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Yuefang Wang, S. Kristine Braman, Carol D. Robacker, Joyce G. Latimer, and Karl E. Espelie

Epicuticular lipids were extracted from the foliage of six deciduous and one evergreen azalea genotypes (Rhododendron sp.) and identified by gas chromatography-mass spectrometry. The relationship of leaf-surface lipid composition with measures of resistance to azalea lace bug, Stephanitis pyrioides Scott, was evaluated. Each genotype had a distinct epicuticular lipid composition. The major surface lipid components from all test taxa were n-alkanes and triterpenoids. In the most resistant genotypes [R. canescens Michaux and R. periclymenoides (Michaux) Shinners] ursolic acid, n-hentriacontane, and n-nonacosane were the most abundant epicuticular lipids. The lipids present in largest proportion among all susceptible deciduous genotypes tested were α-amyrin, β-amyrin, and n-nonacosane. The proportions of the lipid components from the same plant of each genotype varied between spring and fall samples. Among classes of lipids, n-alkanes, n-1-alkanols, and triterpenoids had significant correlations with azalea lace bug behavior on host plants. Among individual components, heptadecanoic acid, n-hentriacontane, oleanolic acid, ursolic acid and one unknown compound (with major mass spectra 73/179/192/284/311) were significantly negatively correlated with host plant susceptibility to azalea lace bug, as measured by oviposition, leaf area damaged, egg and nymphal development, and nymphal survivorship. Triacontanol, α-amyrin, β-amyrin, and three unknowns were significantly positively correlated with host plant susceptibility. Acceptance or rejection by azalea lace bug to a particular plant may be mediated by a balance of positively and negatively interpreted sensory signals evoked by plant chemicals. This study indicated that the high levels of resistance observed in R. canescens and R. periclymenoides may be due to the lesser amount or the absence of attractants and stimulants for feeding or oviposition.

Open access

Rebecca L. Darnell and David C. Ferree

Abstract

The influence of environmental conditions on tree growth and cuticular covering of leaves of apple (Malus domestica Borkh.) was investigated in relation to spary uptake. Various interactions between environmental factors influenced growth responses. Under cooler temperatures (20°C), 75% shade reduced shoot growth and leaf number; however, under warmer temperatures (25°), shading had no effect. High soil water potential (−13 KPa) and 75% shade significantly reduced total leaf area per tree, while under low soil water potential (−33 KPa), shading had little effect. The dry weight of total leaves per tree decreased 46% as soil water potential decreased under full-sun conditions. Under shade, a decrease in soil water potential resulted in a 20% decrease in dry weight. Total stem dry weight decreased as temperature increased under full-sun conditions; however, temperature had little effect on stem dry weight in plants grown under shade. Under 75% shade, an increase in temperature decreased total specific leaf weight (SLW), while under full sun there was no temperature effect. SLW of newly formed leaves was not influenced by environmental interactions. Leaf epicuticular wax quantity increased as soil water potential decreased. A decrease in soil water potential increased the proportion of alkanes and wax esters in extracted leaf waxes. Alkane content also increased as temperature increased. The different environmental growing conditions influenced the photosynthetic mechanism and masked the effect of prometryn, a triazine herbicide, thereby rendering it unreliable as a method for determining foliar absorption.

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Yanrong Lv, Ibrahim I. Tahir, and Marie E. Olsson

( Table 1 ). Table 1. Oleanolic acid (OA) and ursolic acid (UA) (μg·cm −2 ) concentrations in peel of apple from rootstock ‘MM.106’ and ‘M.9’ at three harvest times in 2012 and 2013. Harvest time and storage effects on OA and UA concentrations. The three

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R.D. Belding, T.B. Sutton, and S.M. Blankenship

Apple sooty blotch (SB) is a disease complex caused by Gloeodes pomigina (Schw.) Colby, Leptodontidium sp. and other fungi. This study was undertaken to determine if G. pomigena and Leptodontidium sp. utilize some portion of the apple epicuticular wax as a carbon source for growth. Two isolates of G. pomigena and two of Leptodontidium sp. were used. Isolates were cultured on water agar coated with a thin layer of either nonacosane, ursolic acid, or complete apple wax and an uncoated control. Radial colony growth over a 30-day period was used to assess growth. Preliminary results suggest that G. pomigena differs from Leptodontidium sp. in carbon source preference. Gloeodes colonies were larger when ursolic acid and apple wax were used as a carbon source compared to nonacosane. Leptodontidium isolates grew best on apple wax. Also, growth was greater on nonacosane than ursolic acid. results from laboratory studies were compared to SB severity (percent surface area covered) in the orchard on cultivars of apples where the wax composition was determined. Although fungal genera were not detailed in the orchard, SB severity was positively correlated with the concentration of ursolic acid (r2=0.69) and nonacosane (r2=0.34).

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Zhiguo Ju and William J. Bramlage

Developmental changes in total cuticle and cuticular constituents were studied with `Delicious' fruit. Total wax (0.31 mg/cm2) and total cutin (0.54 mg/cm2, including carbohydrate polymers) were low in young fruit. They increased during fruit growth and reached 1.41 and 2.47 mg/cm2 of fruit peel at harvest, respectively. During fruit ripening at 20 °C, total cutin did not change, but total wax increased rapidly and reached 2.15 mg•cm-2 at 6 weeks. The increase of cuticular wax paralleled the increase of internal ethylene in fruit. Wax was separated by column chromatograph into four portions, hydrocarbons and wax esters, free alcohols, free fatty acids, and diols. More than half of the diols was ursolic acid. During fruit development, more hydrocarbons and diols accumulated in cuticle than free fatty acids and alcohols. During fruit ripening, all of the four portions increased, coincident with the climacteric rise in ethylene, but the increase rates of free fatty acids and alcohols were higher than those of other portions. Aminoethoxyvinylglycine (AVG, 220 mg•L-1) preharvest treatment inhibited internal ethylene synthesis to below 0.5 μL•L-1 during 6 weeks at 20 °C, and also inhibited wax accumulation. Ethephon (200 mg/L) preharvest treatment increased ethylene production and accelerated wax accumulation. α-farnesene accumulation coincided with increased internal ethylene and paralleled free fatty acid and alcohol accumulation.

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Robert D. Belding, Sylvia M. Blankenship, Eric Young, and Ross B. Leidy

Variation in amount and composition of epicuticular wax among several apple (Malus ×domestica Borkh.) cultivars was characterized by gas chromatography, thin-layer chromatography, and gas chromatography-mass spectroscopy. Across cultivars, wax mass ranged from 366 to 1038 μg·cm-2. Wax mass decreased during the 30 days before harvest. Ursolic acid accounted for 32% to 70% of the hydrocarbons that make up the epicuticular wax. Alkanes, predominantly 29-carbon nonacosane, comprised 16.6% to 49%. Primary alcohols of the hydrocarbons ranged from 0% to 14.6% of the epicuticular wax. Secondary alcohols of the hydrocarbons were the most cultivar specific, making up 20.4% of the epicuticular wax in `Delicious' and only 1.9% `Golden Delicious' strains. Aldehydes and ketones of the hydrocarbons represented a small amount of total wax, ranging from 0% and 6.0%. Percentage of primary alcohol in the epicuticular wax increased as fruit developed. Other components showed no distinct trends with fruit development. Examination of the ultrastructure of cuticular wax using scanning electron microscopy revealed structural differences among cultivars.

Open access

William Reichert, Harna Patel, Christopher Mazzei, Chung-Heon Park, H. Rodolfo Juliani, and James E. Simon

accumulate high amounts of essential oil and carvacrol, as well as rosmarinic, oleanic, and ursolic acids for applications in the food, nutraceutical, and cosmetic industries ( Shen et al., 2010 ). The OS10 plants, now named for release as ‘Pierre’, were

Open access

Li Liu, Lin Jin, and Qiaosheng Guo

acid, rosmarinic acid, oleanolic acid, and ursolic acid in G. longituba , respectively. The abbreviations of Haliangi , Acidibac , Flavobac , Nitrospr , Variibac , Steroidb represent the bacteria genera of Haliangium , Acidibacter

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Grant T. Kirker, Blair J. Sampson, Cecil T. Pounders, James M. Spiers, and David W. Boyd Jr

plant preference and feeding. Balsdon et al. (1995) examined epicuticular lipids from the upper and lower leaf surfaces of selected deciduous azalea cultivars and found that certain triterpenoids (more specifically ursolic acid, oleanic acid, and α

Free access

Chaowei Song, Qi Wang, Jaime A. Teixeira da Silva, and Xiaonan Yu

peony as an alternative source of oleanolic and ursolic acids Intl. J. Mol. Sci. 12 655 667 10.3390/ijms12010655