bluuebunny/crossref_metadata_2025 huggingface dataset:
Responses of Wild and Cultivated Barley from West Asia to Net Blotch and Spot Blotch
Authors: Jana Sakti , Bailey K. L.
Published: July 2010

Wild species and cultivated landraces from the center of crop origin may provide new sources of resistance to a variety of plant diseases that plague genetically uniform crops around the world. This study was conducted to assess resistance to Canadian isolates of three foliar pathogens [Cochliobolus sativus (Ito & Kurib.) Drechsl. ex Dastur., Pyrenophora teres (Died.) DrechsL f. teres, and P. teres, f. maculata] in wild and cultivated landrace barley [Hordeum vulgare L. subsp. spontaneum (C. Koch)Thell. and H. rulgare L. subsp, vulgare] from Turkey and Jordan and to determine whether disease resistance was preserved by in situ conservation of the two barley species. Seedlings were inoculated separately with the pathogens in growth cabinet tests. More wild barley accessions were resistant to C. sativus (4.5% vs 0.3%) and P. teres f. teres (21.8% vs. 0.5%) than cultivated barley. An equal number of wild and cultivated barley accessions was resistant to P. teres f. maculata. A larger percentage of wild barley accessions (10.5%) had at least moderate resistance to all three leaf diseases compared to only 1.3% in cultivated barley. The average disease rating on these accessions was lower for wild barley (65%) but not significantly different from cultivated barley (73%). Chi‐square statistics showed significant associations for disease reactions of (i) C. sativus with P. teres f. maculata, and (ii) P. teres f. teres with P. teres f. maculata that were larger in cultivated barley, indicating stronger associations due to agricultural selection. Disease reactions were independent for C. sativus and P. teres f. teres in both wild and cultivated barley. In situ conservation of cultivated barley in the Middle East was successful in preserving resistance in either single or multiple combinations in cultivated landrace populations, but it was less effective in preserving the diversity for resistance than in wild barley.
Post‐Harvest Seed Dormacy Effects on Kleingrass Germination Following Simulated Digestion by Cattle
Authors: Ocumpaugh W. R. , Tischler C. R. , Valle L. S.
Published: July 2010

Grass seed germinability declines linearly with increased exposure to in vivo and in vitro digestion, but the factors that regulate loss of seed germinability are unknown. One potential mechanism of seed survival during digestion is seed dormancy. A recently developed in vitro procedure to simulate grass seed passage through the digestive system of cattle (Bos spp.) has permitted the evaluation of mechanisms controlling seed germinability following digestion. Our hypothesis was that ‘Selection 75’ kleingrass (Panicum coloratura L.) seed with a high level of post‐harvest dormancy would withstand the negative effects of digestion better than TEM‐LD1 kleingrass seed with a low level of post‐harvest dormancy. Seed harvested in 1991 and 1992 was frozen to maintain dormancy status and subjected to 24, 48, and 72 h of in vitro digestion each year. Germinability was tested in half of the seed immediately following digestion, and half was stored at 24°C to allow for natural loss of dormancy. When germinated immediately following digestion, Selection 74 seed maintained most of its dormancy and germinated poorer than TEM‐LD1 kleingrass seed. However, after 6 to 8 mo of storage, digested seed of both genotypes exhibited similar linear declines in germination with increased digestion time. Seed of TEM‐LD1 digested for 48 or 72 h and then stored for 6 to 8 mo, germinated 15 to 25 percentage units poorer than similarly digested seed without storage. We concluded that post‐harvest seed dormancy of kleingrass is not an effective mechanism for maintaining viability of seeds when passed through the digestive system of cattle; however, such dormancy probably is a factor in maintaining seed viability after it is excreted.
Inheritance of Peanut Testa Colors Involved in Market Acceptability
Authors: Branch W. D.
Published: July 2010

The only acceptable testa colors in the U.S. peanut (Arachis hypogaea L.) market are tan, pink, and red. A better understanding of peanut testa color genetics would be helpful to breeders in developing new cultivars to meethese marketing parameters for human consumption. The objective of this study was to gain further knowledge on the inheritance of these very important testa colors. Six single crosses using three tan testa germplasm accessions (PI 203395, PI 203396, and PI 203397) as female parents and two new peanut cultivars (Georgia Runner and Georgia Browne) as male parents were made in 1989. Seed harvested from F1, F2, and F3 generations were classified during 1990, 1991, and 1992, respectively, for testa color, and data were analyzed for goodness‐of‐fit to expected genetic ratios. Testa color segregation fit a 15 tan + pink:l red F2 ratio, which confirmed a duplicate recessive loci model for red testa color. Genotypes, R2R2r3r3 and r2r2R3R3, are proposed for the three germplasm and the two Georgia parental peanut lines, respectively.
Using Best Linear Unbiased Predictions to Enhance Breeding for Yield in Soybean: II. Selection of Superior Crosses from a Limited Number of Yield Trials
Authors: Panter D. M. , Allen F. L.
Published: July 2010

Economic constraints on many plant breeding programs have forced breeders to limit the number of environments for performance testing of new genetic material. The use of best linear unbiased predictions (BLUP), which augments predictions of individuals by using observations on their close relatives, should provide improved predictions of performance under such conditions. The objectives of this study were to determine (i) whether BLUP values were more precise predictors than least squares means [i.e, best linear unbiased estimates (BLUE)] from soybean [Glycine max (L.) Merr.] yield trials conducted in one or two environments, and (ii) how much improvement in the precision of BLUP could be gained by inclusion of historical parental data. Bulks and lines of 24 soybean crosses and four check cultivars were evaluated at 11 different environments in Tennessee to estimate the mean seed yield of each cross and cultivar. Historical yield records on parents of each cross were compiled from trials conducted in Tennessee from 1982 through 1990. Using subsets of the 11 environments, we predicted yield using three methods: (i) BLUE, (ii) BLUP(NP), without parental data, and (iii) BLUP(P), with parental data. Standard errors of differences (S‐d) and rank correlations (rs) between the actual and predicted mean yields showed that either method of BLUP was superior to BLUE for providing precise yield estimates. Because of the high genetic relationships among the crosses used in this study, including historical parental information did little to increase the precision of BLUP(P) over BLUP(NP).
Abscisic Acid and Putrescine Accumulation in Chilling‐Tolerant Rice Cultivars
Authors: Lee Tse‐Min , Lur Huu‐Sheng , Chu Chun
Published: July 2010

Rice (Oryza sativa L.) frequently confronts chilling injury at seedling stage when it is grown in early spring in temperate and subtropical areas. Understanding the physiological and genetic bases of chilling resistance should benefit our improvement of tolerance of rice seedlings to the stress. Previous study revealed that an accumulation of abscisic acid (ABA) or polyamines in rice seedlings responding to low temperature may be correlated with the chilling resistance of seedlings. The objective of this study, using rice seedlings with various genetic backgrounds, was to explore the relationships among the capacity of accumulation in ABA, putrescine, and chilling tolerance. Changes in ABA and putrescine levels in shoots and roots of seedlings after chilling treatment (5°C) were measured and compared among 11 rice cultivars ranging from chilling‐tolerant to sensitive. On exposure of seedlings to chilling, ABA and putrescine accumulated rapidly in both shoots and roots of chilling‐tolerant cultivars. Changes in ABA levels were closely correlated with chilling tolerance of the tested cultivars (r = 0.96 in shoots and 0.92 in roots). Changes of putrescine levels in shoots were also positively correlated with the cultivar resistance to chilling (r = 0.95). Furthermore, among the tested cultivars, there was also a high correlation between the relative changes of ABA and putrescine in shoots. Our results suggest chilling‐induced changes in ABA and putrescine levels may be used as physiological markers for chilling tolerance of rice seedlings.
Differential Accumulation of Carbohydrates in Alfalfa Cultivars of Contrasting Winterhardiness
Authors: Castonguay Yves , Nadeau Paul , Lechasseur Pierre , Chouinard Lucette
Published: July 2010

Soluble sugar composition and starch reserves are significantly altered during cold hardening of alfalfa (Medicago sativa L.). We characterized the relationship between carbohydrate composition of the crown and freezing tolerance in cultivars of contrasting winterhardiness during their acclimation to low temperature under controlled (two cultivars) and natural hardening conditions (three cultivars in 1991–1992 and six cultivars in 1992–1993). During hardening under environmentally controlled conditions, freezing tolerance and crown levels of soluble sugars increased significantly with a concomitant decrease in starch. Differences in freezing tolerance between a cold‐tolerant and a cold‐sensitive cultivar were closely associated to the accumulation of the oligosaccharides raffinose and stachyose but were not related to the levels of sucrose. Incubation of prehardened plants at subzero temperatures (−2°C) increased freezing tolerance and promoted higher accumulations of sucrose, raffinose, and stachyose and further reduction in starch levels. Under natural hardening conditions, sucrose concentration in crowns was poorly related to the differences in midwinter levels of freezing tolerance between cultivars. Stachyose and raffinose accumulated later in fall than sucrose and reached higher levels in winterhardy than in nonhardy cultivars. Our results show that the accumulation of sucrose, stachyose, and raffinose and the decrease in glucose, fructose, and starch levels are temporally related to the development of freezing tolerance in alfalfa. However, differences in the maximum level of freezing tolerance between nonhardy and winterhardy cultivars are better related to the capacity of the plants to accumulate stachyose and raffinose than to accumulate sucrose.
Performance of Blends of Soybean Cyst Nematode Resistant and Susceptible Cultivars
Authors: Anand S. C. , Koenning S. R. , Sharma S. B.
Published: July 2010

Use of soybean cyst nematode (SCN), (Heterodera glycines Ichinohe), resistant cultivars of soybean [Glycine max (L.) Merr.] is common practice to control losses due to this pest. The experiment was conducted to compare blends of resistant and susceptible cultivarswith their yield response when grown in pure monoculture stands. Two SCN‐resistant cultivars Bedford and Bradley, three susceptible cultivars or breeding lines, Essex, York, and N79‐491, and blends of resistant and susceptible cultivars (50:50 ratio) were tested against soybean monoculture in a SCN Race 14‐infested field. The mean yield (over 5 yr) of Bedford, Bradley, Essex, York, and N79‐491 grown in monoculture was 1707, 1703, 903,1063, and 1379 kg ha−1, respectively. Yield of blends were generally similar to their resistant cultivar components in monoculture but they were always greater (P = 0.05) than the susceptible cultivar components. The Bedford and Essex blend resulted in the greatest yield, which was 672 kg ha−1 (51%) greater than the mean of component crop yields in pure stand. The race designation of the SCN population changed from Race 14 to Race 5 when resistant Bedford and Bradley were grown, from Race 14 to 9 when susceptible cultivars were grown, and from Race 14 to 2 in plots containing blends of resistant and susceptible cultivars or lines. Resistant cultivars grown with susceptible cultivars or lines in blends had lower numbers of cysts on the roots 30 d after planting than resistant cultivars grown in pure stands. Blends of resistant and susceptible cultivars can maintain soybean yields at acceptable levels by minimizing the selection pressure on the nematode population for their ability to parasitize resistant cultivars.
Analysis of Diallel Crosses among Colombian Landraces and Improved Populations of Maize
Authors: Pérez‐Velásquez J. C. , Ceballos H. , Pandey S. , Díaz‐Amaris C.
Published: July 2010

Few of the world's maize (Zea mays L.) germplasm collections have been systematically evaluated in spite of the recognized necessity of broadening the germplasm base of this crop. Knowledge of new heterotic patterns and the breeding potential of maize collections stored in gene banks can contribute to a widening of the genetic base. The objectives of this study were to (i) evaluate the breeding potential eight tropical maize germplasms, and (ii) provide further information to clarify the relationships among them. Five Colombian landraces (‘Andaqui’, ‘Común’, ‘Costeñio’, ‘Puya’, and ‘Yucatán’) and three improved maize populations (‘Tuxpeñio‐1’, ‘Suwan‐1’, and ‘ETO’) were crossed in a diallel mating system. The parents and the 28 hybrids were evaluated in six environments for grain yield, days to 50% silking, prolificacy, and ear height. Cuitivar (additive) and heterotic effects were highly significant (P ≤ 0.01) for all traits except ear height. Significant (P ≤ 0.05) cultivar heterosis and specific heterotic effects were found for grain yield, with an average 10% high‐parent heterosis. Cultivar effects were positive for Suwan‐1 (0.86**) and Tuxpeño‐1 (0.62**) and negative for Andaqui (−0.42*) and Puya (−0.78**). The same materials showed significant cultivar heterotic effects (0.29**, 0.12*, −0.23″*, and −0.22**, respectively). Specific heterosis was found in crosses between Tuxpeñio‐1 and Común (0.44″*), Yucatán (0.35*), and Suwan‐1 (−0.67**). The best materials were improved populations, Suwan‐1, and Tuxpeñio‐1. The ETO population did not perform well per se or in hybrid combinations. Yucatán outyielded ETO and was a parent in two of the three highest yielding crosses. The hybrid Tuxpeñio‐1 × Yucatán showed the highest high‐parent heterosis value (25%**). Results generally agreed with the reported relationships among the parents and pointed to Yucatán as a potentially useful genetic resource for tropical maize breeding programs.
Non‐Destructive Measurements of Canopy Volume to Estimate Grazing Activity
Authors: Stringer W. C. , Bridges W. C. , Pinkerton B. W. , Chrestman R. E. , Rice J. S.
Published: July 2010

Assessing livestock preference for entries of forage breeding programs is important because livestock defoliate plants discriminantly, and thus influence plant competition and survival. We compared seven non‐destructive methods for evaluating tall fescue (Festuca arundinacea Schreb.) defoliation. Cross‐section, height, and spread measurements from a grid; hemisphere, cube, and cylinder formulae applied to height and diameter; and settling plate measurements were regressed against non‐subjective determinations using a plane table. The hemisphere equation applied to height and diameter assessed defoliation best. Coefficients of determination ranged from 0.07 to 0.85 for the plate method and hemisphere formula respectively. Our results reflect vegetative plants. Other methods may be better for taller plants.
Recurrent Selection for Grain Yield in Durum Wheat
Authors: Olmedo‐Arcega O. B. , Elias E. M. , Cantrell R. G.
Published: July 2010

Considerable improvements of durum wheat (Triticum turgidum L. var. durum) genotypes with better yield have been achieved with different breeding methods. Because of several constraints in its application in small cereals, recurrent selection in durum wheat has not been used extensively. The objectives of this research were to evaluate two cycles of recurrent selection for grain yield and to assess effects of selection on other agronomic and yield‐component traits. Nineteen semidwarf durum wheat genotypes selected for high yield and broad genetic diversity, were intercrossed to form the base population. Fifty‐five randomly selected S2 lines from three cycles of selection and a set of four checks were planted in two 1989 and three 1990 environments, respectively. Genotype × environment interactions were generally of magnitude rather than of rank order changes for traits evaluated and therefore a combined analysis across environments was performed. Regression analysis indicated an average increase in yield of 0.25 ± 0.03 Mg ha−1 per cycle of selection. Cycle 2 (C2) produced lines with grain yield higher than any line in Cycles 0 (C0) or 1 (Cl). Test weight and plant height increased 8.39 ± 2.01 Kg m−3 and 2.62 ± 0.3 cm per cycle, respectively. Recurrent selection for grain yield did not affect spikelets per spike and kernels per spike. Kernel weight increased 2.8 mg from C0 to C2. When calculated as a percentage of the total variance, the genetic variance of most of the evaluated traits decreased slightly. Genotype × environment variance was the most important component of variances of five of the evaluated traits. The efficiency of recurrent selection for yield was demonstrated. Indications are that recurrent selection solely for yield did not have any negative correlated response to unselected traits.
RFLP and Cytogenetic Analyses of Hybrids between Festuca mairei and Lolium perenne
Authors: Chen C. , Sleper D. A. , West C. P.
Published: July 2010

Information is lacking on the genomic relationships between Festuca mairei St. Yves and Lolium perenne L. Tetraploid (2n = 4x = 28, where x = the related affinity of the more closely related genome) F. mairei, diploid (2n = 2x = 14) L. perenne, and their intergeneric hybrids were used to determine their genomic relationships based on RFLP patterns of parental species and meiotic chromosome pairing of the hybrids. Among 41 heterologous probes randomly chosen from a F. arundinacea PstI‐genomic library, 70 and 87% hybridized to L. perenne and F. mairei, respectively. However, different restriction patterns occurred between the two species, indicating their distant relationship. Eighteen triploid (3x) and two tetraploid hybrids between F. mairei and L. perenne were obtained. The formation of 4x hybrids from 4x × 2x crosses confirmed that L. perenne is a 2n pollen producer. Triploid and tetraploid hybrids had high levels of chromosome pairing with an average of 6.60 and 11.62 bivalents, respectively. Optimization analysis of meioses in 3x and 4x hybrids strongly confirmed that F. mairei is a fragmented allotetraploid with MMM′M′ genomes. The M genome is closely related to the M′ genome. The L genome of L. perenne is, however, distantly related to the M and M′ genomes.
Temperate Maize Inbreds Derived from Tropical Germplasm: II. Inbred Yield Trials
Authors: Uhr David V. , Goodman Major M.
Published: July 2010

Tropical maize (Zea mays L.) is a germplasm resource that may contribute genes for high yield and disease resistance to temperate breeding programs. Yet, this resource has not been utilized extensively, mainly because of the poor agronomic performance and photoperiod sensitivity that often accompany tropical germplasm. The objective of this study was to determine the agronomic performance of 95 inbred lines derived in North Carolina from 100% tropical germplasm. Ninety‐five lines were derived from seven tropical commercial hybrids and intercrosses among them, using two complete cycles of pedigree selection. Visual selection emphasized early flowering, silk‐tassel synchrony, low ear placement, standability, prolificacy, and ear quality. The inbreeding coefficient of plants within these lines was 0.96 to 0.98. Agronomic performance was evaluated in inbred yield trials during 1990 at three locations. Grain yields ranged from 0.68 to 3.76 Mg ha−1. The highest yielding check inbred, NC252 (an improved B73), yielded 3.65 Mg ha−1, slightly less than the best experimental inbred. Mean percent stalk lodging ranged from 0 to 16%, and root lodging was infrequent. Grain moisture at harvest was mostly within the range of the checks. The genetic correlation between grain yield and number of ears per plant was 0.72, while the correlation between grain yield and moisture was not significant. Several fines possessed excellent combining ability and inbred performance. The best line, 1497‐2, produced testcrosses competitive with the best commercial hybrids and as a line per se performed as well as the best public inbreds available for North Carolina.
Evaluation of Onion (Allium cepa L.) Seed after 10 Years of Storage at 5, −18, and −196°C
Authors: Stanwood P. C. , Sowa S.
Published: July 2010

Long‐term storage strategies for seed germplasm are needed to assure preservation of diminishing plant genetic resources. Cryopreservation in liquid nitrogen (−196°C) is being studied as a potential method to reduce the rate of seed deterioration and thus increase the storage life of the seed. Onion (Allium cepa L.) seed was stored for 10 yr at 5, −18, and −196°C (liquid nitrogen) and evaluated for germination, seedling root length, electrolyte leakage, and O2 uptake to determine long‐term storage response. Average germination of seed stored at −18 and −196°C did not decline over the 10 yr period, while germination of seed stored at 5°C dropped from 94 to 68%. Variation in moisture content was observed in seed stored at 5 and −18°C, with no variation noted at the −196°C‐storage temperature. The variation in moisture content may have influenced seed deterioration at the 5°C‐storage temperature. It is less likely that the variation in seed moisture content was a contributing factor at the −18°C‐storage temperature. Electrolyte leakage results, an indication of seed membrane integrity, were inconclusive. Average seedling root lengths of 2.8, 5.7, and 6.6 mm and seedling O2 uptake rates of 124, 156, and 176 pmol mg−1 min−1 (5, −18, and −196°C storage, respectively) were observed, suggesting less physiological deterioration at the −196°C‐storage temperature. Based on seedling root length, O2 uptake rates, maintenance of seed moisture content and seed germination, it was concluded that seed deterioration was greater at 5 > −18 > −196°C. Maintenance of seed germplasm at 5°C in this experiment was not satisfactory. Liquid nitrogen and −18°C storage for up to 10 yr was acceptable. Cryopreservation of seed germplasm appeared to result in superior seed vigor compared with the −18°C storage; however, longer‐term experiments are needed to determine if cryopreservation results in extended seed preservation.
Chloroplast DNA Similarity of Smooth Bromegrass with Other Pooid Cereals: Implications for Plant Breeding
Authors: Pillay Michael
Published: July 2010

Restriction site (RS) variation in the chloroplast genome has been useful in discerning evolutionary relationships. This information enables plant breeders to determine the primary, secondary, and tertiary gene pools of crop plants. In this study, chloroplast DNA (cpDNA) RS maps of smooth bromegrass (Bromus inermis Leyss.) were compared with those of wheat (Triticum aestivum L.), rye (Secale cereale L.), barley (Hordeum vulgare L.), and oat (Arena sativa L.). The number of common RS for the enzymes KpnI, PstI, PvuII, SalI and XhoI was scored, providing data to calculate the genetic distance (p) among the taxa. Clustering analysis showed that smooth bromegrass (tribe Bromeae) is very closely related to wheat, rye and barley of the tribe Triticeae and more distantly related to oat (tribe Aveneae). It was of interest to find that smooth bromegrass was more closely related than barley to wheat and rye. The cpDNA relationships suggest that bromegrasses are a potentially important component of the gene pool in the breeding of pooid cereals. Bromegrasses are a useful source of genes for disease resistance, agronomic properties, and nutritional value that could be introgressed into their close relatives.
Production and Identification of Chromosome Specific RAPD Markers for Langdon Durum Wheat Disomic Substitution Lines
Authors: Wang Richard R‐C. , Chen Jianli , Joppa Leonard R.
Published: July 2010

Random amplified polymorphic DNA (RAPD) analyses were performed with DNA extracted from a complete set of Langdon durum wheat (Triticum turgidum L. var. durum) disomic substitution lines and their parents (Langdon and ‘Chinese Spring’) with the objective of assigning chromosomal locations for RAPD markers. Seven out of 12 arbitrary decamer primers yielded 11 products that could be assigned to a specific chromosome of the A‐ or B‐genome from Langdon durum or to a D‐genome chromosome of Chinese Spring. The 11 RAPD markers were assigned to three A‐genome, five B‐genome, and one D‐genome chromosome. Chinese Spring ditelosomic lines were used to assign four RAPD markets to specific chromosome arms. Most of the markers were present in both Chinese Spring and Langdon, but one was genotype specific (e.g., J11c was present on Langdon chromosome 1B only). These reproducible RAPD markers of specific wheat chromosomes are additional tools for genome mapping.
Selection for Persistence of Tetraploid Ryegrasses and Festulolium in Mixture with Perennial Legumes
Authors: Novy Elissa M. , Casler M. D. , Hill R. R.
Published: July 2010

Forage ryegrass species (Lolium spp.) are seldom utilized in north central and northeastern U.S. hay and pasture systems because of poor persistence in mixtures with common forage legumes. This study was conducted to (i) evaluate genetic responses to one cycle of phenotypic recurrent selection for persistence in tetrapioid perennial ryegrass (L. perenne L.), intermediate ryegrass (L. hybridum Hausskn.), and the meadow fescue (Festuca pratensis Hudson) × Italian ryegrass (L. multiflorum Lam.) intergeneric hybrid, festulolium (Festulolium braunii K.A.), and (ii) identify specific adaptation responses of these populations selected in mLxture with alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and birdsfoot trefoil (Lotus corniculatus L.). Surviving ryegrass and festulolium plants were selected in 1986 after 3 yr of hay production in mixtures with alfalfa, red clover, and birdsfoot trefoil at Arlington, WI, and Rock Springs, PA. The ability of Cycle 1 progeny to persist with each legume species was compared with those of parental cultivars in 1989, 1990, and 1991 at Arlington and Marshfleld, WI. Selection resulted in an increase in mixed‐stand performance for perennial and intermediate ryegrass; grass ground cover increased by 5.2 and 3.6 percentage units for perennial and intermediate ryegrass, respectively, and the perennial ryegrass component of mixtures increased by 69 g kg−1. Mixture yield was usually unaffected by selection. Evidence for adaptive responses of the ryegrasses and festulolium to specific legume species was scant and inconsistent. Nevertheless, heritable variation for persistence in mixture with legumes was found, suggesting that small gains can be made toward breeding ryegrasses for improved adaptation to Wisconsin.
Carbon and Nitrogen Supply during Seed Filling and Leaf Senescence in Soybean
Authors: Hayati R. , Egli D. B. , Crafts‐Brandner S. J.
Published: July 2010

Leaf senescence and N redistribution during seed filling may limit soybean [Glycine max (L.) Merr.] yield by restricting the seed filling period. Experiments were conducted in the field and greenhouse to evaluate the relationship between seed N demand and leaf senescence. Plants (cv. McCall) were grown under shade cloth (which reduced insolation by 63%) from R1 to R5 (beginning seed fill), then the shade was removed from some plants with the objective of increasing photosynthesis, seed dry matter, and N accumulation. Experiments included plants grown in soil with no nodules (NO−3 as primary source), plants grown in soil with many nodules (N from NO−3 and N2 fixation), and in a hydroponics system (NO−3 as primary N source) where N was removed from the media at R5. Increasing photosynthesis at R5 increased seed dry matter accumulation and the response was larger when N was available. Seed N accumulation also increased if N was available. Increasing photosynthesis had no effect on seed N accumulation when N was not available to the plant. Temporal changes in chlorophyll and N of an upper leaf were measured to characterize leaf senescence. Increasing photosynthesis did not accelerate leaf senescence in any of the treatments. If N was available, N uptake increased when photosynthesis increased. If N was not available, seed N concentration decreased. The data suggest that leaf senescence does not occur because of seed N demand, but may be regulated by processes in the leaf.
White Clover Growth and Morphology under Contrasting Cutting Regimes
Authors: Brink G. E.
Published: July 2010

Climatic conditions contribute to reduced white clover (Trifolium repens L.) productivity and plant survival in the southeastern USA, particularly during the summer. Our objective was to determine the influence of cutting height and frequency on yield and plant morphological traits associated with survival of white clover under humid‐subtropic conditions. Regal (large‐leaf), Louisiana S‐1 (medium‐largeleaf),and Grasslands Huia (medium‐small‐leaf) white clover were sown on a Catalpa silty clay (fine, montmorillonitic, thermic Fluvaquentic Hapludoll) and were cut every 7, 28, and 49 d at a 2.5‐ and 10‐cm stubble height from March to November. Forage yield was measured at each harvest. Stolon growth and branching (growing point density; GPD) and post‐harvest leaf area index (LAD were measured in May, August, and November. Dry matter (DM) yield measured by season (spring, summer, and autumn) increased as leaf size increased and cutting height decreased. The effect of cutting height on stolon DM was opposite that of its effect on DM yield. After the spring, stolon DM of all cultivars was reduced by harvesting at 2.5‐ vs. 10.0‐cm stubble, regardless of cutting interval. Within a cutting height, increasing the harvest interval from 7 or 28 to 49 d generally resulted in greater stolon DM accumulation by autumn. During much of the growing season, there was a positive association between stolon GPD and post‐harvest LAI. Our results suggest that close defoliation of white clover (2.5‐cm stubble) during the summer and autumn detrimental to plant survival, particularly when combined with a short (7‐d) defoliation interval.
Genetic Analysis of Fertility Restoration in Wheat Using Restriction Fragment Length Polymorphisms
Authors: Ma Z. ‐Q. , Sorrells Mark E.
Published: July 2010

Fertility restoration for Triticum timopheevi Zhuk. cytoplasmic male sterility in wheat (Triticum aestivum L.) is controlled by both major fertility restorer (Rf) genes and modifier genes together with environment effects. Therefore, the breeding of efficient and stable malefertility restorer lines (R‐lines) should be facilitated by marker‐assisted selection. This study was conducted to identify restriction fragment length polymorphism (RFLP) markers for the Rf genes, Rf1 and Rf4 in restorer line R113, and Rf3 and a Rf gene on 5D in cultivar Primepi.Polymorphic markers were mapped in testcross F1 populations and their association with fertility restoration was analyzed by analysis of variance. The results indicated that Rf4 was linked to Xksug48 located on 6BS in Rl13, Rf3 was linked to Xbcd249 and Xcdo442 on 1BS, and Xcdo786 may be associated with the 5D Rf gene in Primepi. In addition, in Rl13 two other chromosome regions with fertility restoration‐associated loci were detected by CD0786 and H1 on 5AL and CDOl189 on 7BS. A locus on 5DS, detected by BCD1871, showed significant epistatic effect on the expression of Rf genes. In Primepi, a locus on 5AL, detected by Xbcd183 and Xbcd876, had effects similar to Xcdo786. Two loci in ‘Qu Xian Early A’, identified by Xbcd871 and Xwg1026, may be associated with genes controlling ease of restoration in this male‐sterile line (A‐fine). Except for Xbcd1871 and Xwg1026, the effects of other significant RFLP loci were additive in both populations.
Defoliation Effects on Rhizoma Perennial Peanut Rhizome Characteristics and Establishments Performance
Authors: Rice R. W. , Sollenberger L. E. , Quesenberry K. H. , Prine G. M. , French E. C.
Published: July 2010

‘Florigraze’ rhizoma perennial peanut (RPP; Arachis glabrata Benth.) is a high‐quality forage legume vegetatively propagated by rhizomes. The impact of prior RPP defoliation management on rhizome chemical composition and growth after planting is not understood. These two studies, conducted on a Gressarenic Paleudult soil, evaluated the effects of grazing on (i) rhizome mass, total nonstructural carbohydrate (TNC), and N concentration, and (ii) rhizome establishment performance following planting. Rhizomes for both studies were obtained from pastures previously grazed at different combinations of rest interval length (d) and quantity of residual dry matter remaining after grazing (kg ha−1). Specific rest interval‐residual dry matter combiuatious (21‐500, 63‐500, 42‐1500, and 63‐2500) were chosen to represent a wide range of grazing severity. An ungrazed treatment (No‐Grz) was also included. Average rhizome mass was greatest (17.0 Mg ha−1) for No‐Grz and declined as grazing severity increased from 63‐2500 (9.4 Mg ha−1) to 21‐500 (2.3 Mg ha−1). Grazing treatments also provided rhizome planting material with a wide range of TNC concentration (62‐301 g kg−1) and N concentration (12.7‐22.1 g kg−1 Greatest concentrations were observed for No‐Grz and less severely grazed pastures. Planting rhizomes with initial TNC ≥ 228 g kg−1 and N ≥ 20 g kg−1 resulted in the greatest seasonal accumulation of both rhizome and shoot mass. Planting rhizomes with low TNC (62 kg−1; 21‐500) resulted in stand failure in a drought year (1990). Rhizomes with higher TNC (139 g kg−1; 63‐500) produced shoots that survived drought conditions but growth rates were relatively slow. We conclude that grazing affects chemical composition of RPP rhizomes and that chemical composition of planting material is a major determinant of RPP establishment success.
Effect of Pollen Selection for Alachlor Tolerance in Maize
Authors: Frascaroli E. , Landi P. , Villa M. , Sari‐Gorla M.
Published: July 2010

Pollen selection can lead to correlated responses in the subsequent sporophytes because many genes are expressed in both haploid and diploid phases. This study was conducted to evaluate the effects of pollen selection for tolerance to the herbicide alachlor [2‐chloro‐N‐(2,6‐ diethylphenyl)‐N‐(methoxymethyl) acetamide] in maize (Zea mays L.). Tassels of the single cross hybrid K55 (tolerant) ✕ Ky226 (susceptible) were grown in absence (control) and in presence (selected) of alachlor (I g L−1). Mature pollen from this process was used to make backcrosses to Ky226 (susceptibility being recessive). The selected population outperformed the control population (88 vs. 81%; P ≤ 0.01) for percentage of normal seedlings (i.e., not injured by alachlor) when compared in a field trial treated with the herbicide (5 kg a.i. ha−1). Pollen of plants grown without alachlor was analyzed in vitro; in presence of the herbicide in the medium (50 mg L−1) the selected population exceeded the control population for pollen tube length (334 vs. 308 μm; P ≤ 0.01). Two cycles of pollen selection were also conducted in the single cross hybrid KS5 ✕ H99 (susceptible) following the backcross procedure to the susceptible parent. Seeds of control and selected populations were exposed to alachlor (I g L−1), and seedlings were grown in the greenhouse. For percentage of normal seedlings, we obtained a gain (16%) in the first cycle and an additional gain (10%) in the second cycle. The results indicate that genes controlling alachlor tolerance in maize are expressed in both haploid and diploid phases and that pollen selection can be effectively applied to improve the trait.
Backcrossing and Intermating in an Exotic × Adapted Cross of Maize
Authors: Hoffbeck M. D. , Openshaw S. J. , Geadelmann J. L. , Peterson R. H. , Stuthman D. D.
Published: July 2010

Incorporation of exotic germplasm into the U.S. maize (Zea mays L.) germplasm pool has often been proposed. Backcrossing and intermating were studied as techniques for incorporation of exotic germplasm using the populations AS‐A and MN‐ETO. Three levels of backcrossing (0, 1, and 2 backcrosses) and cycles of intermating (1, 3, and 5 cycles) were examined in all combinations by extracting 100 random S1 lines from each treatment for field evaluation. All lines were evaluated for eight traits in six environments. Data for grain yield, grain harvest moisture, lodging, plant height, ear height, number of days to 50% silk emergence, number of days to 50% pollen shed, and a selection index (SI) [SI = grain yield (kg ha−1) −18.8 × harvest moisture (g kg−1)] were analyzed. Analyses on trait means, genetic variances, correlated responses, selection differentials, and frequency distributions indicated that backcrossing generally shifted means and resulted in smaller genetic variances. Phenotypic correlations were both increased and decreased depending on the comparison examined. Changes of selection differentials of secondary traits were consistent with phenotypic correlations. The effect of backcrossing on the means of selected and unselected lines was very similar. Many changes were maturity related. Intermating levels used had no detectable effect on the populations. Significant differences were found, but these were isolated and did not form trends across intermating levels or backcross treatments. The results of this study suggest that backcrossing is useful in the incorporation of exotic germplasm, but results do not support the use of repeated intermating.
Inheritance of Resistance to the Javanese Root‐Knot Nematode in Soybean
Authors: Luzzi Bruce M. , Tamulonis John P. , Hussey Richard S. , Boerma H. Roger
Published: July 2010

The inheritance of resistance in soybean [Glycine max (L.) Merr.] to the javanese root‐knot nematode [Meloidogyne javanica (Treub) Chitwood] was determined for crosses of a susceptible genotype, ‘CNS’, with three resistant genotypes, ‘Gordon’, PI80466, and PI230977. For each cross, F1, F2, and/or F3 populations were screened in a greenhouse for resistance to gall formation by counting individual galls on the roots of plants inoculated with nematode eggs. The distribution of galls for each F2 and/or F3 population was continuous. Variance component heritability estimates for the three crosses ranged from 0.23 to 0.51 on a plot basis and 0.48 to 0.76 on a mean basis. The correlation between gall number on F2 plants and mean gall number on F3 progeny (heritability on a plant basis) was 0.26 for CNS × Gordon and 0.29 for CNS × PI230977. These data suggest that resistance to M. javanica in Gordon, PI80466, and PI230977 is quantitatively inherited. The uniqueness of resistance genes was determined for crosses among Gordon, PI80466, and PI230977. Segregation for gall number within F2 populations and significant differences (P 0.05) among F3 families from each cross indicated that each resistant parent may possess M. javanica resistance genes at different loci or different alleles at the same loci. This information can be used to more efficiently develop soybean cultivars with a high level of resistance to M. javanica.
Reversing Drought‐Induced Losses in Grain Yield: Sucrose Maintains Embryo Growth in Maize
Authors: Zinselmeier C. , Lauer M. J. , Boyer J. S.
Published: July 2010

Large losses in yield can occur in maize (Zea mays L.) growing in water‐limited conditions (low Ψw), particularly during flowering and early embryo growth where grain number is decreased. However, embryo growth is maintained where otherwise none would occur if the stems are infused with photosynthate (sucrose) and other nutrients (amino acids, salts, vitamins, and hormones) during exposure to low Ψw. In the present investigation, we deleted or supplied various components of the complete infusion mediumto identify the active solute. Infusions involved making a cavity in a stem internode, filling the cavity with water, sealing the cavity, and connecting the interior of the cavity to an external reservoir of the medium. A field experiment at high Ψw showed that wounds and enhanced nutrient supplies from the infusions did not alter embryo growth or yield. In controlled environment chambers, low Ψw was imposed by withholding water for 6 d beginning 5 d prior to pollinations. A new infusion was made each day for 5 d as the low Ψw developed around pollination. The low Ψw virtually eliminated grain development. Sucrose infusion reversed this loss and no other component of the medium showed activity under our conditions. In plants receiving no sucrose at low Ψw, ovary sucrose content was moderately lower and starch much lower than in controls. In plants receiving sucrose at low Ψw, ovary sucrose content was higher than in controls and starch recovered moderately. The difference in sucrose and starch responses indicates that carbohydrate metabolism was altered in the ovaries at low Ψw. Embryo survival correlated more closely with the content of starch than sucrose. We conclude that there were two effects of low Ψw that contributed to arrested embryo growth: a decreased sucrose flux and an altered carbohydrate metabolism in the ovaries.
Relationship of Soybean Seed Quality to Fatty Acid and C6‐Aldehyde Levels during Storage
Authors: Trawatha S. E. , TeKrony D. M. , Hildebrand D. F.
Published: July 2010

Lipid peroxidation is thought to be an important factor in seed deterioration. This investigation was initiated to determine if changes in free fatty acids and peroxidation products are related to changes in seed quality during soybean [Glycine max (L.), Merr.] seed deterioration. Seed lots of three soybean cultivars (Century, Pennyrile, and Pharaoh) were stored at 20, 30, and 40°C, sampled periodically, and tested for seed germination and vigor. Embryonic axes excised from deteriorated seeds were tested for contents of total and free fatty acids and C6‐aldehydes. Seed vigor, as measured by accelerated aging, conductivity, and cold tests, was the first seed quality component lost in all cultivars and storage environments, followed by a decline in percentage germination. Conductivity of seed leachates increased about two‐fold during storage for all cultivars. The amount of total fatty acids in the lipid fraction did not change, while free linoleic and linolenic acids increased about two‐fold during seed deterioration. E‐2‐hexenal increased two‐fold but hexanal did not change during storage. Both free linoleic acid and E‐2‐hexenal content were correlated with seed quality, but little association was shown between lipoxygenase activity and seed quality. Free fatty acids may have contributed to seed deterioration by disrupting membranes and/or by toxicity of subsequent peroxidation products.
Switchgrass Biomass Composition during Morphological Development in Diverse Environments
Authors: Sanderson Matt A. , Wolf Dale D.
Published: July 2010

Production of herbaceous biomass for biofuel seeks to maximize lignocellulose yields and minimize N and mineral (especially K) concentrations in the biomass. Our objective was to relate changes in biomass composition of switchgrass (Panicum virgatum L.) to thermal time [degree days (DD), base = 10°C] in several environments. ‘Alamo’ switchgrass at Stephenville, TX, was sampled weekly or every 2 wk from April to June in 1989 and April to September in 1990, 1991, and 1992. Field plots of Alamo and ‘Cave‐in‐Rock‘ at Stephenville were sampled 17 times during 1993, and at Blacksburg, VA, were sampled on II dates in 1992 and nine dates in 1993 from May to September. Biomass samples were analyzed for lignocellulose, crude protein, total ash, K, and Ca concentrations. Linear and nonlinear regressions were used to relate concentrations of constituents to cumulative DD after burning in spring. Concentrations of each constituent were closely related to cumulative DD and a single equation was able to describe the relationship across several years. At Stephenville, lignocellulose concentrations increased linearly up to 800 to 1000 DD. At Blacksburg, lignocellulose concentrations increased linearly up to 400 to 800 DD after burning. At both locations, the time at which the rapid increase in lignocellulose concentration ended coincided with internode elongation. Crude protein, ash, and K concentrations decreased curvilinearly with accumulated DD. There were no differences in composition between Alamo or Cave‐in‐Rock at Blacksburg. At Stephenville, Alamo had a greater concentration of lignocellulose than did Cave‐in‐Rock, but similar concentatious of crude protein, ash, and K. The close relation between DD and composition of switchgrass could be used for predictive purposes.
Characters Related to Leaf Photosynthesis in Wild Populations and Landraces of Common Bean
Authors: González Alonso , Lynch Jonathan , Tohme Joseph M. , Beebe Stephen E. , Macchiavelli Raúl E.
Published: July 2010

Wild populations of commonb bean (Phaseolus vulgaris L.) vary in characters related to leaf photosynthesis. To investigate if such variation exists in leaf photosynthetic characteristics of landraces, and if wild accessions are similar to landraces within a region of origin, 47 wild populations and 47 landraces were evaluated in two field experiments in Colombia. Young unshaded fully expanded leaves of each accession were used to measure stomatal density, CO2 exchange rates (CER), stomatal conductance, chlorophyll, soluble protein, and N content. As a group Andean accessions (both wild and landraces) had lower specific leaf weight, less chlorophyll, lower CER, lower stomatal conductance, less stomatal density, and higher N content as compared with Mesoamerican accessions. The Andean landraces had the lowest CER as opposed to Mesoamerican landraces which had the highest CER value. For most of the variables measured, univariate analysis of variance within a country of origin suggested that landraces were similar to wild populations. However, cluster analysis that included nine variables formed groups that suggested contrast both between centers of domestication and between wild and cultivated types. Cluster analysis performed for Mexico and Peru identified two major groups that corresponded to wild and landraces within those countries. We conclude that wild populations and landraces differ in characteristics related to leaf photosynthesis, at least in Peru and Mexico. Wild Peruvian populations had higher CER than landraces. Wild Andean and Mesoamerican populations were not different in CER; this is a very interesting observation that suggests that during domestication a decrease in CER occurred in Andean landraces.
Flavonols: Effects on Fertility and Fecundity
Authors: Taylor Loverine P.
Published: July 2010

Flavonols are required for successful fertilization in maize (Zea mays L.) and petunia (Petunia × hybrida Vilm.). Pollen lacking flavonols is unable to produce a functional pollen tube, but this defect can be reversed and pollen function “rescued” by the timely application of kaempferol, a flavonol aglycone. Biochemical complementation of mature petunia pollen is achieved (i) at pollination by wild‐type stigma exudate, (ii) by exogenous application of kaempferol to the stigma or pollen at pollination, and (iii) by supplementing a pollen suspension in germination medium with flavonol aglycones. The last method forms the basis of a sensitive in vitro bioassay used to identify compounds that induce pollen germination. It also provides a model system for a focused and systematic investigation of flavonol‐stimulated pollen germination. In addition to increased understanding of basic flavonol biology in reproductive organs, an unexpected bonus was the finding that plant fecundity can be enhanced by manipulating the levels of flavonol aglycones (kaempferol) in stigmas.