bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Freezing on the Hydrocyanic Acid Potential of Field‐Grown Sorghum Tillers1
Authors: Haskins F. A. , Gorz H. J. , Hill R. M. , Youngquist J. Brakke
Published: July 2010

Tissue disruption caused by freezing and thawing may contribute to rapid enzymatic breakdown of dhurrin [p‐hydroxy‐(S)‐mandelonitrile‐β‐D‐glucoside],the cyanogenic glucoside of sorghum [Sorghum bicolor (L.) Moench], but published reports are not in agreement as to the effects of freezing on the hydrocyanic acid potential (HCN‐p) of field‐growns orghum leaves. These effects were investigated in a series of experiments in the fall of 1983, a period during which weather conditions at Lincoln, NE permitted repeated sampling of frozen and nonfrozen leaves of field‐growns orghum tillers. Assays of these samples, both spectrophotometrically and with the cyanide electrode, indicated that the HCN‐p of KS8 and N32 tiller leaves decreased after the tissue was frozen, but potentially dangeroues levels remained in N32 tillers for at least 6 or 7 days after the leaves were frozen. Levels of HCN‐p in KS8 tiller leaves were much lower than those in N32 leaves, p‐Hydroxybenzaldehyde acid, identified by its ultraviolet absorbance spectrum and chromatographic behavior, was found in extracts of frozen N32 tillers. Freezing and thawing of the tillers evidently led to partial breakdown of dhurrin to p‐hydroxybenzaldehyade and subsequent oxidation of this aldehyde to p‐hydroxybenzoic acid.
Field and Growth Chamber Evaluations for Root‐Lesion Nematode Resistance in Alfalfa1
Authors: Nelson D. L. , Barnes D. K. , MacDonald D. H.
Published: July 2010

Large populations of root‐lesion nematodes (Pratylenchus penetrans) have caused difficulties in establishing and maintaining alfalfa (Medicago sativa L.) at the North Central Experiment Station in Grand Rapids, MN. Nematicide application at the time of seeding is necessary to obtain acceptable stand establishment. Our objective was to develop methodology necessary to breed alfalfa with resistance to the root‐lesion nematode. Vigorous and nonvigorous plants were selected from a severely damaged 2‐year‐old cultivar trial having a high population of root‐lesion nematodes (about 13 cm‐3 of soil). These selections, their S1 and half‐sib progeny were evaluated for resistance in the same field. Significant variability existed among alfalfa entries for stand establishment, root weight, and shoot weight under high levels of root‐lesion nematodes. The same entries were inoculated with root‐lesion nematodes and observed in a growth chamber test at 25°C for a 48‐day growth period. Significant variability was observed among alfalfa entries for shoot weight, root weight, fibrous root score, and numbers of nematodes in the root. Screening and evaluation methods in the growth chamber and in the field rated alfalfa entries similarly (r=0.72, 18 degrees of freedom). Both methods would be effective when breeding for resistance. Root weight appeared to be the best selection criterion for growth chamber evaluations and shoot weight was the most important characteristic for field evaluations.
Inheritance of Palmitic, Oleic, Linoleic, and Linolenic Fatty Acids in Groat Oil of Oats1
Authors: Thro A. M. , Frey K. J. , Hammond E. G.
Published: July 2010

Ten matings among adapted oat (Avena sativa L.) cultivars were employed to study the inheritance of fatty‐acid composition of oat groat oil. Heritability estimates in six matings ranged from 0.33 to 0.56 using unreplicated hill plots for palmitic, oleic, linoleic, and linolenic acids. Heritabilities based on progeny means of the same six matings over two replicates at each of three locations were 0.68, 0.72, and 0.64 for palmitic, oleic, and linoleic acids, respectively. Effects of matings and matings ✕ locations interaction and variation among lines within the six matings were significant (P < 0.01) for palmitic, oleic, and linoleic acids. Correlations between contents of fatty acids in groat oil were: palmitic and oleic acid, −0.47; palmitic and linoleic, −0.30; palmitic and linolenic, −0.10; oleic and linoleic, −0.55; oleic and linolenic, −0.43; and linoleic and linolenic, −0.04. Additive gene action was the most important genetic component of variation among generation means of four additional matings for palmitic, oleic, and linoleic acids. Additive ✕ additive effects were significant for oleic acid in one mating and for linoleic acid in a second, but dominance and epistatic effects involving dominance were of no importance in fatty‐acid inheritance. It should be possible to breed oat genotypes with high or low levels of either saturated or unsaturated fatty acids in the groat oil. The importance of additive gene action implies that desired allelic combinations from these matings could be obtained in pureline cultivars.
Spaced‐Plant‐Population‐Progress Test1
Authors: Burton Glenn W.
Published: July 2010

This paper describes a precise and efficient method of measuring the progress realized and expected in a population improvement breeding program. The spaced‐plant‐population‐progress (SPPP) test described here included 100 spaced plant progenies of each entry arranged in 100 blocks with one plant of each entry per block. Analysis of variance of the first‐year spaced‐plant yield data from two tests of Pensacola bahiagrass (Paspalum notatum var. saure Parodi) populations being improved by recurrent restricted phenotypic selection (RRPS) gave significant (P = 0.05) mean differences among selection cycles for all but one entry comparison. The SPPP test also supplied variances and coefficients of variation (CVs) for each population that served as relative indices of the variability left in each population and the progress that might be expected from the next cycle of selection. In a precise seeded plot test, relative first‐year mean yields of the F1 hybrid of clones 2 ✕ 4 (from Cycle 4) and Cycle 9 compared with the commercial check were 167 and 175%, respectively, and were not different (P = 0.05). In the SPPP test, their respective relative mean yields, 226 and 267%, were different (P = 0.01). Likewise, the difference between mean yields of Cycles 8 and 9 that was significant (P = 0.05) with the SPPP test was not significant in the replicated seeded plot test. The SPPP test gives valid relative yields but over estimates the yield potential of a population that will be grown in solid stands established from seed. Samples of 50 or 25 plants compared in SPPP tests gave more variable mean yields and larger variances than the 100‐plant populations.
Evaluation of Improved Maize Populations in Mexico and the U.S. Corn Belt1
Authors: Oyervides‐Garcia M. , Hallauer A. R. , Cortez‐Mendoza H.
Published: July 2010

Genetic variabiltiy is essential for continued genetic improvement of any crop species. One potential sourse of genetic variability is the use of exotic or unadapted germplasm. Although considerable genetic variability may be available in germplasm repositories, indiscriminate introduction of exotic germplasm may lower the breeding value of elite, adapted populations. Exotic germplasm that has been improved by cyclical selection should reduce some of the detrimental effects of incorporating exotic sources into adapted sources. The objective of our study was to determine the relative yields of maize (Zea mays L.) populations developed by recurrent selection in Mexico and in the United States. Trials were conducted in each country to determine the response of the populations per se and their population crosses. The U.S. Corn Belt populations performed better in Mexico than did the Mexican populations in the U.S. Corn Belt and some of the Mexican by U.S. Corn Belt population crosses tested in Mexico did not differ from the check hybrid. The U.S. Corn Belt populations showed better adaptation to Mexican environments than the Mexican populations did to U.S. Corn Belt environments. Of the populations tested, BS13(S)C2, derived from ‘Stiff Stalk Synthetic’ after nine cycles of recurrent selection for yield, had the highest general combining ability with the improved Mexican populations. Thus, it appeared that U.S. Corn Belt populations could be sources of useful alleles for yield, earlier maturity, and shorter plant height for Mexican breeding programs located in tropical and subtropical areas. None of the Mexican populations per se or their crosses approached the yield of the check hybrid when tested in the U.S. Corn Belt; most were taller, flowered later, and had higher grain moisture at harvest.
Genotype ✕ Photoperiod and Genotype ✕ Temperature Interactions for Maturity in Maize1
Authors: Russell W. K. , Stuber C. W.
Published: July 2010

A six‐parent diallel of maize (Zea mays L.) was evaluated for total leaf number (TLN), days to tassel initiation (DTI), and to pollen shed (DPS) in 18 diverse field environments and two phytotron environments to determine the contribution of photoperiod and temperature variables to the genotype ✕ environment interaction. Understanding the interaction of genotype, photoperiod, and temperature is essential, for ultimately the timing of tassel initiation and other major developmental events determines yield. For each trait, but particularly for TLN, the contribution of general combining ability (gca) to the genotype and genotype ✕ environment sums of squares far exceeded that of specific combining ability (sca). For both TLN and DTI, the linear effect of photoperiod was the primary climatic variable contributing to the gca ✕ environment interaction. The same rankings of gca effects in response to photoperiod were observed for TLN and DTI, with a range in parental sensitivity from 0.4 leaves and 0.0 days/h to 1.9 leaves and 4.9 days/h. For neither trait was there evidence of a critical daylength. The primary difference between TLN and DTI was that DTI was more sensitive to temperature, particularly average low temperature, than was TLN. Although the linear term for photoperiod also contributed significantly to the gca ✕ environment interaction for DPS, its effect was overshadowed by that of temperature.
Genetic Nomenclature in Guar1
Authors: Ray D. T. , Stafford R. E.
Published: July 2010

A compilation and revision of gene symbols for guar [Cyamopsis tetragonoloba (L.) Taub.] are presented. The objective is to provide a list of gene symbols devoid of duplications and ambiguities, and propose a system of uniform nomenclature and symbolization for guar. Symbols for 15 characters are recommended and gene descriptions and authorities are cited.
Variability for Yield and Yield Components in IAP1R Grain Sorghum Random‐Mating Population. II. Correlations, Estimated Gains from Selection, and Correlated Responses to Selection1
Authors: Lothrop J. E. , Atkins R. E. , Smith O. S.
Published: July 2010

Estimated gains from selection and interrelationships among plant characters in the random‐mating sorghum [Sorghum bicolor (L.) Moench] population IAP1R were evaluated using data from seven environments. Genetic correlations of grain yield with the primary components of yield were highest for seeds per panicle (0.53‐0.65), variable for 100‐seed weight (0.32‐‐0.16), and low for panicles per plant (0.07‐0.27). Phenotypic correlations were positive for yield with plant height (0.41) and days to midbloom (0.29). Estimates of percentage gain per generation for gridded mass selection indicated that this procedure would be effective for improving 100‐seed weight. Comparisons of gains from mass selection and different family selection methods indicated that grain yield, seeds per panicle, and panicles per plant were best improved by family selection. S1 family testing seemed preferable to other procedures when both estimated gains and operational efficiency were considered. The estimated gain for yield was 4,2% per generation when S1 testing was conducted at both Ames and Castana, IA and population performance was evaluated as the mean of those two locations. Correlated responses to St selection for yield and the components of yield indicated that indirect selection for yield would not be effective. Direct selection for yield was estimated to result in favorable increases in all yield components in Exp. I and in increases in all components except 100‐seed weight in Exp. II.
Mass Selection for Plant Height Using a Systemic Herbicide1
Authors: Sorrells M. E. , Neiss A. M.
Published: July 2010

Efficient mass selection techniques can be used to screen large populations for desirable characteristics at minimal cost. In order to test a mass selection technique for short plant stature, a rope‐wick herbicide applicator was used to apply glyphosate to two heterogeneous populations of winter wheat (Triticum aestivum L.). At 1 to 2 weeks postanthesis, a tractor‐mounted applicator was passed over each of the populations 0, 1, 2, or 4 times at approximately 20 cm below canopy height. One cycle of mass selection using one pass of the applicator significantly reduced the height of both populations without reducing population variance. The systemic herbicide eliminates many of the short tillers of tall plants, thus improving the effectiveness of selection over the use of clipping techniques. The necessary equipment and materials are inexpensive and readily available.
Lint Yield Genotype ✕ Environment Interaction in Upland Cotton as Influenced by Leaf Canopy Isolines1
Authors: Meredith William
Published: July 2010

In order to develop a strategy in cotton (Gossypium hirsutum L.) for determining the optimum leaf canopy type for each major environment and linking physiology with breeding, the interaction of leaf canopy types with environments was investigated. The lint yield genotype ✕ environment interaction of normal, Okra leaf (Lo2, Lo2), and their F1 and F2 near‐isogenic leaf canopy types of eight cotton cultivars and strains was investigated at Stoneville in 1979 and 1980. The 32 combinations were planted on two dates each year at seeding rates of 9.7, 19.4, and 38.8 seeds m,‐2. Average yields for the 27 April and 15 May 1979 plantings were 937 and 654 kg ha‐1, respectively; the 21 April and 14 May 1980 plantings were 577 and 539 kg ha‐1, respectively. Cultivar‐strains average yields ranged from 550 to 816 kg ha‐1. No leaf type consistently produced highest yields. Average yields of normal, Okra leaf, F1, and F2 cotton were 682, 660, 687, and 677 kg ha‐1, respectively. Interactions with the four leaf canopy types accounted for 29% of the total genetic variance, whereas interactions with the eight cultivar‐strains accounted for 13% of the total genetic variance. Significant negative dominance was detected in 1979 and significant positive dominance was detected in 1980. In 1979, there was a trend for negative compensation in the F2; the F2 yielded less than expected based on its three genotypic components. In 1980, there was a trend for positive F2 compensation. As a result, F2 leaf canopy types produced the most stable (least variance) yields across all environments and management variables. This study indicates the high interactive effects of leaf canopy types on yield, which are probably linked to leaf canopy types' known association with leaf area and crop maturity.
Disparity of Cotton Pollen Dispersal by Honey Bees Visiting Upland and Pima Pollen Parents1
Authors: Loper G. M. , Davis D. D.
Published: July 2010

In 1982 and 1983, experimental plantings of a genetic‐cytoplasmic male sterile and a pollen fertile upland cotton (Gossypium hirsutum L.) as well as a pollen fertile Pima cotton (G. barbadense L.) were established near Safford in southeast Arizona to study cross‐pollination using honey bees (Apis mellifera L.). The objective of these studies was to determine whether poor yields in previous interspecific crossing blocks were caused by a lack of pollen transfer, poor bee visitation, or because of plant factors such as poor bloom synchrony. Observations and data on blooming rates, honey bee visitation, pollen deposition (pollen grains/stigma), nectar volume and sugar concentration, boll samples and hybrid progeny ratios were obtained. Flowering of the Pima R line started later than the upland cottons and the early Pima bloom was approximately 40% cleistogamous. Thus, during the first 2 weeks of A‐line bloom, Pima pollen availability was minimal. For 5 consecutive weeks in 1982 when honey bee visitation to the A line was adequate (−1.3%), pollen deposition on A‐line stigmas adjacent to the Pima R line ranged from 11.8 to 42.4% (x = 25) of the pollen deposition on A‐line stigmas adjacent to upland B line. Progeny rows grown from F1 seed of the A × R cross averaged 20.2% Pima hybrids, showing that isolation from B‐line pollen was inadequate. In the 1983 study, pollen deposition on the A line adjacent to Pima was low also. The results are documentation of some of the problems of pollen transfer in producing hybrid cotton seed using a G. hirsutum A line and G. barbadense R. line.
Efficient Selection for Brown Stem Rot Resistance in Soybeans Under Greenhouse Screening Conditions1
Authors: Sebastian S. A. , Nickell C. D. , Gray L. E.
Published: July 2010

Brown stem rot (BSR), caused by Phialophora gregata (Allington and Chamberlain) W. Gams, is a soybean [Glycine max (L.) Merr.] disease, which causes vascular discoloration of stems and necrosis of the leaves. Because of the importance of BSR and the lack of BSR resistance displayed by most soybean Cultivars, BSR resistance has become a major objective of many soybean breeding programs. Efficient selection strategies will facilitate such breeding efforts. The purpose of this study was to determine the relative value of ratings of BSR leaf and stem symptoms in selecting for BSR resistance under greenhouse screening conditions. This was done by comparing the heritabilities of leaf and stem symptom ratings. Heritability estimates were based on variances among and within F3 families from two crosses between susceptible and resistant soybean lines. The broad sense heritabillty estimates (on a single F2 plant basis) for leaf symptoms were two to three times as large as those for stem symptoms (0.88 vs. 0.44 in one cross, and 0.65 vs. 0.21 in the other). Under greenhouse screening conditions, selection for BSR resistance, based on leaf symptoms, should be more effective than selection based on stem symptoms.
Leaf Area Expansion and Shoot Elongation of Diverse Alfalfa Germplasms1
Authors: Volenec J. J.
Published: July 2010

Rapid regrowth of alfalfa (Medicago sativa L.) following harvest is important to maximize use of solar radiation and obtain high herbage yields. The objectives of this study were to evaluate interrelationships among leaf area expansion rate (LAER), shoot elongation rate (SER), and several morphological and physiological characters. Leaf area per shoot and shoot length of four diverse germplasms were measured daily during 28 days of regrowth in the greenhouse. Leaf area per shoot and shoot length both increased in a nearly linear manner, and LAER and SER, calculated during the interval 8 to 21 days following harvest, were linearly related (R2 = 0.73**). In a second study, plant introductions selected for rapid regrowth following harvest had 37% greater SER and produced 32% more leaf area per shoot than plant introductions classified as having slow regrowth. This indicates that SER is an effective indicator of LAER. Averaged across experiments, plants with rapid SER had 55% higher specific stem weight with 26% more internodes and 80% longer internodes than plants with slow SER. This resulted in 74% higher yield per shoot of the rapid SER plants when compared to slow SER plants. The SER and LAER were not consistently associated with root total nonstructural carbohydrate concentrations or number of shoots per plant, and were negatively correlated with herbage N concentrations (r = −0.36 to −0.55). Additional work is underway to elucidate the biochemical and physiological basis for genetic differences in SER.
Earliness Factors in Three Pima Cotton Genotypes1
Authors: Fry K. E.
Published: July 2010

Pima cotton cultivars (Gossypium barbadense L.) were characteristically tall and late maturing, but newly developed Pima genotypes are shorter and earlier. The objective of this study was to ascertain phenotypic differences between the early and late Pima genotypes and relate them to earliness characters in upland genotypes (G. hirsutum L.). Among three Pima genotypes, characters studied were plant height, stem and branch weight, number of mainstem nodes, mainstem internodal length, node of first sympodium, cut‐out node, axillary bolls on mainstem, early bolls set and shed, and late green and mature bolls. Data from dried plants collected at end‐of‐season were obtained for 1980, 1981, and 1982 at Phoenix, AZ. Early season genotypes, when compared to late season genotypes, had i) shorter mainstem and sympodial internodalength, ii) less stem weight, iii) lower first sympodium node, iv) lower cut‐out node, and more bolls on the mainstem that developed in the axils of the sympodia. On the first 30 fruiting sites per plant that flowered, the early genotypes set more bolls and shed fewer bolls on a smaller number of sympodia. The early genotypeshowed a larger fruiting‐efficiency ratio of mature fruit numbers to stem weight, and a larger proportion of all the fruits per plant in the group of first 30 fruiting sites. Many of the earliness characters were similar to those in upland cotton. Fruiting‐efficiency ratio may be the most useful selection parameter.
Water Use in Winter Wheat as Influenced by Cephalosporium gramineum
Authors: Martin J. M. , Mathre D. E. , Johnston R. H.
Published: July 2010

Cephalosporium stripe disease of winter wheat (Triticum aestivum L.) is caused by the soil borne fungus Cephalosporium gramineum [Nisikado & Ikata (Hymenula eerealis Ell. & Ev)]. The effect of C. gramineum on root activity and subsequent soil water depletion is unknown. Our objective was to measure water use and soil water depletion patterns for six winter wheat genotypes with differing reactions to C. gramineum, under disease and nondisease conditions. Six winter wheat genotypes, ‘Marias’, ‘Win° ridge’, ‘Redwin’, ‘Lenore’, MT 7579, and MT 7811 were evaluated for grain yield in replicated control and inoculated plots in 1982 and 1983 near Bozeman, MT, of an Amsterdam silt loam (fine silty mixed family of Haploborolls). Soil water was measured in each plot at 15‐cm depth increments to 145‐cm with a neutron moisture meter. Soil water measurements were taken at roughly weekly intervals commencing in early May and continuing until harvest in early August. C. gramineum reduced grain yield, water use, and water use efficiency in both years but to a greater extent in 1982 than in 1983. Lenore proved least susceptible and Marias and MT 7811 were most susceptible as measured by reduction in grain yield, water use, and water use efficiency when averaged over both years. Genotypes differed in rate of water use in both years in the presence of the disease, but differences among genotypes were detected only in 1982 in the non‐disease situation. Infection by C. gramineum affected water depletion patterns least in Lenore and Winridge, and most in Marias and MT 7811. Genotype ✕ time and genotype ✕ depth interactions were such that relative differences among genotypes were amplified with increasing time and depth. C. gramineum affected soil water extraction throughout the soil profile. Reduction in water extraction may be due to reduced root activity and/or reduced demand for water by infected plants.
Transmittance of Winterhardiness in Segregated Populations of Peas1
Authors: Liesenfeld D. R. , Auld D. L. , Murray G. A. , Swensen J. B.
Published: July 2010

Winterhardiness in Pisum sativum (L.) was evaluated in segregated populations derived from crossing the cultivars ‘Melrose’ (hardy) and ‘Romack’ (intermediate) to ‘Garfield’ (nonhardy). The reciprocal backcrosses and the F2 generations were advanced by single seed descent to derive F5 lines. The F5 lines derived from these six populations and the parental lines were evaluated for winter survival and winter injury at Moscow, Idaho, during the winter of 1982—1983 on a Palouse silt loam (finesilty, mixed, mesic pachic Ultic Haploxeroll). The three populations derived from the cross between Melrose and Garfield were also evaluated for survival and freezing injury in the laboratory. Increasing the dosage of the more hardy parent increased the number of winter‐hardy lines recovered. In populations with 75% of their genetic background from the more hardy parent, approximately half the F5 lines had greater than 70% survival in the field. Percent survival and injury score in the field were significantly correlated (r = 0.80 and r = 0.82; both at the 0.01 level) for both crosses. Screening in the laboratory at −7°C was more closely correlated with the field evaluation than results obtained at either −4° or −10°C. Recovery of lines with the same level of winterhardiness as either parent from populations with less than 50 lines suggests that as few as three or four genes or linkage groups could be responsible for winterhardiness in the pea lines evaluated. Winter survival in Pisum was found to be associated with the genes which produce pigmented hilum (Pl) on Chromosome VI and pigmented seed coat (A) on Chromosome I, suggesting that genes which condition winterhardiness are linked to these genes.
Characteristics and Performance of Male‐Sterile and Hybrid Seed Produced by Cross‐Pollination in Hard Red Spring Wheat1
Authors: Johnson K. M. , Lucken K. A.
Published: July 2010

Wheat(Triticum aestivum L.) seed produced by cross‐pollination on male‐sterile plants in male‐sterile increase and hybrid seed production blocks was characterized and evaluated using several laboratory and field tests. Male steriles (A‐lines) in both types of crossing blocks had lower seed sets and lower seed yields than their pollinators (maintainers or B‐lines and restorers or R‐lines). Seed produced by cross‐pollination on A‐lines had lower test weight, lower germination percentage and less seedling growth, but higher seed weight, higher protein percentage, and higher leachate conductivity than selfed seed produced on their respective B‐ or R‐lines. The crossed seed germinated and grew more slowly under osmotic stress than selfed seed but showed no germination differences after exposure to high and low temperature stresses.
Selection for Tolerance to Frequent Cutting Regimes in Alfalfa1
Authors: Veronesi F. , Mariani A. , Falcinelli M. , Arcioni S.
Published: July 2010

A study was conducted on alfalfa (Medicago sativa L.) to evaluate the effects of two cycles of phenotypic recurrent selection for tolerance to frequent harvest on persistence, dry matter, and crude protein yield. One hundred and eight clones (72 from selected and 36 from control materials) were established in plant nursery in April 1982. An experimental design was used, which subjected the 108 clones to the following harvest treatments during 1983 and 1984 growing seasons: very frequent (14 cuts from April 1983 to September 1984); frequent (12 cuts from April 1983 to September 1984); and infrequent (9 cuts from May 1983 to September 1984). The results can be summarized as follows: i) selection increased persistence of alfalfa materials and both dry matter and crude protein yield within each harvest treatment; ii) the selected materials, even if more persistent and productive than the controls, showed a depression in dry matter and crude protein yield when submitted to frequent and very frequent harvest treatments compared to the infrequent harvest treatment. In general, the selection for tolerance to frequent cutting regimes seems more suitable for improving the average persistence of alfalfa than in synthetizing new cultivars able to overcome the decrease in yield potentialities connected to the increase of harvest frequency.
Androgenic Somaclonal Variation in Tobacco and Estimation of its Value as a Source of Novel Genetic Variability1
Authors: Schnell R. J. , Wernsman E. A.
Published: July 2010

In vitro anther culture of near homozygous tobacco (Nicotiana tabacum L.) cultivars yields haploids which, when chromosome doubled, result in populations of doubled‐haploid (DH) lines exhibiting great among‐line genetic variability with agronomic characteristics inferior to those of the cultivars. Studies were conducted to characterize the nature of this “induced” genetic variability and to determine its potential value in recurrent selection programs. Sixty‐four DH lines from a single plant of cultivar ‘NC 95’ were randomly assigned to eight sets of a North Carolina Design II mating design. The DH full‐sib families and selfed progenies of the parental plant were evaluated for seven variables in two field environments. Genetic variances in the DH population were estimated, heritabilities calculated, and genetic gains from practicing half‐sib and full‐sib family selection for yield improvement in the DH population were predicted. A DH population composite, a random‐mated DH population, and populations resulting from practicing half‐sib and full‐sib family selection, in the DH population were compared to two sublines of the original parental plant. Significant additive genetic variance was detected for six of seven variables measured in the DH population. Dominance variance estimates were zero or negligible. Random mating of DH lines resulted in a recovery of 26% of the yield loss of the DH population composite compared to the cultivar. One cycle of half‐sib and full‐sib family selection resulted in populations yielding 5% and 6.0% respectively, more cured leaf than the random‐mated DH population; both selected populations were lower yielding than the sublines of the original parental plant. Two or more cycles of recurrent full‐sib selection are estimated to be required to achieve a population equal in yielding ability to the parental cultivar. This requirement reduces the appeal of androgenic somaclonal variability as a germplasm source for tobacco improvement.
Effects and Control of Genetic Drift in the Autotetraploid Population1
Authors: Rowe D. E.
Published: July 2010

The effects and the potential for control of random genetic drift were investigated theoretically for an outcrossing autotetraploid population. With reference to breeding acrop such as alfalfa [Medicago sativa (L.)], two situations were considered. First the variance effective population sizes were determined for maintaining a nearly constant phenotype over generations of seed increase assuming additive, monoplex dominance, duplex dominance and recessive types of gene action at a locus. The interaction of gene frequency and type of gene action on the potential change in population phenotype with random genetic drift was shown. For a given confidence level and a range of tolerable variation in phenotypic mean, the population sizes needed with the non‐additive types of gene action were up to three times the population size with additive gene action. Second the variance effective population sizes were determined for keeping the gene frequency in a population above a critical frequency. A critical frequency was defined as either the minimum gene frequency where the desirable gene was recoverable in a breeding population or the minimum frequency where agronomic value was maximized. In this case variance effective population sizes up to near 3000 were indicated to protect some gene frequencies. These results indicated that for the moderate population sizes of 50 to 300, often used in an isolation seed increase, the changes in gene frequencies from generation to generation at all loci not fixed maybe substantial. The actual change in population phenotype for a given change in gene frequency is dependent on gene frequency and type of genic action at a locus. These random changes in population phenotype are expected to be more important for traits controlled with nonadditive gene action by one or only a few genes. For genetic studies using multiple generations the results of this study indicated that for a seed increase either a polycross by hand or the use of 1000 or more plants in an isolation are necessary to be certain of a meaningful interpretable relationship between parents and offspring.
Yield Response of Two Cotton Cultivars to Tobacco Budworm Infestation1
Authors: McCarty J. C. , Jenkins J. N. , Parrott W. L.
Published: July 2010

Two cotton, Gossypium hirsutum L., cultivars were artifically infested with tobacco budworm, Heliothis virescens (F.), larvae for different time intervals during the first 8 weeks of fruiting to determine impact on yield reduction and maturity delay. The cultivars tested were ‘Stoneville 213’ (full‐season) and ‘Tamcot CAMD‐E’ (short‐season) grown in 1 ✕ 13.7 m long single row plots in a two‐planted one‐skip row pattern during the 1982 and 1983 growing seasons on a Leeper silty clay loam (fine, montmorillonitic, nonacid, thermic Vertic Haplaquepts). Treatments consisted of applying 12 first instar larvae in the terminal area of each plant, once per week for the following combination of weeks after fruiting had begun: none (control), Weeks 1 to 2, to 4, 1 to 6,1 to 8, 7 to 8, 5 to 8, 3 to 8, 3 to 4, to 6, and 3 to 6. When larvae were not applied in a given week, plots were protected with an insecticide. Plots were machine harvested three times for yield determinations and delays in maturity. All treatments involving larval applications the first 2 weeks of fruiting resulted in significant reductions in yield, compared with the control, for both cultivars at first harvest. Tamcot CAMD‐E with larval treatments produced a larger percentage of its total yield at first harvest than did Stoneville 213. When first and second harvest were accumulated, the same trends were apparent. Total yield of Stoneville 213 was significantly reduced only when larvae were applied for at least a 4‐week time period. The same trend was apparent with Tamcot CAMD‐E: timing of applications (rather than length of time) had the greatest effects; however, reduction in yield was not significant. Subclass regression analysis of yield as a function of larval application indicated that yield reduction trends averaged over years were significant and the responses of the two cultivars were found to be significantly different from each other as tested by homogeneity of slopes. The yield of Tamcot CAMD‐E was not reduced or delayed as much as that of Stoneville 213 when tobacco budworm larvae were applied during early‐, mid‐, and full‐season. The application of larvae during the early stage of fruiting had a greater impact on reducing yield and delaying maturity than when larvae were applied during mid‐ and late‐season.
Recurrent Selection for Reduced Plant Height in Lowland Tropical Maize1
Authors: Johnson E. C. , Fischer K. S. , Edmeades G. O. , Palmer A. F. E.
Published: July 2010

Reduced plant height is considered a desirable attribute in most maize (Zea mays L.) breeding programs. This study was conducted to evaluate direct and correlated responses to selection for reduced plant height in tropical maize. Fifteen cycles of visual, full‐sib recurrent selection for reduced plant height were conducted in one lowland tropical maize population, ‘Tuxpeño Crema I’. Cycles 0, 6, 9,12, and 15 were evaluated for correlated responses in plant morphology, grain yield, dry matter production and distribution, leaf area index, and duration and rate of kernel growth at three plant densities at two or three locations in Mexico over a period of 2 yrs. Selection resulted in a linear reduction in plant height, from 282 to 179 cm (2.4% per cycle). The estimate of broad‐sense heritability for plant height was 0.84. Optimum plant density for yield increased from 48 000 to 64 000 plants ha−1, an increase of 2.1% per cycle. As height was reduced, yield, when determined at the optimum plant density for yield for each generation, increased by 4.4% per cycle. Later cycles showed reduced total lodging, reduced barrenness, earlier flowering, and fewer leaves per plant. When grown at or near their optimum densities for grain yield, leaf area index, and total dry matter per unit area at harvest for selected cycles were similar. Yield improvement was associated with a linear increase in harvest index from 0.30 to 0.45 from the original to the 15th cycle. At 50% silking, total aboveground dry weight and its proportion as stem were reduced; kernel number per unit area at harvest increased from 1592 to 2667 kernels m −2 when grown at or near optimum density, and there was an increase in crop dry weight production from anthesis to black layer formation. Selection for reduced plant height had little effect on the effective filling period or kernel weight.
Selection for Early Flowering in Corn: 18 Adapted F2 Populations
Authors: Troyer A. F.
Published: July 2010

I measured selection‐for‐early‐flowering effect during corn(Zea mays L.) inbred line development on hybrid performance in two experiments of adapted F2 populations. The first experiment studied eight F2 populations from 11 inbreds; the second experiment studied 10 F2 populations from all possible two‐way crosses of five elite, unrelated, proprietary inbeds. I selected the earliest flowering 11 or 12 plants (2%) of 550 to 600 plants per F2 population grown at 87 000 plants ha−1 and intercrossed them with bulked pollen for two cycles, then selfed the third cycle of selection grown at 105 000 plants ha−1. I random sib‐mated within populations after Cycles 1 and 2. The first experiment's materials were crossed to Iowa inbred B14, then tested at two densities in 1 yr. Selection effect per cycle averaged: 0.6 day less to flower, 0.6 percentage points less grain moisture, 2.4 cm less plant height, 0.1 day less silk delay, 364 kg ha−1 (6%) more yield, and no stalk breakage effect. The second experiment's materials were crossed into the 15 possible unrelated four‐way crosses among populations within cycles, then tested at three densities in 2 yrs. Selection effect per cycle averaged: 1.2 day less to flower, 1.0 percentage point less grain moisture, 7.0 cm less plant height, 0.1 day less silk delay, 238kg ha−1 (4%) less yield, 0.5 more ears 100−1 plants, and 3.7% more stalk breakage. All possible four‐way crosses measured selection effect well, but measured inbred‐lines parent effects poorly.Several important agronomic traits improved during inbred development via selection for early flowering.
Comparative Water‐Use Rates and Efficiencies, Leaf Diffusive Resistances, and Stomatal Action of Healthy and Stripe‐Smutted Kentucky Bluegrass1
Authors: Nus Jeff L. , Hodges Clinton F.
Published: July 2010

Systemic infection by Ustilago striiformis (stripe smut) results in pathogen‐induced water stress of Kentucky bluegrass (Poa pratensis L.). Such pathogen‐induced water stress may arise, in part, from increases in host transpiration due to decreases in cuticular resistance or an inhibition of stomatal movement. This study was conducted in controlled‐environment chambers to compare Kentucky bluegrass ‘Merion’ systemically infected by Ustilago striiformis with healthy plants for water‐use rate (WUR) and efficiency (WUE), leaf diffusive resistance (LDR), and critical leaf‐water potentials for stomatal closure. Leaves of infected plants with immature sori and no visible rupturing of the epidermis did not differ in WUR(mL) day−1) or WUE (g L−1) from healthy plants. Leaves of infected plants with mature sori with moderate to heavy sporulation and subsequent epidermal damage showed sharp decreases in WUR and WUE compared with healthy plants or infected leaves with immature sori and a visibly intact epidermis. No differences were observed in LDR between healthy plants and infected plants with mature or immature sori in the light. The LDR of infected plants in the dark was reduced only slightly by immature sori, but the presence of mature sori and subsequent epidermal rupturing lowered LDR to values similar to those exhibited by both healthy and infected plants in the light. Stomatal closure on infected leaves with immature sori occurred at lower leaf‐water potentials than on healthy leaves, suggesting a degree of osmotic adjustment in response to pathogen‐induced water stress.
Inheritance of Ephemeral Leaf Mutant of Upland Cotton1
Authors: Wilson F. Douglas
Published: July 2010

Developmental mutants of plants may be useful in studies of physiological development and of gene expression and gene action. The objectives of the study were to determine the inheritance of a newly discovered developmental leaf mutant of upland coton (Gossypium hirsutum L.) and to determine whether it was allelic to, or linked to veins‐fused (vf) or to strap leaf (s). This mutant is named ephemeral, because it expresses only for a short time during plant growth. The gene associated with this expression was assigned the symbol ep. It was inherited as a monofactorial recessive in 198S, but in 1984, about half of the (normal ✕ ephemeral)F1 plants were intermediate in expression. In the greenhouse, usually a single leaf is affected at about Node 6, and progressively more leaves are affected until Node IS, but leaves at Node 18 and above appear normal. In the field, expression is much more restricted and may be limited to just a few leaves at Nodes 5 to 10. The mutant phenotype resembles that of veins‐fused, but ep is not allelic to, nor closely linked to vf to s.
Yield Reductions Caused by Stem Canker in Soybean1
Authors: Harville B. G. , Berggren G. T. , Snow J. P. , Whitam H. K.
Published: July 2010

Stem canker (caused by Diaporthe phaseolorum var. caulivora Athow & Caldwell) was first observed in Louisiana on soybean [Glycine max (L.) Merr.] near Rosa in 1981. In 1982, several thousand hectares of soybeans were damaged in the southern part of Louisiana, some of which were heavily damaged. The objective of this study was to assess the extent of yield reductions of soybean cultivars caused by stem canker in Louisiana. Thirty‐two cultivars were field grown in Olivier silt loam (fine‐silty, mixed, thermic Aquic Fragiudalfs) soil. They were grown in a randomized complete block design with four replications. A wide range of responses was observed; several cultivars from Maturity Groups V through VIII were resistant to the disease. Significant negative correlations occurred between yield and disease ratings among cultivars and maturity groups. This study indicated several cultivars that should not be grown in soil where the stem canker organism is known to be present and identified other cultivars that could possibly be grown in the presence of the stem canker organism.
Alfalfa Triploids with Functional Male and Female Fertility1
Authors: Blake N. K. , Bingham E. T.
Published: July 2010

Alfalfa (Medicago saliva L.) triploids (2n=3x = 24) were produced by crossing tetraploid cultivated alfalfa with cultivated alfalfa at the diploid level (CADL) derived by haploidy. Alfalfa triploids usually function only as seed parents in crosses; however, eight of nine triploids in this study functioned as the pollen parent in 3x‐3x, 4x‐3x, or 6x‐3x crosses. Moreover, two triploids produced self‐progeny. In 3x‐3x crosses, most progeny had 31 or 32 chromosomes, but progeny with 29,35,45,46,47,48, and 58 chromosomes were also produced. Triploid self‐progeny had 31, 32, 36, 45, 46, 47, 48, and 52 chromosomes. Several hexaploids (2n=48) and near hexaploids (2n=45‐52) were produced by sexual polyploidy in 3x self, 3x‐3x, 3x‐6x, and 6x‐3x matings.
Taxonomic Investigation of an Accession of Lotus spp.1
Authors: Beuselinck P. R. , Younes M. Ben , McGraw R. L.
Published: July 2010

The large seeded plant introduction (PI) 302921 (MO accession 266) was obtained with the tentative identity as a Lotus tenuis Waldst. & Kit., but preliminary observations of its morphology, except for seed size, were more characteristic of the phenotype described for L. corniculatus L. Our objective was to make morphologic, karyotypic, and idiographic comparisons of entry 266 with four randomly chosen L. tenuis introductions, (MO accessions 250, 253,256, 260) and two L. corniculatus cultivars, ‘Dawn’ and ‘Norcen’, grown in greenhouse and field environments to reidentify entry 266. Entries of L. corniculatus and L. tenuis conformed to taxonomic keys based on morphological characters including leaf length, width, area, length/width ratio, and chromosome number. Entry 266 consistently exhibited small leaf characteristics and leaf pubescence. Leaf length/ width ratio appeared to be the most reliable morphological character for taxonomic placement of entry 266, which was similar to the L. corniculatus entries in this study and previous reports of L. corniculatus morphology. Entry 266 was found to have a somatic chromosome number of 2n=4x=24 and a karyotype and idiogram similar to the L. corniculatus entries. Hybrids obtained from reciprocal crossings among genotypes of the L. corniculatus germplasm, MO‐20, and entry 266 exhibited a relatively high degree of fertility. A higher percentage of abnormal pollen observed in the F1 hybrid was not significantly higher than that of the parents or the first cycle of the randomly mated L. corniculatus population, MU‐81. Geographical isolation of the parents might account for the slightly higher pollen abnormalities in the F1 hybrids. Findings indicate PI 302921 to be a L. corniculatus accession of value for its large seed character.
Performance of Progeny of Adapted and Plant Introduction Soybean Lines1
Authors: St. Martin S. K. , Aslam M.
Published: July 2010

Because of the narrow germplasm base of North American soybean [Glycine max (L.) Merr.] cultivars, new germplasm must be infused into soybean breeding programs. The F3 or F4 bulks derived by crossing 12 soybean lines as females to each of four male lines were evaluated for agronomic traits and seed composition. Parental lines were chosen for maturity (late Group II‐early Group III) and seed yield, and included six adapted (A) and six exotic plant introduction (PI) females and two A and two PI males. The 48 bulks, plus two check cultivars, were evaluated in five environments with three replications per environment. The objectives were to compare male and female effects on bulk performance within and between the A and PI groups, and to determine whether female ✕ male interactions occurred more frequently in association with bulks derived from A or PI parents. Bulks derived from PI males averaged 10% less in seed yield than those from A males; bulks derived from PI females yielded 4% less than those from A females. There were differences within both the A and PI female groups for all traits except seed yield. Significant components of female ✕ male interaction occurred for plant height, seed weight, and, to a lesser extent, protein percentage and lodging score. Female ✕ male interactions, whenever they occurred, were associated with bulks having at least one PI parent. There were no female ✕ male interactions for seed yield or oil percentage. In general, results were consistent with the hypothesis of primarily additive inheritance. It is likely that selection for yield per se would be the most effective method to identify parental strains that would produce superior progeny. If a testcross procedure were employed for this purpose, the results indicate that the choice of tester would not be critical.