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- Author or Editor: J. Benton Storey x
Abstract
Ethephon was trunk injected into the transpiration stream of pecan trees 10 to 21 days before shuck split in an attempt to expedite shuck opening in 1983. Ethephon concentrations were based on the estimated amount of water flowing through the tree per day. At College Station and Hondo, Texas, a 10 ppm injection significantly increased shuck opening. Leaf drop was only 35% at 10 ppm compared to much higher leaf drop in previous research. There was no difference in number of nuts set and the extent of limb dieback between the control trees and those trunk injected with 10 ppm ethephon. At Ft. Stockton and Midkiff, Texas, injections of 10, 20, and 40 ppm increased nut opening and early leaf drop, but reduced fruit set in the following year (1984). There was no limb dieback at these locations. Injections of trees in El Paso failed to cause shuck opening.
Three-dimensional leaf and fruit distribution was studied in a 26-year-old `Success' pecan tree [Carya illinoinensis (Wangenh.) K. Koch]. The tree was typical of the trees in this orchard and typical of thousands of hectares of mature pecan trees growing in a crowded condition. There are fewer leaves and fruit in the lower and central canopy than in the rest of the tree. To obtain an adequate sample, measurements should be taken from branches arising at a height ≥4.75 m and from 1.9 m from the center of the tree trunk to the edge of the canopy around the trees. Fruit could be sampled from branches arising at ≥3.76 m from the ground and from 3.37 m from the center of the tree trunk to the edge of the canopy around the tree.
Preharvest germination (viviparity) can be a problem with nuts of pecan [Carya illinoinensis (Wangenh.) K. Koch]. Two southern-adapted cultivars (`Cherokee' and `Wichita') and one northern-adapted cultivar (`Johnson') were paternal parents in controlled crosses with the maternal parent `Wichita'. `Wichita' × `Johnson' seed took much longer to germinate than seed from either the `Wichita' × `Cherokee' cross or the `Wichita' self, therefore indicating that pollen source may influence germination characteristics.
`Cheyenne', `Mohawk', `Pawnee', and `Osage' grown in different locations in the United States were analyzed for fatty acid composition. The effect of heat units accumulated 12 weeks prior to shuck split were studied. Growing area affected the fatty acid profile for all cultivars. `Cheyenne' and `Mohawk' showed a positive correlation between heat units and oleic/linoleic acid ratios (r = 0.905 and r = 0.720 respectively), a positive correlation between heat units and oleic acid content (r = 0.863 and r = 0.773 respectively), and a negative correlation between heat units and linoleic acid content (r = -0.871 and r = -0.792 respectively). However, no correlation was obtained between heat units and the fatty acid profiles for `Osage' and `Pawnee'.
Evidence of professional competence is needed for those whose activities affect the well-being of the general public. Graduates of BS and MS programs in horticulture are not distinguishable from self styled individuals who assume the title of “Horticulturist” without earning it. Certification of horticultural graduates is the first step in gaining a recognition for the Horticultural Profession. ASHS has established a Certified Professional Horticultural Sub-Board of the American Registry of Certified Professionals in Agronomy, Crops and Soils (ARCPACS). Professional core requirements include courses horticultural crop management, pest management, soil science, plant physiology, botany, chemistry, and genetics. Supporting core courses include math, communication skills, and horticultural specialization courses. Applications from individual horticultural graduates will soon be accepted. Details of the curriculum, continuing education, ethics, and other eligibility requirements will be detailed.
Annual variation in fruiting by pecan [Carya illinoensis (Wangenh.) K. Koch] obtained from anecdotal records and state, district, county, and orchard data from Texas indicate exceptionally high synchronous fluctuations typically occurred every 34 years with a range of 2-7 years over the 66-year data base examined. Synchrony in fruit production was inversely related to the spatial distribution of pecans reflected in coefficients of variation ranging from about 60 at the state level to about 120 for two 10-ha orchards. These characteristics show that pecan exhibits roasting and that the species warrants further examination vis a vis interactions with nut feeders.
`Stuart' pecans were harvested as soon as shucks would split in the fall of 1989 and 45 kg inshell samples were placed in 30 × 30 × 105 cm drying bins. The nuts were dried at air volumes of either 0, 1.27, 1.56, 1.84, or 2.12 m3/min down to 4% moisture. Air temperature in the drying bins was maintained at uniform 35°C with the exception of the 0 air volume treatment which was allowed to dry at room temperature. Four random samples of each treatment were held in frozen storage awaiting fatty acid analysis. Palmitic, stearic, oleic, linoleic, and linolinic fatty acids were separated in a 183 cm × 3 mm packed column using a 10% Silar 10C phase on a Gas Chrom QII, 100/120. The samples dried with a air volume of 1.27 m3/min retained a significantly higher oleic acid content than the 0 and 2.12 m3/min drying volumes. The 1.27 m3/min volume retained 64.55 % oleic acid compared with 61.37'% for the 0 velocity sample and 59.61% for 2.12 m3/min treatment. The more desirable oleic/linoleic ratio of 2.24 was found in the 1.27 m3/min sample compared to a 1.78 ratio in the 2.12 m3/min sample. Increased volume of air in the drying bins was thus deleterious to these samples because of the loss of monounsaturated fatty acid.
Rootstock resistance to soil-borne phytopathogenic fungi, such as Phymatotrichum omnivorum (Shear) Duggar, is an important factor in disease control. Measurement of natural rootstock resistance is often based on plant survival/mortality percentage, and /or growth data. Fungal colonization of host roots in disease screening experiments may not be uniform for many reasons, causing variability in host response. Quantification of fungal colonization is needed in order to better understand rootstock performance. Ergosterol, a structural sterol in cell membranes of fungi, is not found in higher plants, and can thus be a measure of fungal colonization. Ergosterol was extracted from roots of pecan seedlings artificially inoculated with P. omnivorum and grown in an environmental growth chamber. Analysis of extracts with HPLC revealed that seedlings which were killed in screening, or had low root performance ratings, had increased levels of ergosterol. Non-inoculated controls also contained Ergosterol. indicating contamination and possible competition by other fungi.
Previous work in this lab has shown that drying temperatures above 35°C will cause excessive loss of the kernel's natural light color and less oleic (18:1) oxidation to linoleic (18:2) fatty acid. The former is undesirable because of poor consumer appeal and the latter is desirable because of superiority of oleic acid in reducing low density lipoprotein in the blood plasma of consumers and a longer shelf life. The drying temperature of 35°C and an air volume of 45 CFM was superior in 1989 to 75 CFM at the same temperature and an air dried control. Lower air volumes in 1990 proved to be no better than 45 CFM at 35°C The best compromise drying regime was determined to be 45 CFM at 35°C.
Nut count (NC), trunk circumference (TC), competition factor (CF), days from budbreak (DAY), and high or low crop year (YR) data were collected on 40 trees at three sites across Texas in 1985 and 1986, to create a model that would predict pecan [Carya illinoensis (Wangenh.) C. Koch] yield. The model developed predicted the natural logarithm of the total nuts on the tree [In(NUTS)]: In(NUTS) = 2.112 + [0.634 × In(NC)] + (0.00119 × TC) – (0.0701 × In(CF)) + (0.00639 × DAY) + (0.728 × YR). The equation accounts for 87% of the variation in yield. The model is not sufficiently accurate to predict individual tree yields well, but additional data show an ability to accurately predict average tree yields.