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Abstract

Trunk protectors which reduced light (black polyethlene, perforated cardboard or 60% Saran shade cloth) applied to field grown Malus rootstocks (Mailing (M) 26, M 7 and Merton Mailing (MM) 106 an dMM 111) increased burrknot development. Root nodules and subsequent burrknots were formed in bud gap areas. MM 111 had the greatest tendency to produce large burknots.

Open Access

Leaf retention, uptake kinetics, total uptake (per unit leaf area), export kinetics, and the total export of foliage-applied, labeled B (]0B-enriched boric acid) were determined for apple (Malus domestics Borkh.), pear (Pyrus communis L.), prune (Prunus domestics L.), and sweet cherry (P. avium L.). Foliar uptake of labeled B by shoot leaves was 88% to 96% complete within 24 hours of application. More than 50% of the B retained on shoot leaf surfaces following application was absorbed and exported within 6 hours of application. Genotypic differences in shoot leaf surface characteristics among the species tested greatly influenced the amount of solution retained per unit leaf area. Leaf retention capacity was the primary determinant of the quantity of B absorbed by and exported from shoot leaves following foliar application. On average, apple shoot leaves retained, absorbed, and exported at least twice as much labeled B per unit leaf area as prune and pear shoot leaves and three to four times as much as sweet cherry shoot leaves. The sink demand of nearby, mature apples did not affect the export of labeled B when applied to adjacent spur leaves, but the fruit imported 16% of their total B from the applied solution during a 10-day period. Despite extensive documentation for the immobility of B accumulated by leaves naturally (e.g., from the soil), the B accumulated by leaves following foliage application was highly mobile in all four species tested.

Free access

The effect of boron (B) on in vivo and in vitro development of almond [Prunus dulcis (Mill.) D.A. Webb (syn. P. amygdalus Batsch)] pollen and pollen tubes and the resultant effect on fruit set was studied in mature trees. The cultivars Mono (pistil donor) and Butte (pollinizer) in an orchard with low soil B in Fresno, California were sprayed with B at 0, 0.8, 1.7, or 2.5 kg·ha-1 during Fall 1993. Pollen viability as indicated by the fluorescein diacetate method (FDA) was >85% and was not affected by field-applied B, however, in vivo pollen germination and tube growth were enhanced by foliar-applied B. More effect of applied B on in vivo growth appeared as pollen tubes progressed toward the ovary. For in vitro germination, foliar-applied B reduced bursting of tubes, and addition of B to the culture media significantly increased pollen germination and pollen tube growth.

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The effects of alternate bearing on recovery and loss of isotonically labeled fertilizer N and B and on the accumulation of carbohydrate and N reserves were assessed in mature `Kerman' pistachio (Pistacia vera L.) trees. Total recovery of labeled fertilizer N applied once (in late January) was ≈ 60% greater if applied to trees entering an “off' than an “on” year, with respect to fruiting. Eleven percent more labeled B was recovered in off- than on-year trees. Five times more N (1 vs. 0.2 kg N) was lost from the tree in fruit and senescent leaflets from on- than off-year trees. In dormant trees, 144% and 22% more starch and N reserves, respectively, were present after off than on years. Thus, on-year trees were characterized by a greater reproductive demand for N and carbohydrates, reduced accumulation of C and N (i.e., storage) reserves in perennial tree parts, and reduced recovery of January-applied labeled fertilizer N than off-year trees. As B is absorbed passively, the higher transpiration that may accompany the 43% larger leaf area per tree and the probability of increased root growth probably contributes to its increased uptake during off years. The enhanced labeled N recovery in early spring by trees entering their off year preceded fruit and seed development in on-year trees. The differential tree capacity for nutrient uptake in spring may have been conditioned the previous rather than the current year. The increased uptake of labeled N by trees entering an off year (i.e., emerging from an on year) was associated with lower levels of carbohydrate and N reserves than for on-year trees that had just completed an off year. Future experimentation should assess the comparative capacity for nutrient uptake by on-and off-year trees at other stages of phenology, e.g., during seed development and postharvest.

Free access

Estimates of leaflet and fruit macronutrient (N, P, K, Ca, and Mg) accumulation and resorption were developed in six (three heavily cropping, on-year and three noncropping, off-year) mature pistachio (Pistacia vera L. `Kerman') trees over three growing seasons during three stages of phenology [the spring growth flush (April to June); seed fill (late June to September); and leaf senescence (September to November)]. Crop load influenced total nutrient content per tree in annual organs (leaves and fruit), the relative allocation of nutrients between leaves and fruit, temporal patterns of nutrient accumulation in annual organs, and the magnitude of net leaf nutrient resorption per tree prior to leaf fall. In off-year trees, macronutrient accumulation in annual organs (leaves) was concentrated during the spring flush of growth. In contrast, significant macronutrient accumulation in annual organs of on-year trees (leaves plus fruit) occurred not only during the spring flush of growth but also during seed fill. Duration and magnitude of macronutrient accumulation were greater in on-year vs. off-year trees. Fruit N and P demand during seed fill was partially met by a net decrease in the N and P contents of the pericarp. These decreases in pericarp nutrient content during seed fill were equivalent to 32% and 26% of embryo accumulation of N and P, respectively. Fruit demand for N, P, and K during the spring flush of “on” years was accompanied by reduced leaf N, P, and K contents per tree. Net leaf N, Ca, and Mg resorption per tree during leaf senescence differed with crop load. Net leaf N resorption was significantly greater in off-year trees than on-year trees. Leaf N resorption presumably represents an important component of the N pool stored in perennial tree parts during dormancy. The greater leaf N resorption following “off” years was a function of greater leaf N concentration and greater leaf biomass per tree. In contrast, net leaf resorption of Ca and Mg was greater in on-year vs. off-year trees. Experimental validation of the magnitude and periodicity of nutrient uptake by mature pistachio trees is needed during the alternate-bearing cycle, especially in light of the potential contribution of current fertilization practices to groundwater contamination.

Free access

Abstract

Screening of 107 bean cultivars and plant introductions (PI) by 2-dimensional electrophoresis revealed only 3 different phaseolin patterns: Tendergreen (T), Sanilac (S), and Contender (C). The majority of the lines had either the ‘T’ (25%) or ‘S’ (69%) phaseolin patterns, with only 6% having the ‘C’ pattern. Phaseolin pattern was not strictly associated with commercial class but most cultivars with the ‘T’ pattern were snap beans, while the majority of lines with the ‘S’ pattern were dry beans. Furthermore, the phaseolin types of 15 cultivars were associated with previous cultivar groupings that were based on calculations of genetic relationships. A genetic distinction was noted between the groups of cultivars containing the ‘T’ and ‘S’ phaseolin patterns.

Open Access

Fruit from five apple (Malus domestica Borkh.) cultivars were pressure-infiltrated at 103 kPa for 6 min with a 0%, 0.73%, 1.46%, 2.91%, or 5.82% (w/v) Ca-equivalent solution of CaCl2, Ca EDTA chelate, or buffered CaCl2 solution (Stopit). The fruit were stored at 0 ± 1C for 18 weeks and then evaluated for Ca content, firmness, and injury. Fruit treated with Ca chelate had no increase in fruit Ca content and were injured at all treatment levels. No significant differences occurred in fruit Ca levels between CaCl2 and Stopit treatments across all cultivars tested. Apples treated with Stopit were firmer than apples treated with CaCl2, when averaged across cultivars. Fruit Ca levels, firmness, and incidence of injury were positively correlated with concentrations of CaCl2 and Stopit for all cultivars.

Free access

A pilot test was conducted over a 3-year period to determine the feasibility of using postharvest pressure infiltration of calcium into apples to maintain and/or improve the quality of fruit under commercial storage conditions. Fruits obtained from three different orchards were treated each year. `Golden Delicious' fruits were treated the first year, while `Delicious' fruits were treated the 2nd and 3rd years. In all treatments and years, there was a significant increase in calcium concentration of apples from all calcium chloride (CaCl2) treatments. In general, calcium concentration of treated fruit varied significantly among the three orchards. Firmness also varied among orchards, and was related to fruit calcium concentration. `Golden Delicious' apples were more susceptible to skin injury caused by CaCl2 treatment than were `Delicious' fruits. There was also an increase in infection as a result of some of the treatments, possibly due to injury caused to lenticels by the pressure applied or as a result of calcium injury.

Full access

Pgm-1, the gene responsible for variation in the most anodal isozyme of phosphoglucomutase in apple (Malus spp.), is shown to lie ≈8 centiMorgans from the gene Vf , which confers apple-scab resistance. The proximity of the marker and the ease by which allozymic forms can be resolved suggest that Pgm-1 will be useful for following the inheritance of scab resistance conferred by Vf .

Free access

Silver reflective plastic mulches were compared with conventional bare-ground culture of yellow crookneck summer squash (Cucurbita pepo L. var. melopepo Alef.) for reducing aphids and the following mosaic virus diseases: cucumber mosaic, watermelon mosaic I and II, zucchini yellows mosaic, and squash mosaic. Plants grown on silver plastic mulch produced higher marketable yields than those grown on bare ground. Other colors (white, yellow, and black with yellow edges) of plastic mulch were intermediate in their effects on aphid population and virus disease reduction. Silver reflective mulch alone and silver reflective mulch with insecticide were superior to other colors of plastic mulch in reducing aphid populations. Silver reflective plastic mulch, with or without insecticide, resulted in 10 to 13 days delay in the onset of the mosaic diseases noted.

Free access