bluuebunny/crossref_metadata_2025 huggingface dataset:
Phytic Acid Levels in Seeds of Glycine max and G. soja as Influenced by Phosphorus Status
Authors: Raboy Victor , Dickinson David B.
Published: July 2010

Improvement in soybean [Glycine max (L.) Merr.] nutritional quality may be achieved via a reduction in seed phytic acid P. To advance our knowledge of factors that determine seed phytic acid P levels, the relations between external P availability, leaf or shoot P, and seed P fractions (phytic acid and non‐phytic acid P) were studied in soybean and G. soja (Sieb. & Zucc.) germplasm. Mean phytic acid P varied from 4.3 to 6.2 g P kg−1 in mature seeds of 12 soybean cultivars grown under three field environments. Cultivars ranked similarly in each environment and 98% of the variation in phytic acid P was attributable to a positive, linear effect of available soil P. No significant variation was observed in seed non‐phytic acid P. Similar results were obtained when selected soybean and G. soja lines were grown in sand watered with nutrient solutions containing P concentrations ranging from 2 to 50 mg L−1. Leaf or shoot P concentrations and seed phytic acid P concentrations were positively correlated and in G. soja were nearly double those observed with indeterminate soybean cultivars. The higher leaf P and seed phytic acid P concentrations in G. soja as compared with indeterminate soybean lines were attributed to reduced P utilization efficiency defined as reduced biomass production per unit of total shoot P. These results indicate that essentially all variation in seed P is found as variation in phytic acid P, and that this variation is related to leaf P concentration in a complex manner determined by genotype and soil P availability.
Response of Susceptible, Moderately Susceptible, and Moderately Resistant Soybean Cultivars to Race 14 Cyst Nematode
Authors: Heatherly Larry G. , Young Lawrence D.
Published: July 2010

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) infests soils throughout the mid and lower Mississippi River Valley, the Ohio River alley, and the southeastern Coastal Plain in the USA, and can reduce soybean [Glycine max (L.) Merr.] yield significantly. This study compared the yields of susceptible (‘Essex’), moderately susceptible (‘Cordell’), and moderately resistant (‘A5474’ or ‘AS403’) Maturity Group V soybean at different levels of SCN (Race 14) infestation in a greenhouse. Level of initial infestation of SCN was 0, 200, and 600 cysts L−1 in the top IS cm depth of greenhouse pots. Seed yield of all cultivars declined with increasing level of infestation in 1990, but in 1992, seed yield of all cultivars declined significantly only between the 0 and 200 cysts L−1 level. Yields of Essex and Cordell were essentially equal within all infestation levels, while yields of A5474 and A5403 were greater than those of Essex and Cordell in the infested treatments. Yield declines between the 0 and 200 cysts L−1 treatments averaged 55% for Essex, 50% for Cordell, and 20% for A5474 and A5403. Seed yield was significantly correlated with number of pods and number of seed in both years, but not with weight of seeds or seeds per pod. These results indicate that SCN will reduce yield of moderately resistant and moderately susceptible cultivars dissimilarly. These results also indicate that the classification of cultivars for resistance to SCN reproduction is not necessarily indicative of the yield potential of these cultivars in the presence of SCN Race 14.
Leaf Water Potential and Relative Water Content Variation in Creeping Bentgrass Clones
Authors: Lehman V. G. , Engelke M. C. , White R. H.
Published: July 2010

Creeping bentgrass (Agrostis palustris Huds.) often requires daily irrigation and syringing to persist in turf areas in warmer environments with high evapotranspiration rates. Turfgrass performance could be enhanced if turgor maintenance under decreasing soil moisture levels could be incorporated into new bentgrass cultivars. The objectives of this study were to determine: (i) if genetic variation in leaf water potential (LWP) existed among creeping bentgrass clones under declining soil moisture, (ii) if LWP was associated with maintenance of growth under declining soil moisture levels, and (iii) if genotypic variation existed in water‐relation characteristics, including components of LWP, as determined by a hydraulic press. The LWP was measured on four field‐grown creeping bentgrass clones twice per day with a hydraulic press. Leaf water potential and soil moisture levels were determined in a growth room study on five creeping bentgrass clones grown in pots, 17 by 13 cm, during a 17‐d period. Waterrelation characteristics were determined on five creeping bentgrass clones grown in a greenhouse using a hydraulic press. Genetic variation existed among clones in LWP in both field and growth room studies. The most negative LWP was not associated with the greatest leaf firing or decrease in leaf extension. The relative water content at zero turgor represented a substantial difference in the degree of hydration at zero turgor. This study illustrated that genetic variation exists for LWP and relative water content in creeping bentgrass.
Genes for Leaf Rust Resistance in Hard Red Winter Wheat Cultivars and Parental Lines
Authors: McVey D. V. , Long D. L.
Published: July 2010

Knowledge of the genes for resistance to leaf rust caused by Puccinia recondita Roberge es Desmaz. f. sp. tritici present in bread wheat (Triticum aestivum L.) cultivars and breeding lines is useful in developing resistant cultivars, estimating potential disease loss, and determining pathogen over‐wintering. The objective of this study was to postulate the known Lr genes conferring low seedling reaction in 30 cultivars and 56 hard red winter wheat breeding lines from nine winter wheat breeding programs. Entries were inoculated with 17 isolates of P. r. L sp. tritici previously characterized for avirulence/virulence to 16 Lr genes. The genes identified and the cultivars were as follows: Lrl: Karl, Mit, Newton, and Thunderbird; Lr3: Brule, Hail, Karl, Redland, and Pioneer 2180; Lrl0; Arapahoe, Karl, Mit, Sandy, TAM 105, and TAM 106; Lrl4a: Hail, Larned, Pioneer 2157, Pioneer 2163, Pioneer 2172, Pioneer 2180, Vona and Victory; Lrl6: Arapahoe, Brule, and Redland; Lr24: Abilene, Arapahoe, Cimmaron, Collin. Siouxland, Thunderbird, and TAM 200; and Lr26: Siouxland. No genes for resistance were detected in ‘Agseco 7846’ and ‘Agseco 785Y’, ‘Chisholm’, ‘Eagle’, and ‘TAM 107’. Fourteen of the 16 genes were postulated as being present in the parental lines. Lr24, Lr3, Lrl, and Lr2a occurred with the greatest frequent, followed by Lr26, Lrl0, Lrl4a, Lrl6,Lr9, Lrl7, Lr3kn, Lrl8, Lr30, and Lrll. In combination, only Lr9 and Lr24, and Lr9 and Lrl6 of these known genes presently provide resistance to leaf rust in the seedling growth stage in North America. However, the additional incorporation of Lr3ka, Lrl7, and Lr30 would provide added protection.
Progress in Ohio Soft Red Winter Wheat Breeding: Grain Yield and Agronomic Traits of Cultivars Released from 1871 to 1987
Authors: Berzonsky W. A. , Lafever H. N.
Published: July 2010

Significant increases in worldwide wheat (Triacum aestivum L.) grain yield (GY) over years have been due to the release of newer, genetically improved cultivars that are earlier‐maturing, shorter in stature, and more resistant to lodging. Some analyses of wheat GY trends have led to conclusions that future genetic gains could be limited and that, in some cases, a GY plateau would soon be approached. Soft red winter wheat (SRWW) field trials, which included cultivars released from 1871 to 1987, were conducted for 4 yr at Wooster, OH, USA. Trials were conducted to document any changes in GY to determine if a yield plateau was being approached for Ohio SRWW. Grain test weight (GTW) and plant height (PH) measurements time‐to‐heading (TTH) and lodging evaluations were made to determine if changes in these traits were associated with the development of newer cultivars. Linearegression of mean GY on cultivar years since release (YSR) over the four trial years, was significant. Linear regression on YSR accounted for 42% of the variation of mean GY. Mean GY changed 15.5 kg ha−1 yr−1 as YSR decreased. Testing a nonlinear relationship for GY and YSR, indicated that a yield plateau was not being approached. There was no significant change for mean GTW on YSR. Linear regressions for mean TTH, PH, and lodging on YSR were significant. Linear regressions on YSR accounted for 78, 33, and 27% of the variation in mean TIH, mean PH, and mean lodging, respectively. Mean TTH changed −0.05 d yr−1, mean PH changed −0.4 cm yr−1, and mean lodging changed −0.7% yr−1 as YSR decreased. Progress has been made in breeding Ohio SRWW cultivars that produce higher GY. The release of newer, higher‐yielding SRWW cultivars that are earlier‐heading, shorter, and more resistant to lodging, has contributed to a mean GY increase, across Ohio, of approximately 2259 kg ha−1 over a period spanning eight decades, 1910 to 1991.
Inheritance of Tolerance to Soil Acidity in Tropical Maize
Authors: Duque‐Vargas J. , Pandey S. , Granados G. , Ceballos H. , Knapp E.
Published: July 2010

Soil acidity reduces maize (Zea mays L.) yields on ≈8 million hectares of tropical soils. Maize cultivars with tolerance to soil acidity can alleviate this problem in developing countries. We used a North Carolina Design I mating system to study the inheritance of tolerance to soil acidity in a tropical maize population, SA‐3, in order to efficiently develop maize cultivars tolerant to acidic soils. We studied 256 full‐sib progenies, involving 64 males and four females within each male, that were grouped in eight sets and field planted using two replications under one normal and three acidic soil environments during 1990–1991 in Colombia. Across acidic soils, additive genetic variance (VA) was similar to dominance variance (VD) for grain yield (0.15 vs. 0.13) greater than VD for plant height (47.97 vs. 6.83) and ears per plant (0.01 vs. 0.00), and less than VD for days to silk (1.26 vs. 2.98). Heritability, estimated using half‐sib family means, averaged 36.3 ± 19.9% for yield, 30.9 ± 19.8% for days to silk, 51.5 ± 19.3% for plant height, and 40.5 ± 19.8% for ears per plant. Additive × environment interaction was the more important component of genetic variance for all traits studied. Although grain yield showed a positive additive genetic correlation (rA = 0.84**) with ears per plant, direct selection for yield was more effective for improving yield under acidic soils. The magnitudes of additive and additive × environmental variances and of rAs among the environments suggest that recurrent selection, based on multilocation testing, would be effective in improving grain yield, days to silk, plant height, and ears per plant under acidic soils.
Effect of Restricted Cross‐Sectional Peduncle Area on Grain Yield of Maize
Authors: Salvador Ricardo J. , Nepal Tara P. , Pearce R. Brent
Published: July 2010

Field experiments were conducted over 2 yr to determine if maize (Zea mays L.) grain yield is limited by the physical capacity of the peduncle to translocate assimilate to the ear. Treatments consisted of two levels of reduced vascular connections to the ear (50 and 75% of peduncle cross‐sectional area) and two dates of treatment (15 and d post silking). Treatment involved first removing ear leaf and husks at 15 d post silking, to gain complete access to the peduncle, followed by vascular occlusion. One treatment with peduncles left intact was included to measure the impact of dehusking. All treatments decreased grain yield an average of 19.7% from control levels, due to effects on both kernel number and weight per kernel, but there was no general effect of severing vascular connections to the ear beyond the effect of dehusking and removing ear leaves 15 d post silking. There was also no difference in grain yield due to the two dates of treatment. An exception occurred in the second year of the study, when the 75% occlusion treatment at either date reduced grain yield through reduction of kernel weight. We estimate mass transfer rates of 1.37 g h−1 cm−2 phloem in intact peduncles of dehusked plants and infer that rates may have risen to 5.49 g h−1 cm−2 phloem in peduncles with only 25% functional cross.sectional area. The latter mass transfer rate approaches the maximum measured for a number of fruit sinks and may explain the greater impact of 75% peduncle occlusion in the second year. The effect may not have been expressed in the first year, due to unfavorable climatic conditions that shortened the effective grain filling period. Under normal conditions, assimilate transport through the peduncle seems to function at roughly one‐fourth maximum capacity and is probably not a major grain yield limitation.
Phenological Response of Pea to Water Stress during Reproductive Development
Authors: New B. , Duthion C. , Turc O.
Published: July 2010

Drought stress affects yield of indeterminate species, but the effects on yield components, seed number, and individual seed weight at harvest are, in some cases, contradictory. The diversity of effects can result from the complex sequential development of these plants with respect to timing of drought. Two experiments were carried out in a glasshouse to study the effect of short‐term drought (about 6 d) during different periods of reproductive development on the phenology of pea (Pisum sativum L.) cv Solara, and on seed abortion and seed growth rate at each nodal location on the stem. An additional experiment was carried out in the field. Short‐term stresses did not change development except for the progression of flowering along the stem which was stopped prematurely. The duration of the lag‐phase between flowering and initiation of seed filling, and the duration of seed filling, were not affected at any nodal position. Analysis of the distribution of seeds along the stem suggested that the final stage at which seed abortion occurred corresponded approximately to the initiation of linear seed filling. Seeds that reached this stage before the stress was imposed never aborted and their growth was maintained. Seed abortion in lag‐phase was dependent on the intensity of drought. If the stress was imposed when all the seeds were filling, no abortion occurred and seed growth rates were maintained by mobilization of plant reserves. The results suggest that the plant responded to drought by reducing seed number when possible or mobilizing its reserves to maintain a constant seed growth rate.
Grazing Evaluation of Bigalta and Floralta Limpograss
Authors: Pitman W. D. , Machen R. V. , Pond K. R.
Published: July 2010

The use of limpograss [Hemarthria altissima (Poir) Stapf et C.E. Hubb.] as a pasture plant is a relatively recent development. Available cultivars possess distinctly different characteristics. ‘Bigalta’ limpograss has been widely planted on peninsular Florida Spodosols, but stand loss under grazing is common. A more persistent cultivar, ‘Floralta’, has recently become the most widely grown limpograss cultivar in Florida. When grown in the same pasture, Bigalta was heavily grazed by yearling steers (Bos indicus L. and Bos taurus L. spp.) before any noticeable grazing of Floralta occurred. A series of grazing trials was conducted to investigate relative forage quality and plant growth responses of the two cultivars under grazing. Eight 0.5‐ha pastures were established to provide duplicate treatments of two stocking rates on each cultivar. Three summer grazing trials and two autumn grazing trials were conducted. Patterns of grazing differed distinctly between the two cultivars with distinct patchy grazing on Bigalta and rather uniform grazing of the upper canopy of Floralta. Bigalta had higher in vitro organic matter digestibility (IVOMD) and crude protein (CP) than Floralta in most instances, with Bigalta at the light stocking rate averaging 520 g kg−1 IVOMD and 61 g kg−1 CP vs. 480 g kg−1 IVOMD and 51 g kg−1 CP for Floralta. Bigalta produced greater average daily gains (ADG) than did Floralta prior to deterioration of Bigalta stands with 0.5 kg ADG on Bigalta vs. 0.3 kg on Floralta in 1986 and 1987 trials. Bigalta stands deteriorated rapidly especially when subjected to the higher stocking rate, but extended deferment from grazing allowed some stand recovery.
Ergovaline Variability in Acremonium‐Infected Tall Fescue Due to Environment and Plant Genotype
Authors: Agee C. S. , Hill N. S.
Published: July 2010

Competitiveness and persistence of tall fescue (Festuca arundinacea Schreb.) is superior when infected with the endophyte, Acremonium coenophialum Morgan‐Jones & Gams. Acremonium‐derived ergopeptine alkaloids impair animal productivity, and if reduced or eliminated would improve animal performance. This study was conducted to determine: (i) environmental influence on ergovaline concentration in A. coenophialum‐infected tall fescue genotypes, and (ii) the extent that plant genotype influences ergovaline production by the endophyte. A field experiment evaluated five endophyte‐infected tall fescue genotypes grown at three locations (environments) during 2 yr. Plant genotypes, harvested every 28 d, differed in ergovaline concentration (P < 0.05) during spring months. Rank correlations of genotypes were high among harvest dates, locations, and years. A greenhouse experiment was used to evaluate ergovaline concentration among progeny from a reciprocal cross between a high‐ and a low‐ergovaline tall fescue genotype. Parents differed in ergovaline concentration by 630 μg kg−1 but produced similar F1 progeny means that were not different from the midparent (415 μg kg−1). Both F1 populations had similar ranges for ergovaline (122‐938 μg kg−1). Although subject to environmental influence, ergovaline production by tall fescue—Acremonium associations was partially dependent upon plant genotype.
Selection Progress for Ease of Floret Tripping in Alfalfa
Authors: Knapp Eric E. , Teuber Larry R.
Published: July 2010

Breeding alfalfa (Medicago sativa L.) for florets that are more easily tripped by honey bees (Apis Mellifera L.) has been proposed as means of increasing efficiency of pollination and improving seed yield. The purpose of this study was to evaluate the effectiveness of phenotypic recurrent selection in breeding for ease of alfalfa floret tripping, and to compare observed to predicted genetic gain. Easy‐ and hard‐to‐trip populations were developed from ‘CUF101’ (two populations), ‘Saranac’, and a high nectar population derived from ‘CUF101’. Populations were evaluated in the glasshouse and observed genetic gain was compared to genetic gain predicted from genetic variance component estimates. Gain was made from all starting populations for both easy (mean = 17.9% easier to trip) and hard tripping (mean = 25.4% harder to trip) (P ≤ 0.05). Genetic variance components were useful for predicting genetic gain, as observed gain corresponded closely to predicted gain in most populations. Gain was less for easy than for hard tripping from all but the Saranac population. Easy‐to‐trip populations still contained hard‐to‐trip plants, and hard‐to‐trip populations still contained easy‐to‐trip plants. Phenotypic recurrent selection was effective in breeding for ease of tripping in alfalfa.
Genetic Variation for Epicuticular Wax Production in Altai Wildrye Populations that Differ in Glaucousness
Authors: Jefferson Paul G.
Published: July 2010

Epicuticular wax (EW) is reported to be a beneficial trait for the adaptation of plants to water‐limited environments. Glaucousness is associated with increased EW in other species and with a forage yield advantage in Altai wildrye [Leymus angustus (Trin.) Pilger Dewey] grown in a water‐limited environment. The purpose of this research was to determine the variation for EW production, the heritability of EW production, and genetic correlation of EW production with forage yield within three populations of half‐sib lines of Altai wildrye that were glaucous, nonglaucous, or variably glaucous (unselected). Leaf EW was extracted with petroleum ether and expressed as mass per unit leaf area (EW1, g m−2) or as mass per unit leaf dry weight (EW2, mg g−1). The glaucous population produced about twice as much EW as the non‐glaucous and unselected populations in each of 3 yr. The variation among half‐sib lines for both EW1 and EW2 within each population was significant. The distribution of the glaucous population was distinct from the other two populations in all 3 yr. Heritability estimates for EW1 were 0.36 (SE = 0.12), 0.90 (SE = 0.17), and 0.67 (SE = 0.15) for the glaucous, unselected, and nonglaucous population, respectively. Heritability estimates for EW2 were in the same range. The genetic correlations between EW production and forage yield were significant for the glaucous population (r = −l0.25* for EW1, r = −0.53** for EW2) and the nonglaucous population (r = −0.31* for EW2). While selection for increased EW production is feasible for Altai wildrye, it would result in lower forage yield in water‐limited environments.
Indirect Inbred Selection to Reduce Grain Moisture in Maize Hybrids
Authors: Sweeney P. M. , St. Martin S. K. , Clucas C. P.
Published: July 2010

To select indirectly for low grain moisture in maize (Zea mays L.) hybrids, divergent lines were selected from two S2 populations on the basis of three morphological traits (date of husk senescence, husk length, and kernel number) that previously had been shown to be associated with faster drying rates in hybrids. Divergent lines were also selected on the basis of silking date. Nine hybrids for each selection classification were formed by crossing three selected S2 lines from one population with three inbreds, selected on the basis of the same criterion, from the second population. Field evaluation of the hybrids indicated that selection for early husk senescence in the inbreds decreased grain moisture by 27 g kg−1', hastened physiological maturity, and increased lodging in the associated hybrids. Selection for early husk senescence did not affect yield. Selection for the other three traits had no significant effect on grain moisture at harvest. Our results suggest that selection of early husk senescence in inbreds would result in hybrids with lower grain moisture and that evaluation of husk senescence may be useful in monitoring maturity in maize.
Leaf Net CO2‐Exchange Rate and Associated Leaf Traits of Winter Wheat Grown with Various Spring Nitrogen Fertilization Rates
Authors: Frederick James R. , Camberato James J.
Published: July 2010

Periods of drought stress may frequently occur in soft red winter wheat (Triticum aestivum L. em Thell.) grown on the southeastern Coastal Plain because of the low water‐retention capacity of the Ap soil horizon. Nitrogen fertilizer applications generally promote greater leaf area development, thereby potentially increasing transpirational water loss and the severity of plant water deficit. This field study was conducted to examine whether early spring N fertilization increases the severity of plant water deficit in wheat grown on the Coastal Plain. Wheat was grown with early spring N rates of 0,34, 67, and 101 kg N ha−1 at one location in 1990 and at two locations in 1991. All plots received 34 kg N ha−1 at planting. Increased N fertilization generally resulted in higher leaf reduced N concentrations (LRN), leaf area indices (LAI, leaf net CO2‐exchange rates (CER), leaf stomatal conductances (gs), and leaf water potentials before anthesis. Leaf CER, LRN, LAI, and gravimetric soil water content (SWC) of all N treatments decreased rapidly during grain fill. Low leaf area index values were obtained for all N treatments at approximately the same time. During grain fill, CER, gs, and SWC were usually lower the higher the N rate applied. Kernel number per head increased and individual kernel weight decreased with increased N. Grain yield was greatest at the 67 kg N ha−1 rate. These results indicate that increasing the rate of spring N applied to winter wheat grown on the southeastern Coastal Plain may increase the severity of plant water stress during grain fill. Reduced CER during grain fill with increased N may contribute to kernel‐weight reductions.
Competition between Nitrogen Accumulation and Grain Growth for Carbohydrates during Grain Filling of Wheat
Authors: Bänziger M. , Feil B. , Stamp P.
Published: July 2010

It has been hypothesized that N accumulation and carbohydrate synthesis compete for energy and carbon skeletons during the reproductive growth phase of small grain cereals. This study was conducted to determine whether an increased N accumulation during grain rifling of wheat (Triticum aestivum L.) may reduce carbohydrate availability for grain formation. In a 2‐yr field experiment, four spring wheat genotypes, grown under three early N regimes, were supplied with 0, 50, and 100 kg N ha−1 at heading. The effect of late N application on photosynthesis rate (only in 1991), water soluble carbohydrates (WSC), grain growth and yield was recorded. N application at heading reduced WSC content of the shoot at anthesis by 8.5 g WSC per gram of accumulated N. During grain filling, a steady regeneration of WSC reserves in the stem occurred, though N accumulation was still enhanced by late application of N. By 320 degree days (d°) after anthesis, differences in stem WSC reserves between late N levels had disappeared. Measurements of photosynthesis rate and leaf area duration indicated that photosynthetic capacity of the canopy was increased by application of late N. Apart from the detrimental effect of late tillers which were induced by late N application, late N application generally resulted in higher grain yields. Since N compounds can be invested in light interception (photosynthesis rate, leaf area duration) before they are translocated to the grains, the consumption of energy and carbon skeletons for assimilating N cannot be considered alone as reducing carbohydrate availability for grain formation.
Socializing Nature: Technoscience and the Transformation of Rapeseed into Canola
Authors: Busch Lawrence , Gunter Valerie , Mentele Theodore , Tachikawa Masashi , Tanaka Keiko
Published: July 2010

While the constructedness of manufactured products is obvious, plants and animals retain their naturalnes even as they are transformed. Yet, here is little doubt that the transformation of plants is a powerful method by which we socialize nature such that it better suits our purposes. This paper examines the transformation of rapeseed (Brassica campetris L. and B. napus L.) from a minor crop usd largely for marine lubricants into a major global competitor in edible oil markets. This transformation was brought about in part by the elimination of two components defined as potentially toxic, erucic acid and glucosinolates, as well as by changes in the location of production and processing techniques, and by the suitability of the crop for planting and harvesting by equipment designed for wheat. Of particular note is the role of the Canadian State in providing the large‐scale financing necessary for the research to transform the commodity from a specialty crop into a bulk commodity.
Differential Effect of Soil Temperature on Iron‐Deficiency Chlorosis in Susceptible and Resistant Subclovers
Authors: Wei L. C. , Ocumpaugh W. R. , Loeppert R. H.
Published: July 2010

Iron deficiency, which is most prevalent on calcareous soils, reduces the productivity of susceptible clovers (Trifolium spp.). Factors causing differences in Fe‐deficiency chlorosis susceptibility among clover cultivars and species are not well understood. The objective of this study was to determine the influence of soil temperature on chlorosis expression, plant growth, and mineral nutrition of Fe‐deficiency chlorosis susceptible and resistant cultivars of subterranean clover (T. subterraneum L.; subclover). Two cultivars of subclover, ‘Karridale’ (susceptible) and ‘Koala’ (T. brachycalycinum Katzn. and Morley; resistant), were grown in a greenhouse on a low‐Fe Parrita soil (pH 8.2, clayey, mixed, hyperthermic, shallow Petrocalcic Paleustoll) using a Conetainer (Stuewe and Sons, Inc., Corvallis, OR) culture system with seven soil temperature treatments within the range of 7 to 33 °C. Karridale was more chlorotic at low or high soil temperatures than at an intermediate temperature, while the chlorosis of Koala changed only slightly with change of soil temperature. Cultivar difference in chlorosis was greatest at low soil temperature. Shoot dry weight and number of root nodules were higher at intermediate soil temperatures than at low temperatures for both cultivars. Koala had higher values (P < 0.05) of shoot and root dry weight and number of root nodules than did Karridale. Shoot Fe concentration of Koala was greatest at intermediate soil temperature, whereas Karridale exhibited less dependence on temperature. These results indicate that soil temperature affects the differential expression of Fe‐deficiency chlorosis between subciover cultivars and that low soil temperatures can be used to improve screening for Fe‐deficiency chiorosis resistance of subclover.
A Classification of 148 U.S. Maize Inbreds: II. Validation of Cluster Analysis Based on RFLPs
Authors: Mumm Rita Hogan , Hubert Lawrence J. , Dudley J. W.
Published: July 2010

To be useful to breeders, classification of genotypes based on cluster analysis must provide meaningful groupings of the genotypes clustered. We evaluated a classification of 148 U.S. maize [Zea mays L.] inbreds resulting from cluster analysis based on restriction fragment length polymorphisms (RFLPs) to determine if it represented the true associations among the fines. Testing was aimed at the products of the two steps in cluster analysis: the proximity matrix containing estimates of relationship computed from the data and the phenogram displaying groups in the form of a tree diagram. The proximity matrix and a matrix of pedigree relationships were compared by the Hubert F statistic. Dissimilarities indicated in the phenogram were correlated with those defined in the proximity matrix. The grouping displayed in the phenogram was compared to that exhibited in phenograms resulting from three additional cluster analyses generated by different methods for computing proximities. These groupings were then compared to the expected grouping based on pedigree information. The patterns present in the proximity matrix were substantiated by pedigree information. Based on agreement between the phenogram and the proximity matrix, the phenogram depicted estimates of genetic relationship accurately. Inbreds were grouped similarly in the four classifications and the level of correspondence of inbred group assignments to the expected grouping based on available pedigree information was similar across classifications, suggesting that a natural grouping of the fines exists and was generally reflected in each classification. Therefore, the classification was judged to reasonably represent the true associations among the 148 maize inbreds. In addition, the advantages of a method to compute proximities by a formula proposed by Nei and Li were noted.
Yield Component Responses Associated with Increased Groat Yield after Recurrent Selection in Oat
Authors: Moser H. S. , Frey K. J.
Published: July 2010

Analysis of yield into components may provide information for devising efficient selection strategies for improving yield or traits correlated with yield in cereal crops. Our objective was to analyze changes in yield components associated with increased groat yields observed within three S1‐recurrent selection programs for high protein yield (grain yield × groat‐protein concentration) in oat (Avena sativa L.). Selection emphasized high protein yield per se (HGP), with no restrictions in grain yield or groat‐protein concentration; high protein yield due only to high grain (HG) yield; and high protein yield due to both high groat‐protein concentration and high grain yield (HP). Responses of yield components to these selection criteria were evaluated by growing 30 to 60 random S0‐derived lines from each selection cycle (C) in a hill plot experiment at two Iowa locations in 1989. Above ground biomass increased 7%, vegetative growth index (vegetative yield/number of days to heading) increased 9%, and groat index (groat yield/biomass) increased 8% from C0 to C5 in HGP. Changes in biomass, vegetative growth index, and groat index from C0 to C5 of HG were similar to those of HGP in direction, but were greater in magnitude (15,13, and 17% increases, respectively). Biomass increased by 5% from C0 to C5 in HP, but vegetative growth index and groat index did not change significantly. Seed number per plot increased in HGP by 16.6%, in HG by 28.2%, and in HP by 11.4%. Groat weight remained unchanged in all three lines of descent. Thus, the increased groat yields in all lines of descent were due first to greater biomass and second to high seed numbers.
Hessian Fly‐Resistance Gene H26 Transferred from Triticum tauschii to Common Wheat
Authors: Cox T. S. , Hatchett J. H.
Published: July 2010

There is a continuing need for enhanced genetic diversity in common wheat (Triticum aestivum L.) for resistance to the Hessian fly (Mayetiola destructor Say). The objectives of this study were (i) to transfer gene for Hessian fly resistance from the accession TA 2473 of the wild diploid goatgrass T. tauschii (Coss.) Schmal. into an elite, hexaploid wheat genotype and (ii) to determine the chromosomal location of the gene. The F1 and BC1 progenies from the cross ‘Kari’/TA 2473 were male‐sterile and set very few backcross seed, but seven BC2F2‐derived lines were resistant or segregating for resistance to Biotype L of Hessian fly. Homozygous resistant BC2F4 and BC2F5 progeny within those lines were crossed to ‘Wichita’‐based stocks monosomic for six of the seven D‐genome chromosomes and to tester stocks carrying the genes H13, H22, H23, H24, and an unnamed gene, all transferred previously from T. tauschii. Segregation of F2 plants from those crosses showed that resistance derived from TA 2473 is governed by one dominant gene located on chromosome 4D. This gene, designated herein as H26, is the only Hessian fly‐resistance gene known to be located on 4D. Gene H26 conditions a high level of antibiosis to Biotype L and has been transferred into a germplasm line, KS92WGRC26, which has most of the desirable agronomic traits of its recurrent parent, Karl. Therefore, H26 is expected to be a useful addition to the set of Hessian fly‐resistance genes available to wheat breeders.
Flower Bud Development in Greenhouse‐Grown Cotton
Authors: Holt S. J. , Stewart McD. , McNew R. W.
Published: July 2010

The determination of cotton (Gossypium hirsutum L.) bud age in days relative to anthesis (DRA) is of value for studies of fiber differentiation. Bud age is easily judged at l‐d preanthesis (− IDRA) but is less discernible in younger buds. The objective of this study was to relate bud length to bud age relative to antbesis and to determine the effect of bud position on bud length. ‘Stoneville 506’ cotton was grown in a greenhouse in 4‐L pots of potting mixture. Data were taken from 48 plants planted 14 Mar. 1991. Bud length was measured from the midpoint of the base of a bract to the tip of the corolla whorl. Mean bud length at − 1DRA peaked at 3.2 cm at main‐stem node (MSN) 10 for the first sympodial node (Position 1 buds) and 3.0 cm at MSN 8 for Position 2 buds. Also, mean bud lengths at Positions 2 and 3 on sympodial branches below MSN 9 were as long or longer (P ≤ 0.05) than mean lengths at Position 1, but a reverse trend of Position I buds being longer than Position 2 buds was observed from MSN 9 through 13. The peaks in length for Position I and 2 buds were indicative of a period of maximum bud growth around 94 days after planting that impacted buds at both positions simultaneously. Bud length was correlated with bud age only at −2DRA and − IDRA and was affected by sympodial position and MSN as well as by the interaction of sympodial position and MSN.
Reproductive Development of an Indeterminate Soybean as Affected by Morphological Position
Authors: Munier‐Jolain Nathalie , Ney Bertrand , Duthion Claude
Published: July 2010

The indeterminate growth habit of some soybean [Glycine max (L.) Merr.] cultivars results in sequential grain setting; thus, knowledge of the reproductive development of soybean is important for understanding yield variability. The objective of this study was to investigate the influence of the timing of flowering and the morphological position of reproductive organs on individual seed development and growth. ‘Maple Arrow’ plants, Maturity Group 00, were grown under field conditions in Guadeloupe (French West Indies, ferralic Fluvisol) for 2 yr and at Dijon (France, clayey Eutric Cambisol) for 1 yr, with various treatments including different sowing densities, a depodding treatment, and N supply during seed filling. Regardless of their morphological position, reproductive organs that flowered simultaneously also reached the beginning and termination of seed filling simultaneously. Thus, the lag‐phase duration and the duration between flowering and physiological maturity were linearly related to timing of flowering. Slopes for both relationships were significant for all treatments and locations. Conversely, timing of physiological maturity was variable among treatments. The onset of physiological maturity seemed to be determined by the time when N reserves of vegetative parts were exhausted. However, individual seed size seemed to determine physiological maturity when sources were greater than sinks. On the other hand, morphological position had a great effect on growth of individual seed, whereas timing of flowering was the main determinant of further seed development. Organization of reproductive development of the whole plant depends strongly on the timing of flowering of each reproductive organ. Conversely, the occurence of physiological maturity of the whole plant and individual seed growth probably depends on the amount of available assimilates during seed filling.
Peanut Leaf Photosynthetic Activity in Cool Field Environments
Authors: Bell M. J. , Gillespie T. J. , Roy R. C. , Micheals T. E. , Tollenaar M.
Published: July 2010

Controlled environment studies have shown that peanut (Arachis hypogaea L.) leaf CO2 exchange rates (CER) are sensitive to night temperatures <20 °C and that genotypes vary in their ability to acclimate after exposure to continuous cool nights. Our objectives were to investigate the relationship between minimum air temperature (Tmin) and leaflet CER for peanut genotypes grown in the field and to determine the extent of differences between Tmin and minimum canopy temperatures under existing climatic conditions. Eight peanut genotypes were grown in the field at Delhi, Ontario, in 1991 and six genotypes common to the 1991 study were sown in 1992. Leaflet CER was recorded on a number of occasions in both seasons, and canopy temperatures were recorded under both clear and overcast conditions at night during 1992. Variation in leaflet CER between sampling dates was large in 1992 (e.g., 1.5–36.0 μmol m−2 s−1 for Early Bunch) but small in 1991. Effects of Tmin could account for 73 to 95% of the CER variation in 1992, depending on genotype. Genotypes differed significantly in CER response to Tmin in 1992, with relative tolerance to low Tmin of OAC Ruby > OAC Garroy > all other genotypes. The cultivar OAC Ruby showed a reduction in CER of ≈25% when Tmin fell from 20 to 5 °C. In contrast, Early Bunch, Chico, VA910212, and OAC Tango did not differ from each other and were relatively sensitive to low Tmin, with CER reduced by approximately 55% for the same reduction in Tmin. After Tmin of 20 °C, however, CER of sensitive genotypes was 17% higher than that of OAC Ruby. Canopy minimum temperatures at Delhi were 1 to 3°C cooler than Tmin, primarily due to radiative cooling. Microclimate differences between environments will affect the magnitude of differences between Tmin and Tmin (leaf) and therefore affect the utility of Tmin‐CER relationships developed here.
Importance of Variation in Chilling Tolerance for Peanut Genotypic Adaptation to Cool, Short‐Season Environments
Authors: Bell M. J. , Roy R. C. , Tollenaar M. , Michaels T. E.
Published: July 2010

Recent studies have shown genotypic variation in sensitivity of leaflet CO2 exchange rate (CER) to cool night temperatures. However, no information is currently available on the relative importance of this trait for successful peanut production in a cool, short‐season environment. The objectives of this study were to examine the physiological basis of genotype adaptation to a cool, short‐season environment and to assess the importance of genotypic differences in sensitivity to low night temperatures in that adaptation. Eight genotypes were grown in the field at Delhi, Ontario in 1991, and six of these eight were grown in 1992. Phenological development was monitored, dry matter (DM) accumulation was determined from destructive samples, and radiation use efficiency (RUE) was calculated from measurements fractional interception of incident photosynthetically active radiation (PAR). Accumulated degree‐days in 1991 (1245 °C d from sowing to frost) greatly exceeded those in 1992 (885 °C d), despite similar calendar‐day duration. Only five genotypes matured in 1991 and two in 1992. The degree‐days required to reach key reproductive stages including maturity varied considerably among genotypes and between seasons. Seasonal variation was probably due to effects of low temperatures on continuity of reproductive development and the proportion of total kernels that were mature at harvest. Total DM was reduced by 30 to 50% in 1992, compared with 1991, whereas pod and kernel yields were reduced by 40 to 75 and 38 to 83%, respectively. The lower DM in 1992, and genotypic differences in both seasons, were due primarily to the amount of incident PAR intercepted by canopies (i.e., 520–790 MJ m−2 in 1991 and 360–480 MJ m−2 in 1992). The RUE was 13 to 24% lower during 1992, compared with 1991, with relative genotype RUE generally consistent with CER sensitivity to low night temperature. Early maturity combined with an ability to rapidly expand a canopy to intercept incident PAR were the factors most important for peanut production in this environment.
Breeding for Resistance to Alfalfa Root Rot Caused by Fusarium Species
Authors: Salter R. , Miller‐Garvin J. E. , Viands D. R.
Published: July 2010

Fusarium root and crown rot is a significant factor in stand and yield reduction of alfalfa (Medicago sativa L.). The objectives of this study were to develop a greenhouse inoculation procedure for screening alfalfa germplasm for resistance to root rot caused by Fusarium species, collect virulent isolates of Fusarium species from New York, and determine progress from two cycles of recurrent phenotypic selection. Fusarium avenaceum (Fr.: Fr.) Sacc., F. oxysporum Schlechtend.:Fr., and F. solani (Mart.) Sacc. were isolated from rotted alfalfa roots and crowns in each of four regions of New York. At least one of the three species was present in every field sampled, but not all species were found in every field. The V‐V8 inoculation method was developed by culturing the Fusarium species in vermiculite saturated with V8 juice; the inoculum was placed in contact with severed alfalfa root balls in pots. This method was as effective as the application technique for inciting infection of alfalfa roots; however, the Y‐Y8 method was more efficient for mass inoculation of plants. Using the V‐V8 method in the greenhouse, we subjected two alfalfa populations to two cycles of recurrent phenotypic selection for resistance to root rot caused by each of the three Fusarium species. Mean lesion length (vertical discoloration) within taproots was the selection criterion. Only selection for resistance to disease caused by F. solani was effective; mean lesion length decreased by 34% from Cycle 0 to Cycle 2 in Oneida, and by 48% in (Flamande × SaranacAR‐2)AN. Future selection should account for lateral spread as well as vertical length of lesions.
Comparing Conventional Early Generation Selection with Molecular Marker Assisted Selection in Maize
Authors: Stromberg L. D. , Dudley J. W. , Rufener G. K.
Published: July 2010

To be useful to plant breeders, gains made from molecular marker‐assisted selection (MAS) must be more cost‐effective than gains made through traditional breeding. The objective of this research was to evaluate the effectiveness of MAS in an applied maize (Zea mays L.) breeding program. Maize population BS11 (FR) C7 was chosen to improve hybrid FRMo17 × FRB73. FRMo17 and BS11 were crossed, then random‐mated to create F2 plants (families). F2 plants were testcrossed to FRB73 and genotyped with 34 molecular markers. F2 families were selfed to create F2:S4 families. Based on F2 testcross yield, the top 20 families were selected. A second set of 20 families was selected based on a marker‐derived selection index. Marker genotypes were obtained for 20 plants within each of the marker selected families. Index selections were made for favorable and unfavorable genotypes within the 20 families. F2:S4 testcrosses to FRB73 were grown to compare the different selection methods. Selection among F2:S4 families using either method resulted in similar testcross performance. However, neither method selected families that performed significantly better than FRMo17 × FRB73 or the So unselected population testcross. Within‐family index selection was not effective. The selection index, developed with F2 testcross data, was not correlated with F2:S4 testcross performance. Marker‐yield associations were determined using F2:S4 genotypic and testcross performance data. Ten (31%) markers were significantly associated with yield. One marker‐allele combination was favorable (and significant) in both F2 and F2:S4 testcross performance.
Inheritance of Resistance to the Southern Root‐Knot Nematode in Soybean
Authors: Luzzi Bruce M. , Boerma H. Roger , Hussey Richard S.
Published: July 2010

The inheritance of resistance to the southern root‐knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] in soybean [Glycine max (L.) Merrill] was determined for crosses of a susceptible cultivar, Bossier, with two resistant plant introductions, PI96354 and PI417444. Each F1, F2, and/or F3 generation was screened in a greenhouse for resistance to gall formation. In the PI96354 × Bossier population the number of galls per F2 plant and F3 family mean gall numbers were continuously distributed. The PI417444 × Bossier F3 family mean gall numbers were also distributed continuously. for both crosses, each F2 and/or F3 distribution indicated that resistance was quantitatively inherited. Variance component heritability estimates on a mean and plot basis for both crosses ranged from 0.79 to 0.93. The parent‐progeny (F2‐F3) correlation calculated for PI96354 × Bossier was 0.73. The uniqueness of resistance genes was determined for crosses among ‘Forrest’ (resistant), PI96354, and PI417444. F3 progeny from crosses of PI96354 × Forrest and Forrest × PI417444 exhibited transgressive segregation. Individual F3 plants and F3 families were identified with more galls than Forrest, PI96354, and PI417444. Some F3 plants had the same number of galls as Bossier, the susceptible check. These data indicate that Forrest differs from PI96354 and PI417444 for resistance to M. incognita by at least one gene. for PI96354 × PI417444, the similarity of F1, F2, and parental means and variances indicated that PI96354 and PI417444 have resistance genes at the same loci. Soybean breeders can use this information to develop strategies for using these plant introductions to improve the level of M. incognita resistance in adapted cultivars.