Use Of Traits Research Articles

Utility of RAPD markers in identifying genetic linkages to genes of economic interest in peach

The identification of molecular markers linked to economically important traits for use in crop improvement is very important in long-lived perennial species. Three-hundred-and-sixty RAPD primers were used with bulked segregant analysis to identify markers linked to loci of specific interest in peach [(Prunus persica) L. Batch] and peach x almond [(Prunus dulcis) Batch] crosses. The traits analyzed included flesh color, adhesion, and texture; pollen fertility; plant stature; and three isozyme loci. The Mendelian behavior of the RAPD loci was established, and RAPD markers were mapped relative to the loci controlling flesh color, adhesion, and texture, and the isozyme loci Mdh-1, 6Pgd-2 and Aat-1, as well as the existing RFLP genetic linkage map constructed previously using a peach x almond F2 population. This technique has facilitated rapid identification of RAPD and RFLP markers that are linked to the traits under study. Loci controlling these traits mapped predominantly to linkage groups 2 and 3 of the peach genetic linkage map. Linkages to genes with both dominant and co-dominant alleles were identified, but linkages to dominant genes were more difficult to find. In several crosses, RAPD marker bands proved to be allelic. One co-dominant RAPD formed a heteroduplex band in heterozygous individuals and in mixtures of alternate homozygotes. The Mendelian behavior of the RAPD loci studied was established and the results suggest that RAPD markers will be useful for plant improvement in peach.

Host Genetic Variation in the Early Nodulation and Dinitrogen Fixation of Soybean

Soybeans [Glycine max (L.) Merr.] grown on soils low in N can exhibit N deficiency during early plant development. Improved early N2 fixation may alleviate this problem. Our objectives were to (i) examine genetic variation in early nodulation and N2 fixation of soybean, and (ii) identify traits useful in breeding for early nodulation and N2 fixation in this crop. Eighty‐six soybean lines showed considerable genetic variation in efficiency and speed of nodulation with Bradyrhizobium japonicum strain USDA 110. Eighteen lines were then reevaluated for nodulation efficiency with the B. japonicum strains USDA 123, UMR 161, and NA 6407 for differences in nodule number 5 to 12 d after inoculation (DAI) and for differences in plant dry weight, nodule fresh weight, acetylene reduction activity (ARA), nodule enzyme activity, leghemoglobin concentration, and nodule soluble protein concentration (SOLP) 10 to 17 DAI. The 86 lines differed in percentage roots nodulated (PRN; 26–93%) and number of nodules above the root tip mark (NARTM; 0.3–3.0), and in uppermost nodule position (− 17.5 to 19.5 mm). For the 18 lines that were reevaluated, mean PRN and NARTM values were greater for USDA 123 than for USDA 110 (65.1 vs. 57.9%; 1.4 vs. 1.0, respectively). For these lines, correlation analyses showed that PRN correlated with nodule number at 5 (r = 0.69**) but not 12 DAI, while nodule number 12 DAI correlated positively with nodule fresh weight, ARA, enzyme activity, and SOLP 17 DAI. Plant dry weight, nodule fresh weight, and nodule SOLP assayed at 17 DAI are suggested as traits for use in a breeding program to improve early nodulation and N2 fixation in soybean.

Assessment of Western Canadian Barleys of Historical Interest: II. Morphology and Phenology

Assessment of morphological and phenological traits is essential if these traits are to be used as selection criteria in breeding programs. The purpose of this study was to evaluate the role several morphological and phenological traits play in the productivity of spring barley (Hordeum vulgare L.) cultivars released from 1910 to 1987 in western Canada. We were interested in evaluating these traits for use in a barley ideotype for the western Canadian prairies. Twenty 6‐ and 2‐rowed feed and malt barley cultivars were tested at Botha, Lacombe, and Olds, Alberta, Canada, in 1989 and 1990. Modern cultivars had shorter intervals between tiller appearance, were shorter in stature, and had later stem elongation, anthesis and maturity than older cultivars. The interval between tiller appearance decreased by 0.02 to 0.06 d yr−1. Plant height decreased by 0.14 to 0.29 cm yr−1. Spike length increased by 0.015 to 0.018 cm yr2212;1, although significant increases were not expressed in all location‐years. Days‐to‐stem‐elongation increased by 0.06 to 0.11 d yr−1; days‐to‐anthesis, by 0.04 to 0.10 d yr−1; and days‐to‐maturity by 0.04 to 0.22 d yr−1. Two‐ and six‐rowed cultivars were morphologically distinct but were phenologically similar. Future improvements in western Canadian spring barleys may be achieved through lengthening the prestem elongation period, and increasing culm diameters. In two‐rowed cultivars, increasing leaf widths may also be advantageous. Morphological and phenological traits have changed in association with historical yield increases and may be used to help define a barley ideotype for the western Canadian prairies.

Estimation of genetic parameters for conformation traits assessed on a linear scale in ayrshire cattle

Information on the conformation of Ayrshire cattle has been collected by the Ayrshire Cattle Society (ACS) since 1985. Seventeen traits are recorded on a scale of 1 to 9 where 1 and 9 represent the biological extremes of the population. Approximately 2000 records are collected annually and analysed by the Milk Marketing Board using Best Linear Unbiased Prediction to provide sire evaluations on Ayrshire bulls, fitting a sire model. In the past there have been insufficient records to produce reasonable estimates of heritabilities for the traits and those from the Holstein/Friesian population have been used. The purpose of this study was to produce heritability estimates for each trait for use in future analyses.

Genetic Parameters of Egg Shell Quality Traits and Percentage of Eggs Remaining Intact Between Oviposition and Grading ,

This study was performed to estimate heritabilities and genetic as well as phenotypic correlations of the egg shell quality traits specific gravity (SG), nondestructive deformation (DFM), compression fracture strength (CFS), shell weight (SW), percentage shell (% shell), and shell weight per unit surface area (SW/SA) and percentage of eggs remaining intact (% intact) from oviposition to placement in fiber trays after grading. In the first year of the 2-yr study, eggs were obtained from about 1,000 F1 hens from each of two crosses of selected Single Comb White Leghorn strains (01 × 03 and 02 × 04) when they were 42 and 68 wk of age. At each age, the shell quality of eggs collected on Sunday for 3 consecutive wk was measured whereas eggs collected Monday through Thursday of each week passed through egg washing, candling, and grading equipment before being hand candled to determine % intact. Eggs from F2 daughters were measured in a similar manner the following year.Heritability estimates tended to be highest (.29 to .59) for SG, SW, % shell, and SW/SA, somewhat lower (.21 to .33) for CFS, and lowest (.10 to .26) for DFM and % intact. Absolute phenotypic correlations between egg shell quality traits and % intact ranged from .19 to .47 whereas genetic correlations ranged from .23 to 1.04. Estimated genetic correlations between % intact eggs late in the laying year and egg shell quality traits early in the laying year were .50 and .62 (SG), .47 and .59 (CFS), .45 and .49 (% shell), –.37 and –.46 (DFM), .42 and .43 (SW/SA), and .23 and .30 (SW). Taking into consideration heritability, genetic correlation, and ease of measurement, the best shell quality trait for use in selection programs for improving % intact is SG.

THE RELATIONSHIP OF SIRE EVALUATIONS FOR EASE OF CALVING AND BIRTH WEIGHT

Best Linear Unbiased Prediction procedures were used to evaluate 204 Beefmaster, Charolais, Simmental, Limousin, Red Angus and Chianina sires for birth weight (BW) and ease of calving (EC) based on the performance of a total of 6758 progeny. Correlations between BW and EC for sire means ranged from −0.77 to 0.08 with an average of −0.27 and for sire proofs they ranged from −0.90 to 0.14 with an average of −0.41. These results suggest that there is a strong relationship between the traits and that BW may be a valuable trait for use in indirect selection to reduce calving problems. Key words: Beef, ease of calving, birth weight, sire evaluation, correlation of sire proofs

A survey and evaluation of human genetic traits used in classroom laboratory studies.

Twenty-six selected introductory biology and genetics laboratory manuals were examined and were found to include 57 human "inherited" traits as examples for classroom study. Forty-three of these 57 traits are included in McKusick's catalog of human inherited characteristics, Mendelian Inheritance in Man. Of these 43 traits, 26 are annotated with an asterisk, indicating that their modes of inheritance are well documented, while 17 traits are not so annotated, suggesting uncertain mechanisms of inheritance. Fourteen of the 57 traits are not found in McKusick's catalog, implying that they may not be inherited traits at all or that their modes of inheritance may be polygenic. Current literature also suggest that certain traits included in the McKusick catalog may, in fact, not have a genetic basis. Notable examples of such questionable traits are handedness, hand clasping, and tongue rolling. Clearly, a need exists for reliable morphological and easily detected biochemical human genetic traits for use in classroom instruction. Authors preparing instructional manuals for introductory biology and genetics laboratory studies should carefully select the traits with which they illustrate human inheritance. A first requisite for selection of such characteristics must be conclusive evidence that the trait does, indeed, have an established genetic basis. Additional criteria for selection of such traits are also discussed.

PHENOTYPIC CHARACTERIZATION OF BENECKEA PARAHAEMOLYTICA: A PRELIMINARY REPORT

Eighty-six strains which were isolated from cases of gastroenteritis and had the general properties of the genus Beneckea were submitted to an extensive nutritional, physiological, and morphological characterization. The results indicated that this collection of strains, which included the type strain of Beneckea parahaemolytica, was phenotypically homogeneous and distinguishable from the other known species of Beneckea by multiple, unrelated, phenotypic traits. When grown in liquid medium, strains of B. parahaemolytica had single, sheathed, polar flagella; when grown on solid medium, these strains had unsheathed, peritrichous flagella in addition to the sheathed, polar flagellum. Additional traits of use for differentiation of this species from the remaining species of the genus Beneckea were the ability of B. parahaemolytica to grow at 40 C, utilize d-galactose, l-leucine, l-histidine, and putrescine and the inability to utilize sucrose, dl-β-hydroxy-butyrate or give a positive Voges-Proskauer reaction. The validity of some of the traits previously used to identify B. parahaemolytica as well as the possible difficulties encountered in the identification of this organism from marine sources are considered.