bluuebunny/crossref_metadata_2025 huggingface dataset:
Canopy Reflectance as a Measure of Disease in Tall Fescue
Authors: Green D. E. , Burpee L. L. , Stevenson K. L.
Published: July 2010

Measurement of changes in canopy reflectance of tall fescue (Festuca arundinacea Schreb.), which result from deterioration of tissues caused by disease organisms, is a potential unbiased method for quantifying disease. Canopy reflectance in eight spectral bands between 430 and 840 nm and 18 vegetation indices derived from the spectral bands were regressed against visual severity estimates of Rhizoctonia blight, caused by Rhizoctonia solani Kühn, and gray leaf spot, caused by Pyricularia grisea (Cooke) Sacc. Reflectance within the 810‐nm band exhibited the strongest relationship (19% ≤ r2 ≤ 63%) with visual severity estimates of Rhizoctonia blight and gray leaf spot. Reflectance in the visible or near infra‐red wavelengths was similar to tall fescue blighted by either fungal pathogen. A significant (P ≤ 0.05) negative linear relationship was observed between canopy reflectance in the 810‐nm band and the severity of either Rhizoctonia blight or gray leaf spot. As Rhizoctonia blight decreased with increases in the application rate of the fungicide flutolanil (N‐[3‐(1‐methylethoxy)‐phenyl]‐2‐(trifluoromethyl)benzamide) and the proportion of a resistant cultivar in tall fescue blends, canopy reflectance in the 810‐nm band increased. However, models based on canopy reflectance had twice as much unexplained variability than models based on visual severity estimates of Rhizoctonia blight. Factors other than disease influenced variability in reflectance of light from tall fescue canopies.
Effects of High Temperature and Poor Soil Aeration on Root Growth and Viability of Creeping Bentgrass
Authors: Huang Bingru , Liu Xiaozhong , Fry Jack D.
Published: July 2010

Turf quality declines in creeping bentgrass (Agrostis palustris Huds.) with increasing temperatures and decreasing soil aeration. This experiment examined how root activities of ‘Crenshaw’ and ‘Penncross’ were affected by high temperature and low soil aeration. Turfgrass was maintained in growth chambers at day/night temperatures of 22/15°C (optimum) or 35/25°C (high temperature, HT). Aeration treatments were: (i) adequate aeration by maintaining soil medium well‐drained; (ii) low aeration (LA) induced by maintaining soil medium saturated with water. Shoot dry matter production (SDM) declined with HT + LA at 7 days of treatment (DOT) in Penncross, and at 21 and 35 DOT with HT, LA, and HT + LA for both cultivars. Reduced root dry mass was measured at 7 DOT under HT + LA, and at 21 and 35 DOT under HT, LA, or HT + LA for both cultivars. Root viability was lower after 7 DOT and 21 DOT of HT, LA, and HT + LA. Viability was reduced more in Penncross than in Crenshaw after 21 DOT with HT + LA, and 35 DOT with HT and HT + LA. Root porosity increased with LA and HT + LA, beginning 7 DOT for both cultivars, to a greater extent in Crenshaw after 21 and 35 DOT with HT + LA. The combination of HT and LA had more severe effects on viability than either HT or LA alone. Results suggest that reductioin root growth, and particularly root viability, under HT and LA could contribute to the declines and cultivar variations in bentgrass quality.
Influence of Humic Substances on Rooting and Nutrient Content of Creeping Bentgrass
Authors: Cooper R. J. , Liu Chunhua , Fisher D. S.
Published: July 2010

Two greenhouse experiments were conducted to determine if application of humic substances to creeping bentgrass (Agrostis stolonifera L.) turf would improve root mass, root length, or nutrient uptake. A commercially mined granular humate, a commercial liquid humic acid (HA), and liquid HAs extracted from leonardite, peat, and soil were applied to creeping bentgrass growing in either sand or solution culture and maintained at a height of 6 mm. Foliar applications included monthly or biweekly applications of HAs at 0, 100, 200, or 400 mg HA L−1. In sand culture, humate incorporated to a depth of 10 cm stimulated a 45% increase in root mass at the 0‐ to 10‐cm depth and a 38% increase in root mass at the 10‐ to 20‐cm depth compared with the control. Incorporation of granular humate increased maximum root length 15% compared with non‐treated turf in sand culture. No foliar applied HA source consistently provided rooting superior to the control in either sand or solution culture. Nitrogen, Ca, Mg, and Fe uptake were relatively unaffected by humic substance application. The phosphorous concentration of plants in sand culture was increased 3 to 5% by incorporated humate and foliar application of soil, peat, or Leonardite‐derived HA. In solution culture, however, P uptake was unaffected by HA application. The lack of improved rooting or increased P uptake in solution culture supports the hypothesis that humic acids may have limited growth promoting effects on plants adequately supplied with nutrients.
Molecular Characterization of Two Triticum speltoides Interstitial Translocations Carrying Leaf Rust and Greenbug Resistance Genes
Authors: Dubcovsky J. , Lukaszewski A. J. , Echaide M. , Antonelli E. F. , Porter D. R.
Published: July 2010

Resistance genes for leaf rust (Puccinia recondita Rob. ex Desm.) and greenbug (Schizaphis graminum Rondani) were transferred from chromosome 7S of Triticum speltoides (Tausch) Gren. to chromosome 7A of hexaploid wheat (Triticum aestivum L.) by means of the phlb mutation that promotes homeologous recombination. The chromosome segments from T. speltoides were characterized by C‐banding and restriction fragment length polymorphisms (RFLP). Since the segments of T. speltoides chromosome 7S do not recombine with wheat chromosome 7A in the presence of the wild‐type Ph1 locus only one molecular marker per chromosome segment is required to monitor the introgressed genes in marker assisted selection programs. The new leaf rust resistance gene, designated Lr47, and the greenbug resistance gene Gb5 were located on interstitial chromosome segments from T. speltoides translocated to wheat chromosome arms 7AS and 7AL, respectively. Physically, both were located in the distal one third of the arms, but genetically the Lr47 segment was 2 to 10 centimorgans (cM) from the centromere and was 20 to 30 cM long; the Gb5 segment was 18 to 22 cM from the centromere and was 40 to 50 cM long.
Resistance to Alfalfa Mosaic Virus in Transgenic Burley Tobaccos Expressing the AMV Coat Protein Gene
Authors: Xu Dongmei , Collins Glenn B. , Hunt Arthur G. , Nielsen Mark T.
Published: July 2010

There are no known genetic sources of resistance to alfalfa mosaic virus (AMV) in the genus Nicotiana. In this communication, we describe how we genetically engineered an AMV (strain 425) coat protein (CP) gene into three commercial burley tobacco (N. tabacum L.) genotypes, BY 21, TN 86, and KY 8959, and the evaluation of the transgenic lines in greenhouse and field experiments. In a replicated greenhouse trial, 11 AMV‐CP transgenic lines in a BY 21 background were resistant to two AMV isolates, AMV‐425 and AMV‐KY, but the lines were less resistant to another isolate, AMV‐NC. In a 1994 field experiment, we found that nine BY 21 AMV‐CP transgenic lines were resistant to AMV‐KY when inoculated both before and after transplanting. The level of resistance varied among the nine lines. In 1995, 10 randomly selected AMV‐CP lines in each of the three genetic backgrounds were evaluated in a replicated field trial. Mean infection scores of each set of lines were significantly less than those of their non‐transgenic counterparts, but there were no significant differences among these three mean infection scores. However, there were significant differences among lines within a genetic background for their response to AMV infection. High sensitivity to AMV infection, found in genotypes TN 86 and KY 8959 that possess an endogenous gene for resistance to potyviruses, was not evident in their AMV‐CtrPa nsgenic lines. The CP mediated resistance to AMV was effective in reducing viral symptoms in the field and it may provide a valuable source for AMV resistance in tobacco.
Li Jing Xiong (C.H. Li)—Functioning in Adversity
Authors: Chase S. S.
Published: July 2010

Li Jing Xiong (syn. Li Ching Hsiung), member of the Chinese Academy of Sciences (1980), president of the Crop Science Society of China (1984), Chief Scientist, basic agronomy, National Basic Research Program (1992), Cornell University Ph.D. (1948), best known among his American associates as C.H.Li, died on 28 June 1997 at Beijing after a prolonged illness. Dr. Li's direct and personal favorable impact on the food supply of the Chinese people came through two major actions and in a number of contributory ways: first, his sturdy opposition to Lysenkoism and to a compromise with the Chinese Lysenkoists, and second, and only possible with the first contribution, the development of maize (Zea mays L.) hybrids of superior yield; third in importance, a series of minor contributions from his early work on wheat‐rye hybrids (triticale, × Triticosecale Wittmack), Setaria millet [Setaria italica (L.) P. Beanv.], sorghum [Sorghum bicolor (L.) Moench] hybridization, hybrid maize technology, and specialty maize such as quality protein hybrids. In addition, in his early years, he made contributions to understanding the cytogenetics of maize. And, in spite of formal difficulties, Professor Li was always an honored teacher to his colleagues and associates.
High‐Temperature Effects on Photosynthetic Processes in Temperate and Tropical Cereals
Authors: Al‐Khatib Kassim , Paulsen Gary M.
Published: July 2010

High temperature limits productivity of crops in many regions of the world, but the physiological basis of tolerance to the stress is not known. Our objective was to determine the relationship between photosynthetic responses to high temperature at the whole‐plant level and sensitivity of light reactions, the most labile systems, to brief heat treatment. Wheat (Triticum aestivum L.), a C3 species adapted to cool environments; rice (Oryza sativa L.), a C3 species adapted to warm environments; and millet [Pennesitum glaucum (L.) R. Br.], a C4 species adapted to hot environments, were compared. Photosynthesis was measured in plants grown at 22, 32, or 42°C, and light reactions were measured in protoplasts, chloroplasts, and thylakoids isolated from seedlings grown at 27° C and treated in vitro at 22, 32, and 42°C. Leaf photosynthesis of millet and rice increased from 22 to 32°C and then decreased to 42°C, whereas in wheat it was highest at 22°C and decreased as temperature increased. Photosynthetic rates of protoplasts and chloroplasts from all species decreased after being treated in vitro over the same temperature range. Photosystem II (PSII) activity declined steadily in protoplasts, chloroplasts, and thylakoids of millet and rice from 22 to 42°C but decreased abruptly in organelles of wheat from 32 to 42°C. The results suggest that differences in photosynthetic responses to high temperature are associated with light reactions, and extreme sensitivity of wheat may be attributable to injury to PSII.
Soybean Root Morphological and Anatomical Traits Associated with Acclimation to Flooding
Authors: Bacanamwo Methode , Purcell Larry C.
Published: July 2010

Soybean [Glycine max (L.) Merr.] acclimation to flooding has been investigated at biochemical and physiological levels, but longterm acclimation to flooding may be associated with morphological changes. Supplementing legumes with nitrate ameliorates flooding stress, compared with plants dependent on N2 fixation. Two experiments evaluated morphological and anatomical changes induced by flooding for plants relying on N2 fixation or supplemented with nitrate. An additional experiment assessed the role of aerenchyma in flooding acclimation by blocking aerenchyma formation with silver. Flooding soybean for 21 d with nutrient solution without N increased biomass allocation to roots. No aerenchyma was observed in roots of nonflooded plants; however, it was abundant in roots of flooded plants. Porosity measurements of root and stem‐base tissues indicated that 10 to 15% of the volume was gas filled in flooded plants, while gasfilled volume was negligible in the nonflooded controls. Flooding in the presence of nitrate decreased aerenchyma and increased adventitious roots, compared with plants flooded with nutrient solution without N. Increased growth under flooding of nitrate‐supplemented plants, therefore, was not directly associated with increased root porosity. For flooded plants dependent on N2 fixation, silver prevented aerenchyma and adventitious root development and decreased biomass accumulation and N2 fixation by approximately one‐half compared with plants flooded in the absence of silver. These results indicate that acclimation to flooding in soybean involves preferential allocation of photosynthates to development of porous adventitious roots and that aerenchyma formation for soybean relying on N2 fixation is critical for acclimation to flooding.
Rooting, Water Uptake, and Xylem Structure Adaptation to Drought of Two Sorghum Cultivars
Authors: Salih A. A. , Ali I. A. , Lux A. , Luxová M. , Cohen Y. , Sugimoto Y. , Inanaga S.
Published: July 2010

Several mechanisms have been proposed to explain the high tolerance of sorghum [Sorghum bicolor (L.) Moench] to drought. This paper reports a field study on the effects of soil moisture stress on the rooting habits, transpiration rate, and xylem anatomy of two sorghum cultivars, Tabat (drought susceptible) and Gadambalia (drought tolerant). Two levels of water stress, −0.02 MPa (wet) −0.75 MPa (dry), were applied. Tabat had a higher root length density (RLD), higher late metaxylem (LMX) vessels per nodal root, higher leaf area, and higher transpiration rate than Gadambalia. In Tabat, soil moisture stress reduced RLD by 30%, nodal roots by 31%, number of LMXve ssels in the root by 42%, leaf area by 13%, and transpiration rate by 11%. In Gadambalias oil moisture stress did not affect RLD at depths >‐0.2 m, numbero f nodal roots, or numbero f LMXve ssels per nodal root. However, leaf area and transpiration rate were reduced by 3 and 11%, respectively. Under dry conditions, Gadambaliad isplayed a higher water extraction efficiency than Tabat throughout the profile (0‐0.9 m). In Gadambaliau, nlike Tabat, the stem was highly sclerified. A 1‐ to 3‐cell‐thick layer of schlerenchymaw as observed beneath the epidermis. The peripheral vascular bundles were surrounded with a 3‐ to 6‐ceil‐thick schlerenchyma sheath. However, in roots anatomical differences were less prominent. Drought tolerance in Gadambaliias associated with higher water extraction efficiency, fewer nodal roots per plant, fewer LMXv essels per nodal root, a smaller leaf area, and a well developed sclerenchyma.
Somatic Embryogenesis and Plant Regeneration from Suspension Cultures of Switchgrass
Authors: Gupta S. Dutta , Conger B. V.
Published: July 2010

Embryogenic cell suspension cultures represent an enhanced culture type for the selection of mutants, mass propagation, direct delivery of DNA in to intact regenerable cells and isolation of totipotent protoplasts. The objectives of this study with switchgrass (Panicum virgatum L.) were to establish embryogenic suspension cultures and to regenerate plants from these cultures. The cultures were initiated from embryogenic callus obtained from young inflorescences. They were maintained in Murashige and Skoog liquid medium containing 9.0 μM 2,4‐dichlorophenoxyacetic acid (2,4‐D), 4.4 μM 6‐benzylaminopurine (BAP) and 30 g ‐1 maltose. The s uspension was passed througha 210‐μm mesh and was comprised mainly of small, round densely cytoplasmic starch containing cells with distinct nuclei. Somatic embryos developed from these cells directly and were free floating in the medium. A sequence of developmental stages from embryogenic cells to fully developed embryos was observed in the cultures. The embryos had the typical morphology of a grass embryo. Embryogenic calluses were also obtained 4 wk after the suspension was plated onto solid medium containing various combinations of 2,4‐D and BAP. Embryos from suspension and suspension‐derived callus cultures germinated to produce plants that were successfully established in the greenhouse.
Evaluation of a Filter Bag System for NDF, ADF, and IVDMD Forage Analysis
Authors: Vogel Kenneth P. , Pedersen Jeffrey F. , Masterson Steven D. , Toy John J.
Published: July 2010

A new method of determining in vitro dry matter digestibility (IVDMD) was recently developed in which the digestion is conducted with the forage samples in filter bags. Our objective was to compare the filter bag and conventional IVDMD analysis methods using smooth bromegrass (Bromus inermis Leyss.), switchgrass (Panicum virgatum L.), and forage sorghum [Sorghum bicolor (L.) Moench] samples. In addition, the filter bag analysis systems for determining non‐sequential neutral and acid detergent fiber (NDF and ADF), respectively, were compared with the non‐sequential conventional analysis systems. In the filter bag systems, the forage samples are sealed in filter bags and the analyses are conducted on a batch basis rather than on an individual basis as in the conventional IVDMD and fiber analysis procedures. The filter bag analysis methods produced results similar to the conventional methods and ranked the forage samples in the same relative order.
Phenotypic Recurrent Selection Methodology for Reducing Fiber Concentration in Smooth Bromegrass
Authors: Casler M. D.
Published: July 2010

Neutral detergent fiber (NDF) concentration, a laboratory predictor of voluntary feed intake by livestock, has become a popular selection criterion in forage breeding programs. The objective of this study was to make empirical comparisons among six phenotypic recurrent selection methods for reducing NDF concentration in smooth bromegrass (Bromus inermis Leyss.). There were three basic selection methods: vNB2 = vegetative harvest, NIRS (near‐infrared reflectance spectroscopy) evaluation of NDF, and bi‐parental selection; hNU2 = heading growth stage harvest, NIRS, and uni‐parental selection; and hWU2 = heading growth stage, wet‐laboratory analysis of NDF, and uni‐parental selection. Each method was repeated in a replicated polycross nursery of selected individuals (vNP3, hNP3, and hWP3). The vNB2 selection method resulted in the greatest gain for the vegetative growth stage, averaging a 4.0 g kg−1 yr−1 (1.0% yr−1) reduction in NDF concentration. Polycrossing did not improve upon this method, but improved the other two selection methods by an average of 241% because of control of male gametes. The hWP3 selection method resulted in the greatest gain for the heading growth stage, averaging 3.4 g kg−1 yr−1 (0.6% yr−1). Realized gains for the vegetative growth stage selection methods were greater than predicted, likely because of extremely low sampling variation, resulting from uniform selection units. For maximum response, long‐term selection for a target growth stage should be conducted at that growth stage. The use of NIRS was highly effective at the vegetative growth stage, but less effective at the heading growth stage.
Two Cycles of Recurrent Selection for Seed Yield in Common Bean
Authors: Singh Shree P. , Terán Henry , Muñoz Carlos Germán , Takegami Juan Carlos
Published: July 2010

Seed yield of common bean (Phaseolus vulgaris L.) can be improved by exploiting the genetic variability available in the crop's cultivated races and gene pools. The objectives of this study were to (i) compare yield gains obtained through two cycles of recurrent selection, based on S1 family tests, in two types of populations [interracial Middle American (MA) and inter‐gene‐pool Andean × Middle American (AMA)], and (ii) estimate genetic variance, heritability, and expected gains from selection. The MA population comprised 11 parents from race Mesoamerica, three from Jalisco (Mexico), and two from Durango (Mexico). The AMA population had six parents from race Mesoamerica, one from Jalisco, five from Nueva Granada (northern Andes), and two from Chile (also Andean). From the initial cycle (C0,) of each population, 45 S2 families were evaluated at three locations in Colombia in 1992 to select the 10 highest yielding families to be intermated in a diallel fashion (excluding reciprocals) to generate 45 S1 families for cycle 1 (C1). Similarly, 45 S1 families from C1 and cycle 2 (C2) were evaluated in 1993 and 1995, respectively. The 10 highest yielding selected families from each of C0, C1, and C2 and a corresponding bulk of all 45 S1 families from each of the three cycles were evaluated at three sites in 1997. Data were recorded for seed yield, seed weight, and maturity. Genetic variance among 45 S1 families in C1 and C2 was greater in the AMA population than in the MA, diminishing from C1 to C2 in MA and increasing in AMA. Heritability for seed yield ranged from 0.31 to 0.46, for seed weight from 0.75 to 0.86, and for maturity from 0.50 to 0.81. Expected gains from selection for seed yield was lower (3–4%) in C2 compared with C1 (7.9–13.2.%). The mean yields of C0, C1, and C2 of the MA were significantly (P < 0.05) higher than those of the AMA. The C2 of both MA and AMA out yielded their respective C1 and Co families. The average realized yield gain per selection cycle was 15% or higher in both populations. These results justify the use of recurrent selection in interracial and inter‐gene‐pool populations for improving seed yield of common bean.
Management of Root‐Knot Nematodes with Resistant Cotton cv. NemX
Authors: Ogallo Juma L. , Goodell Peter B. , Eckert James W. , Roberts Philip A.
Published: July 2010

Root‐knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] is a serious pest of cotton (Gossypium hirsutum L.) and many crops worldwide. Recent banning of most nematicides has increased the need for development of nematode resistant crop cultivars, such as NemX cotton, which was released in California in 1995. This study was conducted to determine the effectiveness of NemX in suppressing populations of M. incognita and protecting susceptible crops grown in rotation with it. NemX was grown in rotation with susceptible cotton cvs. Maxxa and Pima S7, susceptible lima bean (Phaseolus lunatus L. cv. Henderson), and resistant cowpea [Vigna unguiculata (L.) Walp. cv. CB 88] and alfalfa (Medicago sativa L. cv. WL525HQ). The experiments were done at Shafter, CA, during 1994–1996 on plots with sandy loam soil and natural infestation of M. incognita race 3. NemX suppressed nematode populations strongly in all treatments and one planting was as effective as two successive ones. Lint yield of NemX averaged 1000 kg ha−1, irrespective of preplant nematode density (Pi). In contrast, yields of susceptible Maxxa cotton varied indirectly with nematode Pi and ranged from 530 to 1360 kg ha−1. NemX and resistant cowpea or alfalfa had about equal effectiveness in suppressing nematode population density in soil and in protecting a subsequent susceptible crop. Since different species of root‐knot nematode attack many crops and M. incognita is the only species that reproduces well in cotton, utilization of NemX will greatly enhance the rotational value of cotton for managing the nematodes.
Field Evaluation of Switchgrass Seedlings Divergently Selected for Crown Node Placement
Authors: Elbersen H. W. , Ocumpaugh W. R. , Hussey M. A. , Sanderson M. A. , Tischler C. R.
Published: July 2010

Excessive crown node elevation of warm‐season grass seedlings is a major limitation to successful establishment. Crown node placement at or above the soil surface limits the opportunity for adventitious root development at the crown node. Switchgrass (Panicum virgatum L.) germplasm selected for low‐ (LC) and elevated‐ (EC) crown node placement (at 1.5 (μmol m−1 s−1 photosynthetic photon flux density), has been developed from ‘Alamo’ Switchgrass. The objective of this study was to determine if differences in crown node placement and other seedling morphological traits exist among Alamo (nonselected, parental), LC, and EC germplasm and if these differences affect seedling establishment in the field. Seeds were planted during April and May at Beeville, Stephenville, and College Station, TX. Each location was established with six blocks each consisting of a 2‐m row of Alamo, LC, or EC seed. Seeds were planted at a 1‐cm depth. Three to 10 seedlings were marked at soil level, then dug for detailed seedling measurements. There were no genotype by location interactions for any trait measured. Emergence was more rapid at Beeville for all entries because of prewatering and better soil conditions. Averaged for the three locations, final emergence was 47, 37, and 30% for LC, EC, and Alamo. Mesocotyl length of LC germplasm averaged 5.9 mm compared with 8.4 and 9.1 mm for Alamo and EC germplasm, respectively. Even though LC seedlings had shorter mesocotyles and consequently lower crown node placement than EC or Alamo seedlings, these traits may not be directly responsible for greater establishment success.
Major Gene, Nonallelic Sheath Blight Resistance from the Rice Cultivars Jasmine 85 and Teqing
Authors: Pan X. B. , Rush M. C. , Sha X. Y. , Xie Q. J. , Linscombe S. D. , Stetina S. R. , Oard J. H.
Published: July 2010

Only partial resistance is available for sheath blight, the second most important disease of rice (Oryza sativa L.) worldwide. This partial resistance has been considered to be polygenic. The partial resistance of the cultivars Jasmine 85 (J‐85) and Teqing (TQNG) was studied by evaluating the resistance of F1, F2, F3, F4, and backcross F1 generations of crosses between the resistant parents and the susceptible cultivars Maybelle (MBLE) and Cypress (CPRS). F1 plants from the crosses were resistant. Segregating F2 populations from both crosses showed ratios of 3:1 resistant/susceptible plants. Segregating backcross F1 populations showed a ratio of 1:l resistant/susceptible plants when the F1 was crossed to a susceptible parent and no seregation occurred when the F1, was crossed to a resistant parent. These results were consistent with the partial resistance from the two resistant cultivars being controlled by single dominant genes. When the resistant cultivars were crossed, the segregating F2 population showed a 15:1 resistant/susceptible ratio. The results suggested that the two resistant parents each possessed a nonallelic dominant major resistance gene that segregated independently. Some of the F4 lines from this cross appeared to have both resistance genes and a higher level of resistance than either resistant parent. This suggests that major genes conferring high levels of partial resistance to sheath blight may be incorporated together into lines to give near complete resistance. This makes the identification of major genes for partial resistance to sheath blight critically important to rice breeding programs
QTL for Resistance to Setosphaeria turcica in Tropical African Maize
Authors: Schechert A. W. , Welz H. G. , Geiger H. H.
Published: July 2010

Setosphaeria turcica (Luttrell) Leonard & Suggs causes northern corn leaf blight (NCLB), an important disease of maize (ZZea mays L.) in sub‐Saharan Africa and other tropical and temperate regions. Quantitative trait loci (QTL) for resistance were mapped and characterized in a population of F1:3 lines derived from a cross between the susceptible line Lo951 and the highly resistant CIMMYT line CML202, and tested in three inoculated trials in Kenya (n = 194–256 lines). Incubation period (IP) and area under the disease progress curve (AUDPC, based on three readings) were assessed. Both traits showed a continuous distribution in the population with no transgressive segregation. Variance components for genotypes (G) and environments (E) were highly significant for both traits. G × E interaction was also significant but less important. Heritability was 0.86 for IP and 0.81 for AUDPC. Genotypic and phenotypic correlations between IP and AUDPC were tight (rg = −0.84, rp = −0.71). The genetic map encompassed 110 RFLP marker loci with an average interval length of 17 ceutimorgans (cM). Composite interval mapping revealed different but overlapping sets of QTL in the individual environments. In the combined analysis, 10 QTL were detected for IP and AUDPC. These included two QTL with resistance alleles coming from the susceptible parent, Lo951. Six QTL (on Chromosomes 2,3, 5,8,9) were associated with both traits, two affected only IP, another two only AUDPC. The QTL explained 61% of the genotypic and 52% of the phenotypic variance of IP (AUDPC: 69 and 56%). The magnitude of the individual QTL effects was homogeneous and their gene action additive. Marker‐assisted improvement of NCLB resistance is considered feasible, though not necessarily economically viable.
Quantitative Trait Loci for Antixenosis Resistance to Corn Earworm in Soybean
Authors: Rector B. G. , All J. N. , Parrott W. A. , Boerma H. R.
Published: July 2010

Insect resistance in soybean, Glycine max (L.) Merr., is inherited quantitatively and has been difficult to incorporate into high‐yielding cultivars. The objectives of this study were to: (i) use restriction fragment length polymorphism (RFLP) markers to identify quantitative trait loci (QTLs) for antixenosis (nonpreference) resistance to corn earworm, Helicoverpa zea Boddie, in soybean plant introductions PI171451 and PI227687, (ii) determine the location of the QTLs on the public soybean genetic linkage map, (iii) determine their relative magnitude and gene action, and (iv) compare them to insect resistance QTLs previously detected in PI229358. RFLP maps were constructed in two insect‐susceptible × insect resistant soybean populations: Cobb × PI171451 and Cobb × P1227687. Insect resistance was measured either in the field or greenhouse as percentage defoliation by corn earworm on vegetative soybean plants. Marker‐QTL associations were detected by interval mapping and confirmed by single‐factor analysis of variance. Comparisons were made between QTLs identified in this study and those identified previously using PI229358 as the source of insect‐resistant germplasm. Among the three resistant genotypes (PI171451, PI227687, and PI229358) a QTL on linkage group (LG) ‘H’ was shared among all three genotypes (accounting for an R2 of 19,9, and 17%, respectively), and a major QTL on LG ‘M’ was shared between PI171451 and PI229358 (R2= 37% for each). A minor QTL on LG ‘C2’ was identified which was unique to PI227687 (R2= 11%) and a minor QTL on LG ‘D1’ was identified which was unique to PI229358 (R2 = 12%). In addition, a QTL was found on LG ‘F’ in the susceptible genotype, Cobb (R2 = 20%). This QTL is in a region of the soybean genome which has been previously associated with a cluster of soybean pathogen‐resistance loci.
Using Partial Least Squares Regression, Factorial Regression, and AMMI Models for Interpreting Genotype × Environment Interaction
Authors: Vargas Mateo , Crossa José , van Eeuwijk Fred A. , Ramírez Martha E. , Sayre Ken
Published: July 2010

Partial least squares (PLS) and factorial regression (FR) are statistical models that incorporate external environmental and/or cultivar variables for studying and interpreting genotype × environment interaction (GEl). The Additive Main effect and Multiplicative Interaction (AMMI) model uses only the phenotypic response variable of interest; however, if information on external environmental (or genotypic) variables is available, this can be regressed on the environmental (or genotypic) scores estimated from AMMI and superimposed on the AMMI biplot. The objectives of this study with two wheat [Triticum turgidum (L.) var. durum] field trials were (i) to compare the results of PLS, FR, and AMMI on the basis of external environmental (and cultivar) variables, (ii) to examine whether procedures based PLS, FR, and AMMI identify the same or a different subset of cultivar and/or environmental covariables that influence GEI for grain yield, and (iii) to find multiple FR models that include environmental and cultivar covariables and their cross products that explain a large proportion of GEI with relatively few degrees of freedom. Results for the first trial showed that AMMI, PLS, and FR identified similar cultivar and environmental variables that explained a large proportion of the cultivar × year interaction. Results for the second wheat trial showed good correspondence between PLS and FR for 23 environmental covariables. For both trials, PLS and FR complement each other and the AMMI and PLS biplots offered similar interpretations of the GEl. The FR analysis can be used to confirm these results and to obtain even more parsimonious descriptions of the GEL
Natural Hybrids of Elymus elymoides × Leymus salinus subsp. salmonis (Poaceae: Triticeae) Kevin B. Jense
Authors: Jensen Kevin B. , Redinbaugh M. , Blood M. , Horton W. H. , Asay K. H.
Published: July 2010

Several putative hybrids between Elymus elymoides (Rafin.) Sweezey and Leymus salinus (M.E. Jones) Á. Löve subsp, salmonis (C. Hitchc.) Atkins were found growing on the west side of the Great Salt Lake, near Lakeside, UT in 1995. Naturally occurring hybrids between these two species have not been documented previously. Cytological, morphological, and chloroplast DNA analysis of the hybrids and parents confirmed the hypothesis that these plants were hybrids of the two species. Elymus elymoides and L. salinus subsp. salmonis were the only Triticeae species growing in the area that could have contributed to the intermediate morphological features expressed in the hybrids. Leymus salinus subsp, salmonis (NsNsXmXm; 2n = 4x = 28) and E. elymoides (StStHH; 2n = 4x 28) are allotetraploids that regularly formed 14 bivalents at metaphase I (MI). The hybrids between the two species are also tetraploids and averaged 22.1 univalents and 2.86 bivalent associations per cell at MI. Chromosompea iring in the hybrids suggests essentially no homology between the chromosomes from the two parents; thus the genomic formula for the hybrid can be written as StHNsXm. The hybrids were morphologically intermediate between the suspected parent species, but they resembled L. salinus subsp, salmonis more closely than E. elymoides. Analysis of chloroplast DNA in the hybrid and its putative parents, demonstrates cytoplasmic DNA identical to E. elymoides, suggesting that E. elymoides was the maternal parent. Complete sterility and reduction in chromosome pairing in the natural hybrids between E. elymoides and L. salinus subsp, salmonis suggest that the potential for genetic exchange between the two species is limited or lacking. Due to hybrid sterility, the natural hybrid will have little impact on the native vegetation of the western deserts of Utah and, without restored fertility, has no potential as a restoration grass on semiarid range sites.
Genome Characterization of MT‐2 Perennial and OK‐906 Annual Wheat × Intermediate Wheatgrass Hybrids
Authors: Jones T. A. , Zhang X‐Y , Wang R. R‐C.
Published: July 2010

Montana‐2 (MT‐2; × Agrotriticum intermediodurum Khizhnyak) is a variable perennial F5:15 line derived from hybridization between durum wheat (Triticum turgidum L. var. durum, AABB) and Thinopyrum intermedium (Host) Barkw. & D.R. Dewey (StStEEEE). OK‐906 is a uniform annual line derived from hybridization between hexaploid wheat (Triticum aestivum L., AABBDD) and an unknown Thinopyrum sp. followed by backcrossing to wheat and several generations of selling and selection. We wished to characterize perennial (Thinopyrum) and annual (Triticum) chromosome content of MT‐2 and OK‐906 to determine how chromosome content corresponds to perenniality. When DNA of genomes ABD (T. aestivum) + Eb [Thinopyrum bessarubicum (Savul & Rayss) Löve] was used as the block and DNA of the genome St [Pseudoroegneria stipifolia (Czern. ex Nevski) A. Löve] was used as the probe, the average chromosome content amongl5 MT‐2 lines was 26.2 wheat + 9.4 St + 18.8 E + 1.5 St/E translocation = 55.9 chromosomes (8x). Variation for genomic content was found within as well as among MT‐2 lines, indicating that instability remains in the material. OK‐906 exhibited about 40 wheat + 6 St + 8 E + 2 St/E translocation = 56 chromosomes (8x), but some aneuploidy was present. Its chromosome content is similar to ‘Agrotana’, another wheat × Thinopyrum annual. Perenniality in MT‐2 may relate to its higher perennial chromosome dosage (about 30 of about 56 chromosomes) than OK‐906 or Agrotana (16 of 56 chromosomes). Alternatively, specific genes or chromosome segments may confer perenniality. Development of stable breeding populations from MT‐2 is improbable because of its variable chromosome constitution. However, individual lines could be useful for forage if they could be stabilized with improved seed yield.
Heritability of Lipase Activity of Oat Caryopses
Authors: Hoi S. W. , Holland J. B. , Hammond E. G.
Published: July 2010

Oat (Avena sativa L.) is a potentially economically viable source of lipase, an enzyme used in foods, chemicals, and pharmaceuticals, which occurs on the surface of oat caryopses (groats). The objectives of this study were to: (i) estimate the broad‐sense heritability of the lipase activity of oat caryopses, (ii) determine the genetic and phenotypic correlations between lipase activity and other important agronomic traits, and (iii) test whether five cycles of recurrent selection for test weight caused a correlated response in lipase activity. Entries included 10 check cultivars, 95 randomly chosen S0‐derived lines from the initial cycle (C0), and 19 S0‐derived lines from C5 of a population developed by randomly mating oat cultivars and lines adapted to the midwestern USA. Entries were grown at three Iowa locations in 1996 and 1997. Broad‐sense heritability estimates for lipase activity were 0.22 on a sample basis in the population, and 0.63 on a line‐mean basis. Lipase activity had positive genetic correlations with total biomass (r = 0.31), heading date (r = 0.53), and plant height (r = 0.58), positive phenotypic correlations with heading date (r = 0.18) and plant height (r = 0.26), and negative phenotypic correlations with biomass (r = −0.13), test weight (r = −0.30), weight of 50 seeds (r = −0.18), weight of 50 groats (r = −0.40), and groat percentage (r = −0.34). The C0 and C5 populations did not differ for mean lipase activity, indicating that selection for increased test weight did not affect lipase activity. We suggest that selection for cultivars with higher lipase activity and acceptable grain quality is possible.
Heritabilities and Interrelationships of Water‐Use Efficiency and Agronomic Traits in Irrigated Alfalfa
Authors: Ray Ian M. , Townsend M. Shaun , Muncy Cherokee M.
Published: July 2010

Improvements in alfalfa (Medicago sativa L.) water‐use efficiency (WUE), the amount of forage and root biomass produced per unit of water transpired, could benefit irrigated production environments. Correlations between important agronomic traits and key physiological traits associated with WUE must be determined if benefits from improved WUE are to be realized. This study characterized genetic correlations among carbon isotope discrimination (Δ), canopy temperature, ash concentration, specific leaf mass (SLM), dry matter yield, forage maturity, and leaf‐to‐stem ratio (LSR) in irrigated alfalfa. Heritabilities of the traits on a progeny mean basis were also determined. Twenty‐eight half‐sib families possessing moderate fall dormancy were evaluated in seeded plots that were irrigated every 14 d during 2 yr near Las Cruces, NM. An increase in dry matter yield was associated with higher Δ (r = 0.39; P ≤ 0.05) and reduced LSR (r = −0.75; P ≤ 0.01). Carbon isotope discrimination was negatively correlated with specific leaf mass (r = −0.43; P ≤ 0.05) but was not correlated with canopy temperature or ash concentration. Ash concentration, Δ, LSR, and yield were moderately heritable (h2 = 0.44 to 0.61) indicating that these traits could be altered through breeding and selection. A positive relationship between A and forage yield indicated that both traits should be evaluated when characterizing alfalfa for high WUE to minimize potential yield reductions that may result from selection based only on Δ. The magnitude of the positive correlation between Δ and forage yield indicated that opportunities may exist to simultaneously improve both traits in irrigated environments. Moderate to low correlations between Δ and SLM, canopy temperature, and ash concentration indicated that none of these traits provided highly reliable estimates of Δ in irrigated alfalfa.
Continuous Daily Light Period and Temperature Influence Peanut Yield in Nutrient Film Technique
Authors: Rowell T. , Mortley D. G. , Loretan P. A. , Bonsi C. K. , Hill W. A.
Published: July 2010

The peanut (Arachis hypogaea L.) is under investigation for use in the National Aeronautics and Space Administration's Advanced Life Support (ALS) program as a food source for extended space missions. The objective of this study was an evaluation of the effect of a continuous light period combined with constant or diurnally cyded temperatures on pod and seed yield, plant biomass, harvest index, and gas exchange in ‘Georgia Red’ peanut grown hydroponically under the nutrient film technique. Experiments were conducted in controlled‐environment growth chambers. Treatments were light/ dark periods of 12/12 h or 24/0 h in combination with a constant 28 or 28/22°C. Relative humidity was 70 ± 5% and a photosynthetic photon flux (PPF) at canopy level of 250 or 500 μmol m−2 s−1 for 2410 h and 12/12‐h light periods, respectively. Plants exposed to 24/0 h light produced more foliage biomass, lower pod and mature seed yields, and lower harvest indices. Temperature had no significant effect on foliage biomass yield. However, plants exposed to diurnal 28/22°C produced higher pod and immature seed yield and a higher harvest index. The mean number of flowers reaching anthesis was higher among plants grown at a 12/12‐h light period, regardless of temperature. Leaf net photosynthetic rates and stomatal conductance were higher among plants grown at 12/12‐h light period, regardless of temperature. The results suggest that, while light period influenced, foliage, pod, and seed yield, temperature influenced foliage dry mass, immature seed yield, and harvest index.
Urea Placement and Nitrification Inhibitor Effects on Growth and Nitrogen Accumulation by No‐Till Winter Wheat
Authors: Rao Srinivas C. , Popham Thomas W.
Published: July 2010

Reduced forage production, grain yield, and visual N deficiency symptoms in no‐till winter wheat (Triticum aestivum L.) prompted this study. Our objectives were to determine the effect of urea placement and two nitrification inhibitors—nitrapyrin [2‐chloro‐6 (trichloromethyl) pyridine] (NP) and dicyandiamide (DCD)—on aerial dry matter and N accumulation. A 4‐yr field study was conducted on a Renfrow silt loam soil (fine‐silty, mixed, thermic Udertic Paleustoli) silt loam near El Reno, OK. The seven treatments included urea fertilizer (60 kg N ha−1) with and without the two inhibitors, surface broadcast or banded 3 to 4 cm below the seed row, and an unfertilized control. Aerial dry matter accumulation during autumn was higher for banded urea plus DCD (22%) and broadcast urea plus DCD (25%), than for broadcast urea without an inhibitor. Whole plant N content during autumn also was higher for banded urea plus DCD (28%) than for broadcast urea without an inhibitor. Neither inhibitor nor placement affected total dry matter accumulation measured at tillering, but differences were noted at spike emergence, gainful, and final harvest. At spike emergence in 1991, when climatic conditions were favorable for early season wheat growth, N content was greater for broadcast urea plus nitrapyrin than for broadcast urea or banded urea without inhibitor. At final harvest, both DCD treatments exhibited greater N content than all other N treatments. In 1993, when dimatic conditions were favorable for leaching, DCD was effective in slowing nitrification and increasing N uptake, regardless of fertilizer placement. Our results suggest that fall application of DCD with urea can potentially increase autumn forage production and N content, thus prolonging the grazing season or accommodating increased stocking rates.
Variation in Pathogenicity, Morphology, and RAPD Marker Profiles in Colletotrichum graminicola from Turfgrasses
Authors: Back P. A. , Landschoot P. J. , Huff D. R.
Published: July 2010

Anthracnose basal rot (ABR), caused by Colletotrichum graminicola (Ces.) Wils., is a destructive disease of annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis palustris Muds.) golf course putting greens in North America and western Europe. Typically, only one of these turfgrass species is affected by ABR when both are present in putting greens. The objectives of this study were to determine if isolates of C. graminicola from annual bluegrass and creeping bentgrass are host specific and if differences in pathogenicity, morphology, and randomly amplified polymorphic DNA (RAPD) marker profiles occur among isolates from annual bluegrass, creeping bentgrass, and corn (Zea mays L.). One isolate of C. sublineolum P. Henn. apud Kabat & Bub. from sorghum [Sorghum bicolor (L.) Moench] was included for comparison in morphology and RAPD marker studies. Pathogenicity studies using C. graminicola isolates were conducted in growth chambers on annual bluegrass and creeping bentgrass. Although several isolates were more virulent on the host species from which they were isolated, strict host specificity was not observed. No consistent differences in conidia length were found between annual bluegrass isolates and those from creeping bentgrass. However, differences in conidia length were found between com isolates and isolates from turfgrasses and sorghum. Cluster analyses of RAPD markers showed that isolates from annual bluegrass and creeping bentgrass separated into two distinct groups. Analysis of molecular variance (AMOYA) revealed that significant genetic differences (P = 0.001) exist between isolates obtained from annual bluegrass and isolates from creeping bentgrass.
Salinity Tolerance Mechanisms of Grasses in the Subfamily Chloridoideae
Authors: Marcum Kenneth B.
Published: July 2010

Forage grasses and turfgrasses are increasingly being subjected to salinity stress, due to accelerated salinization of irrigated agricultural lands worldwide, and to increased use of reclaimed and other secondary water sources for irrigating turfgrass landscapes. The objective of this study was to examine salinity responses of a number of important forage and turfgrass genera in the subfamily Chloridoideae in attempt to gain understanding of salinity tolerance mechanisms operating in this subfamily. Grasses were exposed to salinities up to 600 mM NaCI in solution culture. Salinity tolerance decreased in the following order: Distichlis spicata vat. stricta (Tort.) Beetle > Sporobolus airoides (Tort.) Tort. > Cynodon dactylon (L.) Pets. = Zoysia japonica Steud. > Sporobolus cryptandrus (Tort.) A. Gray. Buchloë dactyloides (Nutt.) Engelm. > Bouteloua curtipendula (Michx.) Tort. Relative root length (RL) and relative root weight (RW) increased under saline conditions, relative to control, in salt tolerant grasses. Leaf sap osmolality, Na+, Cl−, and proline concentrations were negatively correlated and glycinebetaine was positively correlated with salinity tolerance. Bicellular salt glands were observed on leaves of all species. Salinity tolerance was positively correlated with Na+ and Cl− salt gland secretion rates. Within the subfamily Chloridoideae, salinity tolerance was associated with saline ion exclusion, facilitated by leaf salt gland ion secretion, and with accumulation of the compatible solute glycinebetaine.