bluuebunny/crossref_metadata_2025 huggingface dataset:
Top Growth and Rooting Responses of Tall Fescue Cultivars Grown in Hydroponics
Authors: Kim Kyoung‐Nam , Shearman Robert C. , Riordan Terrance P.
Published: July 2010

Use of turf‐type tall fescue (Festuca arundinacea Schreb.) as a reduced‐input and drought‐resistant turfgrass species has increased in recent years. Several growth types of tall fescue have been identified. Concerns have been expressed about the rooting responses of cultivars classified as turf type and dwarf type. Turf‐ and dwarf‐type tall fescues may lack the potential drought‐avoidance characteristics associated with cultivars like Kentucky 31. This study was conducted in hydroponics under greenhouse conditions to determine whether potential differences in top and root growth responses exist among tall fescue cultivars, experimental lines, and growth types. Sixteen cultivars and experimental lines, representing four growth types (i.e., dwarf, turf, intermediate, and forage) were evaluated. Tall fescue cultivars, experimental lines, and growth types differed in top growth and rooting responses. All cultivars and lines, except ‘Jaguar’ and ‘Kenhy’, produced roots to the 600‐ to 750‐mm sampling depth. Dwarf‐ and turf‐type cultivars and lines had the best responses for total root production and distribution under the conditions of this study. ‘Silverado’, ‘Eldorado’, ‘Trailblazer’, and 516 had relatively high verdure yields ranging from 5.3 to 5.7 g, low clipping yields ranging from 3.6 to 3.9 g, and a clipping yield to verdure ratio (CY/V) of 0.7. Results from this study refute concerns expressed by some persons in the turfgrass industry regarding the potential for reduced depth and extent of rooting in dwarf‐ and turf‐type tall fescues. These data further support the presence of genotypes with abilities to express deep, extensive root systems and favorable characteristics for drought avoidance potential.
Water Relations, Forage Production, and Photosynthesis in Tall Fescue Divergently Selected for Carbon Isotope Discrimination
Authors: Johnson R. C. , Yangyang Li
Published: July 2010

Carbon isotope discrimination (Δ) has been correlated with the ratio of dry matter production to transpiration (water‐use efficiency, WUE) in C3 plants and is potentially useful for breeding crops with improved WUE. Therefore, an assessment of the selection response of Δ and its relationship to plant water status and forage production is needed. Divergent selection for high Δ (low WUE expected) and low Δ (high WUE expected) was completed for two cycles from a ‘Kentucky 31’ tall fescue base (Festuca arundinacea Schreb.) population (Co ). Water relations, forage production, and Δ were evaluated in Co and the selected populations in irrigated and dryland field environments in 1995 and 1996. Average realized heritability for Δ was 0.49, suggesting that Δ could be successfully manipulated in a breeding program. In 1995, leaf pressure potential (turgor) was higher in the populations selected for low Δ, but in 1996, no differences in water relations measurements were observed. High‐Δ populations always had lower forage production than observed in Co, but the low‐Δ populations never produced more than the Co population. In greenhouse‐grown plants, high‐Δ populations had higher internal substomatal [CO2] than Co, linking Δ with mechanisms that cause lower WUE. However, the internal [CO2] of the low‐Δ populations and Co did not differ, suggesting that selection for low Δ may not have increased WUE as expected. The results show that Δ is a heritable trait in tall fescue, but an absence of increased production in populations selected for low Δ may limit its utility in tall fescue breeding programs.
Expression of Soybean Cyst Nematode Resistance in Transgenic Hairy Roots of Soybean
Authors: Narayanan R. A. , Atz R. , Denny R. , Young N. D. , Somers D. A.
Published: July 2010

Transgenic hairy roots of soybean [Glycine max (L.) Merrill] induced by Agrobacterium rhizogenes support the complete life cycle of soybean cyst nematode (SCN, Heterodera glycines Ichinohe) in vitro. However, expression of SCN resistance in hairy soybean roots has not been investigated. A transgenic hairy root system would be useful in developing an assay for candidate SCN resistance genes. The objectives of this study were to characterize transgene expression in SCN‐infected hairy soybean roots and to evaluate a transgenic hairy root system for investigations of resistance to SCN. Seedling cotyledons of the SCN‐susceptible cultivars, Agassiz and Parker, and SCN‐resistant Bell and Faribault were infected with A. rhizogenes strain K599 transformed with T‐DNA binary vectors containing the gusA gene fused to promoters from either the cauliflower mosaic virus (CaMV 35S), Arabidopsis thaliana phenylalanine ammonia lyase (PAL), or bean (Phaseolus vulgaris L.) chalcone synthase‐8 (CHS) genes. Nine days after inoculating transgenic hairy roots with sterile J2 nematodes, CHS‐regulated β‐glucuronidase (GUS) staining at infection sites increased in hairy roots of resistant Faribault and decreased in susceptible Agassiz. PAL‐regulated GUS staining was absent at infection sites in hairy roots of resistant cultivars, but was increased in infection sites in susceptible cultivars. Thirty‐five days after inoculation with SCN, the mean number of cysts formed on hairy roots of the resistant cultivars was about 14% of the mean number of cysts formed on hairy roots of the susceptible cultivars, indicating that the SCN resistance phenotypes were preserved in transgenic hairy roots. These results indicated that the transgenic hairy soybean root system will be useful for investigating differential transgene expression during nematode infection and evaluation of candidate SCN resistance genes.
Survival of Wheat Curl Mites on Different Sources of Resistance in Wheat
Authors: Harvey T. L. , Seifers D. L. , Martin T. J. , Brown‐Guedira G. , Gill B. S.
Published: July 2010

Wheat (Triticum aestivum L.) yield is limited by wheat streak mosaic virus which is vectored by the wheat curl mite (WCM) Aceria tosicheilla (Keifer). Host resistance to WCM has reduced losses. This study was conducted to evaluate the effectiveness of resistance in wheat to WCM collected from various locations in the Great Plains. Collections of WCM from Montana, Nebraska, South Dakota, Texas, Alberta, Canada, and eight locations in Kansas were compared for their ability to survive and reproduce in the greenhouse on seven lines of wheat and wheat relatives previously identified as resistant. The lines and their sources of resistance were: AC PGR16635 (Aegilops tauschii Coss., Cmc1), PI 525452 (Thinopyrum ponticum (Podp.) Liu and Wang, Cmc2), KS96WGRC40 (Ae. tauschii and Secale cereale L.), TA920 (Triticum timopheevii (Zhuk.) Zhuk spp. armenidcum), PI 475772 (S. cereale), ‘TAM 107’ (S. cereale), PI 222655 (T. aestivum). KS96WGRC40 and TA920 were the only entries that were resistant to all WCM collections. Other sources of resistance were effective against WCMs from some but not all locations. PI 222655 was resistant to WCMs from Nebraska and central Kansas but not to mites from most other locations. WCMs that were virulent to TAM 107 generally were also virulent to PIs 222655 and 475772 but avirulent to Cmc2. The WCMs from western Kansas, where TAM 107 is widely grown, were generally more virulent to that cultivar than WCM from central Kansas where the hectarage of TAM 107 is smaller. WCMs collected at different times or locations may vary in their responses to different sources of resistance; therefore, testing mites for their response to resistance genes advanced in breeding programs may be needed before resistant cultivars are deployed in the field.
Protein Degradability and Forage Quality in Maturing Alfalfa, Red Clover, and Birdsfoot Trefoil
Authors: Cassida K. A. , Griffin T. S. , Rodriguez J. , Patching S. C. , Hesterman O. B. , Rust S. R.
Published: July 2010

Choice of forage species and harvest management may influence protein degradability in cattle diets. We measured forage yield, undegradable intake protein (UIP), and forage quality at three maturities in two cuttings (spring, regrowth) of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and birdsfoot trefoil (Lotus corniculatus L.) in the seeding and two subsequent years. At equivalent harvest stage, trefoil and clover were usually lower in neutral detergent fiber (NDF) and acid detergent fiber (ADF) than alfalfa. Crude protein (CP) was lower in red clover than trefoil or alfalfa for three of six cuttings, but red clover was equal to or higher in UIP than alfalfa or trefoil in all cuttings. Trefoil never had higher UIP concentrations than alfalfa. Trefoil tannin concentrations increased with maturity and were positively correlated with UIP concentration. For all species, UIP was positively correlated with NDF and ADF and negatively correlated with in situ dry matter disappearance (ISDMD). In alfalfa and trefoil, UIP was negatively correlated with CP. In all legumes, dry matter yield (DMY), NDF, and ADF increased with maturity, while CP and ISDMD decreased. Changes in NDF, ADF, CP, and ISDMD with maturity were usually most rapid in trefoil. The proportion of UIP increased with maturity for all species in all cuttings, but it never comprised more than 240 g kg−1 CP. Small increases in UIP as legumes matured were gained at the expense of other forage quality measures.
Isozyme Analysis of Entire and Core Collections of Solanum tuberosum subsp. andigena Potato Cultivars
Authors: Huamán Zósimo , Ortiz Rodomiro , Zhang Dapeng , Rodr í guez Flor
Published: July 2010

The International Potato Center (CIP), near Lima, Peru, holds one of the largest clonal collections of tetraploid (2n = 4x = 48) Andean farmer selected potato cultivars (Solanum tuberosum L. subsp. andigena Hawkes). CIP selected a core collection of 306 Andean cultivars from the 2379 accessions available in the genebank to facilitate the utilization of these genetic resources. Our objective was to investigate the genetic structure in both the entire collection and its respective core subset with nine isozyme markers that have been genetically characterized. Such an analysis provides a means to validate the sampling strategy of the core collection. Allozyme frequencies and average heterozygosity were calculated for each locus investigated. The allozyme frequency distribution for each locus was tested for homogeneity between the entire and core collections by χ2 tests. A total of 38 allozymes were scored in the entire collection. Only two rare allozymes (Idh‐13 and Pgi‐15) with a gene frequency (q) of 0.0002 (or 0.02%) were not included in the core collection. The most frequent allozymes in the entire collection also showed the highest frequencies in the core collection. The allozyme frequency distributions were also homogeneous (P > 0.05) for all loci except for the Pgi‐1 and Got‐1 loci. Average locus heterozygosity was similar (P > 0.05) between the entire and core collection (49 and 50%, respectively). This analysis suggests that the sampling strategy to develop this core collection of tetraploid Andean potato cultivars was adequate to capture a representative sample of the allozyme loci, because only rare alleles (q < 0.0005 or 0.05%) were lost in the selected core subset. Therefore, this core collection may be an appropriate entry point for researchers who wish to utilize the genetic diversity of this gene pool more efficiently.
Genetic Mapping in Maize with Hybrid Progeny Across Testers and Generations: Grain Yield and Grain Moisture
Authors: Austin David F. , Lee Michael , Veldboom Lance R. , Hallauer Arnel R.
Published: July 2010

Most complex quantitative traits in maize (Zea mays L.), especially grain yield, display low correlations between the trait values observed in inbred and hybrid progeny. Comparisons of quantitative trait loci (QTL) controlling inbred per se and hybrid performance are needed to understand the underlying genetic factors, and to determine the utility of QTL detected in the two progeny types. DNA markers were used to identify QTL for grain yield and grain moisture in hybrid progeny of F2:3 and F6:8 lines from a Mo17xH99 population. For both generations, testcross progeny were developed by crossing the lines to three inbred testers (B91, A632, B73). Each testcross population was evaluated in field trials with two replications in eight environments. The testcross progeny from the two generations were evaluated at the same locations but in different years. QTL were identified within each testcross population and for mean testcross (MTC) performance. Individual tester QTL effects were not consistent in rank or detection across generations; however, parental contributions were consistent. MTC effects were more consistent across generations with most of the QTL with large effects being detected across generations. QTL detected with only one tester were not necessarily detected for the other two testers, especially for grain yield, but parental contributions were consistent when QTL were detected in a region for more than one tester. The QTL for grain yield identified in this population for inbred and hybrid progeny show only partial correspondence, indicating that marker‐assisted selection programs would need to identify and incorporate QTL for both progeny types.
Relationship of Elevated Palmitate to Soybean Seed Traits
Authors: Stoltzfus David L. , Fehr Walter R. , Welke Grace A.
Published: July 2010

Soybean [Glycine max (L.) Merr.] oil with elevated palmitate content may be useful for producing solid fat at room temperature without hydrogenation. This study was conducted to determine the relationship between elevated palmitate and soybean seed traits. A total of 92 soybean cultivars and lines with palmitate contents ranging from 103 to 427 g kg−1 were evaluated in a randomized complete‐block design with two replications at each of three Iowa locations in 1997. Seed from each plot was analyzed for protein, oil, palmitate, stearate, oleate, linoleate, and linolenate contents. The phenotypic correlations were significant (P < 0.05 or 0.01) and positive between palmitate and protein (0.25), stearate (0.58), and linolenate (0.86) contents. There were significant (P < 0.01) negative phenotypic correlations of palmitate content with oil (−0.84), oleate (−0.94), and linoleate (−0.96) contents. Lines with >400 g kg−1 palmitate had protein contents equal to conventional cultivars, but their oil contents were reduced by more than 30 g kg−1. None of the lines with >400 g ka−1 had oleate, linoleate, or linolenate contents equal to conventional cultivars. These relationships will influence the feasibility of developing soybean cultivars with elevated palmitate content that are acceptable for other seed components.
Root Elongation of Soybean Genotypes in Response to Acidity Constraints in a Subsurface Solution Compartment
Authors: Ferrufino Armando , Smyth T.Jot , Israel Daniel W. , Carter Thomas E.
Published: July 2010

Aluminum‐tolerant germplasm is needed to overcome subsurface acidity constraints to root growth and plant access to water and nutrients. Root elongation of four soybean [Glycine max (L.) Merr.] genotypes exposed to varying concentrations of Al, H, and Ca were compared in two experiments using a vertically split root system. Roots extending from a limed surface soil compartment grew for 12 d into a subsurface compartment with nutrient solution treatments. In Exp. 1 root growth for cv. Ransom and Plant Introduction 416937 (PI) were compared in solutions with factorial combinations of pH (4.2, 5.2) and Al (0, 7.5, 15 μM) with Ca maintained at 10 mM In Exp. 2 soybean line N93‐S‐179 (N93), PI, and cultivars Ransom and Young were compared in solutions with factorial combinations of Ca (2 and 10 mM) and Al (7.5 and 15 μM) maintained at pH 4.6. Ransom and PI had similar responses in tap and lateral root elongation to solution pH and Al treatments in Exp. 1, but mean tap root length of Ransom in the subsurface compartment exceeded that of PI by 22%. Aluminum inhibited the length of lateral roots more than tap roots in both experiments. Molar activity ratios between Ca and Al3+ {Ca/Al3+} accounted for most of the differences in root elongation response among solution treatments in Exp. 2. A 50% reduction in relative length of tap roots for all genotypes occurred with a {Ca/Al3+} value of 891. Values of {Ca/Al3+} for 50% reductions in relative length of lateral roots differed among genotypes and were 1.6 to 3.5 times greater than for tap roots. On the basis of the {Ca/Al3+} indices for lateral root length, line N93 and Ransom exhibited greater tolerance to subsurface solution Al than PI and Young.
An Alternative Model to Predict Corn Seed Deterioration during Storage
Authors: Tang Shande , TeKrony Dennis M. , Egli Dennis B. , Cornelius Paul L.
Published: July 2010

An assumption of the Ellis‐Roberts viability equation, that all seed lots of a species deteriorate at the same rate in the same storage environment, was not valid for hybrid corn (Zea mays L.) seed. Thus, an alternative model was developed that used a potential storability index (PG, the time for germination to decline to a level G) and a storage environment coefficient (SEC, the factor by which seed longevity is altered by a change in storage temperature and seed moisture content) to predict deterioration of hybrid corn seed. The alternative model was derived from the ratio of seed longevity of the same seed lot in two storage environments. The PG in the storage environment was estimated as the product of PG in a rapid‐aging test and SEC, which was determined with a regression model based on the differences in temperature and moisture between the two environments. The model was evaluated by predicting the time to 90 and 50% germination (P90 and P50) for high‐ and medium‐quality seed lots stored under a range of constant conditions. There was generally good agreement between predicted and observed P90 and P50, with many of the predicted values within 10% of observed values across five seed lots. The storage conditions in the rapid‐aging test had no effect on the predictive ability of the model. This model provides an effective approach to predicting corn seed longevity that may be useful in managing seed storage.
Calcium Effects on Soybean Seed Production, Elemental Concentration, and Seed Quality
Authors: Burton M.G. , Lauer M.J. , McDonald M.B.
Published: July 2010

Soybean [Glycine max (L.) Merr.] plants produce fewer and lower quality seeds when grown in conditions that decrease seed Ca concentration. Indeterminate soybean was grown in modified hydroponic culture to ascertain the effects of Ca deficiency on leaf dry matter, seed production and elemental concentration, and the effect of pod position on seed elemental concentration in 1992 and 1993. Treatments consisted of 2.0 (Control), 0.2 (Low), 0.1 (Very Low) mM Ca in the nutrient media. Some Control plants were switched to Low or Very Low (Con/L, VL) Ca levels at beginning seed growth stage (R5), and some plants grown at the Very Low Ca level were switched to the Control (VL/Con) Ca level at R5. At harvest, plants were divided into four sections: top‐third (T/3), middle‐third (M/3), and bottom‐third (B/3) of the mainstem and branches (Br). Low and Very Low treatments produced 65 and 10% as much seed mass, respectively, as Control in both years. Low and Very Low treatments retained significantly less total leaf dry matter at R5 in both years. Seed Ca levels were 25 to 300% higher in treatments that included the Control Ca level during any part of reproductive growth compared to other treatments in both years. Seed Ca concentration was highest in the T/3 and Br sections in both years. Germination was reduced in treatments not including the Control solution during part of the reproductive growth period in both years. Decreased Ca levels in the nutrient medium reduced soybean leaf dry matter during seed fill, seed production, seed Ca concentration, and seed germination, and increased the incidence of seedling disorders such as watery hypocotyl and epicotyl necrosis.
Genotype × Environment Interactions in Maize Hybrids from Temperate or Highland Tropical Origin
Authors: Giauffret C. , Lothrop J. , Dorvillez D. , Gouesnard B. , Derieux M.
Published: July 2010

Exotic germplasm is often used in maize (Zea mays L.) breeding programs. However, the occurrence of genotype × environment interactions (GEIs) may mask the potential utility of exotic material. Our objective was to understand better GEIs for temperate, temperate × highland, and highland tropical maize genotypes cultivated under temperate or highland tropical conditions. We related yield instability to GEIs observed for vegetative or flowering traits, and determined the response of these vegetative or flowering traits to temperature and photoperiod. Forty‐one hybrids grown in four environments were observed for several pre‐flowering, flowering, and yield traits. Grain yield variation was related to two major adaptation factors: disease resistance and planting‐to‐silking duration (PSD). Yield variations were also related to variation in traits measured before flowering, such as emergence duration or early growth. For emergence duration, leaf stage at a given date, or leaf size, one simple temperature covariate accounted for more than half of the interaction sum of squares. Temperate × highland tropical hybrids had an intermediate behavior and were more stable than the pure temperate or pure highland tropical hybrids. For total number of leaves, photoperiod at tassel initiation explained a higher proportion of the interaction sum of squares than temperature. The response of highland tropical hybrids to photoperiod was larger than for the temperate hybrids. We recommend breeders who wish to introduce exotic material into adapted material utilize mass selection and/or advanced backcrossing, with marker assisted selection for specific traits with low heritability, such as cold tolerance.
Resistance to Fusarium Head Blight in Winter Wheat: Heritability and Trait Associations
Authors: Buerstmayr Hermann , Steiner Barbara , Lemmens Marc , Ruckenbauer Peter
Published: July 2010

Fusarium head blight (FHB) or scab caused by Fusarium Link: Fr. spp. is a widespread disease of cereals, causing significant yield losses and contaminating cereal products with mycotoxins. The complex inheritance of resistance has hampered progress in breeding resistant, agronomically adapted cultivars. To streamline breeding for FHB resistance, we estimated genetic and environmental variance components and broad‐sense heritability in two winter wheat (Triticum aestivum L.) populations, determined the association of FHB resistance with other traits (flowering date, plant height, and awnedness), and determined the level of maternal effects on FHB resistance. The moderately susceptible Austrian cultivar Capo was crossed with two resistant lines, one from Hungary (UNG‐226) and one from the Netherlands (SVP‐72017). A hierarchical design was applied to develop recombinant F4‐derived lines. Head blight resistance was measured by visual assessment of disease symptoms in artificially inoculated, mist‐irrigated field experiments during 2 yr. Artificial inoculation and mist irrigation led to reproducible FHB infections. High broad‐sense heritabilities (H > 0.75) were measured for FHB resistance, allowing for considerable progress by selection. The magnitude of additive genetic variance was greater than additive × additive epistatic variance. Despite a significant negative correlation between visual FHB symptoms and plant height , the successful selection of short and FHB resistant genotypes should be feasible. In only one population, awned progeny showed slightly reduced FHB. Reciprocal effects were significant in one cross only. The development of FHB resistant cultivars should be possible by phenotypic selection under epidemic conditions, and should be largely independent of plant height, flowering date, awnedness, and genotype of the maternal parent within a cross.
Genetic Progress from 40 Years of Orchardgrass Breeding in North America Measured under Hay Management
Authors: Casler M. D. , Fales S. L. , McElroy A. R. , Hall M. H. , Hoffman L. D. , Leath K. T.
Published: July 2010

There has been considerable activity in breeding orchardgrass (Dactylis glomerata L.) cultivars in North America during the latter half of the 20th century, but little effort devoted to quantification of breeding progress. The objectives of this study were to quantify changes in mean cultivar performance for that time compared with the progress achieved from one cycle of half‐sib progeny selection within the USDA population of orchardgrass accessions. Forty‐two cultivars (32 North American cultivars and 10 European cultivars) were tested at three locations (Arlington, WI and Rock Springs, PA, and Ottawa, Ontario, Canada) in 1995 through 1997. Cultivars were grouped into three experiments by maturity class: early, medium, and late. North American cultivars averaged 3, 9, and 12% higher in forage yield than European cultivars for early, medium, and late maturity groups, respectively. Between 1955 and 1997, forage yield and ground cover of early‐maturity cultivars increased by 2.5 Mg ha−1 decade−1 and 4.0% decade−1, respectively. Forage nutritional value of medium‐maturity cultivars increased during that time, although this was probably not due to direct selection. Significant gains were made in forage yield and Drechslera spp. leafspot reaction of cultivars derived from two individual breeding programs, although the majority of orchardgrass cultivars lack improvements in forage traits.
Ripening Habit of Buckwheat
Authors: Funatsuki Hideyuki , Maruyama‐Funatsuki Wakako , Fujino Kaien , Agatsuma Masamichi
Published: July 2010

In buckwheat (Fagopyrum esculentum Moench), the diverse ripening times of seeds and the remarkable seed shattering can make it difficult to determine the optimum harvest time. To provide basic information for the improvement of the ripening habit of buckwheat by breeding and cultural methods, we monitored the changes in the numbers of mature (brown) and immature (green) seeds at each raceme of buckwheat plants in the field during the course of seed maturation. A determinate line was used in addition to an indeterminate one (wild type), since the former had previously been reported to display more uniform ripening. Seed weights were also determined to estimate yields. Seed discoloration proceeded from the main stem to branches, and from basal to apical racemes regardless of genotypes or years. Seed shattering progressed in a similar pattern. In contrast to these consistent habits, differences in maturation speed were seen between years. Seed discoloration progressed slightly slower in 1997, while seed shattering began much earlier, compared with that in 1998. Consequently, in 1997, seed shattering began before all seeds had matured in most plants, while in 1998, this phenomenon was observed in fewer plants. Seed yields accordingly increased slowly until reaching maximum levels, followed by rapid decreases in 1997, relative to 1998. Growth habit (determinate vs. indeterminate) appeared to have little influence on ripening. These results are the first to clearly demonstrate that seed shattering can start before all seeds mature in buckwheat, regardless of growth habit. And that the rates of seed ripening and seed shattering are independent and vary among years.
Inheritance of Resistance to Fusarium Wilt in Two Common Bean Races
Authors: Cross Hugh , Brick Mark A. , Schwartz Howard F. , Panella Lee W. , Byrne Patrick F.
Published: July 2010

Fusarium wilt in common bean (Phaseolus vulgaris L.) caused by Fusarium oxysporum Schlechtend. Fr. forma specialis phaseoli Kendrick and Snyder (Fop) occurs worldwide and can result in severe yield loss. Because cultural methods to control disease loss are not completely effective, cultivars with genetic resistance are needed. The objectives of this study were to determine whether genetic control of resistance to Fop race 4 differs between germplasm of races Durango and Mesoamerica of common bean and to estimate heritability of resistance found in race Mesoamerica. Resistant and susceptible lines of races Durango and Mesoamerica were crossed within races to produce F2 and F3 progeny. Reaction to Fop was evaluated using a root‐dip inoculation method and scored using a CIAT disease severity scale from one to nine. F2 populations derived from race Durango parents showed a 3:1 (resistant/susceptible) plant segregation ratio, and F3 progeny tests confirmed that resistance was controlled by a single dominant gene. F2 data from crosses between parents of race Mesoamerica had continuous distributions for reaction to Fop race 4, suggesting polygenic control of resistance. The narrow‐sense heritability estimate derived from midparent–offspring regression of 10 F2 populations derived from Mesoamerican parents was 0.85 ± 0.34, and realized heritability estimates ranged from 0.25 ± 0.19 to 0.60 ± 0.16 among five populations. The heritability estimates as well as the continuous variation in disease severity observed support the hypothesis that resistance to Fop race 4 among parents of race Mesoamerican is polygenic.
Vestigial Corolla in Flowers of Birdsfoot Trefoil
Authors: Beuselinck P. R. , McGraw R. L.
Published: July 2010

A naturally occurring floral mutant is infrequently observed in some populations of birdsfoot trefoil (Lotus corniculatus L.). The petals of mutant flowers are folded inward and do not extend fully, producing a vestigial corolla (vc), while other floral parts remain normal. The style extrudes through a gap between the rudimentary keel and the folded standard. Consequently, the stigma and style extend beyond the corolla and are exposed. The spatial separation between stigma and anthers could facilitate hand‐pollination as it eliminates the need for emasculation. The objective of this study was to determine the fertility of L. corniculatus genotypes expressing vc floral characters. Sixteen genotypes of L. corniculatus expressing the vc phenotype were collected from field grown populations. Pollen from vc genotypes was compared with pollen from genotypes of the germplasm MU‐81 used as controls. All vc genotypes produced some pollen that appeared normal, although the quantity of such pollen was variable among the vc genotypes. Mean pollen germination among vc genotypes was 22%, compared with 50% for MU‐81. Only five of 16 vc genotypes produced pods when crossed to genotypes of MU‐81 and both pod and seed set were less than in control crosses. Normal and abnormal ovules were observed in ovaries of vc genotypes and the reduced fertility may have resulted from smaller, incompletely developed ovules. Unidirectional reversion of the vc genotypes, from abnormal to normal flower morphology, was common. Using the vc mutant to eliminate the need for emasculation in hand‐pollination programs depends on its fertility. The combination of phenotypic instability and reduced fertility make the vc mutant less desirable for use in breeding programs.
Reexamining the Relationship between Fall Dormancy and Winter Hardiness in Alfalfa
Authors: Brummer E. Charles , Shah M. Maroof , Luth Diane
Published: July 2010

Although phenotypic correlations generally show winter hardiness and late summer and autumn growth (fall dormancy, FD) in alfalfa (Medicago sativa L.) to be strongly associated (r = 0.90), the genetic relationship between the traits has been poorly documented. This study was conducted to rigorously characterize this relationship in a segregating population. We developed an F1 population of 200 plants derived from crossing an elite subsp. sativa clone, ABI408, and a semi‐improved subsp. falcata clone, WISFAL‐6. We clonally propagated the parents and progeny and planted replicated trials at Ames and Nashua, IA in 1998. Plant height, a measure of fall dormancy, was measured in October 1998 at both locations. Winter injury was rated in April 1999. Transgressive segregation in both directions was noted in all cases, except for plant height at Ames, where no F1 genotype was shorter than WISFAL‐6. The heritability of fall growth was estimated at 0.69 ± 0.044 on an entry mean basis and 0.29 ± 0.035 on a plot basis, and of winter injury at 0.73 ± 0.039 and 0.39 ± 0.040, respectively. Phenotypic correlations between the traits based on entry means were not evident (P < 0.05) but were weakly negative based on plot data (−0.11 at both Ames and Nashua, P < 0.01). The genetic correlation between fall height and winter injury was −0.16 ± 0.048. A weak association exists in this population—taller plants in the fall have less winter injury. These results provide compelling evidence that considerable improvement in both fall growth and winter hardiness can be achieved simultaneously. We suggest that the varied pathways controlling winter hardiness provide ample opportunity for selection of agronomically desirable genotypes.
Improvement Strategy for Mature Plant Breeding Programs
Authors: Peel Michael D. , Rasmusson Donald C.
Published: July 2010

In mature plant breeding programs an elite core germplasm forms the backbone of the breeding effort, confronting the breeder with the challenge of maintaining germplasm diversity as genetic distance between the elite core germplasm and donor germplasm widens. This research assessed the effects on grain yield of transferring genes from two‐row barley (Hordeum vulgare L.) cultivars to a six‐row gene pool. We conducted three cycles of recurrent‐type breeding, beginning with crosses involving five two‐row donor parents. The crossing scheme led to progenies with theoretical proportions of two‐row germplasm of 25 to 50% in Cycle 1, 12.5 to 25% in Cycle 2 and 6.25 to 12.5% in Cycle 3. In Cycle 1, yield of the six‐row progeny across the five populations ranged from 86 to 97% of the respective six‐row parent. Kernel weight of the six‐row progeny was also low in Cycle 1. In Cycle 2, grain yield improved to 99% of the check mean and kernel weight improved to 102% of the check mean. In Cycle 3, sets of lines representing three populations yielded from 112 to 119% of the check mean in 1997 and 1998 and individual lines surpassed ‘Stander’, the highest yielding check in both 1997 to 1998. The highest yielding lines in each cycle were derived from populations having the highest theoretical percentage of adapted recurrent parent germplasm, that is, when six‐row gene combinations were predominately left intact. Results from the three breeding cycles support the proposition that a strategy that maintains favorable gene combinations while introgressing relatively small amounts of donor germplasm can lead to incremental yield gains.
Physiological Comparisons of Switchgrass Cultivars Differing in Transpiration Efficiency
Authors: Byrd G. T. , May P. A.
Published: July 2010

Production of forage species like switchgrass (Panicum virgatum L.) is often relegated to areas with minimal inputs of water and fertilizer, therefore, selection should be based on efficient use of these resources. This study examined genotypic variation in switchgrass transpiration efficiency (TE), defined as the weight of dry matter per unit of water transpired, under conditions of water and N stress. Since reports show TE to be correlated with specific leaf weight (SLW) and leaf ash, these easily measured traits were assessed for their potential as predictors of switchgrass TE. In one greenhouse experiment with nine cultivars and two outdoor experiments with two cultivars, plants were grown in closed containers in a soil–peat mix or solution culture and subjected to water or N deficit. Cultivars differed in TE; however, TE did not differ between water stressed and well‐watered conditions. With decreasing N in solution, TE also decreased. Cultivars differed in their values of TE when grown in nutrient solutions containing 10.0 and 1.0 mM N, but not at 0.3 mM N. Transpiration efficiency was positively correlated with SLW in each experiment and across all experiments Correlation between TE and leaf ash was inconsistent, with a negative relationship in the water stress experiment and a positive relationship in the N experiment. The results show differences in TE among switchgrass cultivars and show that SLW is consistently predictive of TE.
Cytoplasmic Male Sterility in Two Wild Helianthus annuus L. Accessions and Their Fertility Restoration
Authors: Jan C.C.
Published: July 2010

Commercial sunflower hybrids have been produced by means of a single male‐sterile Helianthus petiolaris Nutt. cytoplasm and a few fertility restoration genes. The objectives of this study were to characterize cytoplasmic male‐sterility (cms) systems in wild H. annuus L. accessions (PI 413178 and PI 413180) and to determine the inheritance of fertility restoration. Male‐sterile plants were identified and maintained by backcrossing with inbred line HA89. Male‐fertile progenies from crosses between cms plants of the two PIs and USDA inbred lines indicated the presence of fertility restoration genes in P21, RMAX1, and PI 413178 for cms PI 413178 (cms‐ANN2), and P21, RHA280, RHA801, RPET2, and PI 413180 for cms PI 413180 (cms‐ANN3). All heterozygous male‐fertile plants of backcross progenies, except for RHA280, crossed to cms plants resulted in a segregation ratio of one male‐fertile to one male sterile, indicating a single dominant gene controlling fertility restoration. The backcross progeny of cms PI 413180/HA89//cms PI 413180/RHA280 had a segregation ratio of one male‐fertile to three male sterile, suggesting two complementary dominant genes for fertility restoration. Pollinating male‐fertile plants of both accessions with HA89 pollen resulted in male‐fertile and male‐sterile F1 plants, suggesting the existence of male‐sterile cytoplasm and heterozygosity for restoration genes in the male‐fertile plants. In field tests, male‐sterile PI 413178/4*HA89 and PI 413180/4*HA89 plants produced no seed after self‐pollination, and 95 and 98% seed set, respectively, under open‐pollination indicating complete male‐sterility and female fertility. The new cms sources from wild H. annuus and corresponding fertility restoration genes provide diversity for sunflower hybrid production.
Selection for Bean Golden Mosaic Resistance in Intra‐ and Interracial Bean Populations
Authors: Singh Shree P. , Morales Francisco J. , Miklas Phillip N. , Terán Henry
Published: July 2010

Bean golden mosaic (BGM) resistance within any one bean (Phaseolus vulgaris L.) race is inadequate. Pyramiding genes from different races would increase resistance and reduce pesticide use. Our objectives were to: (i) pyramid and compare BGM resistance of genotypes from intraracial versus interracial populations, (ii) verify pyramided resistance by means of molecular markers, and (iii) combine BGM resistance with resistance to other diseases. One intraracial (GV 10625) and four interracial (DC 10622, GV 10624, GV 10626, and GV 10627) populations were developed at CIAT. Plants within each F1‐derived F2 (F1:2) were advanced in bulk. The F3 was grown in the field under common bacterial blight [CBB, caused by Xanthomonas campestris pv. phaseoli (Smith) Dye] and angular leaf spot [ALS, caused by Phaeoisariopsis griseola (Sacc.) Ferraris] pressure. Single plant selections were made in the F3 and F4 Plants within F4:5 were harvested in bulk to screen for ALS, bean common mosaic (BCM), BGM, and CBB. The 39 selected genotypes, 12 parents, and six checks were again evaluated for the four diseases. Seventeen genotypes, parents, and checks also were screened for the RAPD marker OR2530 linked with bgm‐1 gene and the SCAR marker SW12700 linked with a QTL controlling BGM resistance. Selected genotypes differed in their BGM reaction. None of the genotypes from the intraracial population were resistant to BGM. Five genotypes with the highest resistance were obtained from GV 10626 and GV 10627. DC 10622 and GV 10624 produced genotypes with intermediate resistance. Three genotypes from DC 10622 and four from GV 10627 possessed OR2530 marker linked with resistance derived from `Garrapato' and SW12700 marker linked with resistance derived from `Porrillo Sintetico'. All genotypes possessed the I gene for BCM and were intermediate to ALS. Five also were intermediate for CBB. Combined use of interracial populations, disease screening, and molecular markers should be emphasized for resistance breeding.
Inheritance of Cold Tolerance at Emergence and during Early Season Growth in Maize
Authors: Revilla P. , Malvar R. A. , Cartea M. E. , Butrón A. , Ordás A.
Published: July 2010

Adaptation of maize (Zea mays L.) to early planting dates requires the improvement of cold tolerance, which implies high percentage emergence and vigorous seedling growth under cold temperatures. The objectives of this work were to evaluate the combining ability of elite European maize inbreds for cold tolerance and to study the inheritance of cold tolerance. Five maize inbreds, differing in sensitivity to cold temperatures, were crossed by means of a diallel design. Hybrid seed was obtained at two production environments. Hybrids were planted on trays filled with sterilized peat in a cold chamber at four minimum temperatures, and these hybrids were also grown in field trials at two locations in northwestern Spain. The most cold‐tolerant inbreds, according to previous unpublished inbred evaluations in the cold chamber, F7 and EA2087, produced the most cold‐tolerant hybrids. Inbred F7 performed slightly better in hybrid combinations than EA2087 for emergence‐related traits in the cold chamber, and EA2087 was superior in hybrid combinations to F7 for seedling growth. The inbred F7 may contribute cold tolerance at emergence, whereas EA2087 contributed cold tolerance for both emergence and seedling growth. In the field, inbreds F7 and H104W were the best parent for cold‐tolerant hybrids. Percentage emergence was not related to the other traits. Generally, the genetic regulation of cold‐tolerance traits conformed to an additive‐dominance model, and it should be possible to combine both high percent emergence and vigorous seedling growth. A promising source of new cold‐tolerant inbreds is the cross between EA2087 and F7.
Breeding Potential of European Flint and U.S. Corn Belt Dent Maize Populations for Forage Use
Authors: Moreno-Gonza´lez J. , Martı´nez I. , Brichette I. , Lo´pez A. , Castro P.
Published: July 2010

Information about appropriate breeding populations and the type of forage maize (Zea maysL.) hybrids that should be developed for cooler regions of Europe is scarce. Our objectives were to determine the potential, performance, and heterosis of flint (F) and dent (D) populations as base germplasm for developing silage maize hybrids. Four U.S. Corn Belt dent populations which had been selected for early maturity and four European flint populations were included in our study. The eight populations, the 28 possible crosses among them, and topcrosses to inbreds A632 and EC18 were evaluated for stover, ear, and whole plant dry matter yield (DMY), as well as stover and whole plant dry matter content (DMC), digestible organic matter (DOM), and acid detergent fiber (ADF) content in northwest Spain. Means of F × D population crosses for stover and ear DMY (6.98 and 8.71 Mg ha−1, respectively) were greater than those of D × D crosses (6.12 and 8.05 Mg ha−1, respectively) and F × F crosses (6.03 and 7.64 Mg ha−1, respectively). Average heterosis of whole plant DMY was greater for the F × D crosses (2.16 Mg ha−1) than for the D × D and F × F crosses (0.23 and 0.56 Mg ha−1, respectively). No significant heterosis was found for DOM and ADF of the stover and whole plant fractions. The only exception was a negative average heterosis of population BSSS‐M for stover DOM. Results suggest that forage maize hybrids should be developed from the F × D heterotic pattern. Breeding strategies should include selection for stover DOM for both parent lines and hybrids because favorable recessive genes may be involved in this trait.
Nitrogen Rate Effect on Partitioning of Nitrogen and Dry Matter by Cotton
Authors: Boquet Donald J. , Breitenbeck Gary A.
Published: July 2010

Increased understanding of the fate of N in cotton (Gossypium hirsutum L.) fields will improve N efficiency, optimize crop development and yield, and may help to avoid excessive N fertilization. This study quantified the effects of N fertilization rate (0, 84, and 168 kg ha−1) on seasonal uptake and partitioning of N and dry matter in field‐grown cotton during 1989 and 1990. The N rates studied were part of a larger experiment initiated in 1987 where plots received annual preplant applications of 0, 28, 56, 84, 112, 140, or 168 kg N ha−1 Experiments were conducted on Commerce silt loam (fine‐silty, mixed, thermic, nonacid, aeric Fluvaquent) on the Louisiana State University Agricultural Center Northeast Research Station near St. Joseph, LA. Plants were collected at five dates in each year at about 20‐d intervals. Shed plant debris was also collected. The N content and aerial biomass of plant components were determined. Maximum N uptake occurred between 49 and 71 d after planting and was 2.9 and 4.3 kg ha−1 d−1 for cotton receiving 84 and 168 kg N ha−1, respectively. At maturity, plants receiving 84 kg N ha−1 contained 160 kg N ha−1 in aerial biomass and an additional 50 kg N ha−1 in abscised plant debris. The total amount of N assimilated by plants receiving 84 kg fertilizer N ha−1 averaged 111 kg N ha−1 more than plants receiving no fertilizer N for an apparent fertilizer efficiency greater than 100%. By the end of effective bloom, plants receiving 168 kg N ha−1 assimilated 15 to 40% more N, primarily in leaves and lower bolls, than plants receiving 84 kg N ha−1 This excess assimilated N was recovered in surface litter and in N‐enriched plant components. Of the plant components studied, leaf‐blades most consistently reflected the amounts of fertilizer N applied.
Embryo Physiological Responses to Cold by Two Cultivars of Oat during Germination
Authors: Massardo Francisca , Corcuera Luis , Alberdi Miren
Published: July 2010

Physiological responses and mechanisms triggered by cold are known for seedlings and mature plants, but are poorly understood for early developmental stages. Previous research on seedlings of two oat (Avena sativaL.) cultivars, `Ot220×Omihi' (Ot220) and `America', characterized them as cold tolerant and cold sensitive, respectively. This study investigates if cold responses during seed germination, at the phases of coleorhiza (1–2 mm elongation) and radicle (10 mm elongation) emergence, are similar to those described for these same cultivars at later developmental stages. Accumulation of cryoprotective solutes, degree of fatty acid unsaturation, oxygen consumption, and oxidative damage were evaluated. From imbibition until coleorhiza or radicle protrusion, seeds were maintained in darkness at constant temperatures of 17°C (control) or 3°C (low temperature treatment). Number of days to initiate germination (Di), days to reach 50% germination (D50), and lethal temperature for 50% of the population (LT50) were determined. At 3°C, Di and D50occurred significantly earlier in Ot220. LT50values, however, did not differ significantly. At the coleorhiza stage, embryos of both cultivars at 3°C accumulated soluble sugars; fructans accumulated only in Ot220. At the radicle stage, proline and fructans accumulated in both cultivars. No clear differences between cultivars were detected with regard to the relative composition or degree of unsaturation of fatty acids at low temperatures. However, at 3°C, Ot220 exhibited greater oxygen consumption and catalase activity than did America. Significant lipoperoxidative damage occurred only in America. As for the seedling stage, Ot220 can be characterized as cold tolerant and America as cold sensitive during germination. Responses to low temperature at this early development stage, however, were indicative of higher metabolic rates and less oxidative damage, rather than an accumulation of cryoprotective solutes.