Eric A. Curry

Evidence that α-farnesene biosynthesis during fruit ripening is mediated by ethylene regulated gene expression in apples

Abstract The effect of ethylene regulation on α-farnesene biosynthesis in preclimateric ‘Delicious’ and ‘Granny Smith’ apples was studied using an ethylene inducer and inhibitor, α-farnesene biosynthesis precursors, and protein transcription and translation inhibitors. α-Farnesene was not detectable when internal ethylene concentrations were less than 1 μl l −1 . Correlations between internal ethylene and α-farnesene production fit the exponential growth equation and were significant in ‘Delicious’ ( y = e 0.17 ; r 2 =0.68) and ‘Granny Smith’ ( y = e 0.18 ; r 2 =0.83). When applied at harvest, aminoethoxyvinylglycine (AVG) at 200 mg l −1 inhibited both internal ethylene accumulation and α-farnesene production, whereas ethephon at 200 mg l −1 accelerated both. Adding ethephon to AVG-treated fruit after 18 days at 20°C induced internal ethylene accumulation and α-farnesene production. Ethephon induced α-farnesene production in discs from preclimacteric fruit peel as well as AVG-treated fruit peel, but α-farnesene was undetectable when cycloheximide (CHI, 50 mM), actinomycin D (Act D, 50 mM), or silver nitrate (150 mg l −1 ) were added to the ethephon-treated discs. In preclimacteric fruit discs at harvest, with or without AVG treatment, α-farnesene biosynthesis was induced by 50 μM mevalonic acid lactone (MAL) or farnesyl pyrophosphate (FPP), but not by hydroxymethylglutaric acid (HMG). Adding CHI or Act D to these discs did not affect the induction of α-farnesene by MAL or FPP.

Ultrastructure of epicuticular wax aggregates during fruit development in apple (Malus domestica Borkh.)

Summary Development of wax platelets on the surface of ‘Delicious’ (Malus domestica Borkh.) apple fruit was investigated throughout the growing season using field emission scanning electron microscopy. At 5,000 and greater, wax crystalline structures appeared to be composed of microtubules (MT), aggregates of individual MT to form single platelets, and of one or more platelets. The thickness of a single wax platelet ranged from 116–128 nm, approximately the diameter of a single MT; whereas multiple-platelet aggregates ranged in thickness from 307–428 nm. Individual platelets, multiple platelet aggregates and MT were visible throughout fruit development, as well as on different apple cultivars. Examination of the cuticle from young fruitlets (receptacle diameter = 3 mm) of ‘Chinese Crabapple’ (M. hupehensis Rehd.), which develops without trichomes, best demonstrated early platelet formation. A model for wax platelet and cuticle development on apple is proposed based on these data.

Transitory growth control of apple seedlings with less persistent triazole derivatives

Paclobutrazol, triapenthenol (RSW0411), and BAS111 were applied to 4-week-old Delicious apple seedlings (Malus domestica Borkh.) as a root drench at 0.1, 1.0, and 10.0 mg per plant. Paclobutrazol eliminated shoot extension growth for 8 weeks at all three rates. RSW0411 controlled shoot elongation only at the highest rate. BAS111 produced the widest response, with shoot growth ranging from 38% to 93% of controls for the highest and lowest rates, respectively. Generally, leaf area decreased and leaf density increased with increasing rates of all chemicals. Root weight of plants treated with paclobutrazol nearly doubled but increased only slightly with RSW0411 and BAS111. Chemical analysis of the leaf tissue 8 weeks after treatment showed paclobutrazol levels highest, followed by RSW0411 and BAS111.

Rootstock effects on responses of potted ‘Smoothee Golden Delicious’ apple to soil-applied triazole growth inhibitors. I: Shoot and root growth

Abstract Emulsions containing 0, 1, 10 or 100 mg paclobutrazol, uniconazole or triapenthenol in 100 ml water were applied to the soil of potted cultivar ‘Smoothee Golden Delicious’ apple ( Malus domestica , Borkh.) on M 9, M 7a or MM 111 rootstocks (M = Malling, MM = Malling-Merton). Percentage reductions in shoot length were greatest for trees on MM 111 and M 7a, and least for M 9. Mean shoot lengths of treated trees compared to controls were 64% for MM 111, 69% for M 7a and 75% for M 9. Within rootstocks, triapenthenol caused the greatest and uniconazole the least reduction in shoot growth and stem cross-sectional area per unit increase in dosage. The marginal effectiveness for reduction in shoot length and cross-sectional area was greatest for triapenthenol and least for uniconazole, but the reverse was true for a reduction in shoot dry weight. Rootstock effect on root dry weight at the end of the experiment depended on the chemical used and the dosage applied. Total root growth was small in all treatments.

Stripped plant oils maintain fruit quality of 'Golden Delicious' apples and 'Bartlett' pears after prolonged cold storage.

Summary Effects of stripped (α-tocopherol reduced) plant oils (corn, soybean, peanut, cottonseed, and linseed) on ethylene, fruit firmness, colour, titratable acidity (TA), and soluble solids content (SSC) were evaluated in ‘Golden Delicious’ apples after six months’ and ‘Bartlett’ pears after six weeks’ storage at 08C. All oils similarly inhibited ethylene production and accumulation in the first two weeks in ‘Bartlett’ and in the first three months in ‘Golden Delicious’. Compared with the untreated controls, oil-treated fruit were firmer, greener, and contained a higher level of TA after six weeks or six months at 0°C plus 7.d at 20°C. Treating with 200.μl.l–;1 propylene for 6.h at harvest stimulated ethylene production, accelerated fruit softening and degreening, and reduced acidity after cold storage in untreated apples and pears. In oil-treated fruit, however, propylene treatment was ineffective. SSC was not affected by oil or propylene treatment. During one week of storage at 20°C, ethylene production and changes in fruit firmness, colour, and acidity were reduced by oil treatments applied to fruit at harvest (preclimacteric) or applied to fruit after one month of storage at 08°C (climacteric). The effectiveness of oil treatment, however, was higher in preclimacteric than in climacteric fruit.

Temperature dependent reappearance of variable PSII fluorescence of apple cultivars and rootstocks

Abstract The temperature sensitivity of PSII fluorescence recovery was identified for six different apple (Malus domestica L. Borkh) cultivars and rootstocks. Optimal temperatures ranged from 15–20 °C for ‘Yellow Transparent’ and ‘Beverly Hills’ to 20–30 °C for ‘Delicious’. Seedling rootstock had a broad optimal range of 15–25 °C whereas both M 26 and M 9 had more narrow optima centered on 20 °C. Rootstock had no effect on the optimum of the grafted scion, nor did the presence or absence of the scion shoot have any effect on the temperature optimum of the rootstock. It appears the scion/rootstock combination acts as two independent entities, each with its own characteristic optimum temperature for PSII fluorescence recovery.

Bioregulators influence calcium concentration and cold hardiness of young 'Delicious' (Malus domestica, Borkh) apple trees.

Calcium concentration and cold hardiness in woody shoots of young ‘Delicious’ apple trees increased during the first half of the dormant season by early-fall whole-tree application of bioregulators and/or plant protectant. Compared with untreated controls, the plant protectant, α-[(1,3-dioxolan-2-ylmethoxy) imino] benzene acetonitcile [Hytech Polymer, (formerly ProTecTM), Agro-K, Corp., Minneapolis, MN, USA] applied in September at 5 or 10% induced more cold hardiness in late October and November, whereas treating at 0.05% with the bioregulator, 2-chloroethyl-methyl-bis(phenylmethoxy)silane [CGA-15281, Novartis International AG, (formerly Ciba-Geigy Limited) Basel, Switzerland], induced greater cold hardiness and higher woody tissue calcium concentration in November and December. Applied in October, CGA-15281 resulted in woody tissue with the highest cold hardiness rating from November through March. From October 28 through 8 December, tissue from control trees had the lowest calcium concentration and frequently the least amount of cold hardiness. In woody stems of young apple trees, cold hardiness was more closely related to calcium concentration than that of the other eleven measured mineral elements; this was especially apparent from November to March (r = −0.856).