bluuebunny/crossref_metadata_2025 huggingface dataset:
Divergent Selection among Maize Seedlings for Nitrate Uptake
Authors: Teyker R. H. , Moll R. H. , Jackson W. A.
Published: July 2010

Selection applied to seedlings grown under controlled environmental conditions may contribute to plant improvement provided agronomic traits are well correlated to the seedling selection trait. The objective of this research was to utilize techniques for screening maize (Zea mays L.) seedlings for induced NO3 uptake in order to evaluate direct and indirect effects of such selection on populations created. Two cycles of divergent mass selection were performed on the open‐pollinated maize populations ‘Jarvis Golden Prolific’. Resulting populations together with the original ‘Jarvis’ were evaluated under selection conditions in the laboratory and in field trials at three locations in each of 2 yr. Significant changes in the selection trait were observed (selection response = 13.3% per cycle) that were due primarily to effects on plant size. Realized heritabilities of the first generation of selection were 0.25 for high NO3 uptake and 0.10 for low NO3 uptake. Nitrate uptake and seedling size declined in both selection directions in the second cycle. Relative changes in uptake and reduction of NO3 differed between selection cycles. Correlated responses in yield, ear number, and grain N were observed in the field, but significant genotype ✕ environment (year, location, and N supply) interactions were evident. Response to N as measured by yield and N use parameters was not associated with selections based on seedling NO3 uptake.
Seed Germination Rate and Associated Characters in Rice
Authors: Krishnasamy V. , Seshu D. V.
Published: July 2010

Rapid seed germination will facilitate quick plant stand establishment in direct sown rice (Oryza sativa L.) culture. Sixty‐eight rice cultivars were grown in the field and in the phytotron, and the harvested seed evaluated for germination rate. Cultivars ‘Laxmi’, TNAU(AD)103, IR25924‐92‐1‐3, ‘IR50’, PND160‐2‐1, RNR1429, IR31779‐19‐3‐3‐2‐2, and B3981c‐Pn‐165‐2‐l produced seeds in the field and the phytotron that exhibited superior performance. Therefore, these could be useful donor parents for promoting rapid seed germination when breeding rice for direct‐sown culture. One hundred seed weight was negatively correlated with germination rate. Path analysis suggested that 100 seed weight acted through a high indirect effect of free amino acid content on germination rate. Oxygen uptake and dehydrogenase activity also contributed to germination rate variability. Cultivar differences were evident for germination rate following aging and under low temperature (20 and 15 °C) and moisture stress (−5̄ polyethylene glycol 8000). Hulls did not contribute to variability in germination rate.
Variable Transfer of Soybean Genes for Resistance to Soybean Cyst Nematode
Authors: Luedders V. D.
Published: July 2010

Soybean [Glyclne max (L.) Merr.] cultivars may be resistant specific soybean cyst nematode (CN) (Heterodera glycines Ichinohe) populations due to genes for resistance from the genetically different sources of resistance ‘Peking’ and PI 88788. These sources have many genes for CN resistance, thus derived lines, particularly those with “mixed” or combination pedigrees, may not have all of the genes for resistance from either source. Experiments were conducted to determine whether soybean lines developed from the same sources of CN resistance had the same genes for resistance, as indicated by their phenotypes with different CN populations. Nematodes were selected for eight generations, to increase numbers of cysts, on single‐ source pedigree lines ‘Custer’ (source: Peking) and ‘Fayette’ (source: P188788), and on the two‐source lines ‘Pyramid’ and L82C‐ 579. Selection increased the nematodes' ability to reproduce on the selecting lines as expected. Patterns of ratios of numbers of cysts relative to ‘Essex’ indicated that four of the six two‐source lines were similar to Fayette. The exception, L82C‐579, appeared to have mainly Custer's genes for CN resistance. One line was heterogeneous; the phenotypes of individual plants tended to be like those of either Custer or Fayette. One of two one‐source (Fayette) lines was heterogeneous, based on evaluations with several selected nematode populations and inbreds. The results showed that soybean lines developed to be resistant to a specific CN race may not have the complement of genes for resistance that was present in the original sources.
Genetic Studies with TWo Superoxide Dismutase Loci in Soybean
Authors: Griffin J. D. , Palmer R. G.
Published: July 2010

Polyacrylamide gel electrophoresis of water‐soluble seed proteins from soybean [Glycine max (L.) Merr.J, followed by specific staining for superoxide dismutase (SOD) activity, detects up to nine achromatic bands in homozygous genotypes. A variant pattern, in which bands 8 and 9 have decreased mobilities, is observed in some soybean lines. This study was conducted to determine the mode of inheritance of this variant and to test for linkage between two SOD loci and several other loci. The inheritance of the variant pattern for bands 8 and 9 was investigated in segregating populations. The variant is coded by a single locus with codominant alleles Sod2‐a (slow pattern) and Sod2‐b (fast pattern). Sod1 and Sod2 were tested for linkage with several isozyme and morphological marker loci in segregating populations. The Sod1 locus segregated independently of 16 other loci, and Sod2 is independent of 11 other loci. The Sodl locus is independent of the Sod1 locus. Both loci can be used as markers in soybean genetic or breeding research.
Respiratory Rates and Alternative Pathway Capacity during Early Germination of Soybean
Authors: Ismail R. M. , Mullen R. E. , Stewart C. R. , Knapp A. D.
Published: July 2010

Seed respiratory rate generally correlates well with seed quality and germination performance. Alternative pathway respiration has been measured in germinating soybean [Glycine max (L.) Men.] seeds, and has been documented and theorized to play a role under cool temperatures in other species. This study was conducted to determine whether differences in respiratory rates and alternative pathway capacity (determined by sensitivity to salicylhydroxamic acid in the presence of cyanide) of germinating seeds could be detected among soybean lines at different germination temperatures. Respiratory rates and alternative pathway capacity in germinating seeds of four soybean lines of similar maturity paired into two coldtolerant vs. ‐intolerant line comparisons were evaluated at 25 and 10 °C. Neither of the two genotype comparisons showed significant differences in 25 °C‐respiratory rates or alternative pathway capacity. At 10 °C, cold‐tolerant PI 290138 exhibited significantly higher respiratory rates and alternative pathway capacity than coldintolerant PI 189947. Differences in early field establishment between cold‐tolerant PI 290138 and cold‐tolerant PI 189947 but not between the other cold‐tolerant and cold‐intolerant genotypes could be explained, in part, by respiratory characteristics. At 25 °C, alternative pathway capacities of cold‐tolerant and cold‐intolerant genotypes represented approximately 20% of their uninhibited rates. At 10 °C, both cold‐tolerant genotypes retained their capacity for alternative pathway respiration, but the capacity of cold‐intolerant genotypes was severely reduced. The data suggest that the capacity for alternative respiration among germinating seeds from soybean lines differing in cold tolerance may not be affected at warm temperatures, but that differences may exist at low temperatures, possibly influencing soybean seed germination under suboptimal temperatures.
Recurrent Half‐Sib Family Selection for 2,4‐D Tolerance in Red Clover
Authors: Taylor S. G. , Baltensperger D. D. , Quesenberry K. H.
Published: July 2010

Low profit potential as well as environmental residue and toxicology concerns make it difficult for chemical companies to develop and register herbicides for forage crops. Selection of forages with tolerance to currently labeled herbicides may be an alternative. The objective of this research was to develop a 2,4‐D [(2,4‐di‐chlorophenoxy) acetic acid] tolerant red clover (Trifolium pratense L.) population, using recurrent half‐sib family selection. A 20 000 plant base population of equal parts of ‘Nolins’, ‘Kenstar’, and a Florida population (QC5) was sprayed with 1.12 kg ha−1 2,4‐D and 63 individuals were selected and intercrossed. Four cycles of half‐sib family selection were conducted with from 63 to 276 families evaluated in a cycle. Family selections were based on mean visual top and root damage scores using a 1 to 5 visual rating scale. Four cycles of recurrent selection increased levels of 2,4‐D tolerance in red clover by approximately 35% with an average change of 0.30 score units per cycle. The narrow‐sense heritability of the 2,4‐D tolerance trait was near 50% and inbreeding depression was apparently minimal. These results showed that significant progress has been made and that future progress leading to economically valuable field tolerance should be possible.
Inheritance of Resistance in Three Cotton Cultivars to the HV1 Isolate of Bacterial Blight
Authors: Wallace T. P. , El‐Zik K. M.
Published: July 2010

Immunity to the bacterial blight pathogen, Xanthomonas campestris pv malvacearum (Smith) Dye, of cotton, Gossypium hirsutum L., has been stable for over 20 yr. A new virulent isolate of the pathogen (HV1) was identified in Africa and a cultivar (S295) resistant to all known races and isolates was subsequently developed. The objectives of this research were to determine the inheritance of resistance in ‘S295’, ‘Tamcot CAMD‐E’, and ‘Stoneville 825’ to a mixture of USA races and the HV1 isolate, and to examine the relationship between resistance at the cotyledon stage with that at the true‐leaf stage. Progenies from three crosses were artificially inoculated and disease reaction evaluated on a scale of 1 to 10. Disease grade frequency distributions indicated a single gene with complete dominance for resistance to the USA race mixture in Tamcot CAMD‐E and S295. Frequency distributions also indicated a single‐gene difference between S295 and Stoneville 825 for resistance to the HV1 isolate. Resistance in S295 to HV1 and the USA race mixture appears to be controlled by the same gene or two closely linked genes. Resistance to HV1 in S295 was inherited as a single gene, designated B12, with complete dominance for resistance. Correlations between cotyledon and true‐leaf disease grades and phenotypic ratios indicated that resistance was controlled by the same genetic mechanism at both plant stages.
Agronomic and Forage Quality Attributes of Diverse Entries of Birdsfoot Trefoil
Authors: McGraw R. L. , Beuselinck P. R. , Marten G. C.
Published: July 2010

There has not been an extensive evaluation of the accessions of broadleaf birdsfoot trefoil (Lotus corniculatus L.) that are available in the U.S. National Plant Introduction System. Our objective was to determine whether variability exists among a large sample of these accessions for selected agronomic and forage quality traits. Forty‐eight entries from 21 countries were evaluated in a 2‐yr field study. Entries included 43 foreign accessions obtained from the USDA Plant Introduction Station at Geneva, NY, two germplasms, and three cultivars. Entries were evaluated at Rosemount, MN forherbage yield, seed yield, 1000‐seed mass, fall decumbency, and winter injury; at St. Paul, MN for palatability, in vitro digestible dry matter (IVDDM), crude protein (CP), and winter injury; and at Columbia, MO for chalcid damage and root and crown rotting disease. Entries from the USA and Canada tended to have the greatest herbage yield, seed yield, and lowest degree of winter injury when compared to other accessions. Several foreign accessions, however, performed as well as or better than the USA or Canadian entries for these agronomic traits. Differences were found among entries for IVDDM in 1984, fall decumbency, and palatability. No significant differences were found among entries for chalcid damage, root and crown rotting disease, and forage CP concentration. Although the USA and Canadian entries tended to have superior performance for many of the traits measured, the performance of individual foreign accessions warrants further evaluation and use of foreign birdsfoot trefoil germplasm.
Genetic Analyses of Soybean Genotypes Resistant to Soybean Cyst Nematode Race 5
Authors: Anand S. C. , Rao‐Arelli A. P.
Published: July 2010

All soybean [Glycine max (L.) Merr.] cultivars currently grown in the USA are susceptible to soybean cyst nematode (SCN), Heterodera glycines Ichinohe, Race 5. Soybean plant introductions (PIs) with resistance to SCN Race 5 have been identified, but there is very little information on their genetic analyses for resistance. Our objectives were to determine inheritance of resistance in three PIs for reaction to SCN Race 5, and to evaluate five resistant PIs for their genetic relationship to SCN resistance. The F2 plants and F3 families from nine different crosses among resistant (R) and susceptible (S) genotypes were evaluated in the greenhouse. Each seedling was inoculated with about 1000 eggs and juveniles of SCN Race 5. Plant roots were washed after 30 d and white females enumerated. Based on the index of parasitism (IP) F2 plants and F3 progenies were categorized as resistant, susceptible, or segregating. The chisquare test was applied to determine goodness of fit between observed and expected genetic ratios. The segregation data from crosses ‘Peking’ (R) ✕ PI 88788(S), PI 438489B(R) ✕ PI 88788(S), and PI 90763(R) ✕ ‘Forrest’(S) indicated that resistance in Peking and PI 90763 was conditioned by two recessive genes each, whereas PI 438489B had one recessive gene. Crosses between resistant parents, Peking with PI 90763, PI 404166, and PI 84751 have segregated for resistance indicating that genes in Peking compared to other parents are located at different loci. Lack of segregation in crosses of PI 90763(R) ✕ PI 404166(R), Peking(R) ✕ PI 438489B(R) and PI 90763(R) ✕ PI 438489B(R) indicated that the resistance in these parents was controlled by alleles at the same locus. These results showed that there was at least one gene for resistance different in Peking, PI 90763, and PI 404166. Intercrossing these sources of different genes for resistance to SCN Race 5 should result in germplasm with potentially higher levels of resistance. This information will assist breeders in selecting resistant sources to SCN Race 5 for cultivar development.
Plot Configuration in Corn Yield Trials
Authors: Bowman D. T.
Published: July 2010

It is generally assumed that bordered plots are efficient for reducing error variance and the associated bias from border effects. Conflicting results in the literature regarding use of borders in corn (Zea mays L.) grain trials and limited information on use of borders in corn silage (herbage) trials prompted studies on the most efficient plot size and the need for bordered plots in corn grain and silage yield trials. The studies encompassed five and six environments over a span of 4 yr for silage and grain, respectively. Silage trials included from 24 to 28 hybrids each year. Grain trials included three different maturity groups with 18 to 64 entries. Four‐row plots were used with the center two rows representing bordered two‐row plots and the outside two rows considered as unbordered two‐row plots. Bordered two‐row plots were 1.06 and 1.02 as efficient in reducing error variance as unbordered two‐row plots for silage and grain, respectively. The hybrid by border interactions generally were not significant, and highly significant yield and rank correlations suggest that very little border bias was occurring. Four‐row unbordered plots were only 1.30 and 1.48 as efficient as the two‐row bordered plots for silage and grain trials, respectively. The greatest gain in efficiency, while not compromising estimation of relative hybrid yields (1.89 and 2.26) came from using two‐row unbordered plots and doubling the number of replicates for silage and grain yield trials, respectively, vs. the two‐row bordered plots.
Seasonal Trends for Nonstructural Carbohydrates in Stem Bases of Defoliated Switchgrass
Authors: George J. R. , Obermann D. J. , Wolf D. D.
Published: July 2010

Defoliation management of forage species in the northern USA is related to total nonstructural carbohydrate (TNC) concentrations. These energy compounds are closely related to winter survival, stand persistence, and subsequent productivity of stands. Influences of early spring defoliation on TNC concentrations of switchgrass (Panicum virgatum L.) during recovery growth in the humid USA have not been reported. This field study was conducted to observe influences of defoliation time and intensity on TNC concentrations during recovery growth when switchgrass was grown without or with N fertilization (120 kg N ha−1). The experimental site was a Webster‐Nicollet soil complex (fine‐loamy, mixed, mesic Typic Haplaquolls‐Aquic Hapludolls). Defoliation treatments at 2‐wk intervals in 1984 and 1985 consisted of early‐, mid‐, and late‐spring defoliation, each at moderate or severe intensity. Nitrogen fertilization reduced TNC concentrations for all defoliation treatments. Accumulated TNC concentrations remained lower after 3, 6, and 9 wk of recovery growth for 120 compared with 0 kg N ha−1, but relatively little difference was observed among defoliation treatments in TNC concentrations by mid‐October. Severe defoliation at early, mid, and late spring generally contributed to lower TNC concentrations during recovery growth compared with moderate defoliation. However, TNC concentrations 6 to 8 wk or less after spring defoliation were at a relatively high concentration for most defoliation treatments, which suggests that herbage utilization in mid‐ to late‐July should not seriously weaken stands. Lower TNC concentrations in mid‐October of 1985 compared with 1984 suggest that both weather conditions and defoliation management influence TNC concentrations in stem bases of switchgrass.
Indices of Plant Damage and Heritability of Tolerance to the Spotted Alfalfa Aphid in Alfalfa
Authors: Jimenez H. O. , Caddel J. L. , Berberet R. C. , McNew R. W.
Published: July 2010

Alfalfa, Medicago sativa L., cultivars expressing antibiosis or antixenosis resistance to the spotted alfalfa aphid (SAA), Therioaphis maculata (Buckton), impose selection pressure for more‐virulent insect biotypes. Tolerant plants could be useful in reducing pressure for rapid development of new biotypes. Our studies were conducted to quantify tolerance to the SAA by assessing damage to plants that supported infestations with less damage than was typically observed in susceptible plants and to study the inheritance of tolerance. Vegetative propagation was used to provide replicates of tolerant plants for use in estimating the extent of genetic variability in the Oklahoma common cultivar OK08. Heritability of tolerance was estimated by parent‐offspring regression of selfed and polycross progeny. Numbers of SAA were similar on tolerant and susceptible plants after 10 d of infestation and by Day 19, tolerant plants had much higher numbers. A tolerance index that considers stunted growth and percentage of leaves that exhibit no chlorosis was developed based on correlation of these variables with dry‐matter production. After a 19‐d infestation period, variation in expression of tolerance by 39 candidate plants was high and 35% of the variability was estimated to be genetic. Heritability of the tolerance characteristics was estimated at 25% in selfed progeny of these plants and 20% in polycross progeny. Reduction in heritability of tolerance in these progeny suggests that dominant effects may control expression of this trait in alfalfa.
Adjustment of the Soybean Phenology Using the E4 Locus
Authors: Saindon G. , Beversdorf W. D. , Voldeng H. D.
Published: July 2010

Delays in reproductive development of soybean [Glycine max (L.) Merr.l segregants grown under the long daylengths of higher latitudes have impaired the use of elite germplasm from lower latitudes when developing cultivars for short‐season areas. The responses of soybean to long daylength are under the control of at least two loci, but only E3 has been shown to affect the phenology of plants grown in the field. The objectives of this study were to measure the effect of E4 on the phenology of Maturity Group (MG) 00‐I soybeans grown in the field and under incandescent long daylength (ILD) created by extending the natural daylength to 20 h using incandescent lamps, and to identify the growth stage at which selection for ILD‐insensitivity is appropriate. Most ILD‐insensitive plants were able to mature before frost under ILD and selection conducted at or close to R5 under ILD permits identification of ILD‐insensitive genotypes. Growth stage measurements recorded on three different F2 populations (homozygous for e3) grown in the field indicated dominance of E4 over e4. Alleles of E4 influenced the duration of pre‐and post‐flowering periods on ‘Evans’ and ‘Harosoy’ backgrounds, whereas it only affected post‐flowering period in ‘Maple Amber’ background. The E4 locus had a stronger delaying effect in later maturing backgrounds, indicating a potential nonadditive interaction between E4 and other unknown maturity loci. It was concluded that selecting e3e3 e4e4 segregants in a population arising from a late by early maturity cross should help to limit the number of backcrosses to early elite lines required to recover acceptable maturity. This may allow more genes from the late parent to be retained by the early segregants, thereby broadening the gene poll available in a given maturity group.
Semidominant Soybean Mutation for Resistance to Sulfonylurea Herbicides
Authors: Sebastian S. A. , Fader G. M. , Ulrich J. F. , Forney D. R. , Chaleff R. S.
Published: July 2010

A soybean [Glycine max (L.) Merr. I mutation conferring resistance to a wide range of sulfonylurea (SU) herbicides would greatly enhance the weed control options available to soybean farmers. This report describes the selection, characterization, and potential utility of such mutants. Seed mutagenesis (using N‐nitroso‐N‐methylurea and ethyl methanesulfonate) followed by selection for resistance to chlorsulfuron [2‐chloro‐N‐[(4‐methoxy‐6‐methyl‐l,3,5‐triazin‐2‐yl)aminocarbonyl] benzenesulfonamide] yielded a soybean mutant with a high degree of resistance to both postemergence and pre‐emergence applications of a variety of SU herbicides. Resistance was monogenic, semidominant, and not allelic to any of the previously identified recessive genes hs1, hs2, or hs3 that confer tolerance to SU herbicides. Biochemical tests indicate that the mechanism of resistance is reduced sensitivity of acetolactate synthase to SU inhibition. The SU resistance afforded by this mutation (designated Alsl) can be used to enhance soybean weed control options and can serve as a selectable marker for seed purification.
Cultivar Differences in Milling Yields under Delayed Harvesting of Rice
Authors: Berrio L. E. , Cuevas‐Perez F. E.
Published: July 2010

Evaluation of milling performance of rice (Oryza sativa L.) cultivars often has resulted in a wide range of values depending on the growing environment, and harvesting and drying methods. A common stress affecting milling yield evaluations is the delay in harvesting. This experiment was designed to evaluate the performance of 16 rice cultivars under 2 wk of harvest delay. Cultivar plantings were staggered to obtain simultaneous maturity during three consecutive seasons at Palmira, Colombia. A combination of harvesting and threshing‐time treatments was used. Harvesting was done at maturity, and 1 and 2 wk later. Threshing was done immediately after harvest and with a delay of 4 d. Total milled‐ and head‐rice yields were measured. Cultivar response to delayed harvesting followed four patterns ranging from constant head‐rice yields throughout the period to significant weekly reductions. Threshing delays reduced head‐rice yields by an average of 5.8% for all cultivars. Total milled‐rice yields was reduced 3% across cultivars by a 2‐week delay in harvest or by a 4‐day delay in threshing. Cultivar performance patterns detected could be used to check the reaction of other cultivars for harvest delay effects.
Milling Quality of Rice: Cylinder Speed vs. Grain‐Moisture Content at Harvest
Authors: Dilday R. H.
Published: July 2010

Milling quality of rice (Oryza sativa L.) or the percentage of head rice, broken kernels, and total (whole and broken kernels combined) is important economically to the U.S. rice producer. Eleven cultivars were harvested on 10 dates each in 1985 and 1986 and the percentage of broken rice kernels was determined after threshing the grain at cylinder speeds of 600 and 1000 revolutions per minute (rpm). The grain moisture contents ranged from 120 to 260 g/kg. Significant differences in milling yield occurred among cuitivars, cylinder speeds, and grain moisture contents. For example, ‘Newbonnet’ had the fewest broken kernels while ‘Leah’ had the most broken kernels. ‘Lemont’ produced the highest total milling yield; whereas, ‘L202’ produced the lowest total milling yield. Newbonnet produced the highest and Leah produced the lowest head rice yield. Percentage of broken kernels approximately doubled when the cylinder speed was increased from 600 to 1000 rpm. However, more mature kernels remained attached to the stalk at the lower cylinder speed. Generally, the percentage of broken kernels increased and head rice yield decreased significantly as the moisture content of the grain at harvest decreased.
Restriction Fragment Length Polymorphism in a Subclass of the ‘Mandarin’ Soybean Cytoplasm
Authors: Grabau Elizabeth A. , Davis William H. , Gengenbach Burle G.
Published: July 2010

Mitochondrial DNA (mtDNA) from a number of soybean, Glycine max (L.) Merr., cultivars was examined by restriction endonuclease digestion to search for possible differences among cytoplasmic backgrounds. In these analyses it was observed that mtDNAs from certain members of the ‘Mandarin’ cytoplasm, represented by 19 cultivars maternally derived from ‘Lincoln’, were different from 38 cultivars derived from other cytoplasms. A 10.5‐kb (Kilobase) HindIII fragment that was absent from the Lincoln class of mtDNA was present in the mtDNA of the other cytoplasms tested. Use of the 10.5‐kb fragment as a hybridization probe in Southern analyses revealed the presence of a smaller 2.3‐kb HindIII fragment that was unique to the Lincoln‐derived mtDNAs. The 2.3‐kb HindIII fragment was cloned and used in Southern hybridizations of mtDNA to screen for differences among a large number of soybean cultivars. A portion of the 2.3‐kb HindIII fragment was found at a second location common to the mitochondrial genome of all cultivars tested.
Glyphosate Sled for Alley Cleanup in Research Plots
Authors: Nelson L. R. , Ward Steve , Collins Fred
Published: July 2010

A wooden sled with an attached sponge was developed and used to successfully apply glyphosate [N(phosphonomethyl)glycine] to alleyways between small grain plots. The objective for constructing this device was to improve the procedure for killing vegetation in alleyways of small grain experiments. The sponge was attached to the bottom of a hinged platform. The platform allowed the glyphosate‐ treated sponge to follow the contour of the soil surface as the sled was pulled through the alleys. The sponge was wetted with a solution containing 150 mL L−1 of a glyphosate formulation with 356 g (acid equivalent) L−1 of glyphosate. Excellent vegetation control was accomplished with this device. Advantages over other procedures are (i) glyphosate can be applied when small grain is quite tall (20 cm), (ii) dead vegetation remains on the soil to reduce erosion, (iii) the method prevents spray drift, and (iv) construction costs are minimal.
Sporophytic and Gametophytic Responses of Sugarbeet to Two Pathotoxins
Authors: Moser H. S. , Smith G. A. , Martin S. S.
Published: July 2010

In vitro toxin sensitivity has been correlated with in vivo disease resistance for several crop species but little has been reported on the association between disease resistance of the sporophyte and pathotoxin sensitivity in the gametophyte. The objectives of this research were to study the response of the gametophytic and sporophytic generations to cercosporin (CN) and cercospora beticola toxin (CBT) and to determine toxin sensitivity of sugarbeet (Beta vulgaris L.) lines with known levels of leaf spot resistance. Three sugarbeet lines having variedegrees of field resistance to Cercospora leaf spot were evaluated for sensitivity to two pathotoxins produced by the causal fungus, Cercospora beticola Sacc. The toxins, CN and CBT, were isolated and purified from cultures of the fungus, then applied singly or in varied combinations to leaf disks (sporophytic generation) or pollen (gametophytic generation). The CN CBT, separately or together, caused cellular leakage of Na and K in the sporophytic generation and potassium only in the gametophytic generation. This effect was toxin‐concentration dependent, but without synergism. In the sporophytic generation, the least ion leakage response to either toxin occurred in leaf disks taken from the most disease resistant of the three lines evaluated. Gametophyticion leakage responses to the toxins also were significant, but these responses were not directly correlated with leaf disk ion leakage or with sporophytic field disease resistance. The techniques facilitated a controlled study of CN and CBT sensitivity in the sporophytic and gametophytic generations of sugarbeet.
Morphological Characteristics of Tall and Dwarf Pearl Millet Isolines
Authors: Rai K. N. , Hanna W. W.
Published: July 2010

Among all the dwarfing genes reported in pearl millet [Pennisetum glaucum (L.) R. Br.], the d2 gene has been most extensively utilized in breeding programs. Its effect on morphological characters, however, has not been adequately studied in the past due to lack of isogenic lines. The objective of this research was to study the effect of the d2 dwarfing gene on several morphological characters by comparing six pair of tall and dwarf near‐isogenic lines (isolines) developed in genetic backgrounds of two diverse composites. Tests conducted on plant and seed characteristics at the ICRISAT Center, Patancheru, India and Tifton, GA, showed that dwarf isolines were shorter but had longer peduncles, longer panicles, narrower panicles, thicker culms, wider leaves, and smaller seeds than their tall counterparts. The differences between tall and dwarf isolines for number of total and effective tillers plant −1, leaf sheath length, and time to 50% anthesis were either nonsignificant or inconsistent across locations. Plant height was the only characteristic studied that was not influenced by genetic background. Genetic variation among isolines for effects of the d2 gene on numerous characters indicate the gene can be used to advantage by incorporating it into diverse germplasm.
Breeding for High Biomass Yield in Spring Barley
Authors: Boukerrou Lakhdar , Rasmusson Donald D.
Published: July 2010

Breeding for high biomass has been proposed as a way to enhance yield in small grain. The objectives of this study were to evaluate 42 spring barley (Hordeum vulgare L.) genotypes for biomass production and related agronomic traits; to obtain heritability estimates for biomass, vegetative biomass, and grain yield; and to assess changes in biomass and related traits during six decades of barley breeding. Barley genotypes from seven breeding programs, and a set of 10 barley cultivars representing different eras, were evaluated at St. Paul and Crookston, MN in 1984 and 1985. The 42 barley genotypes differed significantly for 12 traits including grain yield, biomass, and vegetative biomass. Biomass ranged from 6.6 to 10.0 Mg ha−1 and vegetative biomass from 3.4 to 6.0 Mg ha−1. The semidwarf genotypes were 16.9% lower in vegetative biomass, but 3.3% higher in harvest index than the tall genotypes. Several genotypes appeared to be good sources of high vegetative biomass with H74140002 exceeding ‘Robust’, the commercial check, by 27%. Heritability on a trial mean basis was 0.75, 0.76, and 0.67 for biomass, vegetative biomass, and grain yield, respectively. Vegetative biomass showed significant positive correlations with grain yield, height, and visual score of vegetative biomass. In the 10‐cultivar set, representing the different eras, grain yield, harvest index, biomass, vegetative biomass, kernel weight, and days to maturity increased significantly over time, whereas height decreased. Biomass increased at a rate of 22.5 kg ha−1 yr−1; vegetative biomass and grain yield increased at rates of 6.8 and 15.7 kg ha−1 yr−1, respectively. It was postulated that enhancing vegetative biomass would lead to higher grain yield and, therefore, be worthy of a breeding effort. However, because of the cost of measuring vegetative biomass, indirect selection based on plant height and visual scoring of biomass was suggested.
Genotype‐Environment Interactions of Bermudagrass Forage Yields
Authors: Chakroun Mohamed , Taliaferro C. M. , McNew R. W.
Published: July 2010

Knowledge of the presence and magnitude of genotype ✕ environment (GE) interactions is important to plant breeders in making decisions regarding the development and evaluation of new cultivars. The forage yields of three cultivars and 21 experimental stains (genotypes) of bermudagrass, Cynodon dactylon (L.) Pers., were determined for 3 yr (1981–1983) at five sites. These data were used to estimate and compare methods of analysis of GE interactions and yield stability in this perennial crop. First harvest (second and third years only), regrowth, and seasonal total dry matter forage yield data were analyzed by: (i) a standard multifactor analysis of variance with locations, years, and genotypes as the main effects, (ii) linear regression of individual genotype means on the mean of all genotypes in each environment, and (iii) an orthogonal contrast analysis that partitioned the variation over environments for each genotype into sources due to years. Genotypes, locations, years, all first order interactions, and the genotype ✕ location ✕ year interaction were significant sources of variation for all yield measurements. Partitioning the GE interaction sum of squares into heterogeneity among regressions and a remainder revealed significant mean squares for both sources. Regression of genotype means on the environmental means resulted in coefficients ranging from 0.61 to 1.38,0.77 to 1.20, and 0.80 to 1.20 for first harvest, regrowth, and seasonal total yields, respectively. Mean squares for deviation from regression for these respective variables were significant for 41, 33, and 46 % of the genotypes. Genotypes differed in their response to years and locations. As stand age increased, yields of some genotypes increased while others decreased, but the response was not consistent from location to location. Use of standard analysis of variance, regression statistics, and partitioning of the year variation into linear and nonlinear components were all appropriate and helpful in characterizing performance of individual genotypes.
Partial Resistance to Septoria Glume Blotch Analyzed in Winter Wheat Seedlings
Authors: Bruno H. H. , Nelson L. R.
Published: July 2010

A diallel analysis was conducted to investigate gene effects for six components of partial resistance of wheat, Triticum aestivum (L. em Thell.), to Septoria glume blotch, which is caused by Leptosphaeria nodorum E. Muller, anamorph Septoria nodorum (Berk.) Berk. Information obtained in this study will allow plant breeders to select parents to allow combining resistance genes for different components. The recorded components were incubation period, latent period, percentage of diseased leaf tissue, initial spore production at the end of the latent period, total spore production at 100% necrosis, and maturation period. Maturation period was defined as time between the first appearance of disease symptoms and the completion of a single life cycle, as indicated by the appearance of the first mature pycnidia. The analysis of variance showed significant differences among the crosses for incubation period, latent period, maturation period, and total spore production. No significant differences were found for percent necrosis or for initial spore production, as high variability within each genotype caused least significant differences for these traits to be inflated. General combining ability (GCA) exhibited significant variability, indicating additive gene action. Specific combining ability also was significant indicating some nonadditive (i.e., dominance and epistasis) gene effects.
Outcrossing in Twelve Hard Red Winter Wheat Cultivars
Authors: Martin T. J.
Published: July 2010

Relative outcrossing (OC) rates with a mixture of awnless pollinators were determined for 12 hard red winter wheat (Triticum aestivum L.) cultivars during the crop years 1982 through 1984 at Hays, KS. Significant differences among cultivars were measured within years and averaged over years. The OC rate ranged from 0.1 to 5.6% for individual cultivars in a given year. The semidwarf experimental line, KS75210, and its sister selection, ‘Newton’, had the highest 3‐yr average OC rate, 3.1 and 2.1%, respectively, whereas a standardheight cultivar, Centurk 78, had the lowest average OC rate, 0.3%. Semidwarf cultivars Vona and Wings were not significantly different from Centurk 78 in any year. The OC correlated positively with length of flowering period only in 1983; there was no significant correlation with either flowering data or plant height. Therefore, increased OC rate was not associated with semidwarf stature. Significant cultivar ✕ year interactions occurred. When the bulk samples were separated into seed‐size fractions, several cultivars showed significant differences in OC rate within their fractions in one or more years. ‘Triumph 64’ was the only cultivar that had greater OC rate in the small‐seed fraction than in the large‐seed fraction when analyzed over years. When bulk samples were separated into highand low‐density fractions on a gravity table, no significant OC‐rate differences were found between fractions of the same cultivar within years or averaged over cultivars. Thus, mechanical separation of seed lots based on seed size or density did not consistently provide a means to reduce outcrossed seed in the seed source.
Simultaneous Improvement of Yield, Fiber Quality, and Yarn Stregth in Upland Cotton
Authors: Green C. C. , Culp T. W.
Published: July 2010

A five‐parent half diallel mating design was utilized to determine the potential for the simultaneous improvement in yield, fiber quality, and yarn strength in upland cotton (Gossypium hirsutum L.). In addition, fiber traits were measured by standard laboratory instrumentation (SLI) and high volume instrumentation (HVI) to compare their usefulness to breeders in population improvement. The 10 FI populations plus the parental lines were grown in a randomized complete‐block design in 1983 at two locations each with a different soil type at the Pee Dee Research and Education Center, Florence, SC. Significant general combining ability (GCA), which may approximate additive genetic effects, was detected for 2.5 and 50% fiber span length (SLI measurement), uniformity (SLI measurement), yarn strength, yield, and lint percentage. Therefore, progress from early generation selection could be expected in these populations. There were no significant GCA effects for any of the HVI fiber measurements, and it was concluded that HVI is not as useful to breeders in detecting small genetic differences as HVI is to the textile industry for which it was developed. There was some evidence of nonadditive genetic effects for some of the fiber traits by a general test of heterosis, although it was not detected by the test for specific combining ability. No single parent exhibited high GCA effects for yield and all fiber traits, thus simultaneous improvement in multiple fiber traits and yield probably will require intermating of several parental lines. However, simultaneous improvements in yield and yarn strength could be expected from crosses with PD 3249 and SC‐1, thus providing further evidence of the breakup of unfavorable linkages.
Use of Hill and Short‐Row Plots for Selection of Soybean Genotypes
Authors: St. Martin S. K. , Dye B. W. , McBlain B. A.
Published: July 2010

Insufficient seed production rules out the use of large, replicated plots for the evaluation of the progenies of single soybean [Glycine max (L.) Merr.] plants. This experiment was conducted to compare two types of small, unbordered plots, (i) hill plots and (ii) single, short (1.5 m) row plots, for selection of soybean lines, and to determine the optimum allocation of testing resources for each type of plot. The genetic material consisted of 33 F2‐derived lines, selected only for similar maturity. Small‐plot tests were conducted in eight environments, using a split‐plot design with plot type as the wholeplot factor. The lines were also tested in four‐row, bordered plots at three locations for 3 yr. Maturity, height, lodging, and seed yield were determined in each test. Genotypic correlations were obtained between each trait in each plot type and each trait in four‐row plots. Variance components were used to calculate expected gains in four row plots following selection in each type of plot. Some of the genotypic correlations involving lodging and height in small plots differed from the corresponding correlations in four‐row plots. Direct selection for maturity, height, and lodging was more effective in fourrow plots than in small plots. Response to direct selection for yield was approximately 30% greater in short‐row plots than in hills. Increased height and lodging was an indirect response associated with selection for yield in hill plots, but to a lesser extent in short rows and still less in four‐row plots. We conclude that short rows are an attractive alternative to hill plots for testing single‐plant progenies. Based on expected gains for different resource allocations and on practical considerations, we recommend that short‐row plot tests be conducted at two or three locations with a single replication per location.
Genetic Variances for Forage Yield in Crested Wheatgrass at Six Levels of Irrigation
Authors: Asay K. H. , Johnson D. A.
Published: July 2010

Rangelands in the western USA are characterized by extreme seasonal and site variations in soil moisture and extended periods of severe water deficit. Development of improved germplasm that is productive over a wide range of soil moisture conditions is a major objective of forage breeding programs in this region. Ample levels of heritable genetic variation are prerequisites for genetic progress in any breeding program. Although expression of genetic variability among breeding lines is known to decrease in some species as water becomes limited, neither this relationship nor the stability of genetic responses at different water levels have been studied in crested wheatgrass, Agropyron desertorum (Fisch. ex Link) Schult. A linesource sprinkler system was used under a field rainout shelter to evaluate the dry matter yield of 29 clonal lines of crested wheatgrass at six levels of water application. Forage yield declined linearly from optimum water levels to levels representative of severe drought. Broad‐sense heritability values along with the range and genetic variance among clonal lines also declined markedly as water application decreased. Experimental error, as reflected by the coefficient of variation, was substantially larger under drought than at higher water applications. Although the clone ✕ water level interaction was significant (P < 0.01), positive and significant (P < 0.01) Spearman correlation coefficients indicated a relatively high degree of consistency among clones at different water application levels. Results indicate that this tetraploid population of crested wheatgrass has sufficient genetic stability to permit selection for forage dry matter yield at water levels substantially above the target level.
Vernalization of Wheat Cultivars and a Triticale
Authors: Gardner F. P. , Barnett R. D.
Published: July 2010

Adaptation of wheat (Triticum aestivum L.) cultivars to southeastern U.S. environments could be improved if their vernalization responses were better defined. Vernalization responses of several cultivars of wheat and a triticale were assessed in 1985 and 1986 in Gainesville, FL (29 ° 38′N lat.) using varying durations of natural winter (NW) cold exposure of potted plants and refrigerator (RF) exposure of germinating seeds. Five soft red winter wheat cultivars, Florida 301, Florida 302, Hunter, Coker 983, and Caldwell; a soft white spring wheat cultivar, Owens; a hard white wheat cultivar, Phoenix; and triticale (✕ Triticosecale Whittmack) cultivar Beagle 82 were investigated. Following cold exposures, all potted plants or vernalized, potted seeds were placed in a warm greenhouse at 18‐h day length. Three types of vernalization responses were observed: (i) cold obligate (qualitative) requiring 6 to 8 wk of cold for heading and including Caldwell and Coker 983, winter‐hardy types; (ii) cold stimulated (quantitative) heading earlier than the control with 2 to 4 wk of cold exposure and included Florida 302, Hunter, and Phoenix, mild‐winter types; and (iii) cold neutral, not stimulated by cold exposure and included Owens, Beagle 82, and Florida 301, spring types. Heading of the cold‐neutral cultivars was in the order Owens, Beagle 82, and Florida 301 and was delayed by increasing exposure to cold. Both NW and RF treatments were effective vernalization methods. While RF (constant 6 °C) required about four times the cold units, the duration of cold exposure required was similar for both methods. We conclude that fall‐sown cultivars grown in the lower USA vary in vernalization response (ranging from cold obligate to cold neutral). Knowledge of this variation enhances opportunity for selection of cultivars to fit the narrow window of wheat adaptation in the southern USA.
Phomopsis Seed Decay in Soybean Isolines Differing in Stem Termination, Time of Flowering, and Maturity
Authors: Thomison P. R. , Kenworthy W. J. , McIntosh M. S.
Published: July 2010

Infection of soybean [Glycine max (L.) Merr.] seed by Phomopsis longicolla Hobbs is a major cause of poor seed quality in regions where the climate is warm and humid during and after seed maturation. The objective of this study was to evaluate effects of stem termination, time of flowering, maturity, and various combinations of these characteristics on seed germination and infection of seed by P. longicolla. The cultivar Clark and seven of its near‐isogenic lines differing in stem termination (indeterminate vs. determinate vs. semideterminate), time of flowering (normal vs. delayed vs. late), and maturity (normal vs. late) were evaluated for seed‐borne disease in Maryland at two locations in 1984 and 1985 and one location in 1986. Seed infection by P. longicolla was increased 20% and seed germination reduced 16% in determinate isolines compared to indeterminate isolines. Semideterminate isolines exhibited levels of fungal seed infection and seed germination intermediate to those of the indeterminate and determinate isolines. Late flowering and late maturity decreased seed infection by P. longicolla 48% and improved seed germination 97%. Effects of delayed flowering on seed infection and seed germination were not consistent. Growing early maturing, determinate cultivars in the mid‐Atlantic region may increase the potential for seed disease problems due to P. longicolla, if weather conditions are conducive for disease development.