstock, and differences for rootstocks within a state. This analysis would not take advantage of all the replication available in the study. To more appropriately utilize the available replication, and to account for the unbalanced number of observations, a macro program was written in SAS. The slice option in PROC MIXED generates individual significance levels for the rootstock factor within a state, but does not make comparisons between rootstocks within a state. The SAS macro was written to use the individual error terms and least squares means generated from PROC MIXED to make each individual Tukey's multiple comparison between rootstocks within a state. The justification for this analytical approach, the SAS macro, and the results of the analysis will be presented.

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Abstract

Diffuse photon flux density of photosynthetically active radiation (PAR) was measured throughout the season in peach trees [Prunus persica (L.) Batsch. cv. Harken] trained to an open center. Penetration of PAR generally decreased as shoot extension continued through the season. PAR was greater at the tree periphery and center than midway between the 2 points. PAR also decreased from the upper levels to the lower levels of the tree canopy. Specific leaf weight (SLW) at all positions increased from early June until August. SLW generally followed the same pattern as PAR, with lowest SLW developing midway between the tree periphery and center. Net photosynthesis (Pn) was greatest for peripheral leaves, lowest for leaves midway into the tree, and intermediate for leaves from the tree center. Pn and SLW were linearly correlated. Leaves developing at different distances from the tree center had similar stomatal resistances. There was no consistent influence of canopy position on chlorophyll content, but interior leaves tended to have greater chlorophyll content than peripheral leaves.

Open Access

A rootstock planting was established with `Starkspur Supreme Delicious' apple (Malus dornestica Borkh.) on nine rootstock near Blacksburg, Va. Five uniformly sized fruit per tree were sampled 1 week before normal harvest and three five-fruit samples were taken at harvest. Rootstock had no consistent effect on the proportion of red surface, which averaged ≈90% Ground color was most yellow for fruit from trees on M.26 EMLA and least yellow from trees on M.27 EMLA, OAR1, and MAC24. Starch was lowest for fruit from trees on MAC9 and (Ottawa) 0.3 and highest from trees on OAR1 and MAC24. Firmness differences were neither large nor consistent and ranged from 71 to 78 N. Soluble solids concentrations (SSC) of fruit were consistently high for fruit from trees on MAC9 and 0.3. A maturity index was calculated from the two harvest samples per year. Data for SSC, starch ratings, and ground color were ranked, and the highest maturity index was for fruit from trees on 0.3, MAC9, and M.26 EMLA.

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`Sweet Sue' peach (Prunus persica L. Batsch) trees were subjected to a factorial arrangement of treatments. At planting, trees were headed at 10 or 70 cm above the bud union and trees were trained to an open-vase or central-leader form. For the first 4 years, high-headed trees were larger than low-headed trees. After 7 years, open-vase trees had larger trunk cross-sectional area, tree spread, and canopy volume than central-leader trees. Open-vase trees had higher yield and crop value per tree, but lower yield and crop value per unit of land area or unit of canopy volume than central-leader trees. Crop density and yield efficiency were similar for all treatments.

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Girdled or nongirdled `Biscoe' peach (Prunus persica [L.] Batsch) secondary scaffold branches were covered with shade fabric to provide a range of photosynthetic photon flux densities (PPFD) from 44 to 20 days before harvest (DBH), from 20 to 0 DBH or 44 to 0 DBH. Fruit quality was affected differently by the various periods of shade during the final swell of fruit development. Shading 40 to 20 DBH did not affect fruit weight or quality, whereas shading 44 to 0 DBH had the greatest effect on fruit weight and quality. Fruit quality was generally similar on branches exposed to 100% and 45% incident PPFD (IPPFD). Fruit on” girdled branches generally responded to shade more than fruit on nongirdled branches. Fruit weight was positively related to percent IPPFD for girdfed but not nongirdled branches shaded 20 to 0 DBH and 44 to DBH. On nongirdled branches, fruit exposed to 45% IPPFD for 44 to 0 DBH had 14% less red color and 21% lower soluble solids content (SSC) than nonshaded fruit. Harvest was delayed >10 days and preharvest fruit drop was increased by shading to <23% IPPFD. Shading branches for 20 to 0 or 44 to 0 DBH altered the relationship between flesh firmness and ground color: Firmness declined as ground color changed from green to yellow for fruit shaded 44 to 20 DBH, but firmness declined with little change in ground color for fruit shaded 20 to 0 or 44 to 0 DBH. Girdling results indicated that fruit weight and SSC partially depended on photosynthate from nonshaded portions of the canopy, whereas fruit redness, days from bloom to harvest, and ground color depended on PPFD in the vicinity of the fruit.

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Field cage experiments were conducted in Ithaca, N.Y. in 2001 to determine the yield effect of potato leafhopper (Empoasca fabae) infestations on early-stage beans (Phaseolus vulgaris). Yields of `Hystyle' snap beans and `Montcalm' dry kidney beans were significantly reduced when infested by potato leafhopper at the cotyledon, two-leaf, and four-leaf stages. For snap beans, no differences in yield response from potato leafhopper were observed among the three plant growth stages. For dry beans, there was a difference in yield response between cotyledon and four-leaf-stage plants. Dynamic economic injury levels for potato leafhopper on early-stage beans are suggested.

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Abstract

Five apple (Malus domestica) cultivars were treated with NAA at 10 mg·liter–1 and dichlorprop at 5, 10, and 15 mg·liter–1 during 2 years. Although the response varied with cultivar, NAA generally delayed fruit abscission compared to the control. Preharvest drop was usually reduced by dichlorprop at 5 mg·liter–1 more effectively than by NAA. Preharvest drop of ‘Stayman’, ‘Rome Beauty’, and ‘Winesap’, but not ‘Delicious’, was inversely related to concentration of dichlorprop. Fruit redness, flesh firmness, soluble solids content, and starch ratings were not affected consistently at harvest or during storage by any treatment for any cultivar. Residue levels of dichlorprop in the fruit were related to treatment concentration and persisted until harvest. Chemical names used: naphthalene acetic acid (NAA); 2-(2,4-dichlorophenoxy) propanoic acid (dichlorprop).

Open Access

Researchers have collected a considerable amount of data relating to apple (Malus ×domestica) cultivars and rootstocks over the past 30 years, but much of this information is not easily accessible. The long-term goal of our working group is to increase access to this information using online technology available through eXtension. In eXtension, researchers and extension personnel are developing a community of practice (CoP) to increase the quality and amount of online information for individuals interested in our work [referred to as a community of interest (CoI)]. For this project, our CoI is broadly defined as commercial apple producers, nursery professionals, county extension educators, Extension Master Gardeners, home gardeners, and consumers. Our CoP is developing diverse educational tools, with the goals of increasing productivity, profitability, and sustainability for commercial apple production. Additionally, we will provide other members of our CoI access to research-based, reliable information on the culture of apples. We chose to begin our focus on cultivars and rootstocks adapted to the eastern United States and will add other U.S. regions as our resources and interest in our project grows.

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