Pecan Fruit Research Articles

Integrated transcriptomic and lipidomic analysis provides key insights into lipid content changes during pecan (Carya illinoensis) fruit development.

Pecans [Carya illinoinensis (Wangenh.) K. Koch] are highly valued for their abundance of quality healthy lipids, positively impacting human health and making themselves a preferred choice for nutritionally rich foods. However, a comprehensive understanding of the high-resolution characteristics of pecan fruit lipid composition and its dynamic changes, as well as the transfer between embryo and pericarp during development, remains incomplete. In this study, through integrated multi-omics analysis, we observed significant spatiotemporal heterogeneity in lipid changes between the pericarp and embryo. It showed smaller fluctuations and more stable lipid levels in the pericarp while exhibiting a dynamic pattern of initially increasing and then decreasing lipid content in the embryo. In this study, a total of 52 differentially expressed genes were identified, related to fatty acid synthesis and metabolism pathways in the two tissues, with changes in oleic acid and linoleic acid composition being the primary features of the embryo. This research lays the foundation for further understanding the differential regulation mechanisms of lipid metabolism between embryo and pericarp. Overall, this study filled the knowledge gap regarding dynamic changes in pericarp lipid metabolites, provided crucial insights into the lipid metabolism network during pecan fruit development, and established a scientific basis for the genetic improvement of pecan crops.

Enhancing Soil Fertility and Elevating Pecan Fruit Quality through Combined Chemical and Organic Fertilization Practices

This study focused on 6-year-old ‘Pawnee’ pecan trees to elucidate the differential responses of physicochemical properties of orchard soil and pecan fruit quality when combining chemical and organic fertilizers. The aim was to unveil the mechanisms that underlie the effects of different fertilization treatments on soil fertility, soil enzyme activities, and pecan fruit quality. Four treatments were established: sole chemical fertilizer (CF; N:P2O5:K2O is 15:15:15), chemical fertilizer combined with cake fertilizer (CF+CC), chemical fertilizer combined with manure fertilizer (CF+M), and chemical fertilizer combined with cake and manure fertilizer (CF+CC+M). Measurements were taken to assess the soil nutrient content, soil enzyme activities, and fruit growth quality in some orchards under different fertilization treatments. The results revealed that the combined application could increase yield and enhance pecan quality. Among these, the CF+M+CC treatment demonstrated the most favorable outcomes, with the pecan kernel oil and unsaturated fatty acid contents reaching 72.33% and 97.54%, respectively. The combined fertilization treatments had no significant impacts on soil trace elements such as Mg, Cu, and Mn; however, it significantly increased the Available Phosphorus (AP), Total Nitrogen (TN), Soil Organic Matter (SOM) and S-ACP (soil acid phosphatase) activities. In summary, the combined application of chemical and organic fertilizers can significantly increase the soil nutrient content and enzyme activities in pecan orchards, to promote the enhancement of fruit quality and economic aspects.

Identification of Fatty Acid Components and Key Genes for Synthesis during the Development of Pecan Fruit

Carya illinoinensis (Wangenh.) K. Koch, a species native to North America, is one of the most famous fruit oil trees worldwide. Fatty acids are essential energy storage substances in the human body. Transcriptome sequencing of pecan kernels was used to screen the key genes of fatty acid synthesis in pecan fruit development. The dynamic changes in the fatty acid fractions of the pecan kernels in different periods were analyzed using GC-MS. This study shows that oil accumulation in seeds follows an ‘M’-shaped bimodal curve, according to the proportion of fatty acid components, from big to small, for oleic acid, linoleic acid, palmitic acid, stearic acid, and linolenic acid. A total of 83.82 Gb of clean data was annotated using the RNA-seq of pecan fruits at distinct stages after flowering, 5376 new genes were discovered, and 2761 new genes were annotated in at least one database. SAD and FAD2 were significantly upregulated at 80–95 and 95–110 days, and downregulated at 110–130 days after flowering. These differently expressed genes (DEGs) were enriched in fatty acid biosynthesis, elongation, and concentration. This study aims to reveal the pecan high-oil synthesis mechanism of unsaturated fatty acids for the genetic improvement of pecan in potential genetic resources in order to promote the work of breeding pecan.

Quantitative Phosphoproteomic Analysis Reveals Potential Regulatory Mechanisms of Early Fruit Enlargement in Pecan (Carya illinoinensis)

Pecan (Carya illinoinensis) is a popular tree nut. Its fruit development undergoes slow growth, rapid expansion, core hardening, and kernel maturation stages. However, little is known about how pecan initiates fruit development and enlargement after pollination. In this study, we performed the first large-scale identification of potential phosphorylation sites and proteins at early development of pecan fruit by a label-free phosphoproteomic quantification technique. A total of 2155 phosphosites were identified from 1953 phosphopeptides covering 1311 phosphoproteins in unpollinated pistils and fruits at 5 and 9 weeks after pollination. Of these, 699 nonredundant phosphoproteins were differentially phosphorylated (DP). Furthermore, the phosphorylation intensity of DP proteins in brassinolide (BR) and auxin signaling were analyzed, and the function of CiBZR1 was investigated. Ectopic expression of CiBZR1 resulted in BR response phenotypes with curled leaves and fruit, while enlarged seed size in Arabidopsis. Subcellular localization and transcriptional activation activity assay demonstrated that CiBZR1 distributed in both the nucleus and cytoplasm with transcriptional activity. When two phosphosites mutated, CiBZR1S201P,S205G moved to the nucleus completely, while the transcriptional activity remained unchanged. Taken together, our data reveal extensive phosphoproteins and lay a foundation to comprehensively dissect the potential post-translational regulation mechanism of early development of pecan fruit.

Design And Build A Double Roll Type Pecan Breaking Machine With A Power Of 0.5 Hp

Pecan is one of the spices that become an ingredient in the process of the food and cosmetic industry. The pecan separator machine is made to facilitate and speed up the process of breaking the pecan fruit in order to increase work efficiency in the hope that the machine can achieve high efficiency in the form of good fruit yields. The purpose of this pecan fruit separator machine is to help facilitate the community in processing pecan fruit to the maximum of its production, and the community can also increase the processing productivity of pecan fruit, which can improve the community's economy. The research method applied in this study is an experimental method, namely the initial stage of designing a double roll type pecan breaking machine using Auto CAD. Then build the machine in the workshop based on the design that has been done before. The stages passed are making design drawings in Auto CAD and analyzing the components used in the pecan breaking machine. Such components are the frame, inlet funnel, shaft, breaker roller, bearing and outlet funnel. From the results of the analysis, the motor power is 0.5 HP with a rotation of 1400 rpm. The belt length used from the calculation of the pulley size on the 3" machine and the pulley on the 10 breaking roll is 42". For breaking rollers the outer diameter of the roller = 120 mm, the inner diameter of the roller = 100 mm, and the length of the roller = 190 mm. The shaft on the drive motor is 24 mm in diameter. The shaft isestimated to be of S30C carbon steel with tensile strength = 48 kg/mm².

Transcriptomic Analysis to Unravel Potential Pathways and Genes Involved in Pecan (Carya illinoinensis) Resistance to Pestalotiopsis microspora.

Fruit black spot (FBS), a fungal disease of pecan (Carya illinoinensis (Wangenh) K. Koch) caused by the pathogen Pestalotiopsis microspora, is a serious disease and poses a critical threat to pecan yield and quality. However, the details of pecan responses to FBS infection at the transcriptional level remain to be elucidated. In present study, we used RNA-Seq to analyze differential gene expression in three pecan cultivars with varied resistance to FBS infection: Xinxuan-4 (X4), Mahan (M), and Wichita (W), which were categorized as having low, mild, and high susceptibility to FBS, respectively. Nine RNA-Seq libraries were constructed, comprising a total of 58.56 Gb of high-quality bases, and 2420, 4380, and 8754 differentially expressed genes (DEGs) with |log2Fold change| ≥ 1 and p-value < 0.05 were identified between M vs. X4, W vs. M, and W vs. X4, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analyses were performed to further annotate DEGs that were part of specific pathways, which revealed that out of 134 total pathways, MAPK signaling pathway, plant–pathogen interaction, and plant hormone signal transduction were highly enriched. Transcriptomic profiling analysis revealed that 1681 pathogen-related genes (PRGs), including 24 genes encoding WRKY transcription factors, potentially participate in the process of defense against Pestalotiopsis microspora infection in pecan. The correlation of WRKY TFs and PRGs was also performed to reveal the potential interaction networks among disease-resistance/pathogenesis-related genes and WRKY TFs. Expression profiling of nine genes annotated as TIFY, WRKY TF, and disease-resistance protein-related genes was performed using qRT-PCR, and the results were correlated with RNA-Seq data. This study provides valuable information on the molecular basis of pecan–Pestalotiopsis microspora interaction mechanisms and offers a repertoire of candidate genes related to pecan fruit response to FBS infection.

First Report of Anthracnose on Pecan (Carya illinoiensis) Caused by Colletotrichum siamense in Korea.

In 2020, severely infected fruit of pecan, Carya illinoiensis, showing distinct anthracnose symptoms were observed from pecan orchards in Uiseong (36°21'31.5"N 128°27'15.9"E) and Miryang (35°22'54.9"N 128°48'06.5"E) in South Korea. Visible symptoms occurred on fruit of the tree between June and July, which included dark, depressed and covered with irregularly shaped lesions. As the disease progressed, the lesions expanded and merged over time, leading to abscission of the fruit, which resulted in severe yield loss of pecan fruit. Of pecan varieties including Caddo, Giles and Peruque that were cultivated in each pecan orchard, Caddo appeared to be most susceptible to the disease. Estimated losses were approximately 30% and 70% for the Uiseong and Miryang pecan orchard, respectively. For pathogen isolation, ten symptomatic fruits of pecan were randomly collected and brought to the laboratory. The fruits were surface disinfested for 30 s with 70% ethanol and 1% sodium hypochlorite. These were then rinsed with sterile distilled water twice, placed in a humid chamber, and incubated at 25 ± 1°C with a photoperiod of 12 h. Acervuli filled with salmon-colored conidial masses were produced abundantly on the fruit a day after the incubation. Conidia were single celled, hyaline, cylindrical having rounded ends, smooth walls, guttulate, 15.5 to 17.7 µm long, and 3.4 to 4.8 µm wide (n = 20). Monoconidial isolates were made on 2% malt extract agar and incubated at 25°Ϲ for two weeks in the dark condition. Of those that were successfully retained, two representative isolates from each orchard were deposited in the culture collection (CDH) of the National Institute of Forest Science, Korea (Accession No. CDH2020-17-18). To ensure the identity of the pathogen, molecular identification was made based on three gene regions, the internal transcribed spacer (ITS) region of rDNA, beta-tubulin (TUB2) gene and a partial sequence of the actin (ACT), which were amplified with ITS1F/ITS4, T1/Bt2b and ACT-512F/ACT-783R, respectively (Weir et al. 2012). These were then submitted to GenBank with accession numbers of MW380423-24 for ITS, MW387129-30 for TUB2 and MW387127-28 for ACT. A BLAST search in GenBank revealed that the sequences showed high similarity to those of Colletotrichum siamense, which were identical to MT434615 and MT274214 for ITS and ACT, respectively, and 99.7% to MK967337 for TUB2. Phylogenetic analysis based on the maximum likelihood method further showed that the isolates recovered in this study clustered with C. siamense, confirming its identity. Pathogenicity was confirmed by inoculating living pecan trees. Healthy fruits from five trees were surface cleaned with cotton soaked in sterile water and air-dried. To inoculate the pathogen, three to five fruit per tree were wounded with a sterilized needle, and an aliquot of 10 μl of spore suspension (1.0 × 105 conidia/ml) of C. siamense (CDH2020-18) was dropped on each wound. To keep moisture, each treated fruit was enveloped by a plastic bag where the cotton soaked in sterile water had been placed. Controls were treated with sterile distilled water drops. The symptoms with dark, depressed and irregularly shaped lesions developed from all inoculated treatments six weeks after the inoculations, which were identical to those observed in the field. However, no symptom was observed on the control. Colletotrichum siamense was successfully re-isolated, fulfilling Koch's postulates. Taken together, it was confirmed that C. siamense is the causal agent of anthracnose on pecan. In Korea, C. siamense was reported causing anthracnose on apple, persimmon and plum (Farr and Rossman 2020). However, to our knowledge, this is the first report of anthracnose on pecan caused by C. siamense in Korea. To control the disease effectively, more attention should be paid to other regions of the country where the disease caused by the pathogen might occur.

Zinc Content and Fruit Quality of Pecan as Affected by Application of Zinc Sulfate

Pecan [Carya illinoinensis (Wangenh.) K. Koch] is an important nut tree species, and Zn nutrition is critical for its growth and nut production. The aim of this study was to provide a perspective on Zn accumulation in pecan fruit over time and to determine the effects of Zn application on fruit quality. Two concentrations of ZnSO4 (0.4% and 1.6%) were sprayed onto the shuck or the nearest pair of leaflets. Purified water was sprayed similarly as the control. The results show that Zn application to the shuck and leaves increased the Zn concentration and content in embryos. The greater the concentration of the Zn solution sprayed, the greater the Zn concentration in the embryo. The greatest zinc concentration in the embryo was found during the early stage of embryo development. In the treatment during which 1.6% ZnSO4 was sprayed onto the shuck, the Zn concentration in the early embryo was 242.91 mg·kg–1, which was 2.2 times that of the control. Thereafter, embryo Zn concentration decreased gradually until maturity. The treatments could be ranked, from greatest Zn concentration in the mature embryo to least, as follows: 1.6% ZnSO4 on shuck (66.36 mg·kg–1) &gt; 1.6% ZnSO4 on leaflets (64.28 mg·kg–1) &gt; 0.4% ZnSO4 on leaflets (55.51 mg·kg–1) &gt; 0.4% ZnSO4 on shuck (49.67 mg·kg–1) &gt; control (47.34 mg·kg–1). A model was presented that showed Zn was transported from the shuck and leaves to the stalks through the conducting tissue, and then to the embryo through the embryo sac. The application of 0.4% ZnSO4 to the shuck resulted in the greatest oil content (74.05%), which was 10% greater than that in the control. Applications of 0.4% ZnSO4 to the shuck and leaflets resulted in a greater proportion of oleic acid (≈69%) and a lower proportion of linoleic acid (≈20%), palmitic acid (≈6.0%), and linolenic acid (≈1.1%). The results of this preliminary investigation are useful for exploring the mechanism of action for Zn on pecans.

Explicit dynamics simulation of Pecan fruit deformation under compressive loading-Part-2: Explicit dynamics simulation procedure

This study, which is divided into two parts, introduces an explicit dynamics simulation procedure for Pecan fruit (Carya illinoinensis) deformation under compressive loading. This second part of the study covers a microstructure investigation for the inner structure of the Pecan fruit components, discussions on the material models used in FEM-based simulation, and the explicit dynamics simulation procedures. An application algorithm based on experimental and theoretical methods is described in the study. Visual understanding and/or presenting a detailed description of the deformation behavior/characteristics for agricultural products through analytical calculations or/and physical experiments is a complicated phenomenon. Most especially, this phenomenon becomes more complicated for shelled edible agricultural products under varying loading cases. Numerical method based advanced engineering simulation techniques may be useful for a deeper visual understanding of agricultural product deformation behavior/characteristics. A major focus of the second part of the study detailed in this paper is finite element method (FEM) based explicit dynamics simulation procedures and the realistic representation of time dependant nonlinear deformation of Pecan fruit (kernel-in-shell) under a two plate compression loading case. Simulation results pointed out that the maximum equivalent stress values were 18.10, 11.50, and 1.14 MPa for whole Pecan fruit (kernel-in-shell), the shell and the kernel respectively. The stress values on the kernel were beyond the defined damage point of the kernel material (0.380 MPa). This indicated a permanent deformation/damage on the kernel at the end of the defined compression case. This study contributes to further research into the utilization of nonlinear explicit dynamics based deformation simulation studies for shelled edible agricultural products. Practical applications The simulation approach and application algorithm introduced in this two-part study is a scientific novelty because the explicit dynamics simulation approach for Pecan fruit deformation has not been previously reported in the literature. This second part introduces deeper investigations on material model description, microstructure investigation and FEM-based explicit dynamics simulation procedures. This simulation aims to represent a realistic nonlinear deformation case of the fruit which is very difficult to obtain through experimental and/or mathematical expressions. As a further step from other researchers, this study has introduced a novel realistic time-dependant nonlinear deformation simulation study based on experimental data. The findings have been presented in a form which may be used as input parameters in design studies for shelled agricultural product processing machinery systems used in related industries.

Explicit dynamics simulation of Pecan fruit deformation under compressive loading—Part‐1: Determination of modulus of elasticity

AbstractThis study, which is divided into two parts, introduces an explicit dynamics simulation procedure for Pecan fruit (Carya illinoinensis) deformation under compressive loading. An original application algorithm based on experimental and theoretical methods has been described in the study. The major aim of this Part 1 is to determine the modulus of elasticity through various calculation approaches for Pecan fruit. In addition to this, some engineering properties of the Pecan fruit components were determined to define them as simulation input parameters in an explicit dynamics deformation simulation which is detailed in the second part of the study. The original geometry of the Pecan fruit and its components were digitized using reverse engineering technology (three‐dimensional [3D] laser scanning). Force–deformation data, which can describe the physical deformation characteristics of the Pecan fruit components, was collected through experimental compression tests. Initial crack points for the Pecan shell (kernel‐in‐shell) in these tests were measured as 335.62, 239.42, and 165.03 N for longitudinal, transverse, and suture orientations, respectively. Hooke's, Hertz's, and Boussinesq's theories and finite element method simulation based linear prediction approach based modulus of elasticity calculations were realized. Results from these calculations revealed that loading orientation is an important factor and there were differences between the results of calculation theories (15.2% on average).Practical applicationsThe simulation approach and application algorithm introduced in this two‐part study is a scientific novelty because the explicit dynamics simulation approach for Pecan fruit deformation has not previously been reported in the literature. This first part focuses on realistic description (digitizing) of the fruit geometry through a reverse engineering approach and determination of modulus of elasticity (by considering various theories) and some engineering properties of the Pecan fruit components (experimentally). These investigations have important roles in this study so that realistic material models of the fruit components can be described in the simulation study which is presented and detailed in the second part of the study. In this part, it has been experienced that loading orientation is an effective factor for fruit deformation behavior and different theories may provide different results during calculation of the specific mechanical properties. These important findings have been presented in a form which may be used as input parameters in design studies of shelled agricultural product processing machinery systems used in the related industry.

Randomized branch sampling to estimatefruit production in Pecan trees cv. ‘Barton’

ABSTRACT: Sampling techniques to quantify the production of fruits are still very scarce and create a gap in crop development research. This study was conducted in a rural property in the county of Cachoeira do Sul - RS to estimate the efficiency of randomized branch sampling (RBS) in quantifying the production of pecan fruit at three different ages (5,7 and 10 years). Two selection techniques were tested: the probability proportional to the diameter (PPD) and the uniform probability (UP) techniques, which were performed on nine trees, three from each age and randomly chosen. The RBS underestimated fruit production for all ages, and its main drawback was the high sampling error (125.17% - PPD and 111.04% - UP). The UP was regarded as more efficient than the PPD, though both techniques estimated similar production and similar experimental errors. In conclusion, we reported that branch sampling was inaccurate for this case study, requiring new studies to produce estimates with smaller sampling error.

Nonlinear FEM based high-speed shell shattering simulation for shelled edible agricultural products: Pecan fruit shattering

This paper introduces an advanced engineering simulation procedure for the nonlinear finite element method (FEM) based high-speed shattering case of shelled edible agricultural products. A high-speed impactor which is targeted at the Pecan fruit (kernel-in-shell) was considered in this case study. Physical compression tests were conducted on Pecan fruit specimens and experimental deformation characteristics were utilized to describe realistic material models in the FEM based engineering simulation. Subsequently, a reverse engineering approach was employed in the solid modeling stage and the Pecan shell shattering case under high-speed loading was simulated, considering the explicit dynamics approach. The effect of the high loading rate on the deformation characteristics of the Pecan fruit components was observed. Visual outputs from the simulation revealed the shattering behavior of the Pecan fruit components under defined boundary conditions. In addition to useful visual simulation outputs, time-dependant stress distributions on the Pecan fruit under high-speed loading rates were represented using graphs. Simulation results have revealed that maximum equivalent stress values were 7.1 (MPa), 5.1 (MPa), and 0.336 (MPa) for shell, packing material, and kernel, respectively. Maximum reaction force at impact was calculated as 996,000 (N). This work contributes to further research into the use of nonlinear numerical method based high-speed deformation simulation studies for shelled edible agricultural products.

Reverse engineering approach for precise measurement of the physical attributes related to the geometric features of agricultural products

The irregular shape of most agricultural products complicates their physical and engineering analysis. Therefore, precise description of the irregular product geometric surface form/shape is significant for any related analyses used in both product quality evaluation and design of agricultural machinery systems. This study describes a reverse engineering application procedure for precise description of the physical attributes related to geometric features (size, shape, volume etc.) of the agricultural products under consideration. In the study, a three-dimensional (3D) laser scanner has been utilised and 3D digital model data of the selected sample agricultural product (Pecan Fruit) processed in the virtual environment through 3D scanner software and 3D parametric solid modelling design software has been collected. After 3D solid models were created, some of the physical attributes related to geometric features of the agricultural products were measured precisely and realistic virtual 3D computer aided design (CAD) data was provided for deeper rheological investigation such as structural deformation, fluid dynamics (flow) and heat transfer analyses of the products by means of computer aided engineering (CAE) techniques. Finally, a comparative deformation simulation case study was concluded. This study contributes to further research into the development of agricultural machinery and equipment through the utilisation of reverse engineering and CAD tools.

Photosynthetic characteristics of leaves and fruits of Hickory (Carya cathayensis Sarg.) and Pecan (Carya illinoensis K.Koch) during fruit development stages

Fruit photosynthesis in both hickory and pecan significantly contribute to the carbon requirements of late growth stage (corresponding to seed development). Plant parts other than leaves can perform photosynthesis and contribute to carbon acquisition for fruit development. To determine the role of fruit photosynthesis in fruit carbon acquisition in hickory (Carya cathayensis Sarg.) and pecan (Carya illinoensis K.Koch), we studied changes in dry mass, surface area and CO2 exchange rate in these fruits during fruit development. Fruit development was divided into two phases: phase one involves the rapid increase of fruit size (from 0 to 59 days after pollination (DAP) for hickory; from 0 to 88 DAP for pecan); phase two involves seed development (from 59 to 121 DAP for hickory; from 88 to 155 DAP for pecan). The net photosynthetic rate (P n) in hickory leaves decreased by 48.5 % from 76 to 88 DAP, while the P n in pecan leaves decreased by 32.3 % from 88 to 123 DAP. The gross photosynthetic rate (P g) in hickory fruit was significantly greater than that of the leaf during the late stage (88 to 121 DAP) of fruit development. Pecan fruit had a significantly higher P g than leaves during ontogeny. The contribution of fruit photosynthesis to fruit carbon requirements increased during fruit development, which was estimated by the gross fruit photosynthesis divided by respiration and increased dry mass. The contribution of fruit photosynthesis to pecan carbon requirements was significantly greater than that of hickory. Fruit photosynthesis in both hickory and pecan significantly contribute to the carbon requirements of late growth stage.

THE PHENOLOGY OF EARLY FRUIT RIPENING IN PECAN

Twenty-two pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars were monitored weekly for stage of fruit development to establish how differences in fruit phenology ultimately define time of ripening. Simple techniques for season-long, field assessment of fruit expansion, kernel fill and shuck dehiscence were developed to allow for the uniform evaluation fruit phenology independent of cultivar differences in fruit size and weight. The earliest fruit ripening cultivars in this trial entered into the period of rapid fruit expansion over two weeks before cultivars that ripen late in the season. Once rapid fruit expansion began, the pace of fruit development for early-ripening cultivars was faster than later maturing pecans. Early ripening cultivars took the least amount of time to fully expand their fruits and achieve maximum ovule expansion (the water stage). Early maturing cultivars were also quicker to split shucks (ripen fruit) once kernel deposition was completed. The time required to deposit solid kernel tissue inside a fully expanded ovule was roughly the same for all early ripening cultivars (two weeks). Only extremely late maturing cultivars, or those cultivars generally not adapted to the 200 day growing season at this study’s location, took longer to fill their kernels (18-21 days). Charting the key phenological events that define time of fruit ripening for all 22 cultivars studied in this test illustrates that pecan fruit phenology is a continuously variable genetic trait. In addition, the simple methods assessing fruit phenology developed in this study may become an important tool for screening a large number new pecan clones for adaptation to northern pecan growing regions.

Oviposition Characteristics of Pecan Weevil1

Abstract. Pecan weevil, Curculio caryae (Horn) (Coleoptera: Curculionidae), is a major fruit pest of pecan, Carya illinoinensis (Wangenh.) K. Koch. The majority of economic damage results from larvae feeding on the kernel. Pecan fruit were collected at three sites to describe oviposition activity related to location on the fruit, cluster size, and determine the likelihood of multiple females ovipositing in the same fruit. Results indicated that oviposition was primarily at the distal (stigma) end of the fruit, although feeding punctures seemed to occur without respect to fruit location. Infestation of a fruit cluster rarely resulted in all fruit in the cluster being infested; in fact, one or two fruit were the most common infestation level, regardless of cluster size. Infestation by larvae typically occurred at greater frequency in larger clusters and less frequency in single fruit clusters than the infestation rate across all cluster sizes, suggesting that more fruit produced a greater concentration of v...

Pink mould of pecan kernels in the southeastern USA is associated with scab, above-normal temperatures, and humidity during nut maturation

SummaryPink mould is a disease caused by the common saprophytic fungus Trichothecium roseum (Pers.:Fr.). Pink mould rarely infects kernels of pecan [Carya illinoinensis (Wangeh.) C. Koch] in the southeastern USA, but the disease was a major problem in 2002. T. roseum enters the pecan fruit via scab lesions on the shuck caused by the fungus Fusicladoporium effusum, (G. Winters) Partridge & Morgan-Jones. This study examined the association between pink mould and weather during nut maturation. Average daily temperatures and two or more consecutive days of rainfall were identified as critical factors in 2002, and were compared with weather data between 1963 – 2001 when there was no recorded evidence of pink mould. Both the average daily temperatures and the number of consecutive rainy days during nut maturation were above the 40-year average in 2002. Consecutive rainy days during the nut drying period in 2002 were more than double the 40-year mean, implicating humidity as a critical factor in mould development at this time. Normal variations in temperature were minor factors in disease development following the initial infection. Thus, the onset of mould was associated with the development of scab lesions in late July, a combination of warm temperatures in September and October, and above-average humidity in September and during nut drying from mid-October until mid-November. This combination of factors occurred in only one year out of the past 41 years, explaining the rarity of the disease. The incidence of mould was sigmoidal, with the log-phase overlapping the period of rapid sugar accumulation in the kernel, and potential substrates for the mould to grow.

Pecan Fruit Shuck Thickness is Related to Nut Quality

Pecan [Carya illinoinensis (Wangenh.) K. Koch] fruit presents a considerable weight for the tree to support during the growing season. A major part of this weight is due to the pecan shuck that surrounds the developing nut and kernel. Pecan clones vary considerably for the amount of shuck per nut, and little is known as to the value of this weight in determining final nut quality. Six cultivars differing in basic nut shapes and sizes were studied and found to vary greatly for shuck thickness, and weight of shuck per unit final nut weight and volume. Shuck thickness was shown to be a favorable genetic characteristic since fruit with thicker shucks had slightly greater nut fresh and dry weight, nut volume, nut density, kernel weight and content, and shuck weight per nut volume. `Sioux' had the thickest shucks (4.70 mm), while `Pawnee' had the thinnest shucks (3.72 mm). Fresh weight per fruit varied from 21.25 g for `Podsednik' to 10.18 g for Osage. Weight of fruit per tree was extrapolated using average shuck and nut weights, and it was determined that the fruit on each tree would weigh about 104 kg. This is a considerable weight, and adds substantially to limb breakage. However, thicker shucks contribute to final nut quality.

Factors Influencing Water Split of Pecan Fruit

Water stage fruit split (WS) is an erratic and complex problem often causing major crop losses to susceptible pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars. This study identified two episodes of WS for `Wichita' pecan—a highly susceptible cultivar. The previously recognized precipitation-induced fruit splitting is the major episode; however, a previously unrecognized precipitation-independent, minor episode can also occured before the major episode. This minor episode was associated with the low solar irradiance and high relative humidity—conditions commonly associated with August rains. The crop characteristics of affected trees also influenced WS in that WS increased as crop load per tree increased. Fruits were also more likely to exhibit WS if located within the lower tree canopy. Treatment of foliage with an antitranspirant immediately before split-inducing conditions increased WS. Maintenance of moist soils for ≈2 weeks before WS-inducing conditions substantially reduced WS-related crop losses. These findings help to explain the erratic nature of WS and indicate that maintenance of trees in a well-watered state for ≈2 weeks before the initiation of shell hardening may substantially reduce WS-related crop losses in certain years.

Phytophthora Shuck and Kernel Rot, a New Disease of Pecan Caused by Phytophthora cactorum.

Phytophthora shuck and kernel rot infection usually started at the stem end of the pecan fruit and progressed distally to encompass the entire shuck within 4 to 6 days. A distinct margin developed between dark brown necrotic tissue and healthy green tissue during rotting of the shucks. Phytophthora cactorum was isolated from the rapidly rotting pecan fruit. Two to three weeks after the symptoms appeared, the diseased shucks dried and stuck tightly to the shell. The seed coat of the kernel turned dark brown and the endosperm rotted. The new disease of pecan was first observed during September 1988 on maturing pecan fruit in central Georgia in the vicinity of the town of Byron where growers estimated losses of 50% or greater in some orchards. In south Georgia near the cities of Albany and Cordele, the disease was present but less severe. The causal agent was identified as P. cactorum and deposited with ATCC as isolate B1, ATCC No. 66186. Laboratory and field inoculations of nut clusters using the B1 isolate produced typical symptoms observed in nature. Symptoms of the disease were observed in 13 orchards, and the pathogen was isolated from the soil of 10 of these orchards in south and central Georgia.