Several new management tools and management practices are being developed for pecan. Major insect pests of pecan are pecan nut casebearer, hickory shuckworm, and pecan weevil. Sex pheromone attractants are being developed for each of these pests that improve monitoring. Also, a pecan weevil trap (Tedder's trap) was introduced recently that is more sensitive to weevil emergence than the previous trap. New models that predict critical periods for pecan scab infection are being tested. Certain legume ground covers are being tested to increase beneficial arthropods in the orchard for aphid control, and to supply N. Mulches are being investigated as an alternative to herbicide management for young trees. A mechanical fruit thinning method has been developed that increases fruit quality and reduces alternate bearing as well as stress-related disorders.
Abstract
Plant germplasm has become a topic of interest and concern at the highest levels of our government and in many other parts of our society. Part of this concern no doubt relates to the increased awareness by leaders in the government and in the public at large that U.S. agricultural productivity and stability is dependent on plant resources that are not native to the United States. The United States, as compared to many agricultural producers in the world, has no centers of origin for important food and fiber crops. In fact, the United States has no major crop native to its geographical area. Of all the crops important to U.S. agriculture, only sunflower (Helianthus spp.), Jerusalem artichoke (Helianthus tuberosus L.), grape (Vitis spp.), pecan [Carya illinoensis (Wangenh.) C. Koch] and other hickories (Carya spp.), blueberry (Vaccinium spp.), cranberry (Vaccinium macrocarpon Aiton), and a few other miscellaneous species of minor importance are native to the United States.
of plantings and R.S. Brazeau and Reemay, Inc., Old Hickory, Term., for providing the spunbonded covers used in this research. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper
Polygalacturonase (PG) in higher plants has been considered to be associated with ripening fruits although it is now known to be present in foliage and storage organs. We recently found very high levels of PG in some grass pollens (Plant Science 59, 57-62, 1989). This prompted an examination of other pollens for PG activity. All of the pollens analyzed contained PG but the range of activities was great. Eastern cottonwood pollen contained the most PG, with a level about 12 times higher than that usually found in ripe tomato fruit. Pollens from the other members of Populus were generally high in PG. Pollens from the oak family also contained very high PG, with the highest amount in white oak pollen. Pollens from pecan, English walnut, willows, birch and hickories contained moderate levels of PG. The lowest amounts of PG were found in pollens from beech, sycamore and conifers. The PG's from the two richest sources (eastern cottonwood and white oak pollens) were partially purified and characterized. Both enzymes were found to be exopolygalacturonases that require Ca2+ for activity. PG may be involved in some function related to pollination but an explanation for the wide range of activities indifferent pollen is not obvious.
Polygalacturonase (PG) in higher plants has been considered to be associated with ripening fruits although it is now known to be present in foliage and storage organs. We recently found very high levels of PG in some grass pollens (Plant Science 59, 57-62, 1989). This prompted an examination of other pollens for PG activity. All of the pollens analyzed contained PG but the range of activities was great. Eastern cottonwood pollen contained the most PG, with a level about 12 times higher than that usually found in ripe tomato fruit. Pollens from the other members of Populus were generally high in PG. Pollens from the oak family also contained very high PG, with the highest amount in white oak pollen. Pollens from pecan, English walnut, willows, birch and hickories contained moderate levels of PG. The lowest amounts of PG were found in pollens from beech, sycamore and conifers. The PG's from the two richest sources (eastern cottonwood and white oak pollens) were partially purified and characterized. Both enzymes were found to be exopolygalacturonases that require Ca2+ for activity. PG may be involved in some function related to pollination but an explanation for the wide range of activities indifferent pollen is not obvious.
A microsatellite-enriched library was developed from `Halbert', a native pecan [Carya illinoinensis (Wangenh.) K. Koch] selection from Coleman County, Texas. A genomic library enriched for simple sequence repeats (SSR) containing 6144 clones was archived in 384 well plates for screening. In total, 439 clones were identified after Southern hybridization using di- and tri-nucleotide repeats as probes. In total, 125 positive clones were sequenced and primers were designed for 24 repeats. The SSR markers chosen for analysis include di-(CT and GA) and tri-nucleotide repeats (CTT, GAA and GAT). Of the 24 primer pairs tested, 19 successfully amplified microsatellites from `Halbert'. DNA was isolated from 48 pecan and hickory accessions selected to strategically represent the genetic diversity of the National Clonal Germplasm Repository (NCGR) Carya collections. The 19 SSR primers that produced good amplification products in `Halbert' were used to evaluate the collection, with 11 revealing polymorphism. The number of fragments amplified with different primer combinations ranged from 4 to 32 in the 48 genotypes tested. Evaluation of the data confirms the utility of the microsatellites in delimiting known relationships.
Abstract
At the meeting of the Crop Advisory Committee for Pecans and Hickories held on 24 Sept. 1984 in Albany, Ga., a question was raised concerning the legitimate scientific name of the pecan tree. Two names are currently in use: Carya illinoensis (Wang.) K. Koch (3, 6, 7, 10, 12, 19) and Carya illinoinensis (Wang.) K. Koch (1, 2, 11, 18, 21). Current usage is heavily in favor of the former epithet. When the 2 names were used as key words in the BIOSIS Previews computer search file for articles written between 1977 and the present, 199 were retrieved under C. illinoensis, whereas only 1 was found under C. illinoinensis. Since Hortus Third uses the latter epithet, articles on pecan submitted for publication in horticultural journals are occassionally returned to their authors for revision. The purpose of this paper is to trace the history of the nomenclature of the pecan as it relates to this dispute and in the process, demonstrate that the strict rules of scientific nomenclature and common sense can both be satisfied by the use of the epithet Carya illinoensis.
A microsatellite library has been developed from `Halbert', a native pecan selection from Coleman County, Texas, using methods developed at the Texas A&M Univ. Crop Biotechnology Center. A total of 6144 DNA fragment clones were archived in 384 well plates for screening. Four-hundred-thirty-nine clones were positive after Southern hybridization using di- and tri-nucleotide repeats as probes. One-hundred-twenty-five positive clones were sequenced on an ABI 377 automated DNA sequencer. Of these, 24 repeats had enough sequences at the two ends to design primers. Primers were designed using Primer Express software, and were synthesized by Genosys, USA. The simple sequence repeats (SSRs) chosen for primer analysis include di- (CA and GA) and tri-nucleotide repeats (CTT, GAA and GAT). The SSRs were amplified under high stringency conditions with temperatures based on length and GC content. Reproducibility was verified using `Halbert' DNA isolated from different inventories. Of the 24 primer pairs tested, 20 successfully amplified microsatellites from `Halbert'. DNA was isolated from 48 pecan and hickory accessions selected to strategically represent the genetic diversity of the NCGR Carya collections (a core collection). The accessions included parent-progeny combinations, individuals from geographically distant native populations, species, and interspecific hybrids. The 20 SSR primers that produced good amplification products in `Halbert' were used to evaluate the collection, with 11 revealing multiple sizes of the repeat. The number of bands amplified with different primer combinations ranged from 4 to 32 in the 48 genotypes tested. We used RFLPscan software to aid in gel scoring (sizing amplified fragments, and comparing amplification profiles), and NTSYSpc software to evaluate genetic similarities. Evaluation of the data confirms the utility of the primers in delimiting known relationships.
Seedlings of nine coarse-rooted species–sawtooth oak (Quercus acutissima Carruth), white oak (Q. alba L.), cherrybark oak (Q. falcata var. pagodifolia Elliott), post oak (Q. stellata Wangenh.), black walnut (Juglans nigra L.), pignut hickory [Carya glabra (Mill.) Sweet], pecan [C. illinoinensis (Wangenh.) C. Koch], Chinese chestnut (Castanea mollissima Blume), and common baldcypress [Taxodium distichum (L.) L. Rich]—were grown for one growing season in nontreated containers or in containers treated on their interior surfaces with white interior latex paint containing 100 g Cu(OH)2/liter. Seedlings of each species and container treatment were harvested twice: once after being transplanted from 3.2- to 15.0-liter containers and at the end of the growing season. Cupric hydroxide-treated containers decreased the amount of circled, kinked, and matted roots formed at the container wall-medium interface in all species tested. Plants grown in Cu(OH)2-treated containers also had altered root dry-weight partitioning. The partitioning patterns were species specific and included 6% to 20% increases in the percentage of root dry weight in interior vs. exterior portions of the rootball (white oak, black walnut, Chinese chestnut, and baldcypress), 10% to 21% increases in the percentage of root dry weight in upper vs. lower halves of the rootball (sawtooth oak, cherrybark oak, black walnut, and baldcypress), and an increase in the percentage of primary lateral roots (lateral roots originating from taproots or roots functioning as taproots) on the upper (proximal) half of taproots (cherrybark oak, pecan, and baldcypress). Nutrients in leaves, stems, and roots of sawtooth oak seedlings were analyzed at both harvests. Seedlings grown in Cu(OH)2-treated containers had more Cu in most plant tissues than nontreated seedlings. Also, seedlings grown in Cu(OH)2-treated containers had higher total Ca and Mg concentrations at transplanting and higher total N and Zn concentrations at the end of the growing season than nontreated seedlings.
, organs, or individuals) plus all other elemental forms ( Salt et al., 2008 )] ( Robinson, 1943 ; Robinson and Edgington, 1945 ; Robinson et al., 1938 , 1958 ). For example, Carya tomentosa (mockernut hickory) reportedly hyperaccumulates REEs in