Cultivar Pioneer Research Articles

Botryosphaeriaceae Infections on Prunus Germplasm: Evaluation of Pathogenicity, Resistance Loci, and Detached Assays of Southeastern United States Isolates

Research of peach fungal gummosis (PFG), which is a vascular disease caused by fungi in the Botryosphaeriaceae family, is particularly important in the southeastern United States, southern China, South Africa, and Western Australia. This disease has been a significant concern for the peach industry in the southeastern United States since the 1970s. The changing climatic conditions in the prunus production areas of the world have worsened the severity of PFG disease. A study of the morphological and genetic profiles of Botryosphaeriaceae species from diseased peach trees found four species in Georgia, Florida, Alabama, and South Carolina. Botryosphaeria dothidea, Lasiodiplodia theobromae, Diplodia seriata, and Neofusicocoum parvum were isolated and identified using conidiospore characters and rDNA sequences of internal transcribed spacer regions and elongation factor α-1 genes. B. dothidea was the most common species from diseased peach trees. A significant implication of this research is the potential resistance in Prunus germplasm, which was genotyped for the resistance locus Botd8 and evaluated for relative susceptibility to one isolate each from B. dothidea, L. theobromae, and D. seriata. Pathogenicity evaluations of peach, almond, and interspecific hybrids used detached stem and leaf assays for susceptibility to PFG based on lesion lengths and gumming scores. L. theobromae inoculation resulted in the most extensive lesions on stems and leaves. Detached stem and leaf assays indicated that Prunus with the Botd8 locus significantly differed in lesion size when infected with B. dothidea and D. seriata. However, the resistant locus had no significant effect on the relative susceptibility of Prunus to L. theobromae. Field and detached stem and leaf assays identified almond cultivars Pioneer and Golden State and Peach × Almond hybrids with Botd8 (+) as tolerant to PFG. Correlations between detached assays and field gumming scores suggested that inoculations on detached stems or leaves under controlled conditions can be used to preliminarily screen for resistance to PFG. These detached assays for specific pathogen isolates provide an opportunity for a relatively fast, nondestructive evaluation of Prunus germplasm and are tools that can be used to identify the components of disease resistance.

Field Screening of Seven Cultivars of Cabbage Against Cabbage Butterfly (Pieris brassicae) and Cabbage Aphids (Brevicoryne brassicae) at Gkuleshor, Baitadi, Nepal

Field screening of seven cultivars of cabbage namely: Green Crown, Green Top, Green Coronet, Pioneer, Nepa Round, Copenhagen Market and Golden Acre were carried out against cabbage butterfly (Pieris brassicae) and cabbage aphid (Brevicoryne brassicae) at the research farm of entomology section, Gokuleshwor Agriculture and Animal Science College, Baitadi in RCBD design from October 2017 to February 2018. Five plants were tagged randomly after transplanting in field excluding border plants in each plot. Data were collected for the population dynamics of cabbage butterfly larvae and cabbage aphid on weekly basis. None of the seven cultivars were found resistant to cabbage butterfly and cabbage aphid, however their population density varied on tested cultivars. Cabbage butterfly population was recorded the highest on the cultivar Pioneer (22.88 larvae/plant) and the lowest on the cultivar Copenhagen Market (10.06 larvae/plant), and other cultivars were of intermediate types. Similarly, the population density of aphid ranged from 36.70 to 105.58 aphids/leaf. The highest population density of aphid was recorded on cultivar Green Crown (105.58 aphids/leaf) and the lowest on cultivar Copenhagen Market (39.82 aphids/leaf. From the results, Copenhagen Market proved to be the best against both cabbage butterfly and cabbage aphids.

Potassium induces carbohydrates accumulation by enhancing morpho-physiological and biochemical attributes in soybean under salinity

ABSTRACT This study evaluates the effectiveness of potassium sulphate (K2SO4) fertilization under salt stressed conditions on physiological and biochemical characteristics and sugar contents of two soybean cultivars (Pioneer and Jack). The treatments including 0 mM K2SO4, 9 mM K2SO4, 0 mM salinity and 90 mM salinity were tested in combination with both cultivars of soybean. Analysis of electrical conductivity, photosynthetic parameters, gas exchange parameters, antioxidant enzymes, malondialdehyde (MDA), sugar contents and glutamine synthetase activities were measured. The results depict that salinity negatively affected the growth, physiological and biochemical attributes of both soybean cultivars, but application of potassium induced salt tolerance in soybean cultivars as the production of MDA contents and electrolyte leakage decreased, while growth parameters, chlorophyll contents, antioxidant enzymes, gas exchange characteristics and sugar contents were improved relative to control plants under saline environment. However, the cultivar Pioneer was more responsive to K2SO4 fertilization as it showed minimum production of MDA contents while maximum antioxidants, gas exchange parameters and sugar contents as compared to Jack. In crux, the salt tolerant cultivar Pioneer was better in utilizing potassium as compared with salt sensitive variety Jack under salt tolerant environment and could be used effectively under salt-affected soils.

First Report of Red Crown Rot of Soybeans Caused by Calonectria ilicicola (Anamorph: Cylindrocladium parasiticum) in Illinois

HomePlant DiseaseVol. 103, No. 7First Report of Red Crown Rot of Soybeans Caused by Calonectria ilicicola (Anamorph: Cylindrocladium parasiticum) in Illinois PreviousNext DISEASE NOTESFirst Report of Red Crown Rot of Soybeans Caused by Calonectria ilicicola (Anamorph: Cylindrocladium parasiticum) in IllinoisN. Kleczewski, D. Plewa, C. Kangas, E. Phillippi, and V. KleczewskiN. Kleczewski†Corresponding author: N. Kleczewski; E-mail Address: nathank@illinois.eduhttp://orcid.org/0000-0001-5671-6727University of Illinois, Department of Crop Sciences, Urbana, IL 61801Search for more papers by this author, D. PlewaUniversity of Illinois, Department of Crop Sciences, Urbana, IL 61801Search for more papers by this author, C. KangasUniversity of Illinois, Department of Crop Sciences, Urbana, IL 61801Search for more papers by this author, E. PhillippiUniversity of Illinois, Department of Crop Sciences, Urbana, IL 61801Search for more papers by this author, and V. KleczewskiGrowmark Inc., Bloomington, IL 61701Search for more papers by this authorAffiliationsAuthors and Affiliations N. Kleczewski1 † D. Plewa1 C. Kangas1 E. Phillippi1 V. Kleczewski2 1University of Illinois, Department of Crop Sciences, Urbana, IL 61801 2Growmark Inc., Bloomington, IL 61701 Published Online:7 May 2019https://doi.org/10.1094/PDIS-01-19-0105-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In September 2018 soybean (Glycine max) disease was observed in a commercial field located near Pittsfield, Illinois. Signs and symptoms resembled those of red crown rot, caused by Calonectria ilicicola (Hartman et al. 2015). Red to brown lesions were observed at the stem base, and red, raised perithecia were observed on the lesion surface. The root systems of affected plants were black and severely rotted, often with only taproots remaining after removal from the soil. The inner pith of the lower stem was light gray in appearance. Foliar symptoms included interveinal chlorosis and defoliation. Disease incidence was estimated at 75%, and yield loss was estimated at approximately 25%. Affected plants were harvested, placed in a cooler on ice, and transported to the University of Illinois. Stems were surface sterilized in 10% bleach (30 s), 75% ethanol (30 s), followed by two rinses in sterile distilled water bleach, and allowed to air dry under a biosecurity cabinet. Isolations were made from sections of symptomatic stems on Petri plates containing half-strength potato dextrose agar placed under a light bank equipped with cool fluorescent lights set on a 12-h light/dark cycle at 20°C. Fungi were isolated from 100% of sections plated, and individual isolates were collected via hyphal tip technique. Isolated colonies initially produced white, aerial mycelia that later turned burnt red to brown with age. Conidia were hyaline, cylindrical with zero to three septae, and measured 28.5 to 87.1 × 3.9 to 7.6 μm. Perithecia were reddish orange, oval to globose, 202.6 to 424.7 μm tall, and 100.3 to 353.8 μm in width. Asci were hyaline and clavate and measured 111.0 to 206.1 × 10.5 to 28.6 μm, and each contained eight falcate ascospores with one to two septa. Morphological characteristics identified this organism as C. ilicicola (anamorph: Cylindrocladium parasiticum [Hartman et al. 2015]). A 600-bp fragment of the β-tubulin gene was amplified using the T1 (O’Donnell and Cigelnik 1997) and Bt2b (Glass and Donaldson 1995) primers. Thermocycler conditions were as follows: initial denaturation for 10 min at 96°C followed by 30 cycles of 96°C for 15 s, 55°C for 35 s, and 75°C for 35 s, with a final elongation step of 75°C for 2 min (Crous et al. 1999). Polymerase chain reaction products were purified and sequenced at the Roy J. Carver Biotechnology Center at the University of Illinois at Urbana-Champaign. A sequence of the representative isolate 3A was submitted to GenBank (MK370992). Comparisons with GenBank showed 99% similarity with multiple sequences of C. ilicicola (top match JX0693831.1, bit score 1,107, E = 0.0, 607/610 bp). Pathogenicity was confirmed by inoculating 3-week-old seedlings of soybean cultivar Pioneer 93Y25 grown in in 15-cm-diameter pots containing autoclaved greenhouse potting media. Six plants were present in each pot, and three pots were used per treatment. Inoculation was conducted by drenching with a 105 conidia/ml suspension acquired from 14-day-old, single-spore fungal isolates. Three unamended pots were used as controls. Plants were watered daily and maintained in a greenhouse set to 23°C and a 14-h/10-h light/dark cycle. After 14 days, inoculated plants showed similar basal stem symptoms and after 30 days developed interveinal chlorosis on leaves. C. ilicicola was reisolated from diseased plants and confirmed through microscopy. This pathogen may pose a threat to >440,000,000 ha of soybean in Illinois, not including surrounding states. Our understanding of impact and management under Midwest production practices is currently unknown.The author(s) declare no conflict of interest.

Evaluation of the growth of young corn plants grown in different types of soil

Corn is a crop of great national importance, being the second most produced grain in Brazil. However, their yield is affected, among other factors, by soil fertility. The objective of this work was to evaluate the initial growth of two cultivars of maize cultivated in different types of soil. The experiment was conducted in the form of a randomized block design, in a factorial scheme two maize cultivars (Pioneer and Bandeirantes) x 3 soil types (clayey, mixed and black soil), with eight replications each. The height and diameter of the stem were evaluated weekly. The dry mass of the aerial part (MSPA), roots (MSR) and total (MST), as well as the MSPA / MSR ratio, were evaluated 21 days after emergence of the seedlings. For the height and diameter data, regression analysis was performed at a 10% probability level. For the other variables, we analyzed the factorial variance at x b at the 5% probability level. The software BioEstat version 5.3 was used. It was observed that T1 and T2, for both cv. of maize, obtained the highest results for stem height and diameter, MSPA, MSR, MST and MSPA / MSR ratio. Regarding the cultivar, Pioneer was superior to Bandeirantes for the variables MSPA, MST and MSPA / MSR ratio. Therefore, clayey and mixed soils were superior to black soil, favoring the initial development of corn plants.

Genetic mapping of a major gene for leaf rust resistance in soft red winter wheat cultivar AGS 2000

Leaf rust (LR), caused by Puccinia triticina (Pt), is a major disease of wheat worldwide. Genetic resistance is the most effective, economic, and environmentally safe method to reduce losses caused by LR. Seventy-nine LR resistance genes have been identified so far; however, only a few of them are still effective due to the constant evolution of new Pt races. The objectives of this study were to characterize the genetic basis of LR resistance in the soft red winter wheat (SRWW) cultivar AGS 2000 at seedling stage, and identify markers for marker-assisted selection (MAS). A mapping population of 175 recombinant inbred lines (RILs) was developed from a cross between the susceptible cultivar Pioneer® variety 26R61 (26R61) and AGS 2000. Two out of four Pt races (MBTNB, MFGKG, TCRKG, and MCTNB) showed segregating reactions for the parental lines and RIL population at the seedling stage. Whole genome QTL analysis detected a single common QTL for resistance to both Pt races (MFGKG and MBTNB) on chromosome 2BS. The gene was flanked by wPt-666389 and wPt-2600 markers and explained up to 75.3% of phenotypic variation for Pt race MBTNB, and is therefore a Mendelian factor. LR resistance genes, Lr13, Lr16, Lr23, Lr48, and Lr73, were all detected on 2BS; however, based on their physical and genetic positions, the gene was distinct and therefore temporarily designated as LrA2K. The closely linked marker Xwmc770 to LrA2K has been validated on a set of wheat cultivars and can be used in MAS for LR resistance.

Molybdenum application forms associated to topdressing nitrogen fertilization in the production of maize crops

Nitrogen fertilization associated to the application of molybdenum (Mo) can increase grain yield in maize crops. Therefore, the objective of this study was to evaluate the effect of molybdenum application forms associated to topdressing nitrogen fertilization on production components and maize crops grain yield. The experiment was conducted with the cultivar Pioneer® 30F53H, under a randomized blocks experimental design, with subdivided parcels and four replications. Four forms of Mo applications were evaluated in each parcel: control (without Mo); seeds treatment (40 g ha-1 Mo); foliar treatment (40 g ha-1 Mo); seeds treatment (20 g ha-1 Mo) plus foliar treatment (20 g ha-1 Mo), using potassium molybdate as Mo source. The sub-parcels received four dosages of nitrogen (N), in topdressing (0, 80, 160 and 240 kg ha-1 N), in the form of urea. The experiment evaluated plant height, ear insertion height, stem diameter, number of grains per ear, 100 grains mass and grain yield in maize crops. The increase in N dosages in topdressing increases plant height, ear insertion height, stem diameter, number of grains per ear, 100 grains mass and maize crop grains yield. The application of molybdenum improves N absorption by maize crops. When applied via seeds treatment, Mo brings better results to foliar application in partial or total dosages.

Maize harvest index and water use efficiency can be improved by inhibition of gibberellin biosynthesis

AbstractPossibilities to improve maize harvest index and nutrient utilization efficiency by application of plant growth regulators were investigated. In container experiments, the effects of different growth regulators on the development of the maize (Zea mays L.) cultivars Pioneer 3906 and Fabregas were tested. Paclobutrazol (PAC) and chlorocholine chloride (CCC), two inhibitors of gibberellin biosynthesis, as well as gibberellic acid (GA3) were applied at growth stage V5. Three weeks after application of PAC, shoot growth of both maize cultivars was strongly affected with a significant decrease in plant height in the PAC treatment by 44% and 36% for Pioneer 3906 and Fabregas, respectively. The growth‐retarded plants had higher leaf areas and reduced transpiration rates. The higher shoot growth after GA3 application was accompanied by a reduction in leaf area and an increase in transpiration rate during 1 week before anthesis. CCC treatment showed no significant effects on plant height, leaf area and transpiration rate. The PAC‐treated cultivar Pioneer 3906 produced several cobs per plant, which were mainly barren at maturity. However, PAC application to Fabregas resulted in just one cob per plant with good kernel development and a grain yield, which was not significantly reduced in comparison with the control. With this similar grain yield in combination with a straw yield decrease of 32%, the harvest index was significantly improved by 12%. In addition, with PAC‐treated Fabregas plants, a 19% increased water use efficiency of the grain (WUEgrain) during the critical period of kernel setting was achieved. In this maize cultivar, CCC application also improved harvest index by 5%, but no effect on WUEgrain occurred. GA3 treatment decreased harvest index of both maize cultivars, and it either reduced WUEgrain (Pioneer 3906) or showed no effect (Fabregas). Utilization efficiencies of N, P and K were not increased with growth regulator application, even in the PAC‐treated Fabregas plants with a significantly improved allocation of assimilates to the grain, mirrored by the higher harvest index. The results indicate that fertilizer applications must be adjusted to the reduced demand of growth‐retarded plants, most likely leading to higher nutrient utilization efficiencies.

Ultraviolet-B Radiation Alters Soybean Growth and Seed Quality

Research on the effects of ultraviolet-B (UV-B) radiation on soybean seed quality is limited. The objective of this study was to quantify UV-B doses, 0, 5, 10 & 15 kJ•m–2•d–1, on soybean growth and seed quality. The experiment was conducted in the Soil-Plant-Atmosphere-Research (SPAR) facility. Chambers located at the R.R. Foil Plant Science Research Facility of Mississippi State University, Mississippi, USA, were used. Each SPAR chamber consists of a steel soil bin to accommodate the root system, a Plexiglas chamber to accommodate plant canopy and a heating, and cooling system connected to air ducts that pass conditioned air to cause leaf flutter through the plant canopy. The SPAR units, supported by an environmental monitoring and control systems, are networked to provide automatic acquisition and storage of the data, monitored every 10 seconds throughout the day and night. Soybean cultivar Pioneer 93Y92 (maturity group IV, Roundup Ready) was used in the study. The desired UV-B radiation was supplied by square-wave UV-B supplementation systems under near ambient PAR and delivered to plants for eight hours, each day, from 08:00 to 16:00 h by eight fluorescent UV-313 lamps. The results showed that increased UV-B did not influence many of the growth parameters because the treatments were imposed at mid-fruiting period. Seed quality parameters that are important for seed industry and human and animal nutrition were all affected by UV-B. Protein and palmitic and oleic acids declined linearly, while oil and linoleic and linolenic acid contents increased with increased UV-B. Sucrose, stachyose, and stearic acid contents showed quadratic trends, increased to about 4 - 5 kJ of UV-B and declined at higher doses. Thus, both current and projected UV-B radiation levels can modify soybean growth and seed quality. The functional algorithms developed in this study could be useful to develop UV-B- specific sub-models for soybean farm management and in policy decision areas.

Effects of tillage practices on drainage and nitrate leaching from winter wheat in the Northern Atlantic Coastal-Plain USA

Management strategies for winter wheat (Triticum aestivum L., cultivar Pioneer “2548”) in the Northern Atlantic Coastal-Plain region of the USA must balance agronomic production with practices to reduce nitrate-N (NO3-N) leaching, because much of this region lies within the Chesapeake Bay watershed. Winter wheat in this region is commonly grown using no-tillage (NT), but few studies have evaluated the effects of NT on NO3-N leaching for winter wheat. A four-year lysimeter study was conducted in Beltsville, Maryland by growing winter wheat in eight tension-drained undisturbed soil-column lysimeters (41cm diameter by 100cm deep) configured to exclude runoff, to compare the effects of NT vs. simulated plow-tillage (PT) and N fertilization practices on drainage volumes and NO3-N leaching. Additional data documented wheat total N uptake and bromide leaching. The temporal pattern of drainage showed that NT produced significant, but modestly higher, drainage volumes than PT during fall establishment (mid-Oct. to mid-Dec.), which increased the potential for NO3-N leaching, especially following high rainfalls. However, the greater risk of NO3-N leaching with NT during establishment decreased in the spring as tillage effects subsided and wheat water-use and N uptake became dominant. The increased fall leaching risk with NT can be managed by reducing fall-N applications, but both NT and PT can benefit from reduced NO3-N leaching resulting from spring split-N applications. The final NO3-N leaching losses depend on the interactions of precipitation timing and amount, fertilizer-N rate and timing, and initial soil water status. Additional winter-wheat NO3-N leaching research is needed to study to a wider range of soils, to assess high-residue vertical-tillage implements, and to evaluate precision application of spring fertilizer-N.

Allometric Relationships of Maize Organ Development under Different Water Regimes and Plant Densities

Allometric relationships of plant organs reflect internal coordination of different aspects of organ development, allowing the linking of plant structural development and underlying physiological processes for the development of functional-structural plant models (FSPMs). This paper aims to (i) explore the allometric relationships between organ morphology and fresh biomass in maize; (ii) develop equations to describe these relationships; and (iii) examine the response of allometric relationships to crop water availability and plant density. Datasets were obtained from field experiments in which threecommercial maize cultivars (Pioneer 34N43, Pioneer 31H50 and NongDa 108) were grown under different water regimes and plant densities. Relationships are described between (i) lamina length and biomass for all phytomers by a power function, (ii)lamina maximum width and biomass by a power and a logarithmic function separated at ear position, (iii) sheath length and biomass by power and logarithmic functions separated at eighth sheath position where the sheath length peaked, and (iv) internode length and biomass by two power functions separated at the ear position across water regimes and plant densities. The allometric relationships of organ development were not affected by the mild water stress, but were modified by the increased plant densities. Consequently, the allometric relationships found in this study and their expressions using mathematical equations enable plant morphology to be predicted from physiological output (biomass accumulation), which provides abiologically robust mechanism of realizing functional-structural communication used in FSPMs.

Co-inoculations of arbuscular mycorrhizal fungi and rhizobia under salinity in alfalfa

Alfalfa (Medicago sativa L.) is cultivated in arid and semi-arid regions where salinity is one of the main limiting factors for its production. Thus, this experiment was conducted to evaluate the efficacy of arbuscular mycorrhizal fungus (AMF), Glomus mosseae, alfalfa rhizobia Sinorhizobium meliloti (R) seed inoculation in the development of salinity tolerance of different alfalfa cultivars (Rehnani, Pioneer and Bami) under a variety of salinity levels. The results revealed that under non-stress condition, root mycorrhizal infection, nodulation (the number and weight of nodules per plant), potassium (K), calcium (Ca), phosphorus (P), zinc (Zn), copper (Cu) and magnesium (Mg) contents of the root and shoot, the value of the K/Na ratio, protein [calculated from the nitrogen (N) content] and proline contents of the shoot and the alfalfa yield were found to be the highest while Na contents of the root and shoot were seen to be the lowest when seeds were double inoculated followed by mycorrhizae, rhizobium and control treatments, respectively. Similarly, under salinity condition, the greatest amounts of mycorrhizal infection, nodulation, root and shoot P contents, the value of K/Na ratio, the shoot proline content and the root Ca content were enhanced with the least amount of leaf Na content related to the cases of seeds which were double inoculated, followed by mycorrhizae, rhizobium and control treatments respectively. The results suggested that inoculation of alfalfa seed with AMF or R, especially double inoculation, causes a considerable increase in alfalfa yield under both saline and non-saline conditions by increasing colonization, nodulation and nutrient uptake.

Crescimento e produtividade do milho, submetido a doses de nitrogênio nos Tabuleiros Costeiros de Alagoas

Este trabalho objetivou avaliar o crescimento e a produtividade de grãos da cultura do milho, submetida a diferentes doses de nitrogênio. O experimento foi conduzido com a cultura do milho híbrido Pioneer 30F35, no período de 25/06 a 28/10/2009, na região de Rio Largo, AL. O delineamento experimental foi em blocos casualizados e os tratamentos consistiram em seis doses de nitrogênio (0, 50, 100, 150, 200 e 250 kg ha-1 de N), com a fonte ureia, e cinco repetições. Os modelos logístico e pico log normal apresentaram ajustes estatísticos significativos (p<0,05) das variáveis de crescimento e coeficientes de determinação máximo de 0,994 e 0,990, respectivamente. Os valores observados e estimados pelos modelos apresentaram alta associação pelo índice de concordância de Willmott, com valores superiores a 0,953. As plantas apresentaram diferenças estatísticas significativas pelo teste F (p<0,05), entre os tratamentos, para altura e índice de área foliar, com crescimento máximo para a dose de 100 kg ha-1 de N. Os tratamentos mostraram diferenças estatísticas significativas (p<0,05) para a produtividade, sobressaindo-se a dose de 200 kg ha-1, que proporcionou maior produtividade de grãos (5,45 t ha-1). Os modelos de crescimento podem ser utilizados para auxiliar a análise de crescimento.

Influência do sistema lavoura-pecuária com Zea mays L. e Brachiaria brizantha nas variáveis produtivas da cultura do milho

Mixed systems of exploitation of crop and livestock have called attention to the advantages over isolated systems of farming or ranching. Therefore, the objective of this study was to evaluate the influence of seeding rates of Brachiaria brizantha (0.0; 5.0; 10.0 e 15.0 kg ha-1) in the variables of corn productivity and B. brizantha plant stand when cultivated in the consortium. The experiment was established in a randomized complete block design with four replications using the maize cultivar Pioneer 30K64Y sown under the spacing of 0.90 m between rows. We evaluated the number of kernel rows, number of kernels per row, ear length, ear diameter, ear height, plant height, plant population and productivity in corn, as well as plant stand in B. brizantha. Only the plant stand of B. brizantha showed significance for treatments. The intercropping maize with B. brizantha no influence did not the development and productivity of the cereal.

Identification of Pm8 Suppressor at the Pm3 Locus in Soft Red Winter Wheat

ABSTRACTThe 1BL.1RS wheat (Triticum aestivum L.)–rye (Secale cereale L.) translocation possesses genes Pm8, Yr9, Lr26, and Sr31 for resistance to several major fungal pathogens of small grain cereals. However, not all wheat cultivars with the 1RS translocation are resistant to Pm8‐avirulent isolates of Blumeria graminis f. sp. tritici (Bgt), the causal pathogen of wheat powdery mildew. A suppressor is postulated to limit the function of Pm8 in certain genetic backgrounds, such as ‘AGS 2000’. To illustrate the genetic basis of the suppressor in AGS 2000, a 178 recombinant inbred line (RIL) population was used by crossing AGS 2000 with another 1BL.1RS cultivar Pioneer 26R61 (Pm8 effective). A single Bgt isolate, Ken‐2‐5, avirulent to Pm8 and virulent to Pm3a was chosen to inoculate the entire RIL population at the seedling stage. One major quantitative trait locus (QTL), QSuPm.uga‐1AS, was stably detected as having an inhibiting effect on Pm8 in AGS 2000, and the QTL was postulated to be Pm3a based on its location. Further evidence of the Pm8‐suppressing nature of Pm3a was obtained when eight lines from the 2010 Gulf Atlantic Wheat Nursery were inoculated with Ken‐2‐5. The eight lines all have Pm8 (1BL.1RS) but were susceptible, as they also have Pm3a. In addition, a functional locus, QPm.uga‐7AL, was identified in Pioneer 26R61, where it accounted for up to 41% of phenotypic variation in resistance to isolate Ken‐2‐5. QPm.uga‐7AL was flanked by simple sequence repeat (SSR) markers Xcfa2257 and Xwmc525 on 7AL, and its relationship with other known Pm loci on this chromosome arm remains uncertain.

Rhizosphere effects of maize hybrids and N forms on Cd bioavailability in a limed soil

Replacing new corn genotypes in agricultural practices requires adequate information on the reaction of the selected hybrids to Cd uptake in Cd-polluted soil and an understanding of interactions with N fertilizers. A 2 × 2 × 3 factorial pot experiment with limed soil (pH 8), two maize (Zea mays) hybrids (Pioneer cultivar yellow and Pioneer cultivar white), two N fertilization forms (NH4 + and NO3 −) and three Cd exposures (0, 2 and 5 mg kg−1 soil) was conducted under greenhouse conditions. Shoot dry mass increased significantly with NH4 + nutrition compared with NO3 − nutrition in both maize hybrids, with greater negative influence of Cd application combined with NH4 + nutrition. The yellow cultivar had significantly greater shoot dry mass and lower Cd uptake than the white cultivar. Both hybrids exhibited similar N uptake in shoots and roots, with the exception of yellow cultivar with NH4 + nutrition without Cd application. NO3 − nutrition always decreased Cd uptake in both cultivars compared with NH4 + nutrition. The N balance (mean across cultivars and Cd supply) after harvest showed most N uptake with NH4 + nutrition (63.4%) and Nmin remains in the soil with NO3 − nutrition (48.7%). Soil pH decreased more with NH4 + (−0.95 pH units) than NO3 − nutrition (−0.21).

Identification and Validation of QTL for Grain Quality Traits in a Cross of Soft Wheat Cultivars Pioneer Brand 25R26 and Foster

ABSTRACTEnd‐use quality is vital to the wheat (Triticum aestivum L.) industry. Understanding the genetics of components of quality is needed for efficient genetic improvement. Our objectives were to determine the genetics of soft wheat quality in a population derived from soft wheat cultivars and to validate the results. We developed 171 families from the cross ‘Foster’ × Pioneer ‘25R26’ and obtained quality data from four environments. We assessed flour yield (FY) and flour protein (FP), softness equivalent (SE), and water (WA), sodium carbonate (SO), sucrose (SU), and lactic acid (LA) solvent retention capacities (SRCs). Families were genotyped with markers and quantitative trait loci (QTL) analyses were performed. All traits were heritable (0.71– 0.93) and transgressive segregants were noted. The traits FY, WA, SO, and SU were correlated to one another as were SE and FP. A total of 29 QTL were detected from 11 genomic regions. Quantitative trait loci for correlated traits were generally coincident. Two regions of chromosome 1B had the greatest effect on WA, SO, FY, and LA (r2 = 0.23 to 0.30); these QTL appeared to be associated with the 1BL.1RS rye (Secale cereale L.) translocation and the Glu‐B1 locus. A region of chromosome 2B had the greatest effect on FP, SE, and SU (r2 = 0.13 to 0.23). The 1B and 2B QTL were validated in crosses between each of the original mapping parents and ‘Hopewell’. We documented the relative importance for soft wheat quality of two known regions of 1B and report on a novel QTL on 2B. Marker‐assisted selection for these three regions could have a significant impact on soft wheat quality.

Gas exchange and leaf metabolism of irrigated maize at different growth stages

Net ecosystem exchange (NEE), leaf gas exchange and biochemical traits were investigated in an irrigated maize crop grown under Mediterranean conditions. Sub-optimal irrigation water supply determined a drought stress during the early vegetative growth stage (45–49 days after swing) that decreased NEE. Drought, in the late vegetative stage, also caused a reduction of leaf gas exchange. In the latter period, proline, glycine and serine, as well as sucrose leaf contents increased, while starch, proteins and glucose contents decreased. In the early reproductive stage, the crop experienced a longer dry spell that induced a reduction in canopy as well as in leaf gas exchanges, while protein and free amino acid contents decreased with respect to the late vegetative stage. Both ecophysiological and biochemical data demonstrate a good capacity of cultivar Pioneer PR32D99 to endure the environmental stress, related to Mediterranean summer drought, leading to an elevated dry matter yield at harvest. Photosynthetic apparatus appeared fairly resistant to soil water shortage due likely to the increased leaf content of organic solutes, such as amino acids and soluble sugars.

Volunteer wheat (Triticum aestivum L.) competition in corn (Zea mays L.)

Volunteer winter wheat (Triticum aestivum L.) is a sporadic weed found in corn (Zea mays L.) fields across southern Ontario. Eight trials were conducted over a 2-yr period (2006 and 2007) at four locations to determine the competitiveness of volunteer winter wheat in corn. A soft red winter wheat cultivar (Pioneer 25R47) was seeded at each location at densities of 0 to 30 seeds m-2 late in the fall, prior to corn planting the following spring. Volunteer wheat competition in corn resulted in reduced emergence of corn leaf collars. Competition with volunteer wheat resulted in a 5% decrease in corn leaf collars present at 21 and 70 d after emergence with volunteer wheat densities of 3.0 and 5.2 plants m-2, respectively. Furthermore, volunteer wheat competition reduced total leaf area, leaf dry weight, shoot dry weight, plant and ear height and yield by 5% with densities of 5.1 to 6.0 plants m-2 compared with the weed-free control. The level of competitiveness was dependent on the density of volunteer wheat.

Efecto de tres tensiones de humedad del suelo sobre la germinación de semillas de diferentes tamaños en maíz (Zea mays L.)

Se estudio el efecto de tres frecuencias de riego que produjeron tres niveles de tensión de humedad en el suelo sobre la germinación de semillas de maíz. Se estimó la curva de retención de humedad del suelo y mediante análisis de regresión, las ecuaciones de ajuste de las rectas y el rango de fluctuación en la tensión del agua del suelo dentro de cada intervalo de riego para cada frecuencia establecida. La siembra se efectuó en bandejas de aluminio, 10 kg suelo bandeja-1 y 50 semillas. El diseño estadístico fue parcelas divididas con cuatro repeticiones, parcela principal: tensiones de humedad del suelo (0, -0,6 y -1,2 MPa), subparcelas: dos cultivares de maíz (Himeca 95 y Pioneer 3031), y sub-subparcelas: tres tamaños de semillas (TS) (< 0.32 g; 0.32, 0.36 g, y > 0.36 g). Se evaluó: porcentaje de germinación (%), índice de velocidad de germinación (IVG) y número medio de días a germinación (NMDG). Fue posible discriminar entre cultivares para esta condición de estrés en el proceso de germinación con una tensión de la humedad del agua en el suelo de -1,2 MPa (Pioneer 3031 superior a Himeca 95). El tamaño de la semilla no influenció el proceso de germinación.