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Abstract
One of the functions of the National Seed Storage Laboratory is the preservation of genetic stocks. The 52,000 accessions now in storage include only 932 lots of seed which fall into this category. These are: 310 barley lines, 112 tomato mutants, 110 red pericarp lines of corn, and 400 radiation-induced mutants of oats. In the near future we should receive for storage 150 translocation stocks of barley. These total only a small fraction of such materials held at various locations throughout the country.
Abstract
Analysis of tissues of lettuce, Lactuca sativa L., seedlings failed to reveal the presence of anthocyanin, pheophytin or phenolic compounds as the cause of red cotyledons (physiological necrosis). Electron microscope study showed that the cells in the necrotic tissues were completely disintegrated with only the mitochondria identifiable.
In greenhouse and field plantings, necrotic seedlings that survived produced heads equal in size and total yield to those from normal seedlings. Seedlings with slight spotting were a few days behind normal seedlings in establishment, whereas those which were badly necrotic were about 2 weeks delayed. After 8 weeks in the greenhouse or field there was no differences in plant sizes. Seedlings with only slight necrosis appeared to be satisfactory for field seeding but badly necrotic ones would probably not give a satisfactory stand.
Mechanical pod strippers are the predominant method of harvesting lima beans (Phaseolus lunatus L.) for processing. Field losses are high, averaging 20% of potential yield in over 90 tests conducted in commercial fields. The three most significant factors that affect lima bean recovery are the field levelness, the relationship between ground speed and picking reel speed, and the lima bean variety. Further study on the relationship between pod location of four lima bean cultivars and the recovery of lima beans harvested with pod stripper combines was conducted in commercial fields. Pod location was categorized into three distinct zones of the plant. These three zones represented pods falling below the point the mainstem comes out of the ground, the first 5 cm from that point up the main stem, and all other pods higher than 5 cm above the stem. Differences in four cultivar's habits of setting pods in the three zones were established. `M-15' placed more pods in the lower zones than other cultivars. `M-15' also exhibited consistently more harvest loss than other cultivars when harvested with pod stripper combines. Other cultivars set pods higher in the plant and exhibited less harvest loss. With the harvest loss and pod set data, a rating procedure for the harvestability of lima beans was explored. While several potential rating systems demonstrated strong correlation with harvest loss data, a simple rating based on the percentage of pods in the canopy of the plant had the highest correlation coefficient (r = 0.96) with harvest loss. New cultivars can be evaluated for their harvestability characteristics using this rating system.
Production and harvesting systems for processing vegetables have been highly mechanized, however, field efficiencies are generally low, and high field losses and fruit damage continue to limit profits for several crops. By comparison, the number of fresh market crops currently machine harvested is small, and research to develop new harvesting technology for these crops is limited. Current mechanization research includes improvements to existing production systems, development of harvesters for crops currently hand-harvested, and the integration of new technologies into current (and future) production systems. Mechanical harvester-based production systems are evolving that reduce field losses and fruit damage, improve recovery, and decrease the foreign materials in the harvested product. However, improved cultural production systems and crop varieties that are adapted for once-over machine harvest are needed. An integrated approach in which crop characteristics along with planting, cultivating, and harvesting techniques are considered will be necessary to develop profitable and highly efficient alternatives to hand-harvest production. The integration of new technologies including differential global positioning systems (DGPS), automatic machine guidance, and computer-based vision systems offers significant performance benefits, and is a substantial component of current vegetable production and harvesting research in the U.S. In time, as the costs of these technologies decline, commercial adoption of these new methods is expected to increase.
The vegetable industry is important to our nation as a provider of nutritious and safe food directly consumed by our citizens. It is also critical to a rich and vigorous national agriculture. During the 20th century, engineering innovations coupled with advances in genetics, crop science, and plant protection have allowed the vegetable industry in the U.S. to plant and harvest significantly more land with higher yields while using less labor. Currently, fresh and processed vegetables generate 16% of all U.S. crop income, but from only 2% of the harvested cropland. Yet, many of the challenges in production that existed a century ago still exist for many crops. Perhaps the most significant challenge confronting the industry is labor, often accounting for 50% of all production costs. A case study of the mechanized production system developed for processed tomatoes (Lycopersicon esculentum) confirms that systematic methodology in which the machines, cultural practices, and cultivars are designed together must be adopted to improve the efficiency of current mechanized systems as well as provide profitable alternatives for crops currently hand-harvested. Only with this approach will horticultural crop production remain competitive and economically viable in the U.S.
The objective of these studies was to evaluate the efficacy of several concentrations of 1-aminocyclopropane carboxylic acid (ACC) for thinning apple at the standard growth stage for chemical thinning timing and a late thinning growth stage. ACC was applied at concentrations of 0, 100, 300, or 500 mg·L−1 to ‘Golden Delicious’/Bud.9 apple trees at 10 mm or 20 mm fruit diameter. Treatments were applied to the point of drip to individual whole trees in a completely randomized design with five (2010) and six (2011) replications. When ACC was applied at 20 mm, there was a linear dose relationship between concentration and fruit thinning in both years. ACC was ineffective at 10 mm. The naturally occurring compound ACC shows potential for use as a reliable late chemical thinner for apple.
Experiments were conducted over a 5-year period to determine the effects of abscisic acid (ABA) and benzyladenine (BA) applied alone and in combination on fruit set, fruit quality, and return bloom of ‘McIntosh’ and ‘Fuji’ apples. ABA thinned in 3 of the 5 years used and it thinned ‘McIntosh’ when applied at bloom, petal fall, and at the 10-mm fruit size stage. On ‘Fuji’, ABA thinned over a range of concentrations from 150 to 1000 mg·L−1. It caused leaf yellowing on ‘McIntosh’ but not on ‘Fuji’. When BA was applied with ABA on ‘McIntosh’, even at a rate as high as 1000 mg·L−1, it either dramatically reduced or prevented leaf yellowing and leaf abscission. The usefulness of applying BA with ABA was inconclusive because of variability in thinning response. ABA advanced surface red color on ‘McIntosh’ and when combined with BA, it reversed the reduction in red color caused by BA.
Renewal of limbs by pruning to leave a short, angled, upward-facing stub is common practice for spindle-type apple (Malus ×domestica) training systems. A short, beveled stub cut is thought to stimulate renewal growth from latent buds present underneath the base of the excised branch, and to stimulate smaller, more fruitful renewal limbs with wide crotch angles. We conducted trials over the course of 2 years that involved dormant pruning of ‘Buckeye Gala’ with renewal cuts to compare two stub lengths, 0.5 and 2 cm, and three stub orientations, upward facing, downward facing, and vertical facing, to determine the effects on renewal shoot number, position, angle, and length. We found no clear advantages with either stub length that we evaluated, and there was no improvement in renewal shoot quality with a bevel cut at any orientation. Stub length and stub angle did not influence limb renewal and may be unimportant for training orchard-pruning crews and for machine-learning and robotic pruning.
Abstract
Green and bleached beans designated as high and low vigor lots were stored at 21C and 50, 70, and 90% relative humidity. At the end of 36 months, no significant loss in viability occurred in either lot at 50% relative humidity. No significant loss of viability was found in the high vigor lot stored at 70% relative humidity but the low vigor lot lost all viability. Both lots were worthless for planting purposes when stored at 90% relative humidity for 3 months.
The objectives of this experiment were to test the efficacy of a mechanical string thinner (Darwin PT-250; Fruit-Tec, Deggenhauserertal, Germany) on apple and to identify an optimal range of thinning severity as influenced by spindle rotation speed. Trials were conducted in 2010 and 2011 at the Pennsylvania State University Fruit Research and Extension Center in Biglerville, PA, on five-year-old ‘Buckeye Gala’/M.9 apple trees that were trained to tall spindle. A preliminary trail on five-year-old ‘Cripps Pink’/M.9 was conducted to determine the relationship between string number and thinning severity. As the number of strings increased, the level of thinning severity increased. A range of spindle speeds (0 to 300 rpm) was applied to the same trees for two consecutive years. As spindle speed increased, blossom density (blossom clusters per limb cross-sectional area) was reduced as was the number of blossoms per spur. In 2010, leaf area per spur was reduced 9% to 45%. In 2011, the fastest spindle speed reduced leaf area per spur 20%. Although increased spindle speed reduced cropload, injury to spur leaves may have inhibited increases in fruit size. The largest gain in fruit weight was 28 g (300 rpm) compared with the control. In both years, the most severe thinning treatments reduced yield by more than 50%. There was no relationship between spindle speed and return bloom. Severe thinning treatments (240 to 300 rpm) caused significant reductions in spur leaf area, yield, and fruit calcium and did not improve fruit size or return bloom. Spindle speeds of 180 and 210 rpm provided the best overall thinning response and minimized injury to spur leaves, but cropload reduction was insufficient in years of heavy fruit set. Therefore, mechanical blossom thinning treatments should be supplemented with other thinning methods. Mechanical string thinning may be a viable treatment in organic apple production, where use of chemical thinners is limited.