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Renae E. Moran

The goal of this project was to evaluate the effectiveness of aminoethoxyvinylglycine (AVG) for increasing effectiveness of 1-methylcyclopropene (1-MCP) for maintaining firmness and preventing scald in `McIntosh' and `Cortland' apples (Malus ×domestica). AVG and 1-MCP used together maintained `McIntosh' apple firmness more than 1-MCP used alone after 120 or 200 days of controlled-atmosphere (CA) storage. AVG and 1-MCP can be used to maintain firmness of `McIntosh' when internal ethylene concentration (IEC) at harvest is as high as 240 μL·L-1, but CA storage life is limited to 4 months. AVG was not effective at increasing efficacy of 1-MCP on `Cortland' when IEC at harvest was not significantly different between AVG-treated and untreated fruit and IEC was less than 2 μL·L-1. AVG increased efficacy of 1-MCP on `Cortland' when IEC was 36 μL·L-1 in untreated fruit compared to undetectable in AVG treated fruit. 1-MCP prevented scald of `Cortland' in 1 year and reduced it to 5% or less in another year when fruit were stored 120 days. 1-MCP reduced `Cortland' scald to 34% or less after 200 days of storage.

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Renae E. Moran

In 2004, prestorage delays and CA storage were compared for occurrence of disorders. Fruit were harvested at a starch index of 5.9. Fruit were exposed to either a 2- or 5-day prestorage delay at 17 °C; or placed immediately into cold storage (control) at 0.5 °C. An additional treatment was CA storage at 2.5 °C. In February, occurrence of soft scald, soggy breakdown, and bitter pit were measured on 40 fruit per replication. Fruit were from `Honeycrisp'/M.26 trees planted in 1994. Treatments were replicated five times with four trees in each replication. Soft scald was very severe in this year, with 84% of control fruit being affected. Two-day prestorage delay reduced it to 48% and 5-day delay to 21%. Soggy breakdown was also severe with 14% of the fruit being affected. Two- and 5-day delays had no effect on occurrence of soggy breakdown, but CA storage increased it to 65%. Bitter pit was very rare and not affected by any of the treatments. These results demonstrate that in severe cases, shorter prestorage delay is not effective in preventing soft scald or soggy breakdown.

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Renae E. Moran and Patricia McManus

1-Methylcyclopropene (1-MCP) maintained firmness of `Macoun' apple (Malus ×domestica Borkh.) above 50 N after 90 to 100 days regular air storage when harvested at a starch index of 2.7 to 3.5, and after 50 days when harvested at a starch index past 4.0. Softening of `Macoun' was slowed by 1-MCP in both preclimacteric and climacteric fruit, but for a shorter duration in climacteric fruit. 1-MCP reduced but did not eliminate the occurrence of senescent breakdown. The effect of 1-MCP on coreline browning was inconsistent, reducing its occurrence in 2002 and 2003, but increasing its occurrence in 2001 when fruit were harvested at an advanced maturity.

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Renae E. Moran and Curt Rom.

Greenhouse grown `Lawspur Rome'/M.111 trained to single shoots were given the following shade (73%) treatments: 1) sun-all-day (control), 2) shade in the morning (am-shade), 3) shade in the afternoon (pm-shade) and 4) shade-all-day. All shade treatments increased shoot length and decreased dry weight/leaf area (DW/LA). Shade-all-day increased leaf no., LA/leaf and shoot dia. DW partitioning to leaves in shade-all-day was 19% greater than control and to roots was 34% less than control. Pn of am-shade did not increase in the afternoon when PFD was maximal. Saturated net photosynthesis (Pn) was 72% of control in am-shade, 84% of control in pm-shade and 62% in shade-all-day. Shade reduced Pn by 40% of control.

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Renae E. Moran and Stephen M. Southwick

Secondary bloom provides fireblight infection sites in pears (Pyrus communis L.) growing in the western U.S. Five types of secondary bloom occur in `Bartlett', and one of these, Type V, occurs mainly as a result of pruning. We examined the effect of pruning dates (Feb. to Sept. 1999), shoot age ranging from 1 to 4 years old, and type of pruning cut (i.e., heading, stubbing, or thinning) on Type V secondary bloom. Pruning date was a significant factor determining whether Type V would occur. There was a greater chance for Type V to occur from pruning in February or March than for pruning from May through September. There was an increase in Type V with increase in shoot age when pruning 11 Feb., 17 Mar., 14 May, or 11 Aug. There was no shoot age effect when pruning 18 June or 30 Sept. Type of pruning cut affected the number of Type V that occurred when pruning 14 May, 18 June, or 11 Aug., but the effect of type of pruning cut was inconsistent between these dates. There was no effect of type of pruning cut when pruning 11 Feb., 17 Mar., or 30 Sept. These results indicate that summer or postharvest pruning may reduce the number of Type V secondary bloom, particularly on shoots older than one year. This information can be used to develop a pruning strategy that reduces the number of Type V secondary bloom and potentially the number of fireblight infection sites.

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Curt R. Rom and Renae E. Moran

Trunk cross-sectional area (TCA) has been used to estimate leaf area (LA) and yield efficiency but variation in LA and TCA relationships have been unexplored. LA and TCA of 10-yr-old 'Starkspur Supreme Delicious' on 9 rootstocks (STKs) were measured in 1989. LA and TCA of 2-yr-old trees of 3 cultivars (CVs) on 5 STKs were measured in 1991. Regression of LA and TCA was performed for each CV, STK and each CV/STK. On mature trees, LA varied significantly with STK. The number and LA of shoot leaves (LVS) and spur LVS varied with STK but the % of total was not significantly different (approx. 52% spur LVS). The relationships of LA and TCA were linear for mature (r2=.94) and young (r2=.44) trees. On young trees, TCA varied with CV, but LA did not. Both LA and TCA were significantly different among STKs. The linear relationships of LA and TCA had unique intercepts with each CV, STK and CV/STK combination but slopes were not significantly different. Leaf area of Jonagold' and 'Gala' tended to increase more with increasing TCA than 'Empire'.

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Renae E. Moran and James R. Schupp

'Macoun'/B.9 apple (Malus ×domestica Borkh.) trees were planted in May 1998 in ± compost or ± monoammonium phosphate (MAP) for a total of four preplant treatments: 1) 90 g phosphorus (P) per tree, 2) 128 kg compost per tree, 3) 90 g P and 128 kg compost per tree, and 4) and an untreated control. MAP did not increase tree growth or yield in any year of the study. Compost increased canopy width into the sixth year after planting, and increased tree height and trunk cross-sectional area (TCA) into the seventh year. Annual yield was increased by compost in the fifth and seventh years, but not fourth or sixth year after planting. Compost increased cumulative yield in the sixth and seventh years.

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Renae E. Moran and James R. Schupp

'Macoun'/Budagovsky 9 apple (Malus ×domestica Borkh.) trees were planted in May 1998 in one of four preplant treatments that were soil incorporation of: 1) control, no phosphorus (P); 2) 90 g P per tree; 3) 128 kg compost per tree; and 4) 90 g P and 128 kg compost per tree. Preplant addition of P had no effect on soil organic matter, P, magnesium (Mg), and calcium (Ca) in the first three seasons after planting, but lowered soil potassium (K) in the second season. Foliar nutrients, tree growth and flowering were also not affected by P. The addition of compost increased soil organic matter and P in the first season after planting, and pH, K, Mg, and Ca in the first three seasons. The addition of compost increased foliar nitrogen and K in all three seasons, and decreased foliar Mg in the first season. Compost incorporation increased shoot length in the first season, trunk cross-sectional area in the first two seasons, tree height and the number of growing points in third season, and flowering in the third and fourth seasons. Compost addition was more effective than P fertilization for increasing tree growth during the establishment years.

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Renae E. Moran and Curt R. Rom

Our objective was to determine the potential for acclimation to high temperature in apple. `Imperial Gala'/Malling 26 EMLA and ungrafted Malling 26 EMLA tree were grown in growth chambers under four temperature regimes: 1) 25C for 42 days; 2) 35C for 42 days; 3) 25C for 21 days, followed by 21 days at 35C; and 4) 35C for 21 days, followed by 21 days at 25C. Response of net CO2 assimilation (A) to leaf temperature from 20 to 35C was measured at 21 and 42 days. Response to CO2 from 0 to 1000 ppm was measured at 42 days. Trees were separated into leaf, stem, and root fractions; dried; and weighed. High temperature increased the number of leaves per tree and reduced leaf size and leaf dry weight but did not affect leaf area, stem, and root dry weight. The apparent and minimal acclimation of A to high temperature is discussed.

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Renae E. Moran and Curt R. Rom

The relationship of variability in flowering and fruiting habit to canopy position and changing diurnal light and photosynthetic pattern was examined in 7 mature spur-type `Red Delicious'/MM106 apple trees. A .5×.5m column was placed in the north, south, east and west sections of tree canopies. Columns were subdivided by height with 3 study areas located at .25-.5m, 1.0-1.25m and 1.75-2.0m from the top of the canopy. In each, section, flowering index, fruit set, individual fruit weight and size, skin coloration, fruit soluble solids content, spur leaf area and spur bud diameter were determined. Photosynthetically active radiation and photosynthesis were measured from bloom through harvest correlated with variability in flowering, fruiting, spur quality and distribution of growth.