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Leonardo Lombardini*, D. Michael Glenn, and Marvin K. Harris

Trials were established in Summer 2002 and 2003 to test the consequences of the application of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural predators (insects and arachnids) on pecan (Carya illinoinensis, cv. `Pawnee') trees. Film application started immediately after bud break and was repeated every 7-10 days for seven (2002) or nine (2003) times during the season. On both years, treated trees frequently showed lower leaf temperature (up to 4 °C) than untreated trees. Leaf net assimilation rate, stomatal conductance and stem water potential were not affected by film application. Nut size and quality did not differ between the two treatments. In 2003, shellout (percentage of nut consisting of kernel) was in fact 54.2% and 55.5% for treated and control trees, respectively. Moreover, the two treatments yielded similar percentage of kernel crop grading as fancy, choice, standard and damaged. Similar were also the percentages of kernels that showed damage caused by stink bugs. Only on one date the number of adult yellow pecan aphids (Monelliopsis pecanis) counted on film-treated leaves was lower than in control leaves. In general, the density of common natural predators (lady beetles, green lacewings, spiders) of pecan pests did not differ between the two treatments; however, the number of green lacewing eggs was frequently lower on film-treated leaves. In film-treated trees the number of nutlets damaged by pecan nut casebearer (Acrobasis nuxvorella) was significantly higher than that observed on trees treated with conventional insecticide (24.2% infested nutlets vs. 9.3%, respectively) and did not differ from trees that did not receive either product (29.9%).

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Jose E. Villarreal, Leonardo Lombardini, and Luis Cisneros-Zevallos

Pecans nuts from `Kanza' and `Desirable' cultivars were irradiated with 0, 1.5, and 3.0 kGy using electron beam (E-beam) irradiation and stored under accelerated conditions (40 °C and 55% to 60% RH). Antioxidant capacity (AC), phenolic (TP) and condensed tannin (CT) content, HPLC phenolic profile, tocopherol content, peroxide value (PV), and fatty acid profile were evaluated in kernels after 0, 7, 21, 55, and 134 days of storage. Irradiation had no detrimental effects in AC and TP; however, variation was found throughout storage. Tocopherol content of 1.5 and 3.0 kGy kernels decreased after irradiation, but no further decrease was observed thereafter. Irradiated `Desirable' samples had greater PV than controls, while `Kanza' 1.5 kGy samples had increased PV only after 134 days of storage. No change in fatty acid composition was detected for any cultivar. Color modification induced by storage included a decrease in lightness and yellowness and an initial increase of redness followed by a decrease after 98 days of storage. No differences in phenolic profile were observed after irradiation. Compounds identified by HPLC in hydrolyzed extracts were gallic and ellagic acid, catechin, and epicatechin. In general, beside the decrease in tocopherol content, no detrimental effects were found in antioxidant composition caused by irradiation treatments. While a faster oxidation rate was seen in irradiated kernels for `Desirable' cultivar, no other quality attribute was affected by E-beam irradiation.

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Leonardo Lombardini, Astrid Volder, Monte L. Nesbitt, and Donita L. Cartmill

After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illinoinensis) trees in 2010, an experiment was conducted to evaluate the consequences of the injury on carbon assimilation and photosynthetic efficiency, and, in particular, to assess if low-to-moderate injury induces a compensatory increase in photosynthesis. Gas exchange and light-adapted fluorescence were measured on non-injured portions of the leaflet lamina adjacent to the injured area as well as on portions of leaflets that included leafminer injury. Results indicate that damage of the photosynthetic apparatus did not extend beyond the injured areas by leafminers. Furthermore, although a strong relationship between the proportion of leafminer injury and area-based net CO2 assimilation rate of injured leaflet tissue was found, there was no evidence that pecan leaves were able to compensate for leafminer injury by upregulating CO2 assimilation in leaflet tissue that was unaffected.

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Xiaoya Cai, Terri Starman, Genhua Niu, Charles Hall, and Leonardo Lombardini

A greenhouse study was conducted to evaluate the response of four garden roses (Rosa ×hybrid L.), ‘RADrazz’, ‘Belinda’s Dream’, ‘Old Blush’, and ‘Marie Pavie’, to drought stress. Plants grown in containers were subjected to two watering treatments, well-irrigated [water as needed: ≈35% substrate moisture content (SMC) at re-watering] and cyclic drought stress (withholding irrigation until plants exhibit incipient wilting: ≈10% SMC, then re-watering to field capacity for subsequent dry down). Shoot growth and flower number were reduced in the drought treatment compared with the well-irrigated plants in all cultivars with least reduction in ‘RADrazz’. Drought stress reduced root growth in ‘Belinda’s Dream’ and ‘Marie Pavie’, whereas there was no difference in root growth in ‘RADrazz’ and ‘Old Blush’. Decreased SMC induced reduction in net photosynthetic rate (Pn), stomatal conductance (g S), transpiration rate (E), and midday leaf water potential (ψ). Leaf water use efficiency (WUE) increased as SMC decreased in all cultivars. However, the relationship between these physiological parameters and SMC differed among the cultivars. At SMC between 10% and 20%, ‘RADrazz’ had higher Pn, g S, E, and WUE compared with the other three cultivars. Therefore, ‘RADrazz’ was the most drought-tolerant during container production among the cultivars investigated. With lower gas exchange rates and greater reduction in flower number at low SMC, ‘Marie Pavie’ was less drought-tolerant compared with the other three cultivars.

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Alison Bingham Jacobson, Terri W. Starman, and Leonardo Lombardini

Wilting during shelf life is a major cause of postharvest shrink for bedding plants shipped long distances from production greenhouses to retail outlets. The objective of this research was to determine if irrigation at lower, constant substrate moisture content (SMC) during greenhouse production would be a feasible way to acclimate plants for reduced shrinkage during shelf life while potentially conserving irrigation water. In two separate experiments conducted in the fall and spring seasons, rooted plugs of Angelonia angustifolia ‘Angelface Blue’ (angelonia) were grown in greenhouse production until a marketable stage in substrates irrigated at SMC levels of 10%, 20%, 30%, and 40% using a controlled irrigation system. At the end of the greenhouse production stage, plants were irrigated to container capacity and subjected to a simulated shipping environment in shipping boxes in the dark for 2 days. After shipping, plants were placed back in the greenhouse and watered minimally to simulate a retail environment. Data were taken at the end of each stage, i.e., greenhouse production, simulated shipping, and simulated retail. Results indicated that as SMC decreased from 40% to 10%, plants were shorter in height but had proportional and more compact flowering sections. The volume of water received by the 40% SMC plants was three times greater (fall) and 12 times greater (spring) than the 20% SMC plants during greenhouse production and two times greater (fall) and nine time greater (spring) during simulated retail. During production, midday water potentials decreased as the SMC levels decreased, but at the end of the simulated retail, the midday water potentials were the same, suggesting that plants that were drought-stressed during production were acclimated to lower water levels experienced in retail settings. Overall, the 20% SMC treatment produced the best postharvest quality plant resulting from reduced plant height without detrimental effects on flowering. The results demonstrate that while conserving water, controlled irrigation at a lower SMC can produce high-quality plants that have equal shelf life to those that are irrigated at high levels.

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Leonardo Lombardini, Tina M. Waliczek, and Jayne M. Zajicek

A study was conducted among the attendees of the Annual Texas Master Gardener Conference held in College Station, TX, in May 2006. Participants were asked to complete a 31-question survey to understand their knowledge of the nutritional attributes and storage guidelines of pecans (Carya illinoinensis). A total of 177 attendees completed the survey, corresponding to 32.2% of the total number of conference attendees. Participants were asked to complete the survey to test their nutritional knowledge, purchasing attitude, consumption, and storage preferences of pecans (23 questions). The remaining eight questions requested biographical and demographical information. Results revealed that taste was the main reason people ate pecans followed by the perception of eating something healthy. Over four-fifths of survey respondents knew that pecans contain heart-healthy fats and proteins. Approximately one-half of the respondents were aware that pecans are a source of minerals and antioxidants. However, 86.9% of the respondents believed that consuming pecans could lead to an increase in the levels of low-density lipoprotein (“bad”) cholesterol, which is opposite of what was reported by clinical studies. Over one-third of the respondents did not think that pecans require refrigeration to maintain flavor. Moreover, over half of the respondents did not believe that pecans store better if kept in the shell. Although the sample was limited because it was one of convenience, in general, respondents had good eating habits and a very positive attitude toward pecans. However, more educational programs are necessary to inform them about the health properties and proper storage methods of pecans.

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Tommy E. Thompson, L. J. Grauke, and Leonardo Lombardini

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Leonardo Lombardini, Mauro Falusi, Roberto Calamassi, and James A. Flore

Aleppo Pine (Pinus halepensis Mill.) is known to be the most drought-resistant Mediterranean Pine. This species is widely distributed throughout the Mediterranean region and displays a high intraspecific variability, with respect to its physiological and morphological response to environmental conditions. In this experiment we evaluated the response of Pinus halepensis seedlings to drought. Sixty germinated seeds (accession A6, Shaharia, Israel) were grown in soil for 8 weeks and then transferred to black plexiglass tanks containing half-strength air-sparged Hoagland solution. After 6 weeks of acclimation to hydroponics, the osmotic potential of the solution was lowered by adding polyethylene-glycol (PEG) 8000. Water potential was lowered in 0.2 MPa increments every 4 days, until a final value of –0.8 was reached. The seedlings were then maintained at –0.8 MPa for a further 8 days. Ultrasonic acoustic emissions, pressure–volume (P–V) curves, shoot and root growth, leaf area, xylem diameter, root apex mitotic index and cell length were measured on control and stressed seedlings. Seedlings were then transferred to normal Hoagland solution for 24 hours to simulate rewatering, and P–V curves and ultrasonic emissions measurements were repeated. Results showed that the final root growth is maintained in the stressed seedlings at the same rate as controls, whereas shoot growth was significantly reduced. The leaf area was reduced by stress to 36%, but the xylem diameter only to 10%, leading to a lower leaf area:xylem section ratio in the stressed plants. Ultrasonic emissions in the stressed plants were 365% of the control, and 182%, after rewatering. Specific details of the growth and physiology data are presented.

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Leonardo Lombardini, Marvin K. Harris, and D. Michael Glenn

Trials were conducted during summer months of 2002 and 2003 to evaluate the effects of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural enemies (insects and arachnids) on pecan (Carya illinoinensis `Pawnee') trees. Film application was repeated for seven (2002) or nine (2003) times during the growing season. In both years, treated trees showed lower leaf temperature (up to 4 °C) than untreated trees. During the warmest hours of the day, kaolin-treated leaves were generally 0 to 2 °C cooler than air temperatures, compared to 4 to 6 °C for control leaves. Leaf net assimilation rate, stomatal conductance and stem water potential were not affected by film application. Nut size and quality did not differ between the two treatments. Shellout (percentage of nut consisting of kernel) was not affected by treatment and averaged about 55%. Crop grade distribution (fancy, choice, standard, and damaged) was also similar among treatments in both years. In both years, numbers of green lacewing eggs was less on kaolin-treated compared to control leaves. The density of common natural enemies (lady beetles, green lacewings, spiders) of pecan pests did not differ between treatments. The average number of developing nuts damaged by pecan nut casebearer (Acrobasis nuxvorella Neunzig) was significantly higher in kaolin-sprayed trees (24.2%) compared to control trees sprayed with conventional insecticides (9.3%). The results suggest that kaolin-based particle film may not be a viable alternative to conventional methods of controlling pecan pests. Also, under adequate irrigation conditions, carbon assimilation, water relations and productivity may not benefit from kaolin particle film application.

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J. Emilio Villarreal, Leonardo Lombardini, and Luis Cisneros-Zevallos

The objective of this study was to evaluate kernels of different pecan (Carya illinoinensis) cultivars for their antioxidant profile and their contribution to nutritional and quality attributes. Kernels were analyzed for their antioxidant capacity (AC), phenolic, tannin, and vitamin C content. Fatty acid (FA) composition and phenolic profile were determined using, respectively, gas and liquid chromatographic techniques. AC was measured using one spectrophotometrical [2,2-diphenyl-1-picrylhydrazyl (DPPH)] and one fluorescence method [oxygen radical absorbance capacity (ORAC)]. Phenolic and tannin content were determined using spectrophotometrical assays. Ascorbic and dehydroascorbic acid were determined using a HPLC. Both AC methodologies gave similar results with marked differences between cultivars. `Desirable' had an antioxidant capacity of 47,747 μg·g-1 TEq/DW with DPPH method followed closely by `Cheyenne' (36,192 μg·g-1 TEq/DW) and, with smaller amounts, by `Cape Fear' and `Pawnee' (16,540 and 13,705 μg·g-1 TEq/DW, respectively). Total phenolic content showed a similar trend, but `Pawnee' showed a higher phenolic content than `Cape Fear'. The FA composition varied between cultivars. This phenolic profile jointly with FA composition and other compositional characteristics will provide the quality and nutritional attributes of each specific cultivar. Furthermore, the high antioxidant profile of pecans suggests that bioactive and anticancer properties should also be evaluated. Results from the present research can be used as an additional tool to evaluate pecan cultivars and help create new guidelines for breeding programs to select “healthier” pecans.