bluuebunny/crossref_metadata_2025 huggingface dataset:
Insect clip cages rapidly alter photosynthetic traits of leaves
Authors: Crafts‐Brandner Steven J. , Chu Chang‐chi
Published: July 2010

In plant‐insect interaction experiments, a clip cage is frequently used to isolate insects or other small pests on a leaf. Clip cage effects on the physiology of the leaf could possibly confound experimental results. Our objective was to quantitate the effects of an insect clip cage of the type typically used for small pests such as whiteflies (Bemisia sp.), aphids (Aphis sp.) and mites (Urticae sp.) on the photosynthetic traits of cotton (Gossypium hirsutum L. cv. Coker 100A‐glandless) and muskmelon (Cucumis melo L. cv. Imperial 45) leaves. Clip cages that enclosed 11.3 cm2 of both the abaxial and adaxial sides of a leaf were attached to young fully expanded leaves. For the leaf tissue within the clip cage, incident radiation was decreased and leaf temperature was increased. After 24 h, chlorophyll content of tissue within the clip cage was significantly increased compared with non‐caged‐control samples taken from the opposite half of the same leaf. Three days after clip cages were attached to leaves, compared with controls, the tissue within the cage had a lower light‐saturated, steady‐state CO2 exchange rate (CER) and leaf soluble protein content. The cage effect on CER and soluble protein could be explained, at least in part, by decreased light‐saturated initial Rubisco activity for leaf tissue within the clip cage. We conclude that the clip cages caused physiological and biochemical alterations of leaves that could alter insect nutrition. Thus, it is suggested that clip cage effects on leaf physiology and microenvironment must be considered when interpreting results of plant‐insect interaction experiments.
Postheading Biomass Distribution for Monocrops and Mixtures of Small Grain Cereals
Authors: Juskiw P. E. , Helm J. H. , Salmon D. F.
Published: July 2010

Biomass distribution during the harvest period can affect the yield and quality of silage produced from cereal crops. Our objectives were to determine the changes in biomass distribution among morphological structures and how management practices could affect those changes. Three field studies were conducted to evaluate the productivity of barley (Hordeum vulgare L.), oat (Avena sativa L.), triticale (× Triticosecale rimpaui Wittm.), and rye (Secale cereale L.) grown as monocrops and mixtures. Seeding rates ranging from 250 to 750 seeds m−2 were evaluated to determine their effects on biomass distribution from heading to the soft‐dough growth stages. While seeding rate had a profound effect on per plant biomass, it had little effect on biomass per unit land area or the distribution of the biomass between leaves, stems, and spikes. During the postheading period for all tests, the leaf component declined and the spike component increased. The stem component declined for all tests, but variation was found for the tests harvested on the basis of the oat and triticale components. Composition biomass weights from our spring cereal tests averaged across the three sampling times (heading to soft dough) were 18% leaf, 50% stem, and 31% head for ‘Noble’ barley; 18% leaf, 44% stem, and 37% head for ‘AC Mustang’ oat; and 22% leaf, 43% stem, and 35% head for ‘Wapiti’ triticale. Plant populations and total, leaf, stem, and spike biomass per plant for mixtures were found to be intermediate to the monocrops. Total biomass quantity and distribution among leaves, stems, and spikes were affected by genotype, production practices, and time of harvest, with the latter having the greatest effect. Understanding cultivar, species, and management effects is important for optimum feed quantity and quality.
Strawberry Yield over Red versus Black Plastic Mulch
Authors: Kasperbauer M. J.
Published: July 2010

Plastic mulches are frequently used in raised‐bed culture of strawberry (Fragaria×ananassaDuch) to conserve water, control weeds with less herbicides, and keep fruit clean. The most commonly used plastic mulch color is black. It was hypothesized that a specially formulated red plastic mulch that reflects a higher far‐red to red photon ratio could regulate photosynthate allocation enough to increase yield of strawberry. Yields over the red plastic (SRM‐Red) were compared with those over standard black plastic in field experiments at a research center and on a commercial strawberry farm. Yield per plant and size per berry were greater over the red than over the black plastic at both locations. The yield advantage of red mulch relative to black occurred whether the red plastic was placed directly over the soil or over a layer of black plastic. It is concluded that strawberries were larger over the new red plastic mulch because reflected far‐red and red light affected phytochrome‐mediated allocation of photosynthate, and more was directed to developing fruit.
Improvement of Bacterial Blight Resistance of ‘Minghui 63’, an Elite Restorer Line of Hybrid Rice, by Molecular Marker‐Assisted Selection
Authors: Chen Sheng , Lin X.H. , Xu C.G. , Zhang Qifa
Published: July 2010

‘Minghui 63’ is a restorer line widely used in hybrid rice production in China. However, this line has become increasingly susceptible to bacterial blight (BB), resulting in a rapid decline of its use in rice production. The objective of this study was to improve the BB resistance of Minghui 63 by introgressing Xa21, a broad‐spectrum BB resistance gene, into Minghui 63 by molecular marker‐assisted selection (MAS). A polymerase chain reaction (PCR)‐based MAS system was established consisting of a marker that is a part of Xa21, a marker located at 0.8 centimorgans (cM) from the Xa21 locus on one side, and a marker at 3.0 cM from the gene on the other side. A total of 128 restriction fragment length polymorphism (RFLP) markers, evenly distributed on the 12 chromosomes, were used to recover the genetic background of Minghui 63. The resulting improved version of Minghui 63, or ‘Minghui 63(Xa21)', was exactly the same as the original except for a fragment of less than 3.8 cM in length surrounding the Xa21 locus. Both Minghui 63(Xa21) and its hybrid with ‘Zhenshan 97A’ referred to as ‘Shanyou 63(Xa21)' showed the same spectrum of BB resistance as the donor parent. Field examination of a number of agronomic traits showed that Minghui 63(Xa21) and Shanyou 63(Xa21) were identical to Minghui 63 and Shanyou 63, when there was no disease stress. Under heavily diseased conditions, Minghui 63(Xa21) showed significantly higher grain weight and spikelet fertility than Minghui 63, and Shanyou 63(Xa21) was significantly higher than Shanyou 63 in grains per panicle, grain weight, and yield.
Geographical Distribution of a Chromosome 7C and 17 Intergenomic Translocation in Cultivated Oat
Authors: Jellen E.N. , Beard J.
Published: July 2010

Previous cytogenetic and molecular genetic investigations have shown variation for the presence of intergenomic translocation segments on chromosomes 7C and 17 of common cultivated oat (Avena sativa L., 2n = 6x = 42) and red oat (A. byzantina K. Koch, 2n = 6x = 42). The objective of this work was to determine the geographic distribution of these translocation segments in 197 landraces and cultivars using C‐banding. Genotypes were selected primarily on the basis of diversity of geographic origins, particularly within the Mediterranean‐Near Eastern center. Eighty‐nine percent of traditional A. byzantina‐type accessions, mostly from the lowland Mediterranean basin and Indian subcontinent, were of the nontranslocation type. Ninety‐seven percent of traditional A. sativa and hulless (A. sativa subsp. nuda) genotypes possessed the 7C‐17 translocation (Δ7C‐17) segments. Presence or absence of the Δ7C‐17 was more loosely associated with spring vs. winter growth habit, but still highly significant. The results support the hypothesis that common cultivated oat and red oat are distinct races of the hexaploid biological species and were domesticated independently of one another.
Structure of Genetic Diversity among Common Bean Landraces of Middle American Origin Based on Correspondence Analysis of RAPD
Authors: Beebe S. , Skroch P. W. , Tohme J. , Duque M. C. , Pedraza F. , Nienhuis J.
Published: July 2010

More than 60% of common bean production worldwide is derived from cultivars of Middle American origin. Understanding the diversity of these will facilitate their use in genetic improvement. The objective of this study was to analyze a collection of 269 landraces of common bean (Phaseolus vulgaris L.) by correspondence analysis of random amplified polymorphic DNA (RAPD) data to determine the genetic structure of the Middle American gene pool of cultivated bean. One hundred eighty landraces originating in Mexico, the remainder in Central America and secondary centers of diversity within the Americas, and two checks were studied. DNA was extracted, RAPD reactions carried out, and polymorphic bands were scored as present or absent on the basis of 39 primers. Groups were formed which in part corresponded to races defined previously by morphological and agroecological criteria. However, tropical small‐seeded Race M was composed of two groups: one largely Mexican that included most small‐seeded black beans of upright plant habit; and one Central American with landraces of various seed colors. Most non‐black small‐seeded germplasm of Race M phenotype from secondary centers grouped with the Central American landraces, except for cream‐seeded and purple‐seeded accessions from Brazil. Races D and J could be distinguished and within races D and J further divisions could be recognized which were related to geographic origin. The more commercial Race D landraces formed a genetic group that was predominant in the western part of the Mexican highland plateau. Another Race D group was concentrated at the eastern extreme of the neovolcanic axis and was differentiated morphologically as well. Guatemalan germplasm contained accessions of climbing bean that did not group with any of the previously defined races and should be considered a separate race. Thus, Middle American germplasm of common bean is more complex than previously thought, and contains diversity that remains to be explored for its practical value.
The Western Wheatgrass Chloroplast Genome Originates inPseudoroegneria
Authors: Jones T. A. , Redinbaugh M. G. , Zhang Y.
Published: July 2010

The octoploidPascopyrum smithii(Rydb.) A. Löve (StHNsXm) arose from hybrization among four diploid genera, three of which are known from genome analysis, but the diploid origin of thePascopyrumchloroplast genome remains unknown. Identification of the maternal parents in the hybridizations leading toPascopyrumwill guide efforts to reconstruct allopolyploid germplasm from ancestral taxa. We compared the DNA sequences of a 762‐base pair (bp) segment of the ndhF (nicotinamide adenine dinucleotide dehydrogenase subunit F) chloroplast gene of western wheatgrass (Pascopyrum smithii; StHNsXm) with that of its putative allotetraploid, i.e.,Elymus(StH) andLeymus(NsXm), and diploid, i.e.,Pseudoroegneria(St),Hordeum(H),Psathyrostachys(Ns), ancestors. To ascertain the 2xto 8xchloroplast phylogeny, the gene sequences were aligned and a phylogenetic tree was constructed by the neighbor‐joining method.Pascopyrum smithiidiffered by 0 to 2 and 6 to 9 bp from its two 4xancestors,ElymusandLeymus, respectively.Elymusdiffered by 2 and 10 to 13 bp from its two 2x ancestors, PseudoroegneriaandHordeum, respectively.Pascopyrum,Elymus, andPseudoroegneriataxa clustered together, but separately fromLeymusandHordeumtaxa. ThePascopyrumchloroplast genome appears to have originated from the diploidPseudoroegneriathrough the tetraploidElymusDe novo synthesis ofPascopyrumgermplasm from its tetraploid ancestors should be conducted with cognizance of the preference forPseudoroegneriacytoplasm found in nature.Leymusdiffered from its diploid ancestor,Psathyrostachys, by 14 to 15 bp, indicating that the second unknown diploid ancestor ofLeymusmay have contributed its chloroplast DNA.
Inheritance of Partial Resistance to Sclerotinia Stem Rot in Soybean
Authors: Kim H. S. , Diers B. W.
Published: July 2010

Little is known about the inheritance of partial resistance in soybean [Glycine max (L.) Merr.] to sclerotinia stem rot, caused by the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary. This information would be useful to soybean breeders who are developing cultivars with resistance to sclerotinia stem rot. Our objectives were to study the inheritance of partial resistance to sclerotinia stem rot and to present the initial results from mapping quantitative trait loci (QTL) that confer this resistance. The research was conducted by testing 152 F3‐derived lines from a cross between a partially resistant cultivar, Novartis Seeds S19‐90 (formerly Northrup King), and a susceptible cultivar, Williams 82, for resistance to sclerotinia stem rot and agronomic traits at two Michigan locations in each of 2 yr. These lines were also evaluated for 123 genetic markers to map resistance genes. The resistance of the lines, measured with a disease severity index (DSI), was normally distributed across environments. Significant (P < 0.05) genotypic variation, genotype × location, and genotype × year interactions were observed for DSI. The broad‐sense heritability estimate for DSI across both locations and years was 0.59. More severe disease was significantly correlated with greater lodging, later date of maturity, later R1 date, and greater plant height. Three QTL, explaining 10, 9, and 8% of the variability for DSI across environments, were mapped with genetic markers. Two of these QTL were also significantly associated with disease escape mechanisms such as plant height, lodging, and date of flowering. The other QTL was not significantly associated with escape mechanisms and may map one or more genes involved in physiological resistance to the disease.
Response to Selection for Increased Individual Grain Mass in Pearl Millet
Authors: Bidinger F. R. , Raju D. S.
Published: July 2010

Although pearl millet [Pennisetum glaucum (L.) R. Br.] is traditionally a small grain crop, a trait associated with adaption to marginal environments, there are both agronomic and usage‐related reasons for seeking to increase individual grain mass (or size). Individual grain mass appears to have a low to moderate heritability in pearl millet, suggesting that genetic improvement based on some form of progeny testing is likely to be effective. The objective of this research was to quantify the percentage increase in individual grain mass that could be achieved in a modern open‐pollinated millet cultivar, ICMS 7703, by two cycles of recurrent S1 progeny selection for increased grain mass and maintenance of grain yield potential. Evaluated across 10 test environments, two cycles of selection achieved an 18% increase in individual grain mass (8.05–9.52 mg per grain), with no change in grain yield per square meter. Substantial improvement in individual grain mass in pearl millet is thus possible with targeted recurrent selection, where larger seed size provides an agronomic or processing advantage, or enhances consumer preference.
Grain Yield of Rice Cultivars and Lines Developed in the Philippines since 1966
Authors: Peng S. , Laza R.C. , Visperas R.M. , Sanico A.L. , Cassman K.G. , Khush G.S.
Published: July 2010

Genetic improvement in grain yield has been intensively studied in wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena sativa L.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.]. Such information is limited in rice (Oryza sativa L.). The objective of this study was to determine the trend in the yield of rice cultivars–lines developed since 1966. Twelve cultivars–lines were grown at the International Rice Research Institute (IRRI) farm and the Philippine Rice Research Institute farm during the dry season of 1996. Seven cultivars–lines were grown at IRRI farm in the dry season of 1998. Growth analyses were performed at key growth stages, and yield and yield components were determined at physiological maturity. Regression analysis of yield versus year of release indicated an annual gain in rice yield of 75 to 81 kg ha−1, equivalent to 1% per year. The highest yields obtained with the most recently released cultivars was 9 to 10 Mg ha−1, which is equivalent to reported yields of IR8 and other early IRRI cultivars obtained in the late 1960s and early 1970s at these same sites. Therefore, the 1% annual increase in yield may not represent genetic gain in yield potential. The increasing trend in yield of cultivars released before 1980 was mainly due to the improvement in harvest index (HI), while an increase in total biomass was associated with yield trends for cultivars–lines developed after 1980. Results suggest that further increases in rice yield potential will likely occur through increasing biomass production rather than increasing HI.
Heritability and Genotype × Environment Interactions for Discolored Rice Kernels
Authors: Gravois Kenneth A. , Bernhardt John L.
Published: July 2010

Discolored kernels are but one component of rice (Oryza sativaL.) quality that requires attention by rice breeders. Discolored kernels are most often caused by damage from rice stink bugs [Oebalus pugnax(Fabricius)] and kernel smut disease (Tilletia barclayanaBref.), but other pathogens and physiological disorders can also contribute to kernel discoloration. Our objective was to further understand the inheritance and genotype × environment (GE) interactions for discolored rice kernels to improve rice kernel quality characteristics. Thirty‐seven genotypes, representing southern U.S. rice germplasm, were evaluated for susceptibility to all causes of discolored kernels in field tests conducted during 1993 and 1994 at three Arkansas locations: Stuttgart, Tupelo, and Rohwer. Traits were inherited quantitatively, with single‐plot heritability values of 0.07, 0.18, and 0.33 for rice stink bug damage, kernel smut, and other discolorations, respectively. The GE interactions were significant for all traits. Closer inspection of the GE interaction revealed that the causes were primarily related to magnitude changes but also included genotype rank changes. The bias of GE interaction during selection could be reduced by multi‐year and multi‐location testing. Phenotypic correlations among traits were low, indicating that selection for lower levels of one trait would not adversely raise the levels of another trait. Cultivars, such as Katy, Kaybonnet, and Drew, were identified as having stable, low susceptibility to rice stink bug damage, kernel smut, and other discolorations. Although breeding for improved kernel quality traits will have certain difficulties because of low heritability, the availability of good germplasm and a proper screening program should minimize this problem.
Effective Population Size and Genetic Variability in the BS11 Maize Population
Authors: Guzman Peter S. , Lamkey Kendall R.
Published: July 2010

Use of adequate effective population size in maize (Zea mays L.) recurrent selection programs is important because of random genetic drift and inbreeding depression. The objectives of this study were to (i) evaluate the performance of the BS11 Cycle 0 (C0) and the BS11 Cycle 5 (C5) populations from four S1‐progeny selection programs each with a different effective population size (5, 10, 20, or 30) but with a common selection intensity of 20%, and (ii) compare the additive genetic variance among the C0 and C5 populations. Five cycles of selection were conducted by intermating 5, 10, 20, or 30 lines. One hundred thirty C5 S1 lines from each of the selected populations (i.e., C5–5, C5–10, C5–20, and C5–30) and 100 C0 S1 lines were topcrossed to BS11 C0. The resulting half‐sib progenies were evaluated at five environments in a replications‐within‐sets incomplete block design. The four selection programs resulted in significant increases in grain yield, reduced grain moisture, and reduced root and stalk lodging. For yield, the 10‐S1 program showed the highest gain cycle−1 of 0.16 Mg ha−1 followed by the 30‐S1 program with 0.13 Mg ha−1 cycle−1 The 5‐S1 program had a higher gain cycle−1 than the 20‐S1 program. The additive genetic variance for yield did not change significantly. Heritability for yield was highest for C5–20, but no significant differences were observed among populations. These results suggest little to no advantage of using larger effective population sizes to maintain genetic variability for short‐term recurrent selection.
Soybean Quantitative Trait Loci for Resistance to Insects
Authors: Terry L. I. , Chase K. , Jarvik T. , Orf J. , Mansur L. , Lark K. G.
Published: July 2010

Resistance to insects was found in a recombinant inbred (RI) population of soybean derived from nonresistant parents, ‘Minsoy’ and ‘Noir 1’ (MN) (240 RI). The objectives of this study were to determine quantitative trait loci (QTLs) associated with this resistance by linkage to either restriction fragment length polymorphism (RFLP) or simple sequence repeat (SSR) markers and to confirm these loci in a new population derived from Minsoy crossed with the elite cultivar Archer (MA) (233 RI). Corn earworm (Helicoverpa zea Boddie) larvae were reared on individual lines of the MN and MA RI and several larval traits were measured. Of the 20 linkage groups (LG) of the composite genetic soybean map, QTLs were found on five LGs in the MN and four in the MA population. The QTL on LG U2 is associated with major effects on larval development in both the MN (r2 > 0.12) and the MA population (r2 > 0.28). All other QTLs had lesser effects (r2 < 0.10). The U2 QTL associated with resistance to insects is of major importance in that: (i) it has been identified in different genetic backgrounds; (ii) it is associated with several larval growth parameters; and (iii) it explains a large proportion of the phenotypic variation. All other QTLs were observed to segregate in only one population. Most of the resistance alleles were associated with the Minsoy parent. Consistent with this observation, Archer and Noir 1 were better corn earworm larval host plants than Minsoy.
Selecting Soybean for Adaptation to Double Cropping on the Basis of Full Season Plant Height
Authors: Pfeiffer T.W.
Published: July 2010

Double‐cropping soybean [Glycine max (L.) Merr.] shortens the growing season and reduces vegetative mass and seed yield. Soybean genotypes which produce greater vegetative mass may be better adapted to the double‐crop system. This study was conducted to determine if tall soybean lines selected from full season plantings were better adapted to double‐crop plantings than lines chosen from the same populations without regard to plant height. Four sets of soybean lines, with a tall and random height group in each set, were compared at Lexington, KY, in full season wide row and late planted narrow row (simulated double crop) cropping systems to determine the interaction between plant height and yield in the two different cropping systems. Soybean grown in the full season cropping system yielded an average of 32% more than when grown in the double‐crop system. The height groups differed in yield in only one of the four sets. The cropping system × height group source of variation was not significant for yield in any set. Six of the eight lines ranked one or two for full season yield in each of the four sets were from the random height groups. Likewise, six of the eight lines ranked one or two for double‐crop yield were also from the random height groups. Greater plant height did not consistently increase yield in the lower yielding double‐crop environments. The selection of tall soybean lines did not provide improved adaptation to the double‐crop cropping system.
Birdsfoot Trefoil Seed Production: III. Seed Shatter and Optimal Harvest Time
Authors: Garcia‐Diaz C. A. , Steiner J. J.
Published: July 2010

Seed shattering is a major problem in birdsfoot trefoil (Lotus corniculatus L.) seed production and limited information is available describing the effects of agronomic practices on shatter losses. The objectives of this research were to: (i) quantify the effects of soil‐water availability on seed shatter and (ii) determine optimal harvest time on the basis of a heat unit method to minimize birdsfoot trefoil seed losses under western Oregon climatic conditions. Six treatments varying in water depletion percentage and replenishment amount were applied in 1994 and 1995 and two treatments in 1996 on a Woodburn silt loam soil (fine‐silty, mixed, mesic Aquultic Argixeroll) near Corvallis, OR. The total amount of shattered seeds was correlated with total harvested seed yield (r = 0.93). Crop water stress index (CWSI) was inversely related to the percentage of seeds shattered (r = −0.76). Increasing amounts of applied water increased the potential of seed yield shattered (r = 0.65). Seed shatter losses fluctuated during the late‐reproductive period, but were not influenced by irrigation or fluctuating climatic conditions. A total of 109 heat units (approximately 11 d), which were determined on the basis of a 10°C base temperature, were accumulated from the time of initial pod dehiscence until rapid seed shattering. The average seed yield losses due to shattering was 3 to 5.3 kg ha− d−1 The non‐irrigated control treatment generally produced more seeds than irrigated treatments. It is, thus, best not to irrigate birdsfoot trefoil grown for seed in western Oregon because increasing amounts of irrigation water increased seed shattering.
Osmotic and Salt Stress‐Induced Alteration in Soluble Carbohydrate Content in Wheat Seedlings
Authors: Kerepesi Ildikó , Galiba Gábor
Published: July 2010

The effect of drought and salt stresses on the water soluble carbohydrate content in wheat (Triticum aestivum L.) seedlings was examined to characterize the involvement of major sugar components in the adaptive processes. Hydroponically grown seedlings of four wheat varieties differing in drought and salt tolerance were exposed to consecutive water (polyethylene glycol, PEG) and salinity (NaCl) stresses. Total water‐soluble carbohydrate (WSC), glucose, fructose, sucrose, and fructan content of stems (non‐photosynthetic tissue) were determined. Tolerant genotypes accumulated more soluble carbohydrate than did sensitive ones. Both ionic and non‐ionic stresses increased the concentration of reducing sugars, sucrose, and fructans. Drought tolerant varieties accumulated sucrose to a significantly greater level than did sensitive ones under non‐ionic stress condition. Changes in fructan content of plants after transfer from PEG to NaCl containing solutions were genotype dependent, increasing in salt tolerant and decreasing in salt sensitive cultivars. These results indicate that WSC might be a useful marker for selecting genotypes that are more drought or salt tolerant. The type of sugar comprising the increase in WSC appears to be a less reliable marker since the initial response was an increase in monosaccharides and the delayed response was an increase in fructan.
Increased Chromosomal Variation in Transgenic versus Nontransgenic Barley (Hordeum vulgare L.) Plants
Authors: Choi H. W. , Lemaux P. G. , Cho M.‐J.
Published: July 2010

Plants from in vitro culture can exhibit somaclonal variation, two characteristics of which are structural rearrangements and variation in chromosome number. These characteristics were studied in barley (Hordeum vulgare L. cv. Golden Promise) callus and plants derived from nontransgenic and transgenic callus of approximately the same age; chromosomes were studied in cells from callus and root tips from plants. Analysis of these data revealed greater variation in ploidy in transgenic compared with nontransgenic plants. Of 59 independent transgenic lines, only 32 (54%) had normal diploid complements of 2n = 2x = 14, while 27 (46%) were tetraploid (2n = 4x = 28) or aneuploid around the tetraploid level (i.e., 26, 27, 29 and 30 chromosomes); no aneuploidy around the diploid number was observed. Nontransgenic plants regenerated after in vitro culture alone had a much lower percentage of tetraploids (0–4.3%). Most diploid plants had normal gross morphology, while tetraploid plants had abnormal morphological features. Ploidy determinations were made on randomly selected cells from callus of immature embryos cultured for 0 to 14 d. The number of tetraploid cells in 1‐d‐ to 7‐d‐old callus was around 2 to 4%; in callus comparable in age to that used to regenerate both the transgenic and the nontransgenic sets of plants, 23% of the cells were tetraploid. This percentage is lower than the percentage (46%) of tetraploid plants from the transgenic lines; however, it is considerably higher than the percentage (0–4.3%) of tetraploid plants from nontransgenic callus. Therefore, although chromosomal variation and abnormalities occur in callus and nontransgenic plants, the extent of ploidy changes in transgenic plants is exacerbated, perhaps due to the additional stresses that occur during transformation.
Aluminum Tolerance Associated with Quantitative Trait Loci Derived from Soybean PI 416937 in Hydroponics
Authors: Bianchi‐Hall C. M. , Carter Thomas E. , Bailey M. A. , Mian M. A. R. , Rufty T. W. , Ashley D. A. , Boerma H. R. , Arellano C. , Hussey R. S. , Parrott W. A.
Published: July 2010

Acid soils with high levels of Al impede root growth, causing increased crop sensitivity to drought and decreased nutrient acquisition. Development of Al‐tolerant cultivars may be a cost effective response to the problem. In previous investigations, we identified an Al‐tolerant soybean [Glycine max (L.) Merr.] plant introduction from Japan (PI 416937), and subsequently determined the heritability of the trait in a cross with Young, a highly productive Al‐sensitive cultivar. The objective of the present study was to identify quantitative trait loci (QTL) which condition Al tolerance by a genetic linkage map of 155 restriction fragment length polymorphism (RFLP) marker loci and a hydroponics‐based Al response. The 120 F4‐derived progeny from Young × PI 416937 were divided into four sets and evaluated with the parents for tap root extension in 0 and 2 μM Al3+ activity solutions (NOAL and HIAL, respectively) employing Al levels as whole plots in a split‐plot experimental design. Aluminum tolerance was defined as (i) root extension under HIAL conditions, and (ii) root extension as a percentage of control [PC = (HIAL/NOAL) × 100]. Multiple regression analysis revealed five QTL from independent linkage groups which conditioned root extension under HIAL stress. Three of the five QTL were also detected by PC as the expression of Al tolerance. While most alleles for Al tolerance were derived from the Al‐tolerant parent, PI 416937, a RFLP allele from Young (for marker EV2‐1) improved Al tolerance expressed as PC and exhibited a similar trend under HIAL stress. At present, it is not known whether the Al tolerance gene from Young, in combination with those from PI 416937, will raise Al tolerance beyond that now observed in the PI. One allele for Al tolerance from PI 416937 (for marker B122‐1) may be difficult to capitalize upon, agronomically, because of its association with a detrimental pod dehiscence factor. Further experimentation is needed to distinguish between linkage and pleiotropic effects near this marker. A favorable epistatic effect for Al tolerance was detected between two alleles from the PI 416937. The relationships revealed by marker analysis indicated that marker‐facilitated selection may be a viable approach in the breeding of Al‐tolerant soybean.
Selection of Wild and Cultivated Sunflower for Resistance to a New Broomrape Race that Overcomes Resistance of the Or5 Gene
Authors: Fernández‐Martínez J. , Melero‐Vara J. , Muñoz‐Ruz J. , Ruso J. , Domínguez J.
Published: July 2010

Broomrape (Orobanche cernua Loefl., syn. O. cumana Wallr.) populations belonging to a new race F in Spain have overcome all known resistance genes Or1 to Or5 in cultivated sunflower (Helianthus annuus L.) and are spreading rapidly. All hybrids currently grown in Spain are susceptible to race F, and sources of resistance genes for this race are needed to develop new resistant cultivars. The objective of this study was to evaluate sunflower germplasm for resistance to race F (virulent population SE296). Using artificial inoculation with broomrape seed, 54 accessions of wild Helianthus spp. representing 27 perennial and four annual species and 55 cultivated accessions of sunflower were evaluated after incubation for ≈1 mo in a growth chamber. Helianthus seedlings were transplanted to the greenhouse for an additional ≈3 mo to evaluate the broomrape infection. Most perennial species of wild Helianthus were completely resistant to race F, but some accessions of the species H. divaricatus, H. maximiliani, and H. pauciflorus subsp. pauciflorus showed different proportions of susceptible plants, with a disease incidence varying from 10 to 80%. The annual wild species, H. anomalus and H. agrestis, were fully resistant, while segregation was observed in H. debilis subsp. cucumerifolius and H. exilis Only 7.2% of the accessions of cultivated sunflower tested were fully resistant, with 20% of them segregating for resistance. The high frequency of broomrape resistance to race F observed in the perennial wild species, as well as the resistance found in wild annual and cultivated germplasm, indicates that development of sunflower cultivars resistant to this new race of the parasite is feasible.
Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought? I. Leaf Growth and Senescence
Authors: Borrell Andrew K. , Hammer Graeme L. , Douglas Andrew C. L.
Published: July 2010

Production of sorghum [Sorghum bicolor (L.) Moench], an important cereal crop in semiarid regions of the world, is often limited by drought. When water is limiting during the grain‐filling period, hybrids possessing the stay‐green trait maintain more photosynthetically active leaves than hybrids not possessing this trait. To improve yield under drought, knowledge of the extent of genetic variation in green leaf area retention is required. Field studies were undertaken in northeastern Australia on a cracking and self‐mulching gray clay to determine the effects of water regime and hybrid on the components of green leaf area at maturity (GLAM). Nine hybrids varying in stay‐green were grown under a fully irrigated control, postflowering water deficit, and terminal (pre‐ and postflowering) water deficit. Water deficit reduced GLAM by 67% in the terminal drought treatment compared with the fully irrigated control. Under terminal water deficit, hybrids possessing the B35 and KS19 sources of stay‐green retained more GLAM (1260 cm2 plant−1) compared with intermediate (780 cm2 plant−1) and senescent (670 cm2 plant−1) hybrids. RQL12 hybrids (KS19 source of stay‐green) displayed delayed onset and reduced rate of senescence; A35 hybrids displayed only delayed onset. Visual rating of green leaf retention was highly correlated with measured GLAM, although this procedure is constrained by an inability to distinguish among the functional mechanisms determining the phenotype. Linking functional rather than phenotypic differences to molecular markers may improve the efficiency of selecting for traits such as stay‐green.
Synchronous Pollination within and between Ears Improves Kernel Set in Maize
Authors: Cárcova Jorgelina , Uribelarrea Martín , Borrás Lucas , Otegui María E. , Westgate Mark E.
Published: July 2010

In maize (Zea mays L.), the later‐fertilized ovaries often abort, thereby reducing kernel set. We examined whether altering the time interval between pollination of florets within an ear or between ears could affect final kernel number per plant. Synchrony of pollination was varied by natural‐ and hand‐pollination of four hybrids, contrasting in prolificacy (ears plant−1). Plants were grown in the field at low (2.5 and 3 plants m−2) and high (7.5 and 9 plants m−2) plant populations, without water or nutrient stress. Increasing plant population generally delayed silk appearance, but most silks were exposed within 5 d after silking (DAS). Synchronous pollination of all exposed silks on apical and sub‐apical ears 5 DAS improved kernel number (KN) per plant and the floret fertility index (FFI = number of kernels/number of pollinated silks), relative to open‐pollinated plants. At low plant populations, the KN plant−1 increase resulted primarily from a large increase (39–535%, depending upon the hybrid) in kernels on sub‐apical ears. At high plant populations, only apical ears set kernels. Synchronous pollination increased KN in these ears 8 to 31%, depending on the hybrid. Thus, timing of pollination had a large impact on kernel set, and the disadvantage associated with an ontogenetic delay in silk emergence could be partially overcome by synchronous pollination. Because delayed pollination of early‐silking ovaries allowed a greater number of the late‐silking ones to set kernels, factors other than assimilate availability per fertile floret likely are involved in controlling kernel set.
Short‐Season Soybean Yield Compensation in Response to Population and Water Regime
Authors: Ball Rosalind A. , Purcell Larry C. , Vories Earl D.
Published: July 2010

Short‐season soybean [Glycine max (L) Merr.] production systems, such as double cropping and late sowing, require high populations to optimize yield, but effects of high populations on seed number and seed mass are unknown. We evaluated plant population effects on yield compensation, stability of harvest index, assimilate partitioning for seed number, and seed‐filling characteristics for 2 yr near Keiser, AR. The study had two cultivars, two levels of irrigation, and three row spacings that each had five levels of population ranging from 6 to 134 plants m−2 Increasing population reduced yield per plant but increased yield per unit area. Harvest index was relatively constant across populations for a given year and irrigation regime, and yield was closely associated with biomass at maturity. At high populations, plants maintained individual seed mass by reducing the proportion of shell mass per pod. Final individual seed mass, seed growth rate (SGR), and the length of effective filling period did not change with increasing population for irrigated or nonirrigated treatments. Reductions in yield caused by low population density were due to low seed number. Seed number per square meter was directly proportional to the ratio of crop growth rate (CGR) to SGR. For short‐season production, high populations ensured early canopy coverage and maximized light interception, CGR, and crop biomass, resulting in increased seed number and yield potential.
Index Selection for Weed Suppressive Ability in Soybean
Authors: Jannink J.‐L. , Orf J. H. , Jordan N. R. , Shaw R. G.
Published: July 2010

The economic and environmental costs of weed management in soybean (Glycine max [L.] Merr.) have led to interest in developing weed suppressive soybean varieties to enhance traditional herbicide and tillage‐based approaches. We evaluated 104 inbred progeny from three crosses among elite soybean lines to determine optimal selection criteria for weed suppressive ability (WSA). We grew the lines in 1996 and 1997 at Becker, MN, an irrigated sandy site, and Rosemount, MN, a rainfed silt loam site, in a split‐plot, with and without white mustard (Brassica hirta Moench). We measured soybean height 7 wk after emergence (WAE), light interception 5 and 7 WAE, specific leaf area 7 WAE, and date of full bloom. We harvested aboveground mustard biomass 8 WAE and calculated each soybean line's WSA as the difference between mustard biomass when grown in competition with that line and the overall mean mustard biomass. We estimated genetic correlations between soybean morphological traits, WSA, and the agronomic traits lodging, maturity date, and yield. Soybean early height's heritability and genetic correlation with WSA (r = 0.81) made it an ideal selection criterion. Indirect selection on height increased predicted selection efficiency by 70% relative to direct selection on mustard dry weight. Restricted index selection combining information on early height and lodging or yield eliminated undesirable correlated responses of lodging and yield while maintaining genetic gain for early height and WSA. Nevertheless, continuing rapid gains in agronomic performance while incorporating WSA may be difficult.
Identification of Tropical and Temperate Maize Populations Having Favorable Alleles for Disease Resistance
Authors: Kraja Aldi , Dudley John W. , White Donald G.
Published: July 2010

A possible use of nonelite germplasm is as a source of alleles for disease resistance. Our objective was to determine the value of tropical and temperate maize (Zea mays L.) germplasm accessions as sources of alleles to improve disease resistance of the Corn Belt hybrid FR1064 × LH185. A group of tropical populations and hybrids from the Germplasm Enhancement of Maize Project (GEM) crossed to either Mo17 or B73 (temperate inbreds), was studied. In addition, a group of temperate accessions was evaluated. Reaction to southern corn leaf blight (SCLB) [Bipolaris maydis (Nisikado & Miyake) Shoemaker = Helminthosporium maydis Nisikado & Miyake], northern corn leaf spot (NCLS) [Bipolaris zeicola (G. L. Stout) Shoemaker = Helminthosporium carbonum Ullstrup Races 2 and 3], gray leaf spot (GLS) (Cercospora zeae‐maydis Tehon & E.Y. Daniels), northern corn leaf blight (NCLB) [Exserohilum turcicum (Pass.) K. J. Leonard & E. G. Suggs = Helminthosporium turcicum Pass., Races 1, 1, 2, 23N and three unidentified races] and common rust (Puccinia sorghi Schwein) was studied using Dudley's method for identifying populations with favorable alleles. All accessions had favorable dominant alleles for resistance not present in FR1064 × LH185 for common rust, GLS, and SCLB. Four accessions had a number of favorable alleles for resistance not significantly different from the best accession for all five diseases. Crosses of the accessions containing Mo17 to FR1064 and LH185 were less susceptible to SCLB, NCLB, and rust than crosses of accessions containing B73. At least seven of the best 10 populations were tropical × Mo17 crosses for SCLB, NCLB, and rust when populations were ranked for presence of favorable alleles for resistance not present in either LH185 or FR1064. Net value statistics for tropical × B73 and tropical × Mo17 accessions differed in indicating whether backcrossing or selfing from the F1 is more desirable. Therefore, if tropical populations are crossed to Corn Belt inbreds to increase adaptation, comparisons among tropical populations should only be made when all populations being compared have been crossed to the same Corn Belt inbred.
Diversity Pays in Crop Pollination
Authors: Westerkamp Christian , Gottsberger Gerhard
Published: July 2010

Pollination is an often overlooked but large cost factor in crop production. In spite of the high diversity of flowers, which requires an adequate diversity of pollinators, almost all animal pollination is simplistically ascribed to the manageable but often less efficient pollinator, the European honeybee, Apis mellifera L. In the case of poor pollination by honeybees, a number of costly techniques is applied to enforce fruit set—often with poor results. Finally, growers may resort to hand pollination, which greatly raises production costs. Knowledge of the appropriate pollinator is already available in many cases, however. This is demonstrated in this paper with examples spanning the whole range of pollination syndromes. To make this knowledge accessible, an expert‐based Internet‐accessible database is suggested.
Effects of Seed Maturation Temperature on Seed Yield Characteristics and Subsequent Generations of Lupin
Authors: Clapham W. M. , Willcott J. B. , Fedders J. M.
Published: July 2010

Phenology and morphology of white lupin (Lupinus albus L.) varied in plants derived from different seed lots of the same cultivar, presumably because thermosensitive genotypes are affected by thermal environment during early development. This study was conducted to determine whether the maternal thermal environment of developing seeds influenced subsequent plant development. We grew white lupin plants cv. Ultra, at the mainstem first flower stage, in controlled growth chambers at 13 or 28C temperature under a 14‐h photoperiod. At harvest maturity, yield components were quantified. The two resultant seed populations were planted in the greenhouse, and at the mainstem first flower stage, one‐half of each group of plants was placed in growth chambers at 13 or 28°C. This regimen was carried out through three generations. Seed dry weight per plant and weight per seed were greater for plants matured at 13°C than at 28°C. All plants produced from maternal seed that had matured at 28°C developed at a slower rate than those at 13°C. Floral events in these plants lagged behind by as much as 15 d. No differences were observed in mainstem vegetative node number. We concluded that phenotypic variability among seedlots of the same genotype can be caused by thermal environmental conditions occurring as embryos develop. These results show that thermal environment during seed production can affect subsequent crop performance, which can impact cultivar production and consistency among years.
Canopy Microenvironments and Applied Bacteria Population Dynamics in Shaded Tall Fescue
Authors: Giesler Loren J. , Yuen Gary Y. , Horst Garald L.
Published: July 2010

Shading of the turfgrass canopy is assumed to support increased microbial activity and therefore more potential disease problems. The goal of this research was to determine how shading affects microenvironmental conditions, and how these conditions affect phylloplane colonization by applied bacterial strains. Shade cloth was suspended over tall fescue (Festuca arundinacea Schreb.) turf in field plots and environmental parameters were measured in shaded and full sun areas. Shading increased leaf wetness duration and relative humidity (RH), but decreased the average and range of canopy air and foliage temperatures. Three species of bacteria (Bacillus megaterium, Stenotrophomonas maltophilia, and Enterobacter cloacae) were applied to all plots. Populations of B. megaterium were the lowest of the three species in both study years. Data showed that measurable differences in microclimate occur as a result of shading and that bacterial colonization was generally favored by shading. The lack of consistency between the two assay methods and among bacterial species regarding the effects of shading suggests that differences in response to microclimate conditions may exist among bacterial species or strains. Results indicate that shading should be considered when screening biological control agents for disease management.
Low‐Mowing Tolerance in Buffalograss
Authors: Johnson P. G. , Riordan T. P. , Johnson‐Cicalese J.
Published: July 2010

Drought‐tolerant turfgrasses that can tolerate low mowing heights need to be identified in order to obtain reduction in water use required of turfgrass in many locations. We have begun evaluation and selection of buffalograss [Buchloë dactyloides (Nutt.) Engelm.] at typical golf course fairway mowing heights. A large number of accessions originating from throughout the Great Plains of North America, with the majority from the northern Plains, are being maintained at 1.6‐cm mowing heights. Seedlings from a polycross of six females and four males provided six half‐sib families to observe under similar conditions. Turfgrass quality and genetic color differed significantly among entries in the trials. Several vegetatively propagated genotypes yielded high‐quality turf and exhibited vigorous and competitive growth under low mowing. When data were analyzed by gender, female genotypes performed better than male or monecious types. Genotypes marginally hardy in Nebraska were not hardy when maintained at low mowing heights. Seeded varieties performed well for fall color, probably because of greater genetic diversity. Preliminary selection may be accomplished at higher mowing heights prior to the more costly and time‐consuming low‐mowing evaluations. Results indicate that low‐mowing tolerance may be heritable in buffalograss.