Biomedical subjects

T G Isleib

Publications and source records attributed to T G Isleib.

5 recordsLinked to original sources

PubMed2005

Taxonomic relationships among Arachis sect. Arachis species as revealed by AFLP markers.

Cultivated peanut, Arachis hypogaea L., is a tetraploid (2n = 4x = 40) species thought to be of allopolyploid origin. Its closest relatives are the diploid (2n = 2x = 20) annual and perennial species included with it in Arachis sect. Arachis. Species in section Arachis represent an important source of novel alleles for improvement of cultivated peanut. A better understanding of the level of speciation and taxonomic relationships between taxa within section Arachis is a prerequisite to the effective use of this secondary gene pool in peanut breeding programs. The AFLP technique was used to determine intra- and interspecific relationships among and within 108 accessions of 26 species of this section. A total of 1328 fragments were generated with 8 primer combinations. From those, 239 bands ranging in size from 65 to 760 bp were scored as binary data. Genetic distances among accessions ranged from 0 to 0.50. Average distances among diploid species (0.30) were much higher than that detected between tetraploid species (0.05). Cluster analysis using different methods and principal component analysis were performed. The resulting grouping of accessions and species supports previous taxonomic classifications and genome designations. Based on genetic distances and cluster analysis, A-genome accessions KG 30029 (Arachis helodes) and KSSc 36009 (Arachis simpsonii) and B-genome accession KGBSPSc 30076 (A. ipaensis) were the most closely related to both Arachis hypogaea and Arachis monticola. This finding suggests their involvement in the evolution of the tetraploid peanut species.

Arachis↗

PubMed2005

Aflatoxin production in peanut lines selected to represent a range of linoleic acid concentrations.

To determine whether concentrations of linoleate in peanut (Arachis hypogaea L.) seed oil could be used to predict an ability to support aflatoxin production, seeds of genotypes representing a range of linoleate content were inoculated with Aspergillus flavus Link ex Fries and assayed for aflatoxin content. Seeds were blanched and quartered, inoculated with conidia of A. flavus, placed on moistened filter paper in petri dishes, and incubated for 8 days at 28 degrees C. Multiple regression analysis was used to account for the variation among lines with the use of fatty acid concentrations as independent variables. In test 1, linoleate accounted for 39 to 44% of the variation among lines for aflatoxin B1 and B2 and total aflatoxin (26 to 27% after log transformation). Oleate accounted for substantial additional variation (27 to 29%) among lines (20 to 23% after log transformation). Other fatty acids accounted for small fractions of among-line variation. In test 2, linoleate accounted for about 35 to 44% of the variation among entries across traits (29 to 37% for log-transformed data); arachidate accounted for 19 to 29% (27 to 33% after log transformation). Eicosenoate accounted for a small part of the total entry variation. In both experiments, residual variation among entries was significant. Low-linoleate lines consistently contained more aflatoxin, whereas normal- to high-linoleate lines contained variable amounts. Although fatty acid concentrations accounted for significant portions of genetic variation, it is not practical to use them as predictors for susceptibility to aflatoxin contamination, especially for lines in the normal range for oleate and linoleate.

Aflatoxins↗

PubMed2000

Investigations into genotypic variations of peanut carbohydrates.

Carbohydrates are known to be important precursors in the development of roasted peanut quality. However, little is known about their genotypic variation. A better understanding of the role of carbohydrates in roasted peanut quality requires first an understanding of the genotypic variation in the soluble carbohydrate components. Ion exchange chromatography was used to isolate 20 different carbohydrate components in 52 genotypes grown in replicated trials at two locations. Inositol, glucose, fructose, sucrose, raffinose, and stachyose were quantitated, and 12 unknown peaks were evaluated on the basis of the peak height of the unknown relative to the cellobiose internal standard peak height. Peaks tentatively identified as verbascose and ajugose could not be properly integrated because of tailing. Of the 18 carbohydrates that were estimated, 9 exhibited significant variation between test environments, 5 among market types, 14 among genotypes within market types, and 11 exhibited some significant form of genotype x environment interaction. Genotypes accounted for 38-78% of the total variation for the known components, suggesting that broad-sense heritability for these components is high. The observed high genotypic variation in carbohydrate components is similar to the high genotypic variation observed for the sweetness attribute in roasted peanuts, which raises the question regarding possible interrelationships. The establishment of such interrelationships could be most beneficial to peanut breeding programs to ensure the maintenance of flavor quality in future peanut varieties.

Arachis↗

PubMed2000

Relationships of sweet, bitter, and roasted peanut sensory attributes with carbohydrate components in peanuts.

Certain roasted peanut quality sensory attributes have been shown to be heritable. Currently the only means of measuring these traits is the use of a trained sensory panel. This is a costly and time-consuming process. It is desirable, from a cost, time, and sample size perspective, to find other methodologies for estimating these traits. Because sweetness is the most heritable trait and it has a significant positive relationship to the roasted peanut trait, the possible relationships between heritable sensory traits and 18 carbohydrate components (inositol, glucose, fructose, sucrose, raffinose, stachyose, and 12 unknown peaks) in raw peanuts from 52 genotypes have been investigated. Previously reported correlations among sweet, bitter, and roasted peanut attributes were evident in this study as well. Where there was positive correlation of total sugars with sweetness, there also was positive correlation of total sugars with roasted peanut attribute and negative correlation of total sugars with bitterness and astringency. The expected generalized relationship of total sugars or sucrose to sweetness could not be established because the relationship was not the same across all market-types. Further work is needed to determine the nature of the chemical components related to the bitter principle, which appear to modify the sweet response and interfere with the sensory perception of sweetness, particularly in the Virginia market-type. Also, certain carbohydrate components showed significant relationships with sensory attributes in one market-type and not another. These differential associations demonstrate the complexity of the interrelationships among sweet, bitter, and roasted peanut sensory attributes. Within two market-types it is possible to improve the efficiency of selection for sweetness and roasted peanut quality by assaying for total carbohydrates. On the basis of the regression values the greatest efficiency would occur in the fastigiate market-type and then the runner.

Arachis↗

PubMed1999

Sensory attribute variation in low-temperature-stored roasted peanut paste.

Length of sample storage can become significant in sensory studies due to panel fatigue limitations and samples needed for a reasonable expectation of finding significant differences. In roasted peanut sensory studies samples are stored between -10 and -23 degrees C to prevent or retard changes. Studies of up to 13 months' duration have examined stability and slow-rate sensory changes. Sweet taste was relatively stable, whereas bitter and tongue burn attributes increased slightly. Stale taste increased, suggesting lipid oxidation was taking place even at -23 degrees C. Painty attribute did not increase until stale was >3. An increase in fruity attribute was unexpected. With increases in fruity and stale attributes a decrease in roasted peanut was expected. However, storage at -23 degrees C seems to stabilize the roasted peanut lability when compared to storage at -10 degrees C. Fruity and stale interactions with roasted peanut and lability of roasted peanut were shown to be three separate and identifiable effects on roasted peanut.

Arachis↗