bluuebunny/crossref_metadata_2025 huggingface dataset:
Partitioning Genotype‐Environmental Interaction in Regional Yield Trials via A Generalized Stability Variance
Authors: Piepho H. P.
Published: July 2010

An analysis of phenotypic stability is usually based on multilocation trials, which yield a two‐way table of genotypes and locations. To analyse stability, it is common to estimate for each genotypes a component of variance (the stability variance) attributable to the genotype × location interaction of the genotype. This approach has the limitation of ignoring genotype × year interactions, which may have a large influence on stability. This paper proposes a new measure of stability, which equally weights estimates of genotypes × year, genotypes × location, and genotype × location interaction variances.
Inheritance of Resistance to the Peanut Root‐Knot Nematode in Soybean
Authors: Luzzi Bruce M. , Boerma H. Roger , Hussey Richard S.
Published: July 2010

The inheritance of resistance in soybean [Glycine max (L.) Merr.] to the peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood; Ma] was determined using crosses of a susceptible genotype, ‘CNS’, with three resistant genotypes, ‘Jackson’, PI200538, and PI230977. For each cross, F1, F2, and/or F3 populations were screened in a greenhouse for resistance to gall formation by counting individual galls on the roots of plants inoculated with eggs of Ma Race 2. The range and continuous pattern of each F2 and/or F3 distribution indicated that resistance to gall formation was quantitatively inherited. Variance component heritability estimates for the three crosses ranged from 0.48 to 0.62 on a plot basis and 0.74 to 0.83 on a mean basis. The correlation between gall number on F~ plants and mean gall number on F3 progeny ranged from 0.29 to 0.44 for CNS × Jackson and PI200538 × CNS. The genetic uniqueness of resistance genes was determined for crosses of Jackson × PI200538 and PI200538 × PI230977. Susceptible genotypes in F~ and F~ populations and significant differences (P < 0.05) among F3 families from each cross indicated that PI200538 has genes for resistance to Ma that are not the same as Ma resistance genes in Jackson and PI230977. This information will enable breeders to efficiently use PI200538 and PI230977 to improve the level of resistance to Ma in soybean cultivars.
Gains from Selection under Drought versus Multilocation Testing in Related Tropical Maize Populations
Authors: Byrne P. F. , Bolaños J. , Edmeades G. O. , Eaton D. L.
Published: July 2010

Ideal maize (Zea mays L.) cuitivars for tropical areas should yield well both in the presence and absence of drought, but optimal selection strategies for accomplishing this goal are not dear. This study evaluated progress from selection of two related tropical populations across a broad range of environmental conditions. ‘Tuxpeflo Sequia’ (TS) had undergone fuli‐sib recurrent selection for eight cycles at one location under managed levels of drought stress, while ‘Tuxpefio 1’ (T1) was selected for six cycles in a modified full‐sib selection scheme that relied heavily on muitilocation yield trial data. Combined over 12 environments (with mean yields ranging from 0.30−7.93 Mg ha−1), regression analysis revealed significantly different rates of change per cycle for TS and T1, respectively, for grain yield (1.68 and 1.06%, P < 0.10), anthesis‐siiking interval (ASI) ( −8.59 and 0%, P < 0.10), ears per plant (1.26 and 0%, P < 0.05), and plant height (−0.83 and 1.29%, P < 0.01). Days to anthesis decreased in both TS and T1 (−0.36 and −0.15% per cycle, respectively), but the difference between populations was not significant at P < 0.10. The interaction of environments with the linear rate of gain in grain yield was not significant in either population, indicating similar progress across the range of environmental conditions sampled. Stability analysis indicated that TS Cycles 6 and 8 and the check variety ‘La Posta Sequia Best’ were the most stable and high yielding entries in the trial. Better yield gain in TS is likely related to its selection for reduced ASI under controlled stress at a single site. Selection under managed levels of drought stress at one location together with muitiiocation testing may be desirable components of maize breeding programs for drought‐prone tropical areas.
Maize Kernel Development in Vitro: Sucrose Concentration, Xenia, and Maternal Effects
Authors: Seka D. , Cross H. Z. , McClean P. E.
Published: July 2010

Grain‐filling rates primarily determine kernel mass, an important yield component in early‐maturing maize (Zea mays L.). To learn how genes control grain‐filling rates, we studied 12 hybrids among strains divergently selected from a single genetic background. We reciprocally intercrossed three strains selected to differ for grain‐filling rates [high (HC), random (RC), and low (LC) R‐nj aleurone color] to a large‐(LG) and a small‐kernel (SM) strain. We pollinated hybrid plants with LG‐ or SM‐strain pollen to produce a (2 × 3 × 2 × 2) factorial set of kernel genotypes. After 3 d, cob pieces with a single attached ovule of each genotypo were explanted and grown in vitro with 80, 120, or 160 g L−1 sucrose. We sampled kernels and cob pieces after 7, 14, and 21 d. Kernel dry weight and water content increased while kernel moisture concentration decreased linearly during the 21 d in culture. Cob dry weight increased until 14 d in culture. Kernels cultured on a medium with 160, compared to 80, g L−1 sucrose grew 27% faster but lost moisture concentration 32% more slowly. Kernels pollinated with LG, compared to SM, pollen accumulated dry matter 27% faster and achieved 36% higher mean dry weights. Kernels explanted from LG, compared to SM, plants grew 29% faster and averaged 34% higher dry matter. Significant (P < 0.01) reciprocal differences among hybrid plants for kernel traits and xenia effects on cob piece growth in culture suggest that exogenous genes influenced development rates. Paternal and maternal genes in the kernel, and sucrose supply also influenced kernel dry matter, kernel water content, and cob dry weight in vitro.
Xenia and Maternal Effects on Maize Kernel Development
Authors: Seka D. , Cross H. Z.
Published: July 2010

Maize (Zea mays L.) kernel mass is a primary grain yield component controlled by genes from both the pollen and the maternal plant. We studied the contribution of genes attributable to kernel weight difference when inherited through the pollen versus the plant. We measured grain‐filling characteristics, kernel moisture concentration, rate of moisture ross, and mature kernel dry weight for apical, mid‐ear, and basal kernels of field‐grown plants. We produced 12 hybrid strains by reciprocally intercrossing three strains that differ for grain‐filling rates [high (tiC), random (RC), and low (LC) R‐nj color expression] with two kernel‐weight strains [large. (LG) and small (SM)]. Plants of each hybrid strain were pollinated with either LG or SM pollen in Fargo, ND, in 1990, 1991, and 1992. Multivariate analyses of variance showed that LG and SM pollen effects differed for rate of grain filling, lag phase duration, and kernel dry weight. Kernels from LG pollen had 0.4% shorter lag phases, grew 5.2% faster, and were 3.9% heavier at maturity than kernels from SM pollen. Developmental similarities among apical, mid‐ear, and basal kernels suggested that a common assimilate supply controlled their growth. Kernels from LG plants had 2.6% higher grain‐filling rates, 5.9% longer effective filling periods, 0.7% shorter lag phases, 7.6% heavier mature kernds, and 23 g kg−1 lower moisture concentration at physiological maturity than kernels from SM plants. We found reciprocal effects among hybrid plants for all traits. Kernel‐weight genes produced xenia effects for three traits determining kernel dry weight, but affected many additional traits when inherited via the plant.
Ineffectively and Effectively Nodulated Alfalfas Demonstrate Biology Nitrogen Fixation Continues with High Nitrogen Fertilization
Authors: Lamb J. F. S. , Barnes D. K. , Russelle M. P. , Vance C. P. , Heichel G. H. , Henjum K. I.
Published: July 2010

Estimates of biological nitrogen fixation (BNF) require a non‐N2‐fixing control preferably of the same species as the crop under evaluation. A field experiment was conducted to evaluate two ineffectively nodulated alfalfa (Medicago sativa L.) germplasms as non‐N2‐fixing controls for estimating BNF under increasing N fertilizer applications. ‘Ineffective Agate’ and ‘Ineffective Saranac’ and their effective parental cultivars, Agate and Saranac, were planted in field plots at Rosemount, MN, in 1985 and 1986. Forage yields were taken in each study at early bloom for 2 yr. Plots received four rates of ammonium nitrate (0, 70, 140, and 210 kg N ha−1 ) after each harvest. Biological nitrogen fixation in the 1986 plots was estimated by both the l5N isotope dilution technique and the difference method. In the presence of adequate inorganic N, ineffectively noduiated plants were comparable to their effective counterparts in herbage yield and N content. No difference in herbage yield or N content at any N fertilizer treatment was observed between Ineffective Agate and Ineffective Saranac, indicating that the two entries would be comparable non‐fixing controls for field assessment of BNF. The isotope dilution technique and the difference method gave comparable estimates of the change in BNF with applied N. Estimates of BNF declined in both Agate and Saranac in response to increasing N fertilization, but continued at high rates at the highest fertilizer N addition. A first production year stand of alfalfa under an annual N application rate of 840 kg/ha obtained 20 to 25% of its N from BNF. This is the first report that BNF continues with high levels of N application.
Phyllochron Response to Vernalization and Photeperiod in Spring Wheat
Authors: Mossad Moussa G. , Ortiz‐Ferrara Guillermo , Mahalakshmi Viswanathan , Fischer Ralph A.
Published: July 2010

An understanding of how environment controls the initiation and development of the leaf is required to construct dynamic crop simulation models. The aim of this study was to determine the effect of vernalization and photoperiod on total number of leaves at anthesis, leaf emergence rate, and phyllochron in 20 spring wheat genotypes (Triticum aestivum L.). An experiment was conducted under greenhouse conditions during spring 1992 at ICARDA, Tel Hadya, Syria, with all combinations of three photoperiods (8‐, 12‐, and 16‐h daylength) and two vernalization treatments (vernalized and nonvernalized). Total number of leaves on the main stem at anthesis decreased with increasing photoperiod. Vernalization reduced the total number of leaves on main stem at anthesis in the eight vernalization‐sensitive genotypes. Leaf number on the main stem was linearly (r = 0.99) related to accumulated growing degree days (°C d). Genotypes differed in leaf emergence rates. Leaf‐emergence rate increased with increasing photoperiod. Phyllochron decreased with increased daylength from 124 °C d leaf−1 at 8 h to 97 °C d leaf−1 at 16‐h photoperiod. These results suggests that, to model leaf appearance and canopy development in wheat, genotypic coefficients of phyllochron need to be determined in relation to photoperiod. Additionally, the effect of vernalization at inductive photoperiods on the phyllochron in genotypes adapted to heat‐prone tropical environments needs further study.
Impact of Growth Retardants on Corn Leaf Morphology and Gas Exchange Traits
Authors: Kasele I. N. , Shanahan J. F. , Nielsen D. C.
Published: July 2010

Growth retardant (GR) application often produces compact plants with dark green foliage and reduced leaf size. These morphological alterations can affect leaf gas exchange and biochemical traits associated wiith photosynthesis. We conducted greenhouse experiments by growing corn (Zea mays L.) plants under optimum water and nutrient conditions to evaluate the impact of two GR treatments a seed‐applied treatment of BAS110.. W[1‐(2,4‐dichlorophenyl)‐2methoxy‐1‐methyl‐2(1H‐1,2,4‐triazol‐1‐yl) ethanol] at 250 mg kg‐1 of seed and an ethephon (2‐chloroethyl phosphonic acid) treatment (a foliar‐applied solution containing 100 μg a.i ehephon L−1 of water applied at three‐leaf stage), on leaf gas exchange characteristics [leaf stomatal conductance to H2O vapor (g5), leaf intercellular CO2 concentration (Ci) and leaf CO2 exchange rate (CER)] and water use efficiency, and other plant morphological traits. A CER vs. Ci response curve was also determined to assess the carboxylation efficiency for control and treated plants. Both GR reduced total plant leaf area and dry weight by about 21 to 31% relative to the control but increased specific leaf weight and weighted stomatal density by 7 to 19%. Leaf protein and chlorophyll contents were nearly doubled in GR‐treated plants. Leaf g3 Ci and CER were significantly higher in GR‐treated vs. control plants while CER/gs was significantly lower in GR‐treated plants. The CER vs. Ci response curve exhibited higher initial slope in GR‐treated plants compared to control plants, indicating a higher carboxylation efficiency. Our data indicate that GR application reduced leaf sie, concentrated photosynthetic pigments and enzymes, and enhanced CER of corn.
White Clover Morphology and Physiology in Response to Defoliation Interval
Authors: Kang J. H. , Brink G. E.
Published: July 2010

Yield response of white clover (Trifolium repens L.) to defoliation varies with leaf size. Our objective was to determine how specific aspects of plant morphology and physiology are responsible for differences in growth of diverse white clover cultivars in response to defoliation interval. Individual plants of ‘Aberystwyth S184’ (small‐leaf), ‘Grasslands Huia’ (medium‐smali‐leaf), and ‘Osceola’ (large‐leaf) were clipped to remove all fully expanded leaves and petioles 55 d after sowing in the greenhouse and then clipped every 7, 14, or 28 d for the next 28 d. Plant fraction dry matter (DM) accumulation and morphological and physiological characteristics were measured 1, 3, 7, 14, and 28 d after the final clipping. Stolon growth rate was inverse to leaf size classification (Aberystwyth S184, 7.6 cm d−1 Grasslands Huia, 5.8 cm d−1 > Osceola, 3.6 cm d−1). In contrast, maximum stolon weight/length ratio of Osceola increased 31% vs. a 1% increase for Grasslands Hula and Aberystwyth S184 as defoliation interval increased to 28 d, which resulted in greater stolon DM accumulation by Osceola at the 14‐ and 28‐d intervals. Stolon and root carbohydrate concentration of Osceola was greater than and leaf carbohydrate concentration was less than the other cultivars at all defoliation intervals, indicating greater reliance on stored carbohydrates for regrowth by Osceola. Although plant leaf area of Oseeola was greater than that of Grasslands Hula and Aberystwyth S184 at the 28‐d interval only, forage DM accumulation of Osceola was greatest at all intervals due to petiole length. In grazed swards, however, greater petiole length would likely increase accessibility to and removal of leaf tissue, subsequently reducing new leaf and stolon growth.
Processing Foreign Turfgrass Germplasm through Federal Quarantine
Authors: Waterworth Howard , Donnelly Kevin
Published: July 2010

Foreign germplasm will continue to be an important component of turfgrass breeding programs. Hundreds of alien pathogens overseas are not found in the USA, and some are responsible for major economically devastating losses. Vegetative propagules, but not imported seeds of turfgrass genera, are quarantined on arrival in the USA. They are closely observed for insects and diseases, and are tested for some 50 viruses reported worldwide to infect grasses. Two virus‐indexing tests are conducted in duplicate under quarantine control 6 to 12 mo apart. They are (i) mechanical transmission of viruses in extracted sap to eight genera of monocots (herbaceous test) such as wheat (Triticum aestivum L.) and corn (Zea mays L.), each of which is sensitive to one or more viruses, and (ii) sap examination under the electron microscope (EM) for the presence of virus particles. More than 95% of the accessions are released from quarantine after completion of 12 to 18 mo of virus testing. Status of quarantined germplasm is maintained in the Germplasm Resources Information Network (GRIN), which any U.S. scientist can access via computer. Processing turfgrass germplasm through quarantine will continue to be an important component of the Federal program of safeguarding exotic germplasm introduction and eventual introgression.
Fine Fescue Germplasm Diversity and Vulnerability
Authors: Ruemmele B. A. , Brilman L. A. , Huff D. R.
Published: July 2010

Festuca spp., fine fescue turfgrasses, include several species: Festuca rubra L. rubra, strong creeping red fescue; F. rubra L. litoralis (G.F.W. Meyer) Auquier, slender creeping red fescue; F. rubra L. commutata Gaud., Chewings fescue; F. longifolia Thuill. (F. ovina var. duriuscula L. Koch), hard fescue; F. ovina L., sheep fescue; F. ovina L. glauca Lam. (F. glauca Lam.), blue fescue; and F. tenuifolia Sibth., hair fescue or fine‐leaved sheep fescue. Extensive variability exists within these species. Fine fescues are shade tolerant and drought resistant. Improvements sought for these species include better wear tolerance, insect and disease resistance, and sod‐forming ability. Additional germplasm for breeding may be acquired from areas of European origin and naturalized stands in the USA, such as the eastern seacoast, where initial colonization occurred. A major limitation to germplasm enhancement among species results from differences in anthesis date and time of flowering each day, as well as chromosome number. Taxonomic classification of species is disputed. Certain species, such as Sheep fescue are indigenous to the USA or may have native components, but further collection and study is needed for genomic clarification. Chromosome similarities determined by chromosome counts and flow cytometry of nuclear DNA content may determine feasible crosses leading to taxonomic clarification.
Diversity of Turfgrass Germplasm in the Asian Pacific Rim Countries and Potential for Reducing Genetic Vulnerability
Authors: Brede A. Douglas , Sun Suichang
Published: July 2010

The Asian Pacific Rim countries have traditionally been noted for their wealth of botanical diversity. Many cultivated agronomic, ornamental, and turfgrass species trace their primary or secondary origins to this region of the world, including turf species of the genera Zoysia, Eremochloa, Axonopus, Stenotaphrum, and Paspalum. Compared with Europe and North America, the indigenous turfgrasses of the Pacific Rim have been minimally collected and exploited by plant breeders. Plant collectors early in this century introduced exotic Asian turfgrass species to the West, but only within the last 12 yr have collectors returned in earnest to explore Asia's diversity of turfgrass germplasm. Many have found that the fertile grasslands well suited to the growth of high‐maintenance turfgrass species have been replaced with production agriculture, urban sprawl, or desert. Nevertheless, the future prospects for low‐maintenance germplasm from the Asian Pacific Rim appears good. Many remote, rocky, or infertile sites are relatively untouched and contain an abundance of turfgrass plants capable of withstanding adverse conditions. The future for discovery and collection of previously unutilized turfgrass species from the region is promising and may help to reduce the genetic vulnerability of present cultivars.
Diversity and Vulnerability of Bermuda Turfgrass Species
Authors: Taliaferro C. M.
Published: July 2010

Widespread use of relatively few clonally‐propagated turf bermudagrass (Cynodon spp. Rich.) cultivars in the USA creates a high risk for extensive damage from new pests. Knowledge of the genetic diversity within Cynodon, and access to that diversity would be important in counteracting pest epidemics. This paper reviews information on the distribution and cytotaxonomic diversity of Cynodon turfgrass species and the status of the current Cynodon collection in the U.S. National Plant Germplasm System (NPGS). Cynodon taxa containing germplasm of importance, or potential importance, as turf are C. arcuatus J. S. Presl. ex C. B. Presl., C. barberi Rang, et Tad., C. dactylon (L.) Pers. var. dactylon, C. dactylon var. polevansii (Stent) Harlan et de Wet, C. incompletus Nees var. incompletus, C. incompletus var. hirsutus (Stent) Harlan et de Wet, C. transvaalensis Burtt‐Davy, and C. × magennisii Hurcombe. Cynodon dactylon var. polevansii, C. incompletus vars. incompletus and hirsutus, C. transvaalensis, and C. × magennisii are endemic to South Africa. Cynodon barberi is endemic to southern India while C. arcuatus is distributed from Malagasy through south Asia to northern Australia. Cynodon dactylon var. dactylon is distributed worldwide between latitudes of 45°N and 45°S. The current Cynodon germplasm collection maintained by the NPGS contains 455 accessions of the indicated species plus 29 accessions classified as C. hybrid or C. species. Cynodon dactylon (L.) Pers. is the best represented taxon having 411 (85%) accessions from 39 geographic areas. The magnitude of genetic variation differs among the Cynodon taxa, being greatest in the cosmopolitan taxon C. dactylon var. dactylon. Taxa endemic to southern Africa are less variable and more susceptible to genetic erosion. To guard against this vulnerability and to exploit the maximum available genetic diversity of the genus for scientific use and breeding improvement will require a more comprehensive and better evaluated collection in the NPGS.
The Global Plant Genetic Resources System: A Competition‐Cooperation Paradox
Authors: Lacy William B.
Published: July 2010

The international plant genetic resources system is a loosely coordinated, often politicized network among national germplasm collections, which has encouraged the exploration, collection, evaluation, preservation and distribution of germplasm. During the last two decades, the system has been the focus of major debates, characterized as Seed Wars, over the international control of plant genetic resources. Key organizations such as the International Board for Plant Genetic Resources, the United Nations Food and Agriculture Organization's Commission on Plant Genetic Resources, and the United Nations' Convention on Biological Diversity have attempted to address the central issues of access to genetic resources including elite lines, funding and responsibility for biodiversity protection, treatment of biotechnology and intellectual property rights, and the technical and social challenges of conserving genetic materials. Despite these efforts, all nations are caught in a paradox of competition and cooperation. While each nation wishes to capture as much of the world's genetic resources as possible, each is dependent on many other nations for a continued supply of these dynamic and widely dispersed resources. The paradox, however, is not felt equally by all nations with some, particularly among the developed nations, apparently capable of both competing and cooperating successfully. Nonetheless, in both the short run, and particularly in the long run, it is in the best interest of all nations in this global community to find efficient and socially just ways to cooperate in conservation of biodiversity and to use it sustainably and equitably.
Plant Genetic Resources in the Andes: Impact, Conservation, and Management
Authors: Castillo Raúl O.
Published: July 2010

The Andean region harbors a variety of ecological niches including tropical mountains, Pacific coastal and Amazonian humid lowlands, and many intermediate microclimates. These areas contain a great diversity of crops and their wild relatives. Much of this diversity is indigenous and much has been selected by man. This genetic diversity includes food plants and their wild relatives, in addition to medicines, condiments, colorants, and spices. Both great empires and small indigenous groups have used various plants over thousands of years. Unfortunately, many landraces and their wild relatives have disappeared and others are near extinction. Although many collecting expeditions and some research projects have been conducted on these plants, more funding is needed for germplasm collection and conservation. National programs of plant genetic resources have been formed in the Andean countries to preserve and maintain this diversity and develop additional research. Both the Andean countries and the whole world will benefit from the discovery and market development of indigenous food, medicine, and industrial crops. These new agricultural products can be an important economic resource in emerging world markets and international trade.
Recurrent Selection for Extended Plant Height and Herbage Yield in Cicer Milkvetch
Authors: Townsend C. E.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.) produces about 50% of its total herbage in the first harvest and only about 12% in the third harvest under a three‐harvest regime. The photoperiod‐induced‐dormancy response offers an opportunity to improve herbage yield during the third growth period (1 August–10 September). Therefore, the objective of this study was to improve herbage yield during the third growth period without sacrificing yield in the other two growth periods. This study was conducted with spaced‐plants under irrigation near Fort Collins, CO, from 1984 through 1990. Extended plant height (length of longest stem) relative to the cultivar Monarch was increased 105, 108, and 114% in the first, second, and third harvests, respectively, by two cycles of recurrent selection. Mean plant herbage yield relative to Monarch was increased 113, 107, 116, and 111% for the first, second, and third harvests and for total yield, respectively, by two cycles of recurrent selection. Although herbage yield was increased substantially in the third harvest, simultaneous increases in the first and second harvests resulted in no difference for seasonal distribution of total yield. The 15 clones with the best performing polycross progenies for extended plant height and herbage yield were used as parents for the cultivar Windsor. Recurrent selection for lack of the photoperiod‐induced‐dormancy trait was an effective procedure for improving extended plant height and herbage yield of cicer milkvetch during the third growth period of a three‐harvest system.
Characteristics of Elite Population Selected on Ratio Criterion: I. Traits with Equal Genetic Variances
Authors: Rowe D. E.
Published: July 2010

In breeding, multiple trait selection is often a complex problem. One straightforward possibility when selecting for two traits is to base selection on the ratio of two trait values, particularly if the ratio has a biological or economic interpretation. In this study, selection was simulated on the ratio of two polygenically inherited Traits X and Y which were normally distributed and had genetic variances of one. The criterion for selection was the ratio (X/Y). The research objectives were to determine in the selected elite population (i) the responses of the numerator and denominator traits and the ratio, per se, to increasing selection pressure, (ii) the effect of genetic correlation between two traits on ratio selection, and (iii) the selection differentials of ratio trait for estimation of realized heritability. When the two traits had equal variances and means, selection to increase the ratio caused a greater decrease in the mean value of the denominator trait than an increase in the numerator trait. Conversely, selection to decrease the ratio always decreased the mean of the numerator trait more than it increased the denominator trait. For a highly negative genetic correlation (−0.75) between traits, the selection response of the ratio was maximized. When genetic correlation was 0.50 or 0.75, the response of one component trait was near zero. The standardized selection differential for the ratio trait, in comparison with the normally distributed trait, was biased upwards with selection for increased ratio and biased downwards with selection for decreased ratio.
Variation in Early Vigor between Wheat and Barley
Authors: Lóopez‐Castañeda C. , Richards R. A. , Farquhar G. D.
Published: July 2010

In dryland Mediterranean‐like climates, barley (Hordeum vulgare L.) generally has higher grain and biomass yields than other temperate cereals. The advantage of barley compared with wheat (Triticum aestivum L.) is associated with barley's faster leaf area growth during vegetative development. Experiments were conducted in a glasshouse (average 25/15°C) and outdoors (average 17/5°C) to determine the traits associated with barley's greater early growth. Five cultivars each of barley and wheat were grown in large pots. Five harvests were made from the time there were about 2 leaves on the main stem to the time plants had about 4.5 leaves on the main stem. The weight of the caryopsis of all seeds sown was 35 mg. Barley produced ≈40% more aboveground biomass and two times greater leaf area than wheat by the two‐leaf stage. Barley had a 17% faster average leaf appearance rate and a 35% faster average tiller appearance rate than wheat but there was no evidence that either contributed to the differences in vigor between the two species. The relative growth rates for biomass and leaf area were also similar in the two species, although it was achieved in different ways. The average net assimilation rate (NAR) was 25% greater in wheat than in barley in both experiments, whereas the average leaf area ratio (LAR) was 23% higher in barley. Variation in specific leaf area (SLA) was largely responsible for the variation in NAR and LAR in both the glasshouse and outside. Factors between germination and the appearance of the second main stem leaf must be responsible for the greater early vigor in barley compared with that of wheat.
Characteristics of Photosynthesis and Translocation of 13C‐Labelled Photosynthate in Husk Leaves of Sweet Corn
Authors: Sawada Okihiro , Ito Junki , Fujita Kounosuke
Published: July 2010

Some corn genotypes produce husk leaves, i.e., laminae extending from the husk. However, the role of husk leaves in grain production is unclear. Hydroponic and field experiments were conducted to determine the contribution of husk leaves to dry matter and grain production and the characteristics of photosynthesis and translocation of 13C‐labelled photosynthate of the husk leaves in comparison to culm leaves. A husk leaf and calm leaves at different positions of hydroponically grown sweet corn (Zea mays L. cv. Laramie 83) were exposed to 13CO2. Field treatments consisted of a control and partial or complete defoliation at the silking stage. The 13CO2 feeding in both experiments and measurement of field photosynthetic rate were made 14 d after silking. Husk leaves alone produced ≈45% of the whole plant weight and grain yield, respectively, relative to the control plants. Dry matter and grain production per unit leaf area was greater for the husk leaves than culm leaves of defoliation plants. Photosynthetic rate of the husk leaves was almost equivalent to that of culm leaves of the control plants. Percentage export of 13C from husk leaves (96–97%) was higher than from culm leaves (87–92%). Percentage of plant 13C was highest in the ear (45–87%), followed by the culm. When 13CO2 was fed to a husk leaf, defoliation increased 13C accumulation in the ear but decreased it in other parts. When 13CO2 was fed from a culm leaf, however, the reverse trend was true. These results suggest that the husk leaves play an important role in grain production due to efficient translocation of photosynthate.
Carbon Isotope Discrimination and Indirect Selection for Seed Yield in Lentil
Authors: Matus A. , Slinkard A. E. , van Kessel C.
Published: July 2010

Carbon isotope discrimination (CID) has been proposed as a secondary trait to indirectly select for improved seed yield and water‐use efficiency. To determine the effectiveness of CID to indirectly select for seed yield, 10 diverse lentil (Lens culinaris Medikus) genotypes were grown at four locations in Saskatchewan in 1992 and 1993. Samples were collected for CID determination from leaves at flowering (CIDLF), leaves at maturity (CIDML) and seed at maturity (CIDMS). Variability for CID was present, but no crossover G × E interactions were observed. A significant crossover genotype by sampling date interaction for CID resulted from a change in ranking of genotypes for CIDLF and CIDML. Seed yield was positively correlated with CIDLF and CIDML. The phenotypic correlation between seed yield and CIDLF was 0.82** (dr = 8). However, this highly significant relationship was an artifact resulting from the fact that samples for CIDLF were collected for all genotypes on the same day, although PI 244026, an early maturing genotype, flowered about 15 d earlier than the other lentil lines. When PI 244026 was removed from the analysis, variability in CID was greatly reduced and the correlation between CIDLF and seed yield approached zero (r = 0.22, df = 7). The correlation between seed yield and CIDML remained positive and significant, but was inconsistent across locations and years. The broad sense heritability for CIDML (0.73 ± 0.16) was lower than the broad sense heritability for seed yield (0.98 ± 0.029). These results suggest that under the conditions tested CID should not be used to indirectly select for seed yield in lentil.
Growth and Development in an Oat Mutant Expressing Giantism
Authors: Taylor John S. , Yeung Edward C. , Kibite Solomon , Pharis Richard P.
Published: July 2010

Sources of germplasm for a forage oat (Avena sativa L.) program are limited. A recently isolated mutant oat, PI546363, exhibits characteristics (late maturity, tallness, leafiness, and low grain/straw ratio) that are desirable in a forage oat cultivar. As part of an investigation into the genetic/physiological basis for the mutant characteristics, a morphological and anatomical comparison was made between the mutant and its parents (two standard oat cultivars Tibor and OT745) during growth and development. The mutant and its parents were grown in a controlled‐environment chamber (21/17°C, day/night temperature; 16‐h photoperiod; approximately 400 mol m− 2 s− 2 photosynthetic photon flux at canopy height). Measurements of height, tillering, and leaf stage were made, and tissue samples were collected at weekly intervals until panicle emergence. Panicle emergence occurred after 16 wk (1568 heat units) for the mutant, and 6 wk (588 heat units) the parents. At panicle emergence, the mutant averaged 17 leaves compared with eight leaves for the parents; the height of the mutant was approximately 195 cm compared with 96 cm for the parents; and the number of live tillers was similar for both. The shift of the apex from vegetative to reproductive growth occurred at approximately 8 wk in the mutant and at 2 to 3 wk in the parents. The apex of the mutant was longer and larger (i.e., it had increased amounts of parenchymatous tissue), and produced more leaf primordia than its parents. Because of the delay in flowering and the increased vegetative growth, the mutant may be a useful source of germplasm in the development of superior forage oat cultivars.
Mechanisms of Resistance to Sclerotinia minor in selected Peanut Genotypes
Authors: Chappell G. F. , Shew B. B. , Ferguson J. M. , Beute M. K.
Published: July 2010

Sclerotinia minor (Jagger) Kohn is serious and increasingly prevalent pathogen of peanut (Arachis hypogaea L.). Peanut stem tissues were reported to differ in their resistance to S. minor, but field performance is not always correlated with laboratory evaluations of resistance to Sclerotinia diseases in other crops. Differences in genotype performance in field and laboratory results may reflect differences in mechanisms of resistance. The objective of this study was to characterize mechanisms of resistance to S. minor in selected peanut genotypes by using agar culture tests, wounded and nonwounded stem inoculations, and field trials. For the culture test, sap was expressed from five genotypes with different levels of field‐resistance toS. minor. Each extract was incorporated into an agar medium, which was overlaid with a dialysis membrane. The fungus produced distinctive infection hyphae on the media. Genotype extracts differentially affected size of terminal and secondary hyphae and the number of hyphae per organized cluster. Nine genotypes were evaluated for resistance to S. minor in two stem inoculation tests. Inoculation sites were wounded in the first method, and were not wounded in the second method. Significant differences in lesion size were found with both methods, but more differences were found among genotypes in the nonwounded inoculation. Genotype performance in culture and stem inoculation tests was not correlated with performance in the field. These studies demonstrated that although some genotypes had resistance to stem colonization by S. minor, other mechanisms account for most of the resistance expressed in the field.
Genetic Analysis of Hessian Fly Resistance in Eight Durum Wheat Introductions
Authors: Cambron Sue E. , Patterson F. L. , Ohm H. W. , Ratcliffe R. H. , Safranski G. G.
Published: July 2010

Breeding for resistance in wheat, Triticum spp L., to Hessian fly, Mayetiola destructor (Say), has been the most successful method of controlling damage from this pest. New genes for resistance are needed because virulence evolves in Hessian fly populations. Progenies of selected plants of eight durum wheat, Triticum durum Desf., introductions were compared for expression of resistance to Hessian fly Biotype L at temperatures of 19, 23, and 26°C. Biotype L is currently the most virulent biotype identified. The eight introductions had been shown previously to be resistant to Biotypes C, D, E, and L. All tested plants of the eight introductions were resistant to Biotype L at 19°C. At 23°C, all plants of four of the introductions were resistant, and four had from 88 to 98% resistant plants. At 26&C, all plants of three introductions were resistant, whereas five introductions had from 78 to 95% resistant plants. From testcross analyses, resistance in seven of the introductions appeared to be conferred by one, two, or three dominant or partially dominant independent genes. Resistances of CI3146‐6, CI3241‐2, and CI7335‐10 were different from genes H5, H9, H14, and H16 of tester stocks. The single gene resistance of CI3146‐6 was different from genes for resistance in CI3241‐2 and CI3984‐12. The two genes for resistance of CI7066‐1 were different from H9 and the two genes of CI7041‐3. Two lines, CI3170‐2 and CI3146‐6, appeared to have one gene in common.
Clonal‐by‐Environment Interactions Influence Isoflavonoid Accumulation in Cicer Milkvetch
Authors: Lenssen A. W. , Townsend C. E. , Martin S. S.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.) is a perennial, nonbloatinducing forage legume adapted to temperate environments. For unknown reasons, however, ruminants grazing cicer milkvetch in pure stands have become photosensitized, or sunburned, in some environments, Isoflavonoids are involved with diverse biological activities, including estrogenism, disease resistance, and, potentially, photosensitization. We conducted a series of studies from 1991 to 1993 to identify factors that influence the accumulation of isoflavonoids. In separate greenhouse studies, elicited leaflets from the parental clones of ‘Monarch’ and. ‘Windsor’ cicer milkvetch were analyzed for isoflavonoid accumulation. Growth chamber studies were conducted to investigate the clonal variability of leaflet isoflavonoid concentrations following different UV‐C exposure times, incubation times, shoot positions, and growth × incubation temperature interactions. In both parental gene pools, clones differed significantly for the accumulation of mucronulatol, astraciceran, acicerone, and cajanin. The interactions of clone × UV‐C exposure time, clone × incubation time, clone × shoot position, and clone × incubation temperature were significant for mucronulatol, astraciceran, maackiain, acicerone, and cajanin. Among all experiments, maximum mean concentration of mucronulatol, astraciceran, maackiain, acicerone, cajanin, biochanin A, and afrormosin was 2327, 152, 18, 63, 3, and 5 μg g−1 FW, respectively. Clone and environmental interactions with clones strongly influenced qualitative and quantitative accumulation of isoflavonoids in cicer milkvetch.
Combining Ability of Tropical Maize Accessions with U.S. Germplasm
Authors: Holland J. B. , Goodman M. M.
Published: July 2010

To supplement minimal information regarding the utility of tropical maize (Zea mays L.) germplasm to temperate maize breeding programs, agronomic evaluations of typical accessions of the Latin American races were made. Based on data from previous evaluation stages, 40 accessions exhibiting superior agronomic performance in tropical environments were chosen for photoperiod conversion and combining ability evaluations with U.S. germplasm in temperate environments. Accessions were converted to photoperiod insensitive semiexotic populations by crossing each to Mo44, a temperate‐adapted inbred unrelated to either of two major U.S. heterotic groups. Four families from each semiexotic population were crossed to two U.S. testers. Testcrosses were evaluated in three North Carolina locations for 2 yr. Based on these results, 29 agronomically superior semiexotic testcrosses were tested a third year. The variation for combining ability for yield was estimated to be two times greater among vs. within accessions, suggesting that sampling among accessions be given priority compared with sampling within to maximize genetic diversity for combining ability. Family yields were highly correlated across testers (r = 0.78), suggesting that a single temperate tester would be sufficient for evaluating large samples of Latin American accessions. Grain yields, resistance to gray leaf spot disease (incited by Cercospora zeae‐maydis Tehon & E.Y. Daniels), and other agronomic traits of superior semiexotic testcrosses were competitive with the public U.S. hybrid Mo17 × B73. The best accessions should be a promising source of useful genes for commercial U.S. maize breeding programs.
Growth Simulation Outputs for Detection of Differential Cultivar Response to Environmental Factors
Authors: Saulescu Nicolae N. , Kronstad Warren E.
Published: July 2010

Despite considerable research on genotype‐environment (GE) interactions, breeders still need a simple way to describe the specificity of each genotype's response to environmental factors. A new approach is suggested based on (i) use of growth simulation outputs (simulated water deficit, anthesis date, maximum leaf area) as environmental indices, (ii) use of simulated yield as a check, and (iii) use of simple correlation coefficients to describe the association between environmental indices and deviations from the average difference computed for each pair entry‐check. Simulated grain yield can be considered a better indicator of environmental adaptability, unaffected by factors like diseases, lodging, or winter‐kill that can reduce the average yield in the best environments. Other outputs of simulation models, which integrate weather and soil factors with proper timing according to plant development, can provide a better description of environments than the raw weather data. Yield data of sixteen wheat (Triticum aestivum L.) genotypes, grown at three locations in Oregon for a 5‐yr period (1988‐1992) were analyzed. Correlation with water availability indices clearly differentiated the cultivars that were unable to adapt to improved environments, because of lodging and/or disease susceptibility. Correlation with other environmental indices identified genotypes that responded more to low winter temperatures, to high temperatures after anthesis, or to delayed anthesis following cooler springs. The results indicated that the use of outputs from growth simulation models as covariates in analysis of GE interaction could be a useful tool in characterizing differential responses of genotypes to environmental factors.
Responses to a Modified Reciprocal Recurrent Selection in Two Maize Synthetics
Authors: Landi P. , Frascaroli E.
Published: July 2010

The early genotypes of maize (Zea mays L.) selected for the northern Corn Belt regions can perform poorly when grown as a delayed‐sowing crop in warmer regions. Two early synthetics, A and B, were developed and two cycles of a modified reciprocal recurrent selection were conducted in a delayed‐sowing crop by using A632 as a tester for Synthetic A and W117 as a tester for Synthetic B. Selection was based on a multitrait index involving grain yield, percent erect plants, and grain moisture. This study was conducted in three environments to evaluate the effects of selection. The source and selected populations of the two synthetics were tested per se and in hybrid combination to each other, to their inbred tester, and to the unrelated hybrid, A188 × W64A. The gain in the cross between the two synthetics was 4.9% cycle−1 (P ≤ 0.01) for the performance index (calculated similarly to the selection index), and this was mainly due to the gain in grain yield (12.2% cycle−1). However, undesired increases were found for grain moisture and silking date. The gains for performance index and grain yield were due to a balanced contribution of both changes per cycle of populations per se and of heterosis. Synthetic B contributed more than Synthetic A to the gain in the population cross for performance index, grain yield, and to the loss of earliness. Population crosses of both synthetics with corresponding testers and A188 × W64A showed a positive response for performance index and grain yield, and a loss of earliness for Synthetic B. The results indicated that the selection procedure was effective in improving the performance index of the two synthetics both per se and in hybrid combinations.
DNA Amplification Fingerprinting and Hybridization Analysis of Centipedegrass
Authors: Weaver Kristal R. , Callahan Lloyd M. , Caetano‐Anollés Gustavo , Gresshoff Peter M.
Published: July 2010

DNA amplification fingerprinting (DAF) with arbitrary oligonucleotide primers provides germplasm analyses for cultivar identification and protection of proprietary rights, and constitutes an effective tool in marker‐assisted breeding and in the study of genetic variation within natural and domesticated populations. In this study, DAF was used to infer genetic relationships in centipedegrass [Eremochloa ophiuroides (Munro) Hack.]. An optimization of reaction components defined amplification conditions that reproducibly fingerprinted centipedegrass and other turfgrass species. Cultivars Tennessee Hardy, Tennessee Tuff, Oklawn, Centennial, and Tifton common were analyzed with 14 octamer primers. Four primers produced polymorphic patterns, two of which differentiated all cultivars. Phylogenetic analysis using parisomy (PAUP) distinctly separated cold‐tolerant Tennessee Hardy. Numerous monomorphic bands were obtained, suggesting that the centipedegrass cultivars are closely related and are from a common origin. Several DAF bands were isolated from silver‐stained polyacrylamide gels for use as hybridization probes. A monomorphic 200‐base pair (bp) band that hybridized to a single amplification product detected eight homologous regions in genomic centipedegrass DNA. When hybridized to DAF patterns obtained from other turfgrass species, such as bermudagrass [Cynodon dactylon (L) Pers. × Cynodon transvaalensis Burtt‐Davyl, rough bluegrass (Poa trivialis L.) and Zoysia (Zoysia japonica Steud.), the 200‐bp fragment, and a 175‐bp fragment generated with a different primer, resulted in smearing patterns. While these products are only present within one size amplicon in centipedegrass fingerprints, the smearing indicated that the putative sequence was present in multiple copies throughout the amplification profile, was abundant in the heterologous grass genomes, and may have represented a family of repetitive DNA sequences. Our results indicated that DAF can generate molecular markers that can be used reliably for DNA fingerprinting of important centipedegrass cultivars. This tool would be useful in determining genetic relationships and diversity, and in establishing possible origins of cultivars.