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Pecan America
Inspired by the mystique of a uniquely American tree, the pecan, Oklahoma writer John Gifford set out to explore the US pecan industry, which provides 80 percent of the world's supply of this special tree nut. What he discovered during his two-year immersion was a nut-one that's suprisingly symbolic of America itself-that's poised to become the next superfood and an industry that today finds itself in the most important juncture in its history. Though the US pecan belt extends from the Carolinas to California, the pecan tree, which was revered by some of our nation's founders, has its origins in the South Central United States, where wild pecans still grow along the region's rivers and streams, and in its floodplain forests. The pecan is the only native tree nut that has been developed into a significant agricultural crop. Though native pecans continue to figure into the 280-million-pound annual US crop, wild pecan trees face an uncertain future as worldwide demand centers on the larger and more lucrative \"improved\" varieties. Pecan America provides readers with a look at how the rising demand for pecans around the world is transforming the way this nut is grown, promoted, and consumed here in the United States. Along the way, Gifford explores its presence in American folk art and culture, documents the pecan industry's quest for share of stomach in a market brimming with other tree nuts, examines the pecan's surprising array of health benefits, and profiles some of the fascinating people who bring this food to our tables. In the end, Gifford reveals the pecan to be much more than a food, but also a cultural curiosity and even a metaphor for America itself, one whose diverse nature may be its greatest quality.
eBook
Nell plants a tree
\"Three generations of a family grow up and come together around one pecan tree\"-- Provided by publisher.
Book
Transcriptome analysis under pecan scab infection reveals the molecular mechanisms of the defense response in pecans
Pecan scab, caused by the fungal pathogen Venturia effusa , is the most devastating disease of pecan ( Carya illinoinensis ) in the southeastern United States. Resistance to this pathogen is determined by a complex interaction between host genetics and disease pathotype with even field-susceptible cultivars being resistant to most scab isolates. To understand the underlying molecular mechanisms of scab resistance in pecan, we performed a transcriptome analysis of the pecan cultivar, ‘Desirable’, in response to inoculation with a pathogenic and a non-pathogenic scab isolate at three different time points (24, 48, and 96 hrs. post-inoculation). Differential gene expression and gene ontology enrichment analyses showed contrasting gene expression patterns and pathway enrichment in response to the contrasting isolates with varying pathogenicity. The weighted gene co-expression network analysis of differentially expressed genes detected 11 gene modules. Among them, two modules had significant enrichment of genes involved with defense responses. These genes were particularly upregulated in the resistant reaction at the early stage of fungal infection (24 h) compared to the susceptible reaction. Hub genes in these modules were predominantly related to receptor-like protein kinase activity, signal reception, signal transduction, biosynthesis and transport of plant secondary metabolites, and oxidoreductase activity. Results of this study suggest that the early response of pathogen-related signal transduction and development of cellular barriers against the invading fungus are likely defense mechanisms employed by pecan cultivars against non-virulent scab isolates. The transcriptomic data generated here provide the foundation for identifying candidate resistance genes in pecan against V . effusa and for exploring the molecular mechanisms of disease resistance.
Journal Article
Metabolomics based on GC-MS revealed hub metabolites of pecan seeds germinating at different temperatures
Background
As an important plant source of food and edible oils, pecans are rich in metabolites. Few studies have focused on metabolites involved in pecan seed germination at different temperatures.
Results
In our study, we germinated pecan seeds at different temperatures and found that, the germination rate and water content were highest at 30°C. It was found that the radicle of pecan seeds could sense seed coat cracking by observing the microstructure and cell ultra-structure of the seeds at the early stage of germination. We compared the metabolomes of seeds at different temperatures with different germination processes. A total of 349 metabolites were identified, including 138 primary metabolites and 211 secondary metabolites. KEGG enrichment analysis indicated that the differential metabolites were mainly enriched in the metabolic pathways, amino acid synthesis pathways and ABC transporters. Using weighted gene co-expression network analysis (WGCNA), three modules of closely related metabolites were identified. In the brown module, most of hub metabolites were amino substances, whereas in the blue module, many hub metabolites were sugars.
Conclusions
Amino acids and carbohydrates play an important role in pecan seed germination. Differential metaboliteanalysis showed that 30°C was the temperature at which metabolites differed most significantly. This study provides useful information for further research on the seedling establishment of pecan seeds.
Journal Article
Aphids and associated parasitoids exhibit vertical canopy distribution differences in pecans
In agricultural systems, aphids (Hemiptera: Aphididae) have been shown to exhibit differences in within plant vertical distribution in vegetation. In addition, natural enemies, such as parasitoids, may have canopy micro-climate preferences. Currently, the within plant vertical distribution of aphids is primarily documented in row crops with few studies in tree systems. Pecan orchards under commercial production range from new to old with variable tree height between these orchards. This height difference highlights the need to examine the vertical canopy distribution of pecan aphids in trees of varying height. In this study, we evaluated the vertical canopy distribution patterns of aphids, parasitized aphids (
i.e.,
mummies), and the primary parasitoid
Aphelinus perpallidus
(Gahan) (Hymenoptera: Aphelinidae) in pecan trees (Fagales: Juglandaceae) within younger (~ 9 m) and older trees (~ 15 m). Pecan aphids and mummies were often more abundant in the lower canopy, especially in older trees. Conversely, parasitoid adults were observed at higher abundance in the upper canopy of younger trees in 2021 and in both the lower and upper half of older trees, but there was variability in parasitoid distributions between years. Results indicate that scouting the lower canopy for aphids may be sufficient to estimate populations. The presence of
A. perpallidus
in the upper canopy can be beneficial as it may allow for biological control in areas where insecticide application may fail.
Journal Article
Comprehensive genomic analysis of the expansin gene family in pecan (Carya illinoinensis) and their transcriptional responses to stresses and fruit abscission
Background
Expansins (EXPs) are important components of the plant cell wall. They are involved in plant growth and development and diverse environmental stress responses by promoting cell-wall loosening and cell enlargement. Although EXPs have been characterized in many plant species, little is known about the EXPs in
Carya illinoinensis
.
Methods
The
CiEXP
gene family was systematically analyzed using bioinformatics. RNA-seq data (both from our study and public databases) and qRT-PCR were employed to analyze the expression patterns of the
CiEXP
family in different tissues, under biotic and abiotic stress, and in persistent versus abscised fruit.
Results
In this study, a total of 39
EXP
genes unevenly distributed on 14 chromosomes were identified in the
C. illinoinensis
genome, which were classified into four subfamilies (27 CiEXPAs, 3 CiEXPBs, 2 CiEXLAs, and 7 CiEXLBs), and the motif and gene structures were consistent with this subfamily classification. Thirty-six pairs of duplicated genes were identified, suggesting that gene duplication may have contributed to the expansion of the
EXP
gene family. Collinearity analysis provided further phylogenetic insights into the
EXP
gene family.
Cis
-acting element analysis revealed that the promoter regions of the
CiEXPs
gene were associated with hormone-responsive, plant growth and development, and stress-responsive, particularly ABA response element (ABRE) and MeJA-responsive element. The expression results showed that most
CiEXPs
exhibited tissue-specific expression patterns, and some
CiEXPs
were highly responsive to abiotic and biotic stresses. Additionally, most
CiEXPA
genes,
CiEXPB1/2
, and
CiEXLA2
were up-regulated in persistent fruit.
Conclusions
Our study findings enhance the understanding of the
CiEXP
gene family and facilitate the selection of suitable candidate genes for further study, which lays a foundation for future investigations into the functional roles of specific
CiEXPs
.
Journal Article
Association mapping revealed phenolic content-related SNPs and haplotypes in pecan (Carya illinoinensis)
Phenolics are essential quality components in pecan nuts, influencing the nutritional value of various varieties. Conventional breeding methods for pecan trees are time-consuming and laborious due to their considerable height and extended juvenile period. Molecular marker-assisted selection offers the potential to expedite the breeding process. In this study, we examined the allelic variations of five phenolics biosynthesis-related genes within a germplasm population. The linkage disequilibrium (LD) values (r2) between single nucleotide polymorphisms (SNPs) of each gene were analyzed, demonstrating a decrease in r2 to less than 0.2 within a 1.0 kb distance. The contents of total phenolics, total flavonoids, and condensed tannins in the kernels of each individual were assessed over two consecutive years. Following this, association mapping was conducted. A total of 29 significant marker-trait pairs and eight significant haplotype-trait pairs were observed. Among these, three SNPs in CiPAL4 and two haplotypes in CiCHS3 were consistently identified over both years. The explanation rates of the SNPs for the observed traits ranged from 3.45 to 14.39% (p < 0.05). This study offers valuable insights into the molecular basis underlying phenolic biosynthesis in pecan trees, which will enhance the efficiency of quality improvement in this plant and other species within the Carya genus.
Journal Article
Cytotoxicity of subcritical water extracts obtained from byproducts generated at commercial pecan shelling operations on cancer cells
This study examined potential of the extracts obtained from the byproducts generated at commercial pecan nut-shelling operations in cancer treatment. The subcritical water extracts obtained from two varieties, Native and Pawnee, were analyzed for their phenolic contents and compositions. Effects of the extracts on viability and IC50 of the human cell lines representing a broad range of cancer types, cervical, lung, skin, breast, colon and prostate cancers, were investigated. Although the effect of the temperature on the phenolic contents and compositions of the extracts was not statistically significant, the influence of the variety was extensive. The pecan shell extracts were not cytotoxic to the healthy cell line Vero in the concentration range examined. Some of the pecan shell extracts had greater efficay than Doxorubicin, a drug used in cancer chemotherapy, in reducing cancer cell viability. This study is novel and practical implications of the data generated in this study are noteworthy, because this is the first report on the beneficial effects of subcritical water extracts obtained from pecan shelling industry byproducts on a broad range of cancer cell lines. It is likely that the experimental data presented in this study will support and encourage future research on the biological pathways involved in the interactions of the cancer cells and the extracts. The findings of this study will facilitate research on downstream processing and purification of the crude extracts exhibiting high cancer cell cytotoxcity, potentially improving the final product efficacy and lead to commercial applications.
Journal Article
The Effect of Impactor Geometry on End-to-End Pecan Cracking
During the industrial pecan shelling process, kernels are often damaged. To address this problem, a study is conducted to experimentally determine improved impactor geometries for end-to-end pecan cracking. Four impactors of varying internal angles (from 30° to 52.5°, in increments of 7.5°) are tested. After cracking, the pecans are passed through an image analysis software designed to detect and measure cracks in their shells. These measurements help classify each pecan into one of four categories: under crack, standard crack, ideal crack, or over crack. Cracked and ideally cracked pecans are preferred for their processability, so the impactor geometries are then evaluated based on their ability to maximize these crack types across the widest impact energy range. For the four impactors tested, the 30° impactor is found to more consistently produce preferred cracks in a larger energy range relative to the other impactors.
Journal Article