Heritability estimates for pecan [Carya illinoinensis (Wangenh.) K. Koch] nut weight, nut buoyancy, nut volume, nut density, kernel weight, and percentage kernel were determined from 8748 nut samples representing 152 families collected during 25 years in the U.S. Dept. of Agriculture (USDA) pecan breeding program at Brownwood, Texas. Measurements were corrected for year-to-year environmental variability using least-squares constants of individual year effects. Adjusted values were then regressed on midparent means. Generally, heritability (h2) estimates were low to moderate: nut weight 0.35, nut buoyancy 0.18, nut volume 0.35, nut density 0.03, kernel weight 0.38, and percentage kernel 0.32. The low values are probably due to the extreme alternate bearing tendency of this species, since crop load affects pecan nut characteristics so directly. Phenotypic correlations among these traits showed that larger or heavier nuts had significantly higher kernel weight, buoyancy, and percentage kernel. Nut density increased with higher nut and kernel weight, but decreased with nut volume.
were at a similar stage of crowding. The second aim was to examine the effects of manual and mechanical pruning on yield, nut characteristics, tree size, and economics in crowded orchards. Three pruning experiments were conducted. In the first
( Gilmour et al., 2009 ). Phenotypic and genetic (based on BLUPs) correlations (Pearson’s) were calculated among the three nut characteristics. Narrow-sense heritability was calculated using the GRM with the pin.r function in R ( White 2013 ), and broad
The ‘Jahong’ chestnut ( Castanea crenata Siebold & Zucc) was released from Korean native chestnut trees by the Korea Forest Research Institute (KFRI) to develop cultivars with desirable nut characteristics such as high sweetness, easy peeling, and
Pecan [Carya illinoensis (Wangenh.) C. Koch] tree height was gradually reduced by removing one, two, or three limbs per year at a height <9 m. Pruning improved tree vigor and color, increased trunk circumference, terminal shoot growth, nut size, and leaf N, P, and Mg, but reduced leaf K and percentage of fancy grade kernels relative to unpruned trees. Yield was not influenced by selective limb pruning.
Abstract
Drip irrigation on 1 and 2 sides of pecan [Carya illinoensis (Wang.) Koch.] trees was programmed to irrigate when soil water suction 61 cm from the emitter was greater than 0.1 bar at either 15, 30, or 45 cm depth. Results were compared with no irrigation. The data indicate little advantage of 2 lines of emitters over one line when the same number of emitters/tree are used. The data often favored 1 line over 2 lines. Total yield of pecans was increased substantially by drip irrigation on one side (‘Desirable’ and ‘Elliott’) or both sides of the tree (‘Elliott’), but increases from ‘Farley’ were not significant. In 1968, an extremely dry year, ⅓–½ of the shucks did not dehisce completely on nonirrigated trees while 1 to 7% of the shucks did not dehisce on irrigated trees. Irrigation increased nut size. Percentage kernel was increased by irrigation in 1968 but not in other years. In 1968, percentage fancy kernels was almost doubled by irrigation for ‘Desirable’ but was reduced for ‘Elliott’.
Although irrigation is a common practice in pecan (Carya illinoinensis) orchards, the effects of different methods of irrigation on young tree growth, nut quality, and nutrient uptake have not been estimated. Five irrigation systems and one nonirrigated control system were established. Tree performance was characterized by change in trunk diameter, weight per nut, average kernel percentage, and total trunk diameter growth. Nutrient uptake was determined by foliar levels. The five irrigation systems were a microsprinkler with a 35-ft diameter, a microsprinkler with a 70-ft diameter, two subsurface driplines irrigating for 2 days/week alternating between water for 2 hours and no water for 2 hours, two subsurface driplines irrigating 1 day/week for 20 hours continuously (LI2), and four subsurface driplines irrigating for 10 hours continuously for 1 day/week (LI4). Irrigation systems affected foliar levels of potassium (K), boron (B), and manganese (Mn) levels. Irrigation system did not affect change in trunk diameter or kernel percentage. A spatial Durbin error model was estimated to use trunk diameter estimates from all trees in the orchard. This model found the trunk diameters of nonirrigated and LI4 system trees to be significantly less than those trees that were irrigated by the LI2 system. When observations were pooled over all years, LI4 trees had individual pecan nut weights that were significantly less than all other systems.
Pecan [Carya illinoinensis (Wangenh.) C. Koch] fruit were thinned from `Mohawk' trees in Oklahoma and `Giles' trees in Kansas with a mechanical trunk shaker. All trees bore an excessive crop load before shaking. Fruit thinning improved the kernel percentage, individual nut weight, and kernel grade of `Mohawk', but nut characteristics of `Giles' were not affected by fruit thinning. Cold injury, caused by a sudden temperature drop in November, was positively related to the percentage of fruiting shoots in both cultivars. Fruit set in 1992 was negatively related to the percentage of fruiting shoots in 1991 in both cultivars. Consistent annual fruit set could be induced in `Giles' by fruit thinning, but return fruit set in `Mohawk', even at high levels of thinning, was low. Fruit thinning reduced yield the year of thinning in both cultivars. Thus, `Mohawk' trees should be thinned so that 50% to 60% of shoots bearing fruit at mid-canopy height would remain, and `Giles' trees should be thinned similarly to 65% to 70%.
for bursting time of leaf bud and leaf characteristics, flowering and fructification characteristics, harvesting time, yield and morphological nut characteristics, and nut traits on five grafted seedlings according to guidelines for the conduct of
trees. Nut characteristics. Several parameters including nut weight (grams), kernel weight (grams), kernel percentage [(kernel weight/nut weight) × 100], kernel size > 12 mm (percent), and some defects [percent (blanks, shrivel and glassy appearance