bluuebunny/crossref_metadata_2025 huggingface dataset:
Starch Hydrolytic Enzyme Activities Following Defoliation of White Clover
Authors: Gallagher J. A. , Volenec J. J. , Turner L. B. , Pollock C. J.
Published: July 2010

White clover (Trifolium repens L.) is an imporlanl legume in grassland ecosystems. Its persistence in mixed grass‐dover swards, however, is dependent on utilization of stored carbohydrates during over‐wintering and subsequent spring regrowth. Reserve carbohydrate is stored as starch in stolons. Our objective was to determine how activities of starch hydrolytic enzymes change during defoliation‐induced starch mobilization in clover stolons. Starch degradation was induced by defoliating clonally propagated plants maintained in a controlled environment. Defoliation resulted in rapid, extensive starch remobilization from older stolon tissues, and prevented starch accumulation in young, developings tolon tissues. Amylasea ctivities of stolon tissue were determined immediately, 1, 2, 4, 8, and 12 d post‐defoliation. Total amylolytic activity decreased following defoliation. Of the starch hydrolytic enzymea ctivities determined, only the activity of α‐amylasc increased as a consequence of defoliation (two‐fold, with respect to the control). β‐amylase, which constituted the greatest proportion of total amylolytic activity, decreased two‐ to three‐fold in stolons of defoliated plants, but increased six‐fold in young stolon tissue, and almost two‐fold in old stolon tissue. The increase in enzyme activity correlated with starch deposition in control plants. Starch phosphorylase activity also decreased as a result of defoliation, while activity of α‐glucosidase changed little following the defoliation treatment. Our results suggest starch degradation in stolons of white clover is regulated by α‐amylase activity.
Pendimethalin and Corn Gluten Meal Combinations to Control Turf Weeds
Authors: Gardner D. S. , Christians N. E. , Bingaman B. R.
Published: July 2010

Concerns over ground water contamination and other environmental issues have prompted research to reduce synthetic herbicide use. Corn (Zea mays L.) gluten meal, a by‐product of wet milling, inhibits germination and the establishment of many annual and perennial weed species. Our objective in the field was to investigate crabgrass control (Digitaria spp.) in Kentucky Bluegrass (Poa pratensis L.) turf established on a Nicollet soil (fine‐loamy, mixed, mesic Aquic Hapludoll). In the greenhouse, we investigated the control of large crabgrass [Digitaria sanguinalis (L.) Scop.] on the same soil with no turfgrass cover. Experiments were conducted with corn gluten meal at 0, 49, 98, and 147 g m−2 combined in a factorial arrangement with pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine] at 0, 29, 59, 88, and 117 mg ai m−2. The minimum label rate for pendimethalin is 176 mg ai m−2. Field crabgrass control was improved by application of a sublethal rate of pendimethalin in addition to corn gluten meal. As the application rate of corn gluten meal increased from 49 to 147 g m−2, the level of pendimethalin required to provide 75 to 85% control for 15 wk decreased from 88 to 29 mg ai m−2. There was no increase in crabgrass control in plots that received amounts of corn gluten meal and pendimethalin exceeding these combined rates.
Modified Gibberellins Retard Growth of Cool‐Season Turfgrasses†
Authors: King R. W. , Blundell C. , Evans L.T. , Mander L.N. , Wood J.T.
Published: July 2010

Several modified gibberellins which inhibit shoot elongation have been assessed as turfgrass growth retardants. Dichloro‐methano 16,17‐dihydro GA5 (DMDGA5) effectively inhibited growth of the cool season grasses, Festuca arundinacea Schreb., Poa pratensis L., and Lolium perenne L. Turf growth (weekly cutting dry weight) was reduced by up to 70% in three separate field trials over three seasons. This inhibition lasted up to 5 wk before recovery to control growth rates and, often, there was then a transient enhancement of growth. DMDGA5 inhibited turf growth to the same extent as did the commercial turfgrass retardant, Trinexapac‐ethyl (commercially formulated as Primo, Novartis, Inc., Basel, Switzerland). Daily water use was also 25 to 30% less over at least 4 wk in studies with mini‐swards growing in controlled environment conditions. With isolated plants of two cultivars of P. pratensis (cvs Holt and Bronco) grown in controlled conditions leaf elongation rates were more than three‐fold greater in long than short daylengths. Both Trinexapac‐ethyl and DMDGA5 blocked most of this growth increase as did a related derivative, 16,17‐dihydro GA5. Since these compounds inhibit gibberellin biosynthesis it appears that the extra growth in long days arises from an increase in gibberellin content.
Resistance to Systemic Spread of High Plains Virus and Wheat Streak Mosaic Virus Cosegregates in Two F2 Maize Populations Inoculated with Both Pathogens
Authors: Marçon A. , Kaeppler S.M. , Jensen S.G.
Published: July 2010

High plains virus (HPV) has the potential to cause significant damage in susceptible maize (Zea mays L.) genotypes. The virus is vectored by the wheat curl mite (WCM), Aceria tosichella, Keifer, which also vectors wheat streak mosaic virus (WSMV). We have previously characterized susceptibility of maize inbred lines to double infection of HPV and WSMV. The objective of this study was to characterize the inheritance of resistance to systemic spread of HPV and WSMV in mixed infection. Genetic analysis was done with crosses B73 (resistant) × Wf9 (susceptible) an B73 × W64A (susceptible). Parental, F1, and F2 plants were WCM‐inoculated with HPV and WSMV, and scored for their reactions both visually and by enzymelinked immunosorbent assay. F1 plants were resistant to systemic spread of HPV and WSMV, indicating that resistance is dominant in these lines. Segregation (based on symptomology) in the F2 generation fit a 3:1 resistant:susceptible ratio in both B73 × W64A and B73 × Wf9 (P = 0.34 and 0.11, respectively), consistent with a single chromosome region segregating for resistance to both viruses. The resistant allele was contributed by B73 and was linked to marker bnl6.29 on the short arm of chromosome six. This chromosome region has been shown to control resistance to WSMV (wsm1). Two independent sets of inbred‐backcross‐derived near‐isogenic lines confirmed the effect of this chromosome region. This study reveals the genetic basis of symptomology observed upon mixed infection with HPV and WSMV in these populations. Identification of molecular markers linked to virus resistance genes may enhance inbred line development efforts.
Mapping Genes Conferring and Suppressing Leaf Rust Resistance in Wheat
Authors: Nelson J. C. , Singh R. P. , Autrique J. E. , Sorrells M. E.
Published: July 2010

Leaf rust, caused by Puccinia recondita Roberge ex Desmaz. f. sp. tritici Eriks. & E. Henn., is a serious disease of wheat (Triticum aestivum L.) worldwide. We evaluated leaf rust resistance in a RFLP‐mapping population of wheat inbred lines developed from a synthetic [T. turgidum L. × T. touschii (Coss.) Schmal.] × T. aestivum cross, using inoculation trials performed on seedlings and adult plants. Map locations were assigned for seedling resistance genes Lr10 (chromosome arm 1AS), Lr23 (2BS), Lr27 (3BS), and Lr31 (4BL), and the adult‐plant resistance gene Lr34 (7DS). The previously reported interaction between Lr27 and Lr31, requiring the presence of both genes for resistance to avirulent rust pathotypes, was confirmed. Lr23, effective in the durum parent (‘Altar 84’) of the synthetic, was suppressed in the synthetic and in one fourth of the inbred lines by a T. tauschii gene on homoeologous chromosome arm 2DS. This suppressor, designated as SuLr23, appears to be specific for Lr23 and may be orthologous to the gene. DNA markers are useful in refining the characterization of resistance genes and their interactions, toward the goal of constructing durably resistant cultivars via marker‐controlled accumulation of specific genes.
Interplot Interference Disorts Yield Estimates in Spring Wheat
Authors: Clarke F. R. , Baker R. J. , DePauw R. M.
Published: July 2010

Research in Europe and the USA indicated that interference between plots in cultivar trials can distort yield and result in misleading conclusions from yield comparisons. Field trials were conducted at Swift Current and Saskatoon in 1993 and 1994 to determine if interplot interference is a concern in the wheat growing region of Saskatchewan. Four spring wheat (Triticum aestivum L.) cultivars, Biggar, Oslo, Genesis, and Glenlea, were grown in four‐row plots in a diallel competition treatment design, with the competition treatments applied randomly to each of the eight replications. Generally, yield was distorted from pure stand yield when flanking plots differed for height. On average, yield was reduced 0.34% per centimeter increase in height of the flanking plots, and the reverse occurred when height of the flanking plots was less. Plots of the short cultivars Biggar or Oslo flanked by the tall cultivars Genesis or Glenlea yielded less than when flanked by themselves, and the reverse occurred when the tall cultivars were flanked by the short cultivars. Interplot interference affected spike density in the same fashion, did not significantly affect height, and was inconsistent with regards to kernel weight. It was concluded that when plots differ for height, yield distortion can occur in the Saskatchewan wheat growing region.
Soluble Oligosaccharides and Galactosyl Cyclitols in Maturing Soybean Seeds In Planta and In Vitro
Authors: Obendorf Ralph L. , Horbowicz Marcin , Dickerman Alexandra M. , Brenac Patrick , Smith Margaret E.
Published: July 2010

Stachyose, sucrose, and other non‐reducing soluble carbohydrates are associated with the onset of desiccation tolerance during seed development and with seed storability. Mature soybean [Glycine max (L) Merr.l seeds contain several galactosyl cyclitols in addition to sucrose, stachyose, and raffinose, but except for galactinol, the accumulation of these galactosyl cyclitols has not been reported for developing soybean seeds. Fifteen soluble carbohydrates including members of the raffinose, galactinol, galactopinitol, and fagopyritol series were analyzed in extracts from axis and cotyledon tissues of seeds and zygotic embryos matured in planta and in vitro. Galactopinitol A, galactopinitol B, and fagopyritol B1 accumulate in axis tissues of developing soybean seeds in planta in association with the onset of desiccation tolerance, yellowing of axis tissues, and in parallel with stachyose accumulation. Galactopinitol A, galactopinitol B, fagopyritol B1, and stachyose also accumulate in parallel in cotyledons in planta and in axis tissues during in vitro growth of zygotic embryos at 15 and 25°C. Axes of soybean seeds matured at 25°C contained higher concentrations of sucrose, raffinose, D‐pinitol, D‐chiro‐inositol, fagopyritol B1, and total soluble carbohydrates than axes of seeds matured at 18°C. Soybean seeds accumulate mostly galactosyl pinitols and only small amounts of free pinitol. In future work, It would be of interest to determine if gaiactosyl cyclitols may substitute for the role of stachyose in providing desiccation tolerance and prolonged seed storability.
Plant Population Density Effects on Maize Inbred Lines Grown in Short‐Season Environments
Authors: Modarres A. M. , Hamilton R. I. , Dijak M. , Dwyer L. M. , Stewart D. W. , Mather D. E. , Smith D. L.
Published: July 2010

Development of maize (Zea mays L.) types that produce leaf area quickly and tolerate high plant densities could enhance yields in midto short‐season environments. The leafy and reduced‐stature traits each make contributions to this end, but have not previously been combined. Our objective was to evaluate the effect of plant densities on leafy normal‐stature (LNS), non‐leafy normal‐stature (NLNS), leafy reduced‐stature (LRS), and non‐leafy reduced‐stature (NLRS) inbreds. Twenty‐one inbreds were field‐grown over 2 yr at low (65 000 plant ha−1) and high (90 000 plant ha−1) densities. Above‐ear leaf number, above‐ear leaf area, and single plant grain yield were lower for LNS and NLNS at the high, as compared with the low, plant density, but were not affected for LRS or NLRS. The corn heat unit (CHU) requirements from planting to tasseling, and from planting to silking, as well as days between tasseling and silking, were greater under high plant density for LNS and NLNS, but were not affected for LRS or NLRS. Grain yield increased to a greater extent under high density compared with low density for LRS and NLRS than for LNS or NLNS. The LRS inbreds had a shorter vegetative period, longer grain‐filling period, highest yields, and were more tolerant of high plant density than the normal‐stature genotypes. These characteristics indicate potential both for increased yields and production in areas with lower CHU availability. These advantages are expected to be conferred to LRS hybrids.
Interpreting Genotype ✕ Environment Interaction in Wheat by Partial Least Squares Regression
Authors: Vargas Mateo , Crossa José , Sayre Ken , Reynolds Matthew , Ramírez Martha E. , Talbot Mike
Published: July 2010

The partial least squares (PLS) regression method relates genotype ✕ environment interaction effects (GEI) as dependent variables (Y) to external environmental (or cultivar) variables as the explanatory variables (X) in one single estimation procedure. We applied PLS regression to two wheat data sets with the objective of determining the most relevant cultivar and environmental variables that explained grain yield GEI. One data set had two field experiments, one includingseven durum wheat (Triticum turgidum L. var. durum ) cultivars and the other, seven bread wheat (Triticum aestivum L.) cultivars, both tested for 6 yr. In durum wheat cultivars, sun hours per day in December, February, and March as well as maximum temperature in March were related to the factor that explained more than 39% of GEI, while in bread wheat cultivars, minimum temperature in December and January as well as sun hours per day in January and February were the environmental variables related to the factor that explained the largest portion (>41%) of GEI. The second data set had eight bread wheat cultivars evaluated in 21 low relative humidity (RH) environments and 12 high RH environments. For both low and high RH environments, results indicated that relative performance of cultivars is influenced by differential sensitivity to minimum temperatures during the spike growth period. The PLS method was effective in detecting environmental and cultivar explanatory variables associated with factors that explained large portions of GEI.
Drought Avoidance Aspects and Crop Coefficients of Kentucky Bluegrass and Tall Fescue Turfs in the Semiarid West
Authors: Ervin Erik H. , Koski Anthony J.
Published: July 2010

Increasing demand for the scarce water resources of the semiarid western USA, coupled with the highly visible practice of landscape irrigation, has fostered concern regarding turfgrass water conservation. Our objectives were (i) to assess some of the physiological responses and morphological factors which contribute lo the drought avoidance capabilities of Kentucky bluegrass (KBG, Poa pratensis L.) and tall frescue (Festuca arundinacea Schreber) turfs subjected to increasing levels of drought through the use of a line‐source irrigation system (LSIS), and (it) to develop water‐conserving crop coefficients (Kc) to be used with Penman equation estimates of al falfa (Medicago sativa L.) reference evapotranspiration (ET,), while maintaining these turfs at an acceptable level of quality. The effects of turfgrass species and irrigation level on root dry weight, leaf firing, canopy temperatures, gravimetric soil moisture content, and quality were investigated ai Fort Collins, CO on a Nunn clay loam (fine, monimorillonitic, mesic Aridic Argiustoll). Irrigation treatments were delivered with a LSIS. In 1993, turf‐type tall fescue (TF) had 65% more root dry weight from 31 to 90 cm than KBG. In 1994, tall fescue had 45% more total root dry weight from 31 to 90 cm than KBG. Consequently, tall fescue gravimetric soil moisture contains at the two deeper sample depths (31–60 and 61–90 cm) were generally lower than those of KGB. Tall fescue's capacity to exploit deep soil moisture when surface inputs became limiting were reflected in significantly higher quality ratings, lower leaf‐firing ratings, and lower canopy temperatures relative to KBG. Our conclusion is that, in Colorado, water can be conserved while maintaining acceptable turfgrass quality by irrigating these two turfs every 3 d by adjusting ET, with a KBG coefficient of 0.70 and a TF coefficient of 0.60, provided that soil conditions are such that tall rescue can produce a deep root system.
Leaf Area Development, Light Interception, and Yield among Switchgrass Populations in a Short‐Season Area
Authors: Madakadze I. C. , Coulman B. E. , Peterson P. , Stewart K. A. , Samson R. , Smith D. L.
Published: July 2010

Cool spring and early summer temperatures have limited the adoption of warm season grasses in northern environments like eastern Canada. This study characterized the performance of nine switchgrass (Panicum virgatum L.) populations (‘Blackwell’, ‘Cave‐in‐Rock’, ‘Dakota’, ‘Forestburg’, ‘New Jersey SO’, ‘Pathfinder’, ‘Sunburst’, ‘Shelter’, and ‘ND3743’) in southwestern Quebec. These populations were evaluated for 3 yr on a St. Bernard sandy clay loam (Typic Hapludalf) near Montreal. Leaf area development patterns during the season fitted second degree polynomial models, increasing with time after planting and decreasing in the fall. Maximum leaf area index (LAI) ranged from 6.1 to 8 m2 m−2 with Cave‐in‐Rock and New Jersey 50 having the highest LAIs. The populations had different vertical leaf area distributions. For Blackwell, Cave‐in‐Rock, and Shelter, more than 50% of the leaf area was in the top third of the canopy. New Jersey 50 and Pathfinder had uniform vertical leaf area distributions through the canopy. Light extinction coefficients (k) ranged from 0.57 to 0.72. Average end‐of‐season biomass yields were 8477, 9943 and 10 869 kg ha−1 in 1993, 1994, and 1995, respectively. The relationship between end of season yield and leaf area duration was linear. Cave‐in‐Rock, New Jersey 50, and Blackwell produced the greatest yields. All entries had high neutral detergent fiber (NDF) [810‐870 g kg−1 dry matter (DM)] and acid detergent fiber (ADF) (510‐570 g kg−1 DM). Nitrogen and ash concentrations ranged from 3.2 to 8.2 and 47 to 66 g kg−1 DM, respectively. This study showed that switchgrass can be successfully grown in southwestern Quebec.
Recovery of Photosynthesis after Environmental Stress in Soybean Grown under Elevated CO2
Authors: Ferris Rachel , Wheeler T. R. , Hadley P. , Ellis R. H.
Published: July 2010

Episodes of high temperature and water deficit may be more frequent under predicted future climates of warmer mean temperatures and elevated CO2. This study investigated whether the effects of an episode of high air temperature (HT, 43°C as a daily maximum), water deficit (WD), or both, had the same effect on the recovery photosynthesis and on leaf water relations of soybean [Glycine max (L.) Merr., cv. Fiskeby V] grown at ambient CO2 (aCO2) or elevated CO2 (eCO2). An 8‐d period of HT, WD, or both (HTWD) were imposed during early seed filling of soybean grown in glasshouses at either 362 or 685 ;μmol mo1−1 CO2. Photosynthesis (Amax), stomatal conductance (g5), and water relations were measured in fully expanded upper‐canopy leaves. Immediately after the 8‐d treatments at 60 d after sowing (DAS), Amax was reduced by 31, 48, and 64% in aCO2 and by 28, 39, and 49% in eCO2 under HT, WD, and HTWD, respectively, but no significant interactions were detected. At 60 DAS, g5 was reduced by WD and HTWD in aCO2 but not by HT while there was little change in g5 by WD, HT, and HTWD under eCO2. Amax fully recovered under WD in eCO2 by 66 DAS, while Amax remained reduced under WD in aCO2. Under each CO2 concentration, almost full recovery of Amax occurred under HT by 75 DAS but under HTWD Amax never attained control values. At 60 DAS, early morning leaf water potential (ψ) was lower after HT, WD, and HTWD and Amax was a negative function of ψ, at each CO2 concentration. The results suggest that full recovery of Amax from WD was only possible under eCO2, because at aCO2, immediately after the stress episode, ψ was below the threshold for chloroplast damage.
Sulfur Availability, Cotyledon Nitrogen:Sulfur Ratio, and Relative Abundance of Seed Storage Proteins of Soybean
Authors: Sexton P. J. , Naeve S. L. , Paek N. C. , Shibles Richard
Published: July 2010

The nutritional value of soybean [Glycine max (L.) Merr.] seed protein could be enhanced by increasing its concentration of the S‐containing amino acids, methionine and cysteine. Two greenhouse pot studies and one field study were conducted with soybean grown under varying levels of S availability to observe the relationship between S availability, seed S content, and relative abundance of poor and high quality storage proteins. Abundances of the [β‐subunit of β‐conglycinin (poor quality) and of glycinin (high quality) seed storage proteins were determined by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). Cotyledon‐S concentration more than doubled, and the N:S ratio of the seed decreased sharply (from about 40‐20 g N g S−1), as S availability increased from 12 to 62 mg available S per plant in the first greenhouse trial. The amount of the poor‐quality [β‐subunit of β‐conglycinin was linearly related to the N:S ratio of cotyledon tissue and varied from less than 15 up to 40% of storage proteins. On the other hand, the high‐quality glycinin fraction of storage protein showed a linear, negative relation to N:S ratio of cotyledon tissue and decreased from 60 to less than 30% of storage proteins as the N:S ratio increased under S stress. Even in high S environments the β‐subunit of β‐conglycinin comprised 10% or more of total storage proteins. Since poor quality storage protein was synthesized even in high S environments, we hypothesize that the plant's ability to reduce sulfate and synthesize S‐containing amino acids during seed filling may be a factor limiting soybean protein quality.
Nitrogen Fertilizer Management Effects on Maize Grain Quality in the West African Moist Savanna
Authors: Oikeh S. O. , Kling J. G. , Okoruwa A. E.
Published: July 2010

Until recently, breeding programs in Africa placed little emphasis on grain quality improvement. Consequently, some farmers have not adopted improved high yielding varieties because they lacked desired quality characteristics for processing and other end uses. We conducted this study to determine the effects of N application on some maize (Zea mays L.) grain quality parameters. In 1993 and 1994, five maize cultivars under four N levels (0, 30, 60, and 120 kg ha−1) were evaluated at Zaria (11° 11′ N), northern Nigeria, on a Plinthustalf (fine‐loamy isohyperthermic). Increasing N levels increased grain yield, kernel weight, and grain protein quadratically for all the cultivars. The hybrid 8644‐27 had the highest grain yield and kernel weight of 5.3 Mg ha−1 and 26.62 mg kernel−1, respectively. Average grain protein yield per unit area was not significantly different among cultivars in both years. At 30 to 60 kg N ha−1, the cultivars 8644‐27 and TZPB‐SR had a greater percentage of floaters, than the other cultivars in both years, reflecting a greater proportion of floury endosperm, indicating that they would be best for traditional dry milling, where the whole grain is ground to produce flour. Also, at 30 to 60 kg N ha−1, SPL and TZB‐SR had a relatively low percentage of floaters and high test weights of over 811 kg m−3 in 1993 and 778 kg m−3 in 1994, and should give high yields of grits when processed. Thus, both cultivars have high value for industrial dry milling. Results showed that the choice of cultivar and N level may affect grain quality and they should be considered in producing maize for dry milling purposes.
Molecular Markers Associated with T and Z, Two Genes Controlling Partly Colored Seed Coat Patterns in Common Bean
Authors: Brady L. , Basset M. J. , McClean P. E.
Published: July 2010

Five genes control the expression of partly colored seed coat patterns in common bean (Phaseolus vulgaris L.), viz., T, Z, L, Bip, and J. Because these genes have complex interactions, giving various seed coat patterns, it is often difficult to assign specific effects to a particular gene. The problem is compounded by multiple alleles at T, Z, and L. Molecular markers linked to those pattern genes have the potential to assist in identifying the genes involved in specific interactions. We have begun a series of experiments to identify useful molecular markers linked to these genes. A group of three parental genotypes and five backcross lines were screened by random amplified polymorphic DNA (RAPD) techniques to identify putative markers. Potential markers were then mapped in appropriate BC3‐F2 populations. To date, recombination has not been detected between RAPD markers OAM131350, and OMI9400 and the T gene. A single recombinant was detected between RAPD marker OAMl0560 and the Z gene, and the marker mapped at a distance of 1.4 centimorgans (cM).
Haploid Durum Wheat Production via Hybridization with Maize
Authors: Almouslem A. B. , Jauhar P. P. , Peterson T. S. , Bommineni V. R. , Rao M. B.
Published: July 2010

Haploids are useful in basic studies on intergenomic relationships, in molecular studies, and in practical breeding. Haploid production in durum wheat has had limited success. The objective of this study was to develop an efficient method of durum haploid production via maize pollination. Pollination of seven agronomically superior durum wheat (Triticum turgidum L.,2n = 4x = 28, A ABB) cultivars [Durox, Langdon (LDN), Lloyd, Medora, Monroe, Renville, and Vie] and three important cytogenetic stocks [LDN 5D(5B), LDN Ph1 ph1b, and Cappelli ph1c ph1c with pollen from three maize (Zea mays L.) cultivars resulted in haploid embryos. In vitro culture of these embryos produced haploid green seedlings. Post‐pollination treatment with 3 mg L−1 2,4‐D and 120‐180 mg L−1 AgNO3, gave the best yield of embryos, whereas 3 mg L−1 2,4‐D plus 120 mg L−1 AgNO3 promoted the conversion of embryos into plantlets. We produced a total of 142 mature, green haploid seedlings which included haploids with and without the homoeologous pairing suppresser gene, Ph1. Clear genotypic differences in haploid production were observed, Medora with 3 mg L−1 2,4‐D + 180 mg L−1 AgNO3 being the highest yielder. Renville proved to be more consistent yielder of haploid embryos as well as seedlings, over all treatments. Among the three Langdon genotypes —Langdon Ph1 ph1b, Langdon 5D(5B) substitution line, and normal Langdon —the substitution line gave the best response. It appears, therefore, that the substitution of chromosome 5D for SB confers on durum higher ability to produce haploids.
Genetic Diversity and Heterosis of Spring Wheat Crosses
Authors: Fabrizius Martin A. , Busch Robert H. , Khan Khalil , Huckle Linda
Published: July 2010

Genetic diversity between parents may contribute positively to both heterosis and transgressive segregation. The objectives of this study were to determine (i) whether genetic diversity in spring wheat (Triticum aestivum L.) affected F2 bulk heterosis and (ii) whether genetic diversity affected the amount of transgressive segregation among progeny from a cross. Genetic diversity was measured by pedigrees, morphology, and gliadin seed proteins. Heterosis was evaluated for 137 F2 bulks tested at two Minnesota locations in 1993 and three locations in 1994. These bulks were developed from crosses among 91 cultivars. No linear relationship between genetic distance and F2 bulk heterosis was detected. However, when crosses were divided into related and unrelated groups, crosses with parents unrelated by pedigree or morphology expressed greater heterosis than crosses with related parents. Bulks of crosses between cultivars that were classified as unrelated by two or more of the distance measures showed more heterosis than related crosses. Thus, part of heterosis seems to be due to parental diversity, though not in a linear fashion. Expression of greater‐than‐average heterosis by the highest yielding bulks, without an increase in genetic distance, suggested additional factors were influencing the expression of heterosis. Transgressive segregation was evaluated for six of the 137 crosses; 30 to 40 inbred lines from each of the crosses was evaluated in three environments. Data for these populations were consistent with an additive genetic model. The expression of heterosis was due in part to genetic diversity but was unpredictable and also depended on factors not elucidated by this study.
Defense Mechanisms of Maize against Pink Stem Borer
Authors: Butrón A. , Malvar R. A. , Revilla P. , Ordás R. A.
Published: July 2010

The pink stem borer (Sesamia nonagrioides Lef.) is the most important pest of maize (Zea mays L.) in northwestern Spain. The objective of this work was to evaluate defense mechanisms against Sesamia in 10 inbred lines and the 10‐parent diallel among these inbreds. Hybrids and inbred lines were tested over 2 yr in northwesternSpain under natural and artificial infestations. Yield of infested and non infested plants per plot were computed to calculate yield loss caused by the pink stem borer attack. Principal component analyses for stem damage traits and for ear damage traits were made for each infestation condition. From the principal component analysis, an index was computed to measure stem damage and ear damage. Damage index under artificial infestation was used to evaluate antibiosis while antixenosis was detected when damage index of each genotype was compared under artificial and natural infestation. The regressions of yield loss on the damage index were used to separate the genotypes into four groups according to the possession of antibiosis and/or tolerance mechanisms. A509, A661, EP31, F7, PB60, and Z77016 showed stem antibiosis. A637, A661, EP31, F7, and PB60 exhibited stem tolerance. A509, A661, and EP31 stood out by their ear antibiosis. A637, A661, F7, and PB60 were tolerant to ear damage. We conclude that the three mechanisms of defense to the pink stem borer attack (antixenosis, antibiosis, and tolerance) were found among inbred lines and hybrids. A multitrait selection scheme using damage traits and yield could improve the defense level against pink stem borer.
Marker‐Assisted Selection as a Strategy for Increasing the Probability of Selecting Superior Genotypes
Authors: Knapp Steven J.
Published: July 2010

Marker‐assisted selection (MAS) has been shown, in theory, to produce greater selection gains than phenotypic selection for normally distributed quantitative traits. Theory is presented in this paper for estimating the probability of selecting one or more superior genotypes by MAS (PrMAS). This paramater was used to estimate the cost efficiency of MAS relative to phenotypic selection (Ec). PrMAS and Ec are functions of heritability (h2), heritability of a MAS index (h2I), the phenotypic selection threshold (i), the genotypic superiority threshold (g), and p = σ2M/σ2G, where σ2M is additive genetic variance associated with markers and 2G is additive genetic variance, h2I increases as p increases. Heritability can be increased to 1.0 by increasing p to 1.0; however, estimated marker effects (p̂) and true quantitative trait locus effects (p) must be perfectly correlated to achieve this in practice. PrMAS increases throughout the range of p when i ≥ g, decreases as g increases, and increases as i increases for most p. The frequency of superior genotypes among selected progeny increases as selection intensity increases. Ec ranged from 1.0 to 16.7 for i and g from 1.282 to 2.326, h2 from 0.1 to 1.0, and p from 0.0 to 1.0; thus, a breeder using phenotypic selection must test 1.0 to 16.7 times more progeny than a breeder using MAS to be assured of selecting one or more superior genotypes. Ec increases as g or iincrease and h2 decreases and increases asp increases when i = g. Ec predicts that MAS substantially decreases the resources needed to accomplish a selectiOn goal for a low to moderate heritability trait when the selection goal and the selection intensity are high.
Fiber Yield and Quality of Cotton Grown at Two Divergent Population Densities
Authors: Jones Michael A. , Wells Randy
Published: July 2010

Poor seed germination and early seedling damage often reduce plant populations in the north‐eastern cotton (Gossypium hirsutum L.) producing region of the USA. A field study was conducted at Clayton, NC, on a Dothan sandy loam (fine‐loamy, siliceous, thermic Plinthic Kandiudult) to investigate responses of cotton reproductive development to reduced plant population. All flowers on plants grown at 2 and 12 plants m−2 were tagged so that associations among boll and lint quantity and quality, flowering date, and fruiting position could be determined. On plants grown at 2 plants m−2, 33 and 65% of their fiber came from flowers initiated before 88 days after planting (DAP) in 1992 and 1993, respectively. Plants grown at 12 plants m−2 produced 63 and 88% of their fiber from flowers initiated before 88 DAP in 1992 and 1993, respectively. Plant population did not affect total lint yield, however. Because of favorable late‐season weather, plants grown at 2 plants m−2 produced more bolls on vegetative branches and at more distal sympodial positions than did plants grown at 12 plants m−2. Boll weight and micronaire were generally higher for earlier bolls at all positions for the lower population density. Later bolls exhibited poorer boll and fiber properties, indicating negative effects of reduced heat unit accumulation by later bolls. Our findings indicate that replanting, which might delay stand establishment by 3 to 4 wk, would be of little help toward improving fiber yield because it would rely more heavily on later produced bolls.
Identification of Molecular Markers Linked to ant28‐484, a Mutation That Eliminates Proanthocyanidin Production in Barley Seeds
Authors: Garvin D. F. , Miller‐Garvin J. E. , Viccars E. A. , Jacobsen J. V. , Brown A. H. D.
Published: July 2010

Barley (Hordeum vulgare L.) seed proanthocyanidins play a primary role in beer colloidal haze formation. The barley ant28‐484 mutation eliminates proanthocyanidin synthesis and beer brewed with barley homozygous or ant28‐484 exhibits intrinsic haze stability. The recessive nature of this mutation, coupled with the fact that the proanthocyanidin‐free phenotype it confers is discernable only in maternal tissues of the seed, makes introgression of ant28‐484 into new cultivars arduous. The goal of this study was to identify molecular markers for use in marker‐assisted selection of ant28‐484. An F2 barley population derived from the cross Arapiles ✕ Caminant was scored for ant28‐484 segregation. DNA pools from F2 plants homozygous for ant28‐484 or the contrasting wild‐type allele were used for bulked segregant RAPD analysis. RAPD bands differentiating the two DNA pools were then analyzed for linkage to ant28‐484 in the F2 population. Five linked RAPD markers were identified, with linkage estimates to ant28‐484 ranging from 0 to 11 centimorgans (cM). Three of the markers were linked in cis to ant28‐484 and two were linked in trans. The three most tightly linked RAPD markers were cloned, and southern analysis indicated that they represent low or single copy sequences. The ant28‐484 mutation was localized to barley chromosome arm 3HL, on the basis of results of southern analysis with wheat‐barley ditelosomic addition lines probed with the cloned RAPD markersa nd on the basis of linkage to the previously mapped isozyme locus Est4. These markers will enhance the efficiency with which ant28‐484 can be introgressed into barley germplasm.
Identification of Diverse Soybean Germplasm Using RAPD Markers
Authors: Thompson Jeffrey A. , Nelson Randall L. , Vodkin Lila O.
Published: July 2010

The genetic base of soybean [Glycine max (L.) Merr.] breeding in North America is very limited. The focus of this research was to assess the diversity of 18 soybean ancestors and 17 selected plant introductions (PIs) maintained in the USDA Soybean Germplasm Collection. Estimates of genetic relationships among the 35 genotypes were calculated from 281 random amplified polymorphic DNA (RAPD) markers using the simple matching coefficient (SMC) expressed as Euclidean distances. Two forms of hierarchical and nonhierarchical duster analysis as well as multidimensional scaling (MDS) were employed to reveal associations among the genotypes. The average genetic distance among all genotypes was 0.56. All methods of cluster analysis identified distinct groups of ancestors or PIs. Grouping of the ancestors generally agreed with known pedigree, origin, and maturity data. The four methods of clustering produced similar results, and genotypes were assigned to the same cluster 87% of the time. The MDS plots displayed relationships among the genotypes and may be a useful method of selecting genetically distinct individuals. The genotypes within the distinct PI dusters may possess useful genetic diversity that could be exploited by soybean breeders to increase yield.
Utilization of Diverse Germplasm for Soybean Yield Improvement
Authors: Thompson Jeffrey A. , Nelson Randall L.
Published: July 2010

Introgression of diverse germplasm into the current soybean [Glycine max (L.) Merr.J genetic base may increase genetic variability and lead to greater gains from selection. The objective of this research was to evaluate the genetic diversity and agronomic performance of experimental lines derived from plant introductions (Pis) maintained in the USDA Soybean Germplasm Collection. These Pis are known to be genetically distinct from the ancestors of the modern North American soybean cultivars. Experimental lines containing 25 to 100% PI germplasm (based on pedigrees), their parents, and recently released public cultivars were evaluated for yield in seven environments in 1994 and 1995. Data from random amplified polymorphic DNA (RAPD) fragments were collected and genetic relationships among all genotypes were estimated using hierarchical and nonhierarchical cluster analyses. Experimental lines were identified that yielded significantly more than their domestic parent. Comparisons of pairwise distances revealed that many of the high‐yielding experimental lines were more diverse than their domestic parents from the nonparental cultivars. The increased genetic diversity and yield provide evidence that exotic germplasm can contribute genes for high yield.
DNA Analysis of Turfgrass Genetic Diversity
Authors: Caetano‐Anollés Gustavo
Published: July 2010

Turfgrasses constitute an heterogeneous group of species differing widely in reproductive strategy, genome organization, and evolutionary history. Cultivars derived from vegetative propagation or from apomictic or self‐pollinated species can be homogeneous at the genetic level, exhibiting little genetic variation. Alternatively, cultivars with an outcrossing breeding system can be genetically heterogeneous, such as those from open‐pollinated seeded species. A careful study of the degree and distribution of turfgrass genetic variation is therefore essential for the efficient selection of superior plant material for breeding, an adequate management of genetic resources, and the effective preservation of biodiversity. An array of molecular techniques have targeted nucleic acids to evaluate molecular diversity at the species, population, and within‐population levels. These techniques have only recently been applied to the breeding and management of turfgrass germplasm. Using the hybridization and amplification of nucleic acids, DNA profiling techniques have established patterns of genetic variation at the species level in grass systematics, and at the subspecies level in the study of natural populations, breeding lines, cultivars, and accessions. In some cases, chromosome analysis by flow cytometry and genomic in situ hybridization have notably complemented the use of nucleic acid markers. DNA profiling techniques have also assessed the genetic stability of cultivars and the appearance of off‐types, and have provided molecular estimates of turfgrass evolution. The review of current efforts to evaluate turfgrass genetic diversity clearly indicates that the application of the tools of genome analysis to the study of germplasm diversity may finally unlock the genetic potential of wild and cultivated turfgrass resources.
Use of Gene Substitution Values to Quantify Partial Dominance in Low Palmitic Acid Soybean
Authors: Stijšin Duška , Ablett Gary R. , Luzzi Bruce M. , Tanner Jack W.
Published: July 2010

Several low palmitic acid mutants have been developed in soybean [Glycine max (L.) Merr.] to improve oil quality. Single locus mutations have been identified which control low palmitic acid: fap1 allele in C1726 and fap3 allele in A22. Each allele was found to be additively inherited at the intralocus level. There is less understanding of the inheritance of low palmitic acid controlled by alleles at more than one locus. The objectives of this study were to: (i) determine the number of loci and type of gene action associated with the cross between two low paimitic lines, and (ii) propose a simple calculation method that accounts for partial dominance at the intralocus level. Two independently developed low palmitic lines (ELLP2 and C1726) were crossed. The analyses of F2 and F3 generations indicated that the combination of alleles at two loci (temporarily designated Fap* locus in ELLP2 and the previously described Fap1 locus in C1726) were controlling the transgressive segregation of palmitic acid. The Fap* allele was partially dominant over the mutant fap* allele in ELLP2. A simple calculation method was proposed to account for the degree of dominance in order to explain and predict the F2 segregation in the ELLP2 × C1726 cross. The (ELLP2 × C1726) F2 seeds segregated into six distinct phenotypic groups that fit a 1:2:3:5:4:1 ratio. The ratio corresponded well with the expected genetic pattern on the basis of the gene substitution values. The results indicated the segregation of two loci in the ELLP2 × C1726 cross: Fap* with partial dominance and Fap1 with additive gene action, and no epistasis at the interlocus level. Furthermore, the calculation based on gene substitution values may be used in predicting other complex segregation Ratios.
Root Growth of Green Pea (Pisum sativum L.) Genotypes
Authors: Thorup‐Kristensen Kristian
Published: July 2010

Root development of 12 genotypes of green pea was followed using a minirhizotron system. Rooting‐depth development followed a simple pattern, consisting of an initial lag phase during germination and early growth, followed by a linear phase that ended ≈10 d after the onset of flowering. All genotypes followed this general pattern. Significant differences were found in the length of the linear phase of rooting‐depth development. These differences were due to variation in the length of the initial lag phase, and variation in the time until the onset of flowering. The genotypes with the lowest seed weight also showed the longest lag phase. No significant differences in the rate of rooting‐depth development during the linear growth phase were found among the genotypes. The rate of rooting‐depth development was estimated to be 0.086 cm d−1 °C−1 across the genotypes. Measurements on six of the genotypes in root‐observation boxes showed the same differences between genotypes as found in the field, although the rate of rooting‐depth development was much higher. The observed differences in rooting depth and the fact that these differences could also be observed in a simple way in the root‐observation boxes, suggest that efficient breeding methods for rooting‐depth development can be developed.
Variation for Insect Resistance and Horticultural Traits in Tomato Inbred Backcross Populations Derived from Lycopersicon pennellii
Authors: Hartman J. B. , St. Clair D. A.
Published: July 2010

Insect resistant accessions of wild Lycopersicon species were identified long ago, yet insect resistance has not been successfully introgressed into tomato cultivars. The effectiveness of the inbred backcross method for introgressing resistance to beet armyworm (Spodoptera exigua Hübner), tomato fruitworm (Helicoverpa zea Boddie), and potato aphid (Macrosiphum euphorbiae Thomas) from the resistant Lycopersicon pennellii (Corr) D'Arcy acc. ‘LA 716’ into Lycopersicon esculentum Mill. ‘Peto 95’ was examined. Inbred backcross populations at two backcross levels (BC2 and BC3) were developed and tested at two levels of selfing over 2 yr (i.e., S3 in 1994 and S4 in 1995) for resistance in no‐choice egg‐inoculated field assays to beet armyworm and tomato fruitworm and to natural populations of potato aphid. Variation among inbred backcross lines (IBL) in the amount of fruit damage from beet armyworm and tomato fruitworm and the proportion of potato aphid infested plants was observed. Significant line × year interactions suggest that genotype × environment effects may be important to beet armyworm and tomato fruitworm resistance. Differences between observed and predicted gain in beet armyworm and tomato fruitworm resistance of post hoc selected IBL were found, which might be attributed to underestimation of genotype × environment effects, or to non‐additive genetic effects. Large genetic correlations (r2g) between reduced fruit damage and later maturity, lower fruit yield, and smaller fruit mass were estimated. The inbred backcross method was used to successfully introgress insect resistance from L. esculentum to cultivated tomato, but the development of commercially acceptable cultivars will require further cycles of breeding.
Increasing Seed Protein in Soybean with Eight Cycles of Recurrent Selection
Authors: Wilcox James R.
Published: July 2010

Inverse relationships between seed protein and both seed yield and seed oil have limited progress in developing economically profitable high protein soybean [Glycine max (L.) Merr.] cultivars. This study evaluated changes in and limitations to seed protein concentration, associated changes in seed oil concentration, and variability for these traits during eight cycles of recurrent selection for seed protein. Seed of a line with 483 g kg−1 protein was blended with seed of two F2 populations segregating for male sterility (ms2ms2). S0 plants from randomatings in the population were evaluated in each cycle for plant maturity and for seed protein and oil concentration. The 20% of plants with highest seed protein in Cycles 0 through 3 and the 10% of plants with highest seed protein in Cycles 4 through 7 were randomly intermated to initiate the next cycle. Plant maturity was not consistently associated with either seed protein or oil in the eight cycles of selection. Recurrent selection increased mean seed protein 5.8 g kg−1 and decreased mean seed oil 2.3 g kg−1 per cycle. A stronger inverse relationship between seed protein and oil was observed in later than in earlier cycles as indicated by steeper slopes of and decreased variability around regression lines in later cycles. Most of the alleles for this trait were accumulated in the high protein selections by Cycle 5. An average of 53% of the plants in Cycles 6 through 8 had 480 g kg−1 or greater seed protein. Progenies of these plants would be excellent sources of phenotypes that combine high seed protein with good agronomic traits.