Search Results

You are looking at 31 - 40 of 903 items for :

  • multiple trait selection x
  • Refine by Access: All x
Clear All
Open access

Tong Geon Lee, Reza Shekasteband, Naama Menda, Lukas A. Mueller, and Samuel F. Hutton

can account for as much as a half of the total production cost ( Davis and Estes, 1993 ; USDA ERS). Thus, there is a significant need to research traits which will facilitate a transition to broader mechanization in fresh-market tomato production

Free access

Christopher S. Cramer

Realized heritability estimates of bolting percentage, pink root and fusarium basal rot severities and incidences, and percentage of single-centered bulbs were estimated for half-sib families of an intermediate-day, open-pollinated onion (Allium cepa L.) population using selection response analysis. Half-sib families were selected based upon an index that equally weighted bolting percentage, pink root and fusarium basal rot severities and incidences, percentage of single-centered bulbs, and bulb quality. Families were subjected to one cycle of half-sib family recurrent selection. Pink root and fusarium basal rot severity was reduced by 17% and 7%, respectively, with realized heritability estimates of 1.28 and 0.65, respectively. More progress for pink root severity was made than was selected. Disease incidence was reduced by 18% and 12%, respectively, with heritability estimates of 0.65 and 0.60, respectively. Very little progress was made for the percentage of single-centered bulbs and this was reflected in a heritability estimate of 0.17. Selection based upon multiple characters at the same time may reduce the effectiveness of making improvements in a single trait. However even with low to moderate heritability, improvements were made, and suggest that further improvements can be made through selection.

Free access

R.C. Grube, Y. Zhang, B. Huang, and M.M. Kyle

Resistance to cucumber mosaic virus (CMV) in Capsicum from two sources is being transferred into three commercial types (bell, jalapeno, and Anaheim) using a backcross breeding scheme. We have optimized our CMV seedling screening protocol, which involves multiple inoculations beginning at the cotyledon stage with a severe CMV serogroup I isolate. Both sources of resistance, C. annuum `French Perennial' and a C. frutescens accession (BG2814-6), exhibit oligogenic recessive inheritance and share some but not all resistance alleles. Selection for type in the BCF1 generation had no effect on the frequency of resistant individuals in the BCF2 generation. We have determined that it is necessary to self-pollinate every other backcross generation to screen for resistance. Occasionally disease symptoms appear in adult plants that were initially resistant to multiple inoculations at the seedling stage, and we are investigating the correlation between seedling resistance and adult plant resistance. We are also exploring the extent to which the different sources of resistance behave differently as a function of genetic background. Additionally, we are mapping quantitative trait loci (QTLs) for CMV resistance in pepper with the goal of converting RFLP and/or RAPD markers into PCR-based markers to facilitate molecular marker-assisted selection for CMV resistance.

Free access

S.L. Noffsinger, A.D. Draper, and C.L. Gupton

Although southern highbush (Vaccinium sp.) is replacing rabbiteye (Vaccinium ashei L.) blueberry, rabbiteye will continue to be grown on marginal soils of the southeastern United States. Dwarfism or short, compact growth habit is a trait that could be used to reduce labor costs in rabbiteye blueberry production. Parental backgrounds, and flowering and fruit traits were studied in seven Mississippi (MS) and five Georgia (T) selections. Six of the MS selections are available for propagation and bloom late enough that cold damage should not be a problem. Four (MS63, MS454, MS546, MS891) of the six have acceptable fruit quality and will be used in breeding. Ethel and MS134 were the only known dwarf ancestors, with Ethel, Myers, Black Giant, and Tifblue (Ethel × Clara) dominating the parental background. Based on the variation in growth habit and ancestries, it would appear that Ethel has several genes for dwarfism and multiple allelic interactions are involved, similar to what Garvey and Lyrene found (1987). Future breeding will include crosses of MS63, MS454, MS546, and MS891 with germplasm outside of the common ancestors, to broaden the genetic base of the dwarf rabbiteyes.

Free access

Patrick J. Conner, Susan K. Brown, and Norman F. Weeden

Molecular markers (isozyme and DNA) have been used to map apple and have helped to elucidate the inheritance of some morphological traits. In this project random amplified polymorphic DNA (RAPD) and isozyme markers were used to create maps for `Wijcik McIntosh, a columnar (reduced branching) sport of `McIntosh' and NY 75441-67, an advanced selection from the multiple disease resistance breeding program. NY 75441-67 is resistant to scab source of resistance from M. floribunda) and resistant to cedar apple rust. `Wijcik McIntosh' is being used in the breeding program as a source of the dominant gene, Co, for reduced branching, but there is also interest in this genotype because of the tremendous variation in plant form observed in progenies segregating for columnar habit. Some of these form variants may be of greater commercial interest than the parental material. Morphological traits examined in this progeny included plant height, stem diameter, suckering, branching habit, spur production, and internode length. The usefulness of molecular markers to pre-select for components of plant form is being examined. Molecular markers promise to aid our understanding and manipulation of quantitative morphological traits.

Free access

F. Serquen and J. Staub

Sex expression (SE), stem length (SL), and number of laterals plant (NL) are important morphological traits of a cucumber plant ideotype adapted for machine harvesting. Two inbred lines, the determinate, gynoecious G-421, possessing high fruit quality, and the monoecious H-19, with multiple lateral branching and sequential fruiting habit, and their F1 and F3 (100) progenies were planted in Wisconsin and Georgia. Data on SE, SL, and NL were recorded on individual plant basis. Genetic parameters were estimated using all generations. Phenotypic correlations were calculated from the trait means, and genotypic correlations were estimated from the analysis of variance of F3 progeny. The additive genetic variance was the highest of the variance components for SL and NL. Dominance genetic variance was more important than the additive variance for the control of SE. Narrow-sense heritability were 0.41, 0.83, and 0.85 for SE, SL, and NL, respectively. The genotypic (g) and phenotypic (p) correlation coefficients (r) indicated negative association between SE and SL (r g = –0.57, r p = –0.45**) and between SE and NL (r g = –0.56, r p = –0.27**). The association between SL and NL was positive (r g = 0.63, r p = 0.35**). Results suggest that gain from selection can be made for this plant ideotype.

Free access

Kevin M. Crosby

Improving melon root systems by traditional breeding is one component of the program to develop multiple-stress-resistant melons at the Texas Agricultural Experiment Station, Weslaco. Ten diverse melon lines representing four horticultural groups were intercrossed utilizing a Design II mating scheme. The male parents were: `PI 403994,' `Perlita,' `Doublon,' `Caravelle', and `PI 525106.' The female parents were: `Créme de Menthe,' `Magnum 45,' `BSK,' `PI 124111 × TDI', and `Deltex.' F1 progeny were grown in pasteurized sand in the greenhouse using a randomized complete-block design with four reps. After 4 weeks, root systems from all plants were carefully washed to remove the sand. Each root system was then placed onto a glass, plated, and scanned into the computer software Rhizo Pro 3.8 (Regent Instruments, Quebec). This software calculated root lengths of various diameter classes, root area, and root tip number. All data was input into Agrobase software for calculation of genetic variances based on Design II analysis. Significant differences of contributions by male parents to progeny variation were few. Only length of roots with 1.0- to 1.5-mm-diameter and vine length were significantly different. Differences in contributions by female parents to all traits except root tip number were highly significant. No significant interaction effects were observed for any trait. Narrow-sense heritability estimates were moderate to high for all traits. The range was from 0.56 for root tip number by males to 0.81 for both length of 0.5- to 1.0-mm-diameter roots and vine length for females. Estimates for total root length (0.76) and root surface area (0.77) were high. The lack of male by female interaction suggests very low dominance genetic variation and contributed to high heritability estimates, which represent predominantly additive gene action. Additive genetic variation allows more-efficient progress by selection, making the potential for root system improvement favorable.

Open access

Felipe Barrera Sánchez, Larissa Pereira Ribeiro, Mayara Fávero Cotrim, Carlos Antonio da Silva Junior, Leonardo Lopes Bhering, and Paulo Eduardo Teodoro

main goals of cherry tomato breeding programs is to select genotypes that simultaneously promote high yield and good taste quality. However, selection based on one or a few traits may result in unfavorable changes to other traits, due to negative

Free access

R. Karina Gallardo, Diem Nguyen, Vicki McCracken, Chengyan Yue, James Luby, and James R. McFerson

efficient in the use of financial, human, and time resources ( Alpuerto et al., 2009 ; Luby and Shaw, 2001 ). In MAB, mating and selection decisions are informed both by the observable parental traits (their phenotypes) and by genetic knowledge of the DNA

Free access

M.J. Striem, G. Ben-Hayyim, and P. Spiegel-Roy

Excluding seeded offspring at an early stage could be of great value to the breeder concerned with the development of seedless grapes (Vitis vinifera L.). We used the random amplified polymorphic DNA (RAPD) technique to identify molecular genetic markers, analyzing 82 individuals of a progeny resulting from a cross between `Early Muscat' (seeded) and `Flame Seedless'. Seven variables representing the traits of seedlessness were analyzed: mean fresh weight of one seed, total fresh weight of seeds per berry, perception of seed content, seed size categories evaluated visually, degree of hardness of the seed coat, degree of development of the endosperm, and degree of development of the embryo. Among 160 10mer primers, 110 gave distinct band patterns. Twelve markers yielded significant correlations with several subtraits of seedlessness, mainly with the mean fresh weight of one seed and the total fresh weight of seeds per berry. Multiple linear regression analysis resulted in high coefficients, such as R = 0.779 for fresh weight of seeds per berry, when the seven markers were included as independent variables in the model. Most of the seeded individuals, about 44% of the progeny, could be excluded using a two-step process of marker assisted selection.