bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Hybrids from Induced × Natural Tetraploids of Russian Wildrye
Authors: Jensen Kevin B. , Larson Steven R. , Waldron Blair L. , Johnson Douglas A.
Published: July 2010

Because of restrictions imposed by hybridization barriers, Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski] breeders have usually limited themselves to selection and hybridization within ploidy levels. Plants of diploid (2n = 2x = 14) Russian wildrye tend to be shorter, finer stemmed, leafier, and generally higher in forage production than tetraploids (2n = 4x = 28), which have larger seeds and superior seedling vigor. The principle objectives of the present study were to combine the genes from diploid and tetraploid Russian wildrye into a stable population, and evaluate variability in chromosome behavior, molecular genetic diversity, forage production, seed characteristics, and seedling vigor of the hybrids. Cytologically, the hybrid population behaved as an autotetraploid averaging 0.50 univalents + 9.37 bivalents + 0.24 trivalents + 1.98 quadrivalents per cell. Narrow‐sense heritabilities were 31, 63, 17, and 23% for dry matter yield (DMY), total seed yield, 100‐seed weight, and rate of seedling emergence, respectively. Coefficients of determination (r2) among parent and half‐sib family means were 0.12, 0.29, 0.09, and 0.72 for the above traits, respectively. Essentially all variation among half‐sib families for rate of seedling emergence was associated with environmental effects. Positive responses to selection pressure for improved seed yield, rate of seedling emergence, and dry matter production were achieved and additional gains are expected. Any major improvement in seed mass would be limited without broadening the genetic base of the hybrid.
Inheritance and Genetic Mapping of Resistance to Rhizoctonia Root and Hypocotyl Rot in Soybean
Authors: Zhao G. , Ablett G. R. , Anderson T. R. , Rajcan I. , Schaafsma A. W.
Published: July 2010

Rhizoctonia root and hypocotyl rot, caused by Rhizoctonia solani Kühn [teleomorph Thanatephorus cucumeris (Frank) Donk], is an important disease of soybean [Glycine max (L.) Merr.]. Planting resistant cultivars would be an effective and environmentally sound strategy to minimize economic losses from this disease. To facilitate developing resistant cultivars, a study was conducted to: (i) investigate inheritance of resistance to Rhizoctonia root and hypocotyl rot in the moderately resistant soybean PI 442031, and four moderately susceptible commercial cultivars and (ii) identify simple sequence repeat (SSR) markers associated with resistance to Rhizoctonia root and hypocotyl rot. Genetic analysis of several segregating populations indicated that resistance to Rhizoctonia root and hypocotyl rot in soybean was quantitatively inherited and controlled by both major and minor genes with additive gene effects. The estimates of broad sense heritability of resistance were low to moderately high. Transgressive segregants with enhanced levels of resistance were developed by crossing adapted but moderately susceptible commercial soybean cultivars. Three SSR markers (Satt281, Satt177, and Satt245) were significantly associated with host resistance in both F2 and F4:5 populations of PI 442031 × Sterling, wherein both parents contributed resistant alleles. This is the first report on mapping of Rhizoctonia root and hypocotyl rot resistance genes in soybean. Our results indicate that marker assisted selection, coupled with phenotypic selection in later generations, should help to facilitate the development of soybean cultivars resistant to Rhizoctonia root and hypocotyl rot.
Oat Caryopsis Size and Genotype Effects on Wild Oat–Oat Competition
Authors: Willenborg Christian J. , Rossnagel Brian G. , Shirtliffe Steven J.
Published: July 2010

The inherent similarity between wild oat (Avena fatua L.) and oat (A. sativa L.) precludes selective herbicide control of wild oat. Previous studies have reported improved crop yield and competitiveness with the use of large seed. Therefore, a greenhouse experiment was conducted in 2002 and 2003 to examine the effect of caryopsis (dehulled kernel) size and genotype on wild oat–oat competition. Seeds of three oat cultivars (AC Assiniboia, CDC Boyer, CDC Orrin) were classified into three size classes based on caryopsis size (large, ≈35 mg; medium, ≈25 mg; and small, ≈15 mg). Whole oat seeds of each genotype and caryopsis size treatment were grown either in monoculture or in mixture with wild oat (250 plants m−2). Neither genotype nor caryopsis size significantly influenced (P < 0.05) oat emergence. Nonetheless, oat plants established from large caryopses produced 17% more biomass (P < 0.001) and 15% more panicles m−2 (P < 0.001) than plants established from small caryopses. Wild oat produced 23% less biomass (P = 0.004) and fewer panicles m−2 when grown with oat plants established from large caryopses. Genotype only influenced oat panicle production (P = 0.05) and did not affect oat (P = 0.09) or wild oat (P = 0.34) aboveground shoot biomass production. These results suggest that oat plants derived from large‐seeded caryopses may be better able to tolerate wild oat interference. However, further investigation is needed to examine the response of oat–wild oat competition to oat caryopsis size and genotype under field conditions.
Associations among International CIMMYT Bread Wheat Yield Testing Locations in High Rainfall Areas and Their Implications for Wheat Breeding
Authors: Lillemo M. , van Ginkel M. , Trethowan R. M. , Hernández E. , Rajaram S.
Published: July 2010

A good understanding of how the target environments for a breeding program differentiate the germplasm with respect to yield is crucial and allows plant breeders to better target their germplasm. To determine the relationships among high rainfall yield testing locations, yield data from 8 yr of CIMMYT's High Rainfall Wheat Yield Trial (HRWYT) were analyzed by shifted multiplicative model (SHMM) and incremental sum of squares (ISS) classification analyses to group sites within and across years. In the cumulative cluster analysis, about half of the sites clustered into a group characterized by increasing temperature toward maturity. The SHMM analysis identified several sites with high overall association with other sites around the world, and which can be considered as good predictors of global yield performance within the high rainfall megaenvironment. These are autumn‐sown locations, which fall into the biggest group of the cumulative cluster analysis with increasing temperature during the growing season. On the other hand, remarkably low associations with global yield ranking were shown for Sta. Catalina (Ecuador) and CIMMYT's primary high rainfall yield‐testing location at Toluca (Mexico), which in contrast experience decreasing temperatures toward maturity. Although excellent sites for disease screening, this analysis shows that they do not associate well with the world's high rainfall wheat growing areas for yield.
Differential Sowing Time of Turfgrass Species Affects the Establishment of Mixtures
Authors: Larsen Søren U. , Andreasen Christian , Kristoffersen Palle
Published: July 2010

Kentucky bluegrass (Poa pratensis L.) is often poorly established when sown in turfgrass seed mixtures with slender creeping red fescue (Festuca rubra L. ssp. litoralis Vasey) and perennial ryegrass (Lolium perenne L.), possibly because of its slow emergence and slow seedling growth. This study investigated the effect of sowing Kentucky bluegrass earlier than red fescue and perennial ryegrass on the botanical composition of the established turfgrass. In field experiments established during 2 yr, red fescue and perennial ryegrass were sown at weekly intervals from zero to 35 d [0–679 degree‐days (°days) with a base temperature of 0°C] after Kentucky bluegrass had been sown in the same plot. Nine or twelve months after establishment, the botanical composition was estimated. When the species were sown simultaneously, Kentucky bluegrass only constituted 3 to 30% of the tillers, although the species constituted 50 to 59% of the viable seeds of the seed mixture. Delayed sowing of red fescue and perennial ryegrass significantly improved the establishment of Kentucky bluegrass, i.e., the percentage of tillers could be increased by up to 0.08% for every °day Kentucky bluegrass was sown before red fescue and perennial ryegrass. There was a corresponding negative effect on the percentage tillers of red fescue and primarily perennial ryegrass. In certain cases, the relationship between percentage tillers and difference in sowing time was better described by a nonlinear function, indicating an increasing effect when difference in sowing time was large.
Tolerance of Seedling Bermudagrass to Postemergence Herbicides
Authors: McCalla J. H. , Richardson M. D. , Karcher D. E. , Boyd J. W.
Published: July 2010

The introduction of improved seeded cultivars of bermudagrass [Cynodon dactylon (L.) Pers.] has generated significant interest from the turfgrass industry. An important component of successfully establishing these new cultivars will be to develop effective weed control strategies for the critical establishment period. A field study and a greenhouse study were conducted to evaluate the tolerance of several seeded bermudagrasses to commonly used postemergence herbicides at different periods of establishment. In a field study, ‘Princess’ bermudagrass was seeded at a rate of 48 kg ha−1 during the early summer of 2000 and 2001. Postemergence herbicides were applied at either 1, 2, or 4 wk after emergence (WAE). Herbicide treatments included MSMA (monosodium salt of methylarsonic acid) at 1.12 kg ha−1, metsulfuron (2[[[[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2yl] amino] carboxyl] amino] sulfonyl]‐2‐benzoic acid) at 0.021 kg ha−1, diclofop ((±)‐2‐[4‐(2,4‐dichlorophenoxy) phenoxy]propanoic acid) at 1.12 kg ha−1, clopyralid (3,6 dichloro‐2‐pyridinecarboxylic acid) at 0.56 kg ha−1, dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) at 0.56 kg ha−1, 2,4‐D amine D [(2,4‐ dichlorophenoxy) acetic acid at 0.56 kg ha−1, and quinclorac (3, 7‐dichloro‐8‐quinolinecarboxylic acid) at 0.842 kg ha−1 Visual injury ratings were recorded at 3, 5, 7, 15, and 30 d after treatment (DAT) and percent turfgrass cover was recorded at 30 and 60 DAT. In the greenhouse study, the same herbicides and treatments were used with the cultivars Princess, Yukon, NuMex Sahara, Jackpot, and Mirage. In both the field and greenhouse studies, there was no clear effect of application timing on the tolerance of seedling bermudagrass to herbicides. Diclofop and metsulfuron caused the highest levels of injury in both years of the field study and in the greenhouse study. The other herbicides tested caused less injury. The bermudagrass recovered from all herbicide injury by 30 d after treatment. The results from this study indicate that seedling bermudagrass is relatively tolerant of many commonly used postemergence herbicides as soon as 1 WAE. These results will be useful to turfgrass managers who are considering use of improved cultivars in various turf situations.
‘Florigraze’ and ‘Arbrook’ Rhizoma Peanut as Pasture for Growing Holstein Heifers
Authors: Garay A. Hernández , Sollenberger L. E. , Staples C. R. , Pedreira C. G. S.
Published: July 2010

‘Florigraze’ and ‘Arbrook’ are the most widely used cultivars of rhizoma peanut (Arachis glabrata Benth.), but performance of ruminants grazing these cultivars has not been compared. The objective of this study was to determine sward characteristics and performance of Holstein replacement heifers (Bos taurus) on continuously stocked pastures of Florigraze and Arbrook growing on a loamy, siliceous, hyperthermic Grossarenic Paleudult soil. Herbage mass and allowance did not differ between cultivars during 3 yr of grazing and averaged 2840 kg DM ha−1 and 2.25 kg of forage kg−1 of animal live weight, respectively. Percentage of Arbrook in pasture herbage mass decreased from Year 1 (89%) to Year 3 (66%), while percentage of Florigraze remained relatively constant (90 to 87%). Average herbage crude protein (CP) concentration and in vitro organic matter digestibility (IVOMD) were greater in Florigraze than in Arbrook (177 vs. 161 g kg−1 and 705 vs. 661 g kg−1, respectively). Average stocking rate varied little between cultivars, and animal performance was generally similar until Year 3. With a much lower percentage of rhizoma peanut in herbage mass for Arbrook than Florigraze pastures in Year 3, average daily gain (ADG; 701 vs. 516 g) and gain ha−1 (575 vs. 418 kg) were greater for heifers grazing Florigraze than for those grazing Arbrook. Florigraze appears better suited for pasture programs with continuous stocking, primarily because of superior persistence, leading to greater animal performance with time.
Growth, Water Relations, and Nutritive Value of Pasture Species Mixtures under Moisture Stress
Authors: Skinner R. Howard , Gustine David L. , Sanderson Matt A.
Published: July 2010

Pasture productivity under harsh environments can be increased by planting more drought‐resistant species or by increasing species diversity. This research was conducted under two large (10.2 × 26.8 m) rainout shelters combined with a drip irrigation system to provide deficit, normal, and excessive moisture conditions. A two‐species mixture containing the relatively drought‐tolerant species, orchardgrass (Dactylis glomerata L.) and red clover (Trifolium pretense L.) and two five‐species mixtures were compared with a mixture containing the drought‐sensitive species, white clover (Trifolium repens L.) and Kentucky bluegrass (Poa pratensis L.), which are the predominant species in northeastern USA pastures. Plots were clipped from mid‐May to early October in 2000 and 2001 on a schedule that mimicked management‐intensive grazing practices. The five‐species mixture containing chicory (Cichorium intybus L.), orchardgrass, Kentucky bluegrass, perennial ryegrass (Lolium perenne L.), and white clover had the greatest dry matter yield at all moisture levels. Yield in that mixture increased 89% in the dry, 61% in the normal, and 43% (by weight) in the wet treatments compared with the white clover/Kentucky bluegrass mixture. Increased yield was primarily due to the robust growth of chicory which dominated the mixture, accounting for 71% of harvested biomass by the fall of 2001. In addition, white clover growing in the mixture with chicory had improved leaf water relations and greater relative growth rates than white clover growing in the two‐species mixture. Including the functional attribute of a deep‐rooted forb appeared to be more important than species richness, per se, in improving forage yield.
Nutritive Value of Virginia Wildrye, a Cool‐Season Grass Native to the Northeast USA
Authors: Sanderson Matt A. , Skinner R. Howard , van der Grinten Martin , Kujawski Jennifer
Published: July 2010

Interest in native plant species for conservation and production has increased because of new federal policies. We evaluated accessions of the native cool‐season grass Virginia wildrye (Elymus virginicus L.) from the northeastern USA for nutritive value and its association with plant morphological traits. Thirteen accessions, one cultivar (Omaha), and one commercial ecotype of Elymus were transplanted into single‐row field plots in late summer of 2000 at Beltsville, MD, Rock Springs, PA, and Big Flats, NY. Two orchardgrass (Dactylis glomerata L.) cultivars were included. Primary growth was harvested in April (Beltsville) or May (Rock Springs and Big Flats) of 2001 and 2002 and analyzed for neutral detergent fiber (NDF), crude protein (CP), and digestible NDF (dNDF). Nutritive value measures were related to plant morphological attributes [leaf width, length, area, and leaf‐to‐stem mass ratio (LSR)]. Virginia wildrye accessions differed (P < 0.01) in nutritive value and often had lower NDF and higher CP and dNDF than the commercial ecotype, Omaha cultivar, and orchardgrass. The LSR accounted for most of the variation in nutritive value. Orchardgrass was more mature at harvest than Elymus entries and thus lower in nutritive value. Neutral detergent fiber was negatively correlated with LSR (r = −0.26 to −0.74, P < 0.05), whereas CP and dNDF were positively correlated (r = 0.36 to 0.80 for CP and 0.44 to 0.74 for dNDF, P < 0.05). Neutral detergent fiber was also positively correlated (r = 0.27 to 0.86, P < 0.05) with leaf length. Virginia wildrye is comparable to other cool‐season grasses in nutritive value.
A Study of Cytology, Isozyme, and Interspecific Hybridization on the Big‐Achene Group of Buckwheat Species (Fagopyrum, Polygonaceae)
Authors: Chen Qing‐Fu , Hsam Sai. L. K. , Zeller Friedrich J.
Published: July 2010

Eleven accessions of eight species belonging to the big‐achene group of genus Fagopyrum Moench were studied on the basis of interspecific hybridization, GOT (i.e., glutamate oxaloacetate transaminase) isozyme band characteristics, and cytology. Following normal pollination, there were high crossabilities (8–37%) among these different species, but all hybrid seeds were empty except the crosses among F. esculentum Moench, F. esculentum var. homotropicum (Ohnishi) Q‐F. Chen (= F. homotropicum Ohnishi), and F. esculentum subsp. ancestrale Ohnishi, indicating that there are no reproductional isolations among F. esculentum, F. esculentum var. homotropicum, and F. esculentum subsp. ancestrale The cytological observation showed that the hybrid F. esculentum × F. esculentum var. homotropicum shows eight normal bivalents in meiosis of pollen mother cells. In addition, the results of GOT isozyme showed that F. esculentum, F. esculentum var. homotropicum, and F. zuogongense possess common GOT isoenzyme bands. Fagopyrum megaspartanium and F. pilus show unique GOT bands as well as karyotypes supporting the classification of individual species. The cytological analyses showed that tetraploid F. cymosum and F. giganteum are allotetraploids with two different size genomes. The identities of the different genomes in the big‐achene group of genus Fagopyrum and the putative progenitors of common buckwheat are discussed.
Diallel Analysis of Spider Mite Resistant Maize Inbred Lines and F1 Crosses
Authors: Bynum Edsel D. , Xu Wenwei , Archer Thomas L.
Published: July 2010

Banks grass mite [BGM; Oligonychus pratensis (Banks)] and the twospotted spider mite (Tetranychus urticae Koch) cause significant yield reductions in maize (Zea mays L.) grown in the Great Plains states. Understanding the inheritance of mite resistance will be useful in developing mite resistant hybrids. A Griffing's Method 2 diallel mating design was used to evaluate the range of resistance and combining ability of parents in F1 crosses of seven mite resistant maize lines (T1, U2, A3, A4, A5, A7, and T9). Parent lines, F1 crosses, and three checks (Mo17, B73 × Mo17, and Pioneer hybrid 34K77) were included in a randomized complete block design with three replications at Halfway, TX, in 2002 and Lubbock, TX, in 2001 and 2002. Following artificial infestations, mite resistance was evaluated for differences in mite infestations and feeding damage. Weekly mite densities and damage samples were used to calculate total mite densities, total damage ratings (TDRs), mite per damage ratio (M/D), and a seasonal damage ratio (SDR). Total damage rating was significant for environments, genotype, and environment × genotype interaction. Total mite density (TMD) and M/D were significant for genotype and environment × genotype interaction. The SDR was significant for environment and genotype, but no interaction. Broad‐sense heritability estimates showed that >90% of the TDR and SDR were associated with genotypic effects. Crosses with T1, U2, and T9 consistently supported larger mite populations, but had higher M/D values than those with A3, A4, A5, and A7, indicating greater tolerance to mite feeding. Crosses between tolerant lines or between tolerant lines and antibiotic lines had overall better resistance than crosses between antibiotic lines. Diallel analyses showed that T1 and U2 had the highest general combining ability (GCA) for reducing damage. T1 × A4, T1 × A7, A3 × A5, and A4 × A7 were the best crosses for specific combining ability (SCA) for resistance to spider mites.
Combining Ability for Resistance to Sclerotinia Head Rot in Sunflower
Authors: van Becelaere Guillermo , Miller Jerry F.
Published: July 2010

Sclerotinia head rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a major disease in sunflower (Helianthus annuus L.). The development of hybrids with adequate genetic resistance is necessary to reduce yield losses caused by this disease. The objective of this study was to estimate the general (GCA) and specific (SCA) combining ability of a set of female and male oilseed sunflower inbred lines in hybrid combinations for resistance to Sclerotinia head rot. Six female and six male lines were crossed in a factorial mating design. The hybrids were planted in three U.S. environments and in Argentina. Plants were inoculated with a suspension containing 5000 ascospores per milliliter. Sclerotinia head rot disease incidence was measured as percentage of plants attacked on a plot basis. The GCA effects accounted for a greater proportion of the treatment sum of squares than the SCA effects, suggesting that additive gene effects were relatively more important than nonadditive gene effects in the phenotypic expression of resistance to Sclerotinia head rot. The importance of additive gene effects suggests that selection could start at the inbred line development stage. However, hybrids should also be tested since nonadditive gene effects were significant in the individual environments and certain hybrid combinations showed higher or lower disease incidence than would be expected based on the average performance of their parents.
The Role of Pericarp Cell Wall Components in Maize Weevil Resistance
Authors: García‐Lara Silverio , Bergvinson David J. , Burt Andrew J. , Ramputh Al I. , Díaz‐Pontones David M. , Arnason John T.
Published: July 2010

The maize weevil (MW), Sitophilus zeamais (Motsch.), is a storage pest that causes serious losses in maize (Zea mays L.) in developing countries. This study was conducted to investigate the role of pericarp cell wall components as factors that contribute to MW resistance in nine genotypes of tropical maize. Six susceptibility parameters to MW were measured and related to cell wall components such as simple phenolic acids, diferulic acids (DiFAs), hydroxyproline‐rich glycoproteins (HRGPs), and nutritional and physical traits. Weevil susceptibility was negatively correlated (P < 0.001) with total DiFAs (r = −0.77), HRGPs (r = −0.82), grain hardness (r = −0.87), pericarp/whole kernel (P/K) ratio (r = −0.68), and pericarp thickness (r = −0.86). A detailed analysis of phenolics indicated the presence of trans‐ferulic acid (FA), p‐coumaric acid (CA), and four isomers of DiFA. The most prominent were 5,5′‐DiFA, 8‐O‐4‐DiFA, and 8,5′‐DiFA benzofuran form (DiFAb). On the basis of regression models, 5,5′‐DiFA, 8‐O‐4‐DiFA, trans‐FA, and p‐CA were the most important phenolic components of resistance. Grain hardness was correlated (P < 0.001) with cell wall bound HRGPs (r = 0.61) and DiFAs (r = 0.75). Cell wall cross‐linking components could contribute to MW resistance by fortification of the pericarp cell wall as well as increase grain hardness. This structurally based mechanism should be considered in the development of hybrids and varieties where storage pests are prevalent.
Differentiation of β‐Amylase Phenotypes in Cultivated Barley
Authors: Zhang Wensheng , Kaneko Takafumi , Ishii Makoto , Takeda Kazuyoshi
Published: July 2010

β‐Amylase types coded by the Bmy1 locus were investigated by analyzing the thermostability and isoelectric focusing (IEF) patterns in 8270 accessions of cultivated barley (Hordeum vulgare L.) from different regions of the world. The β‐amylase types were classified into three main thermostability types (A, high; B, medium; C, low) and three major IEF patterns (I, Ia, and II) together with several rare mutant types. By combined analysis of the thermostability types and IEF patterns, we found 14 β‐amylase phenotypes. Among them, A‐II, B‐I, B‐Ia, B‐II, and C‐II were confirmed to be the major types comprising more than 99% of cultivated barley, and accessions belonging to types A‐Ia, A‐IIa, C‐I, C‐Ia, and C‐IV were reported here for the first time. We also confirmed a clear geographical differentiation of β‐amylase phenotypes: In East Asia, nearly 90% of the accessions were of the A‐II type, while 97% of the Ethiopian accessions were of the C‐II type. The B‐I type accessions were mostly restricted to the former USSR and Europe. In Nepal, Bhutan, India, and Pakistan, 90% of the B type accessions were of the B‐Ia type. The B‐II type barley seems to have originated in Turkey and then mainly spread to North Africa, Europe, and the former USSR.
Genetic Variation in Component Traits of Heading Date in Hordeum vulgare subsp. spontaneum Accessions Characterized in Controlled Environments
Authors: Karsai I. , Hayes P. M. , Kling J. , Matus I. A. , Mészáros K. , Láng L. , Bedő Z. , Sato K.
Published: July 2010

Ancestral germplasm may be a useful source of genetic variation for crop improvement. Genetic variation in developmental traits that contribute to heading date may be useful in developing varieties that are uniquely tailored to specific stress environments. Hordeum vulgare subsp. spontaneum (K. Koch) A. & Gr. is the ancestor of cultivated barley and useful developmental trait alleles may have been lost in the domestication process. Accordingly, we surveyed a sample of 16 subsp. spontaneum accessions for vernalization requirement, photoperiod sensitivity, photoperiod response, and relative earliness. We compared the subsp. spontaneum accessions to four H. vulgare L. subsp. vulgare accessions representing spring, facultative, and winter growth habit. Thirteen subsp. spontaneum accessions originating from the Fertile Crescent and the one subsp. spontaneum accession from the Caucasus region required vernalization; they were responsive to long photoperiods and most were very early. Two subsp. spontaneum accessions from the Himalayan region had no vernalization requirement but were extremely sensitive to short photoperiods. We used a clustering procedure to define two groups of subsp. spontaneum accessions, a group of subsp. spontaneum that included the two subsp. vulgare accessions of spring and facultative growth habit, and a fourth group comprised of the two subsp. vulgare winter habit cultivars. These data indicate that subsp. spontaneum may be a source of novel alleles for growth habit.
Variability of Barley Radiation‐Use Efficiency
Authors: Kemanian Armen R. , Stöckle Claudio O. , Huggins David R.
Published: July 2010

Radiation‐use efficiency (e) is a crop‐dependent coefficient widely used in crop simulation models and in the physiological interpretation of crop response to the environment and management practices. Our objectives were to: (i) determine the e of spring barley (Hordeum vulgare L.), (ii) analyze the impact of weather variables and fraction of solar irradiance intercepted (fi) on e, and (iii) compare reported estimates of e for barley and wheat (Triticum aestivum L.) with our measurements for barley. Field experiments were conducted in 2000 and 2001 at Pullman, WA. Treatments consisted of factorial combinations of two cultivars of spring barley (Baronesse and Steptoe), two seeding densities (250 and 100 plants m−2), and two seeding dates (normal and late). Intercepted radiation was measured with tube solarimeters installed below the canopy during the crops life cycle and aboveground biomass obtained from weekly to biweekly samples. The extinction coefficient for solar radiation of both cultivars was 0.43, with no effect of seeding date and density. Cultivar, plant density, and fi did not affect e; however, e at the normal seeding date was greater than at the late seeding date in both years (1.15 and 1.19 g MJ−1, first seeding date, and 0.90 and 0.95 g MJ−1, second seeding date, Years 2000 and 2001, respectively, P < 0.01). These variations were correlated with daytime vapor pressure deficit (D). The e of barley and wheat reported in the literature and those obtained in this study were linearly related to D (kPa): e = 1.88 − 0.53D (r2 = 0.70, n = 22). Maximum values of e reported for barley and wheat are near 1.6 g MJ−1, but our analysis suggests that these high values can only be achieved in low D environments. The effect of the evaporative demand of the atmosphere should be considered in the interpretation of measured e or in the use of e in crop simulation models.
Dynamics of Root Growth in Spring Wheat Mulched with Plastic Film
Authors: Niu J. Y. , Gan Y. T. , Huang G. B.
Published: July 2010

Quantifying root growth can improve our understanding of the development of rhizoplane and rhizosphere structure of a crop and its relation to seed yield. A study was conducted in a semiarid environment in northwestern China to determine the seasonal and spatial patterns of root growth in spring wheat (Triticum aestivum L.) grown with and without plastic mulches. The seed of ‘Lun‐chun 20’ was grown in polyvinyl chloride tubes filled with Yellow Mein sandy loam soil (Aridic Haplustoll). Mulched wheat had a greater (22%) root dry weight (DW) than unmulched wheat at Zadoks Growth Stage (GS) 22. Root DW increased rapidly from GS22 to GS73, with the rate of increase in root DW peaked at GS61. At a given GS during this period, the mulched wheat produced a significantly greater root DW than the unmulched wheat. For both mulched and unmulched wheat, the rate of increase in root DW declined after GS61 where roots penetrated down into the 100‐cm soil layer. The greatest percentage of root DW was in the 10‐ to 20‐cm soil depth, followed by the root DW in the 40‐ to 50‐cm soil depth. At any given soil depth between 10 and 60 cm, the mulched wheat had a greater root DW than the unmulched plants. Root DW below 60‐cm soil depth accounted for a small portion of the total weight and did not differ between the two mulch treatments. On average, the mulched wheat had 23% greater number of seeds per plant, 5% higher seed weight, and 28% higher grain yield than unmulched wheat. In semiarid northwestern China, the use of plastic mulches promoted spring wheat root development, root biomass production, and seed yield.
Investigations on the Influence of Neotyphodium Endophytes on Plant Growth and Seed Yield of Lolium perenne Genotypes
Authors: Hesse U. , Hahn H. , Andreeva K. , Förster K. , Warnstorff K. , Schöberlein W. , Diepenbrock W.
Published: July 2010

The aim of this study was to investigate whether Neoptyphodium spp. endophytes, fungal symbionts of cool‐season grasses, can be selected to improve plant growth and seed yield of perennial ryegrass (Lolium perenne L.). Endophyte‐infected (EI) and endophyte‐free (EF) clones of 13 L. perenne genotypes, collected from native habitats with stressful environmental conditions, were evaluated in a field experiment for symbiotic effects on plant growth (herbage yield, reproductive tiller number), seed production, and seed quality parameters [1000‐seed weight (TSW), germination] over 3 yr in an area with low rainfall (Halle, Germany). The results revealed high variability in endophyte effects on the investigated parameters. In seven genotypes, endophyte presence improved plant growth and seed production during the first harvest year. However, in four of these genotypes, endophyte effects were reversed in the following harvests. In the remaining six genotypes, endophyte infection reduced plant performance. The impact of the fungus on TSW was inconsistent, while seed germination was either improved or not affected by the endophyte. A positive endophyte effect was detectable for genotypes with low performance of EF clones, whereas genotypes with high‐yield EF clones were not, or negatively, affected by the endophyte. Genotypes originating from sites exposed to flooding and periodic drought showed consistent negative endophyte effects on herbage yield and seed production. Since reduced shoot growth is a drought avoidance mechanism, further studies are needed to determine whether endophytes in these genotypes improve adaptation to drought, or represent a “metabolic cost.” Our results indicate that some Neotyphodium endophytes have the potential to improve plant performance of L. perenne, but the selection of strains with consistent beneficial effects on plant growth is difficult.
Evaluation of Drought Resistance for Texas Bluegrass, Kentucky Bluegrass, and Their Hybrids
Authors: Abraham Eleni M. , Huang Bingru , Bonos Stacy A. , Meyer William A.
Published: July 2010

Kentucky bluegrass (Poa pratensis L.; KBG) has good turf quality with adequate irrigation, but moderate to low drought resistance. Interspecific hybridization of Kentucky bluegrass with Texas bluegrass (Poa arachnifera Torr.; TBG), a drought resistant grass native to Texas, has been made to transfer genes of drought resistance from TBG to KBG. The objectives of this study were (i) to investigate whether the hybrids have improved drought resistance compared with either TBG or KBG by examining physiological responses to drought stress; and (ii) to determine major physiological factors associated with recuperative ability of those plants from drought stress. Plants were exposed to drought stress by withholding irrigation for 42 d in a greenhouse. The experiment consisted of 29 fourth‐generation backcrossed hybrids, one third‐generation hybrid (BDF), two KBG parents (‘C‐74’, ‘Midnight’), and one TBG parent. The genotypes classified into three cluster groups of drought resistance (high, moderate, and low) based on the responses of relative water content (RWC), electrolyte leakage (EL), and photochemical efficiency (Fv/Fm) to drought stress. The RWC and Fv/Fm declined with drought stress, but were maintained at higher levels in the high resistance group than the other group, while EL increased during drought and was lower in the high resistance group. Texas bluegrass, Midnight KBG, and two hybrids were ranked highest in drought resistance. Other hybrids varied in drought resistance, with more hybrids of BDF × Midnight ranked in the high drought resistance group than the hybrids of BDF × C‐74. Among all physiological parameters examined, EL was the most sensitive indicator to drought stress, as demonstrated by its most rapid increase in response to the stress. High Fv/Fm and retaining of green leaves during drought stress contributed to fast recovery from drought stress following rewatering.
Diurnal Effects on Nutritive Value of Alley‐Cropped Orchardgrass Herbage
Authors: Burner D. M. , Belesky D. P.
Published: July 2010

Nonstructural carbohydrates, crude protein, and in vitro dry matter digestibility (IVDMD) are important measures of herbage nutritive value and can vary at seasonal and diurnal time scales in conventional agronomic systems. Our objective was to determine diurnal trends of nutritive value components in orchardgrass (Dactylis glomerata L.) herbage harvested daily on 1 through 15 June 2001 and 2002 from three microsites: unshaded control, loblolly pine (Pinus taeda L.) alleys, and shortleaf pine {(P. echinata Mill.) alleys at three time intervals [0500, 1100, and 1700 h, Central Standard Time (CST)]}. Diurnal responses were defined as a regression response or change in mean (P ≤ 0.10) with time. Orchardgrass herbage exhibited temporal change in total nonstructural carbohydrate (TNC), water‐soluble carbohydrate (WSC), starch, and IVDMD. At any given sampling time, TNC was greater (P ≤ 0.05) in control than in pine microsites. Diurnal response of TNC differed among microsites (P = 0.10), with more rapid TNC change in the control and shortleaf pine than loblolly pine (P < 0.01). The differential response of TNC in pine microsites compared with the control was attributed to an altered amount and temporal distribution of solar irradiance. Diurnal responses of WSC, starch, and IVDMD were unaffected by microsite. Herbage levels of crude protein and IVDMD were greater, but yield and nonstructural carbohydrates were lower in pine microsites compared with the unshaded control. We conclude that diurnal change in herbage nutritive value tends to be buffered against irradiance constraints in alley crop environments.
A PCR Marker for Growth Habit in Common Wheat Based on Allelic Variation at the VRN‐A1 Gene
Authors: Sherman J. D. , Yan L. , Talbert L. , Dubcovsky J.
Published: July 2010

Growth habit varies among accessions of hexaploid wheat (Triticum aestivum L.). The winter habit genotype (homozygous recessive for vrn‐A1, vrn‐B1, vrn‐D1) requires a cold treatment to induce flowering and is generally planted in the fall. Spring habit genotypes flower in the absence of a vernalization treatment. Spring habit is conferred by a dominant allele at any of the three VRN‐1 loci, but varieties carrying the VRN‐A1 locus are the most frequent and usually flower earlier. To facilitate selection in populations segregating at the VRN‐A1 locus and to assist in genotyping wheat accessions of unknown VRN‐1 composition, a PCR‐based marker for growth habit would be useful. The VRN‐A1 gene was recently cloned allowing for the development of markers for growth habit. In this report, we designed primer sets specific for the VRN‐A1 locus, and used them to amplify an 810‐bp segment of the VRN‐A1 gene between intron 4 and exon 8 from 40 spring wheat lines and 37 winter wheat lines. Three diagnostic nucleotide changes were identified that differentiated the dominant Vrn‐A1 and recessive vrn‐A1 alleles in 75 out of the 77 genotypes analyzed in this study. One of these differences resulted in the presence of an additional AciI restriction site in the allele for spring growth habit. This difference was exploited to develop a cleavage amplification polymorphic sequence (CAPS) that can be used to determine the allelic state at VRN‐A1 in germplasm collections, and as a marker in backcross breeding projects. An additional pair of dominant markers was developed from a different polymorphism.
A Gene‐Based Model to Simulate Soybean Development and Yield Responses to Environment
Authors: Messina C. D. , Jones J. W. , Boote K. J. , Vallejos C. E.
Published: July 2010

Realizing the potential of agricultural genomics into practical applications requires quantitative predictions for complex traits and different genotypes and environmental conditions. The objective of this study was to develop and test a procedure for quantitative prediction of phenotypes as a function of environment and specific genetic loci in soybean [Glycine max (L.) Merrill]. We combined the ecophysiological model CROPGRO‐Soybean with linear models that predict cultivar‐specific parameters as functions of E loci. The procedure involved three steps: (i) a field experiment was conducted in Florida in 2001 to obtain phenotypic data for a set of near‐isogenic lines (NILs) with known genotypes at six E loci; (ii) we used these data to estimate cultivar‐specific parameters for CROPGRO‐Soybean, minimizing root mean square error (RMSE) between observed and simulated values; (iii) these parameters were then expressed as linear functions of the (known) E loci. CROPGRO‐Soybean predicted various phenological stages for the same NILs grown in 2002 in Florida with a RMSE of about 5 d using the E loci–derived parameters. A second evaluation of the approach used phenotypic data from cultivar trials conducted in Illinois. Cultivars were genotyped at the E loci using microsatellites. The model predicted time to maturity in the Illinois variety trials with RMSE around 7.5 d; it also explained 75% of the time‐to‐maturity variance and 54% of the yield variance. Our results suggest that gene‐based approaches can effectively use agricultural genomics data for cultivar performance prediction. This technology may have multiple uses in plant breeding.
Understanding and Improving Salt Tolerance in Plants
Authors: Chinnusamy Viswanathan , Jagendorf André , Zhu Jian‐Kang
Published: July 2010

One‐fifth of irrigated agriculture is adversely affected by soil salinity. Hence, developing salt‐tolerant crops is essential for sustaining food production. Progress in breeding for salt‐tolerant crops has been hampered by the lack of understanding of the molecular basis of salt tolerance and lack of availability of genes that confer salt tolerance. Genetic evidence suggests that perception of salt stress leads to a cytosolic calcium‐signal that activates the calcium sensor protein SOS3. SOS3 binds to and activates a ser/thr protein kinase SOS2. The activated SOS2 kinase regulates activities of SOS1, a plasma membrane Na+/H+ antiporter, and NHX1, a tonoplast Na+/H+ antiporter. This results in Na+ efflux and vacuolar compartmentation. A putative osmosensory histidine kinase (AtHK1)‐MAPK cascade probably regulates osmotic homeostasis and ROS scavenging. Osmotic stress and ABA (abscisic acid)‐mediated regulation of LEA (late‐embryogenesis‐abundant)‐type proteins also play important roles in plant salt tolerance. Genetic engineering of ion transporters and their regulators, and of the CBF (C‐repeat‐binding factor) regulons, holds promise for future development of salt‐tolerant crops.
Identification of Optical Spectral Signatures for Detecting Cheat and Ryegrass in Winter Wheat
Authors: Girma Kefyalew , Mosali J. , Raun W. R. , Freeman K. W. , Martin K. L. , Solie J. B. , Stone M. L.
Published: July 2010

Precision weed management technology has immense potential for treating weed species at a small scale. To this end, however, crop and weeds must be recognized. One approach to this involves identification of reflectance signatures of crops and weeds that differ in the visible and near‐infrared (NIR) wavelength region. Reflectance spectra were used for the detection of cheat (Bromus secalinus L.), ryegrass (Lolium multiflorum Lam.), and winter wheat (Triticum aestivum L.) under greenhouse conditions. A total of three experiments (two in December 2002 and one in February 2003) were conducted at the Agronomy Research Station, Stillwater, OK. The three species and two N levels were arranged in a completely randomized design with three replications. Spectral readings were taken at Feekes 3 and 5 winter wheat growth stages with a spectrometer. Two spectral measurements were obtained from each pot. The spectral measurements from the three experiments were combined by the two growth stages because preliminary analysis revealed that date of measurement and N levels were not significant. The spectral readings were measured at 1‐nm intervals and averaged into 10‐nm bandwidths for the wavelengths from 400 to 865 nm. Data were analyzed using a discriminant analysis procedure. The discriminant function with the band combinations 515/675, 555/675, and 805/815 resulted in the best overall correct classification (94%) of observations at Feekes 3, while for spectral data at Feekes 5 the discriminant function with the band combinations 755 and 855/675 resulted in 66.7% overall correct classification of observations. In several instances, ryegrass was classified as either cheat or winter wheat, while cheat was classified as rye. Cheat was not classified as winter wheat in most instances. This suggests that it is possible to identify cheat in winter wheat using wavelength ratios developed from spectral readings in 10‐nm bands between 500 and 860 nm.
Quantifying a Daily Light Integral Requirement of a ‘TifEagle’ Bermudagrass Golf Green
Authors: Bunnell B. Todd , McCarty Lambert B. , Faust James E. , Bridges William C. , Rajapakse Nihal C.
Published: July 2010

‘TifEagle’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] is a fine textured hybrid bermudagrass used for golf course putting greens in the subtropical and tropical regions of the world. The growth and performance of TifEagle and other bermudagrass often decline in reduced light environments (RLEs). This study quantified a daily light integral (DLI; mol m−2 d−1) required to maintain commercially acceptable TifEagle bermudagrass maintained under golf green conditions. Three levels of shade, none, low, and high (0, 41, and 92%), were applied to mature TifEagle bermudagrass during morning (sunrise to 1100 h) and afternoon (1500 h to sunset) hours, allowing full irradiance from 1100 to 1500 h to mimic a golf green situation where trees or structures are adjacent to, but rarely directly overhead. The study was performed for 8 wk in June to August 2001 and 2002. An average minimal DLI of 32.6 mol m−2 d−1 was needed to maintain commercially acceptable TifEagle turf quality (TQ ≥ 7). Other plant responses measured included percentage lateral regrowth (RG), total shoot chlorophyll, and total nonstructural carbohydrates (TNC). These responses declined significantly when the DLI ≤ 32.6 mol m−2 d−1 Differences in diurnal shade exposure occurred. High afternoon shade reduced TifEagle bermudagrass TQ, percentage lateral RG, shoot chlorophyll, and TNC by 3.0 rating units and 17, 39, and 27%, respectively, compared with no afternoon shade (NSA). High morning shade reduced TQ, percentage lateral RG, and shoot chlorophyll by 1.5 rating units and 11 and 16%, respectively, compared with no morning shade (NSM). Overall, afternoon shade applications were more detrimental to TifEagle bermudagrass growth and performance compared with morning shade.
Agronomic and Seed Traits of Soybean Lines with Low–Phytate Phosphorus
Authors: Oltmans Sheilah E. , Fehr Walter R. , Welke Grace A. , Raboy Victor , Peterson Kevin L.
Published: July 2010

About 75% of the total P in conventional soybean [Glycine max (L.) Merr.] seed is phytate P, which cannot be readily digested by nonruminant livestock, such as swine and poultry. The phytate P in soybean lines homozygous for the recessive alleles pha1 and pha2 is reduced to about 25% of the total P. The objective of this study was to determine the influence of low phytate (LP) on agronomic and seed traits of soybean. Three populations were developed by crossing three cultivars with normal phytate (NP) to the LP line CX1834‐1‐6. From each population, 10 LP and 10 NP lines were selected and grown in replicated tests at three Iowa environments during 2003. The mean total P of the LP and NP lines was not significantly different, but the mean phytate P, inorganic P, and other P were significantly different for the two types of lines in the three populations. The mean seedling emergence of the LP lines was 45% compared with 68% for the NP lines. The mean differences between the LP and NP lines for the other agronomic and seed traits were not significant in one or more of the populations. On the basis of these results, reduced seedling emergence will be a major factor to consider in the development of commercially viable cultivars with the pha1pha1pha2pha2 genotype for LP.