bluuebunny/crossref_metadata_2025 huggingface dataset:
Genotypic Differences and Water‐Deficit Induced Enhancement in Epicuticular Wax Load in Peanut
Authors: Samdur M. Y. , Manivel P. , Jain V. K. , Chikani B. M. , Gor H. K. , Desai S. , Misra J. B.
Published: July 2010

The epicuticular wax load (EWL) on leaves reduces surface transpiration and thus improves crop water use efficiency. The objectives of this study were to evaluate peanut (Arachis hypogaea L.) genotypes for their ELW and also to determine the influence of water deficit stress on EWL. Peanut genotypes were grown in fields in two dry seasons (2000 and 2001) and one rainy (2000) season. Withholding irrigation water resulted in a significant increase in water saturation deficit in the stressed crop. At 45 d after sowing (DAS), significant genotypic differences were observed in EWL of 12 genotypes grown in the rainy season (2000). The values of EWL ranged from 0.91 mg dm−2 in Chico to 1.74 mg dm−2 in PBS 11049, with a mean of 1.27 mg dm−2 Among six genotypes, which were also sampled subsequently, the mean values were 1.10, 1.58, 2.05 mg dm−2 at 45, 75, and 95 DAS, respectively. In both dry seasons, significant genotypic differences were found in the EWL. In the dry season of 2001, the effect of various moisture deficit treatments and their interactions with the genotypes were highly significant. The values ranged from 0.653 to 2.878 mg dm−2 On an average, the highest EWL was found in PBS 11049 (2.24 mg dm−2). Even under irrigated conditions, in summer 2001, the EWL increased with increased age of the crop. However, there was a greater increase in the treatments that were subjected to moisture deficit stress. It was concluded that genotypic differences exist in EWL of peanut and also that EWL increases with increased crop age. This increase is more pronounced in plants that are subjected to protracted moisture deficit stress.
Thirty Years of Cassava Breeding for Productivity—Biological and Social Factors for Success
Authors: Kawano Kazuo
Published: July 2010

The Centro Internacional de Agricultura Tropical (CIAT, headquartered in Colombia) established a cassava (Manihot esculenta Crantz) breeding program in the beginning of the 1970s with the aim of extending the Green Revolution success to less privileged sectors of the tropical populations. The initial decade was mainly dedicated to the collection of germplasm and generation of basic breeding materials. The later decades were devoted to applied breeding in collaboration with international and national programs in Latin America, Asia, and Africa. This paper focuses on the basic breeding at CIAT/Colombia (CIAT/HQ), applied breeding at CIAT/Thailand (CIAT/Thai), and distribution and selection of improved materials with many collaborators in Asia. Fresh root yield of populations was improved by >100% and root dry matter content by >20%. The national program collaborators used these populations to develop many improved cultivars in many countries. The biological factors considered as critical for this successful breeding effort were as follows: inclusion of a broad base of genetic variability obtained in the center of crop origin and diversification; evaluation of breeding materials under diverse environmental conditions including high stress environments; and a clear understanding of the different operational principles at different stages of breeding advancement, as illustrated by the emphasis on harvest index in selection within populations and on biomass in population building. The understanding of crop germplasm being a common heritage and the determination of agricultural scientists to use this for the welfare of the neediest people were the social factors for the overall success.
The Impact of Temperature on Leaf Appearance in Bambara Groundnut Landraces
Authors: Massawe Festo J. , Azam‐Ali Sayed N. , Roberts Jeremy A.
Published: July 2010

Ten bambara groundnut [Vigna subterranea(L.) Verdc] landraces of diverse origin were used to examine the effect of temperature on the rate of leaf appearance (RLA) and to determine the base temperature (Tb) among landraces. Knowledge of leaf development is required in breeding programs where crop morphological development is considered an important selection criterion. The ability to predict leaf appearance would also facilitate modeling of plant development. Plants were grown in controlled‐environment growth rooms under different temperatures (20, 25, 30, 32, and 35°C ± 1). The study to examine the effect of temperature on leaf appearance in bambara groundnut landraces indicated that the base temperature (Tb) for leaf appearance ranged from 8.1 to 12.0°C. Within the range of temperatures evaluated in this study, the observation of differences in Tbvalues among the landraces suggests that Tbvalues for leaf appearance are landrace dependent. The phyllochron was also variable among landraces ranging from 40.9 to 53.0°C. The RLA ranged from 0.19 to 0.63 leaves d−1depending on temperature and landrace. The landrace variations in relation to leaf appearance may allow selection of landraces for different environments.
Root and Shoot Responses to Bird Cherry‐Oat Aphids and Barley yellow dwarf virus in Spring Wheat
Authors: Riedell Walter E. , Kieckhefer Robert W. , Langham Marie A. C. , Hesler Louis S.
Published: July 2010

There is little information available that describes the effects of bird cherry‐oat aphids (Rhopalosiphum padi L.) and Barley yellow dwarf virus (BYDV) on cereal plant root systems. This 2‐yr field experiment was conducted to determine how spring wheat (Triticum aestivum L.) root characteristics, shoot characteristics, and grain yield respond to R. padi infestation, BYDV infection, or a combination of R. padi plus BYDV. Treatments were applied at the 2‐ to 3‐leaf stage. When measured at anthesis, plants that received R. padi treatments (300 aphid days) had about a 30% greater total root length (as measured with a minirhizotron) than control plants. Plants that received BYDV as well as those that received R. padi plus BYDV had about a 40% decrease in total root length when compared with the control. Root system characteristics at different soil depths responded differently to BYDV infection across the 2 yr of the study. In the first year, BYDV‐infected plants had less root length at all soil depths measured than plants that did not receive BYDV infection. In the second year, which was drier near anthesis, root lengths of both BYDV infected and uninfected plants were similar at the 0‐ to 18‐cm soil depth, while at deeper soil depths, plants that had BYDV infection had less root length than plants that did not receive BYDV infection. Plants that received either R. padi or BYDV had fewer tillers, less tiller height, and less shoot dry weight than control plants. The lack of R. padi × BYDV interaction for above‐ground variables suggests that shoots responded to BYDV in a similar manner regardless of whether or not they received R. padi treatment. Treatments consisting of R. padi infestation or BYDV infection reduced individual kernel weight by 8 or 22%, respectively. Infection with BYDV also caused a 53% reduction in the number of kernels per meter of row and a 62% reduction in total grain yield. We conclude that R. padi infestation caused acute injury to spring wheat plants while BYDV caused chronic injury. Most of the dependent variables measured in this experiment responded to BYDV in a similar manner regardless of whether or not the plants received R. padi treatment.
Effect of Dazomet on Annual Bluegrass Emergence and Creeping Bentgrass Establishment in Turf Maintained as a Golf Course Fairway
Authors: Park Bradley S. , Landschoot Peter J.
Published: July 2010

Dazomet (tetrahydro‐3,5‐dimethyl‐2H‐1,3,5‐thiadiazine‐2‐thione) is a soil fumigant labeled for turfgrass renovation. Little is known about dazomet efficacy on annual bluegrass (Poa annua L.) seedling emergence, particularly when it is surface‐applied. The objectives of this field study were to determine (i) the effects of rate and plastic covering of surface‐applied dazomet on annual bluegrass seedling emergence in turf; and (ii) effective creeping bentgrass seeding intervals following surface applications of dazomet. All treatments were applied to established turf during late summer in 2000 and 2001. Covering dazomet treatments with plastic sheets resulted in fewer annual bluegrass seedlings than in noncovered treatments. All plastic‐covered dazomet treatments (388, 340, 291, and 194 kg ha−1) provided greater than 98% reduction in annual bluegrass seedlings when compared with the plastic‐covered controls during 2000 and 2001. When not covered with plastic, the 388 kg ha−1 dazomet treatment provided 97% fewer annual bluegrass seedlings in 2000 and 92% fewer seedlings in 2001 than the noncovered controls. Results of the seeding interval experiment revealed that creeping bentgrass (Agrostis stolonifera L.) groundcover and yields were not inhibited when seeded 3 d after a surface application of dazomet at 388 kg ha−1
Near‐Infrared Spectroscopy on Chopper to Measure Maize Forage Quality Parameters Online
Authors: Welle Roland , Greten Willi , Rietmann Bernhard , Alley Scott , Sinnaeve Georges , Dardenne Pierre
Published: July 2010

Improving maize (Zea mays L.) forage yield and quality is a major goal for corn breeders in northern Europe. The objective of this research was to measure maize forage dry matter (DM) content and quality parameters with near‐infrared spectroscopy (NIRS) directly on a harvesting machine. Coupling NIRS with harvesting eliminates time‐consuming sample preparation and laboratory‐based analyses. Calibrations were developed with 281 samples from the 1998‐1999 growing seasons using a diode array spectrometer mounted on a forage chopper. Standard errors of cross‐validation (SECVs) were 11.8 g kg−1 for DM, 23.6 g kg−1 for starch, 19.2 g kg−1 for in vitro digestibility, and 13.8 g kg−1 for soluble sugars. An independent validation study with 159 samples from the 2000 harvest resulted in standard errors of prediction (SEP) of 12.5 g kg−1 for DM, 22.1 g kg−1 for starch, 19.8 g kg−1 for in vitro digestibility, and 16.7 g kg−1 for soluble sugars. The results indicate that NIRS on chopper (NOC) can determine DM accurately, rank hybrids for starch plus sugars, and group for in vitro digestibility. Dry matter NIRS determinations were more precise than the reference method, enabling improved selection for forage yield, the key factor in product development. Instrument standardization could be achieved through spectral matching and including spectra from different instruments into the calibration database. Approximately 10 000 and 16 000 plots were analyzed by the fully automated NOC system during 2000 and 2001. The dramatic increase in the number of plots analyzed expedites development of new maize forage products.
Mapping of the Ur‐7 Gene for Specific Resistance to Rust in Common Bean
Authors: Park Soon O. , Coyne Dermot P. , Steadman James R. , Skroch Paul W.
Published: July 2010

Bean rust, caused by Uromyces appendiculatus (Pers.: Pers.) Unger, is a major disease of common bean (Phaseolus vulgaris L.). A recommended strategy to obtain durable rust resistance is to use molecular markers linked to rust resistance genes for pyramiding monogenic resistance genes into a single bean cultivar. However, markers linked to the Ur‐7 gene for specific resistance (SR) to rust present in the cultivar Great Northern (GN) 1140 have not been reported. Our objectives were to identify random amplified polymorphic DNA (RAPD) markers linked to the Ur‐7 gene for SR to rust race 59 using bulked segregant analysis in an F2 population from the Middle American (MA) common bean cross ‘GN1140’ (resistant) × GN Nebr. #1 (susceptible) and to map the Ur‐7 gene on an existing RAPD marker‐based linkage map constructed by means of recombinant inbred lines (RILs) from the MA cross GN BelNeb‐RR‐1 × A 55. A single dominant gene controlling SR to race 59 was found in the F2 and confirmed in the F3 Six RAPD markers were detected in a coupling phase linkage with the Ur‐7 gene. Cosegregating coupling‐phase markers OAD12.550 and OAF17.900 were found. These were also present in pinto US‐5 from which the rust resistance of GN1140 was derived. Among the three repulsion‐phase markers, marker OAB18.650 was the most closely linked to the Ur‐7 gene at a distance of 7.6 centimorgans (cM). All linked markers detected in the F2 population also segregated in the RILs and were located on linkage group 11 of the existing linkage map. These markers linked to the Ur‐7 gene of MA origin identified here, along with other independent rust resistance genes from other germplasm, could be utilized to pyramid multiple genes into a bean cultivar for more durable rust resistance.
Evaluation of Diversity among and within Accessions of Illinois Bundleflower
Authors: DeHaan L. R. , Ehlke N. J. , Sheaffer C. C. , DeHaan R. L. , Wyse D. L.
Published: July 2010

Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMillan] is a native herbaceous warm‐season perennial legume that has potential as a forage and grain crop. Many research objectives with the species depend on knowledge of available genetic resources, but the diversity in northern accessions of Illinois bundleflower is unknown. Our objective was to test the hypothesis that genetic variation for selected characters exists within and among a set of northern accessions of Illinois bundleflower. From this, we could determine the distribution of variation among the accessions and examine the phenotypic correlations among characters. We evaluated 20 accessions at Becker and St. Paul, MN, and 18 accessions at Sioux Center, IA. Within‐accession diversity was determined by a progeny test at Rosemount and St. Paul, MN. Every measured character was influenced by accession (P < 0.05) in at least one location. Therefore, the accessions evaluated can provide much of the genetic diversity needed to develop cultivars adapted to the northern USA. Much of the variation can be explained by latitude of origin. Southern accessions had the greatest forage and seed yield potential, were later maturing, but lacked persistence in Minnesota. Variation (P < 0.05) for characters including seed yield and survival was also found within accessions. Within year and location, average seed crude protein (CP) concentration and seed weight were correlated (average r = 0.71, P < 0.05). Within location in August, forage neutral detergent fiber (NDF) was negatively correlated with leaf fraction (average r = −0.89, P < 0.001), and leaf and pod fraction were negatively correlated (average r = −0.80, P < 0.01).
On the effectiveness of early generation selection in self‐pollinated crops
Authors: Bernardo Rex
Published: July 2010

Breeders of self‐pollinated crops often discard inferior lines at an early selfing generation so that more resources can be devoted to the further testing and selection of the more promising lines. Empirical studies have led to contradictory estimates of the correlation between the performance of lines at early and late selfing generations. Here I examine the theoretical effectiveness of early generation selection. When dominance is absent, the genetic correlation (rG) between the performance of an Ft–derived Fg line (i.e., Ft:g) and a descendant homozygous line is equal to the square root of [1 + F(t)]/2, where F(t) is the inbreeding coefficient at generation t Dominance, when present, has little effect on rG The minimum value of rG is high; that is, 0.707 for an F2–derived line. From a genetic standpoint, early generation selection is expected to be effective, but in practice it becomes ineffective if nongenetic effects are large.
Transgenic Herbicide Tolerant Canola—The Canadian Experience
Authors: Stringam G. R. , Ripley V. L. , Love H. K. , Mitchell A.
Published: July 2010

Canola is a Canadian development, having been derived through conventional plant breeding of rapeseed (Brassica napus L. and B. rapa L.). The acceptance of canola in the marketplace has been assisted by the proliferation of new cultivars registered under the mandate of the Canadian Food Inspection Agency (CFIA). New cultivars, whether conventional or transgenic, are evaluated and approved for registration by a national committee known as the Western Canada Canola/Rapeseed Recommending Committee (WCC/RRC). Regulatory approval for transgenics is granted by the CFIA and Health Canada, who oversee the confined and unconfined release of these products into the environment. Transgenic canola cultivars, Roundup Ready {glyphosate [N‐(phosphonomethyl)glycine] tolerant}, and Liberty Link {glufosinate [2‐amino‐4‐(hydroxymethylphosphinyl)butanoic acid] tolerant} were first registered in Canada in 1995, while Navigator [bromoxynil (3,5‐Dibromo‐4‐hydroxybenzonitrile) tolerant] cultivars appeared later. Herbicide tolerant (HT) transgenics have enjoyed increased market share since their development, and now occupy ≈55% of the canola acreage in western Canada. The popularity of these cultivars appears to arise more from agronomic rather than economic advantages. Tolerance tests have failed to show any significant effect of the herbicides on the cultivars.
BSSS53 as a Donor Source for Increased Whole‐Kernel Methionine in Maize
Authors: Olsen Michael S. , Krone Todd L. , Phillips Ronald L.
Published: July 2010

Increasing the whole‐kernel methionine [MET; 2‐amino‐4‐(methylthio)‐butyric acid] level of maize (Zea mays L.) would improve the quality of the grain for poultry feed. Our objective was to increase the MET levels of A632, B73, Mo17, A632/Mo17, B73/A632, and B73/Mo17, with the high‐MET inbred BSSS53 as a donor parent. Backcross‐derived lines were evaluated per se in trials during 3 yr, and hybrids among subsets of these lines were evaluated in three replicates during 1998. Methionine levels of the best A632 recoveries were increased by 17% after three backcrosses and 11% after four backcrosses. Methionine levels of the best B73 recoveries were increased by 20% after three backcrosses and 17% after four backcrosses. In the Mo17 genetic background, MET levels of the best recoveries were increased by 55% after three backcrosses and 31% after four backcrosses. Crosses among the highest MET backcross‐derived lines produced hybrids with significant 23 to 43% increases in whole‐kernel MET compared with corresponding control hybrids. Significant increases in the MET levels of experimental hybrids indicate that BSSS53 is a useful donor source of whole‐kernel MET and that selection within normal dent maize germplasm can be effectively utilized to produce high‐MET hybrids.
Understanding the Effect of Rye Chromatin in Bread Wheat
Authors: Kumlay A. M. , Baenziger P. S. , Gill K. S. , Shelton D. R. , Graybosch R. A. , Lukaszewski A. J. , Wesenberg D. M.
Published: July 2010

Most experiments on 1RS translocations in wheat (Triticum aestivum L.) cannot separate the effects of introgressions of rye (Secale cereale L.) chromosome arm from the absence of corresponding wheat chromosome arms. The objective of this research was to determine the contribution of individual wheat and rye group 1 chromosome arms. Five group 1 ditelosomics, six substitutions, and 16 translocations of 1R in wheat were compared with appropriate controls. All ditelosomics were significantly different from controls for 100‐kernel weight (100‐KW), flour protein content (FP), Mixograph peak time (MT) and tolerance (MTO), and sodium dodecyl sulfate sedimentation (SDSS) volume. Among the long arms, 1DL was the most important for end‐use quality and 1AL the least important, ranking even below the 1RL tested. The contribution of all short arms was low. Substitutions of 1R negatively impacted agronomic performance with the long arm being entirely responsible for this effect. Among translocation lines, those with 1RS.1BL had the highest yield and those with 1RS.1DL the lowest. Negative impact of all translocations of 1RS on the end‐use quality was far greater than the absence of the corresponding 1S arms of wheat. Translocation 1RS.1AL was the least detrimental to quality and 1RS.1DL the most detrimental. Both the source of the rye chromatin and its position in the wheat genome affected agronomic performance and quality. These results suggest that it may be possible to create new translocations of 1RS in wheat with improved performance. Translocation of 1RS to 1AL is preferred from a quality point of view; that to 1BL appears more beneficial for agronomic performance.
Effect of Recurrent Selection on Combining Ability in Maize Breeding Populations
Authors: Doerksen T. K. , Kannenberg L. W. , Lee E. A.
Published: July 2010

Recurrent selection (RS) is a population improvement method that increases the frequency of favorable alleles while maintaining genetic variation in breeding populations. Twelve University of Guelph RS maize (Zea mays L.) populations selected via reciprocal recurrent selection (RRS), selfed‐progeny recurrent selection (S), or a method combining RRS and S (COM), were assessed for changes in the genetic structure of grain yield, grain moisture, and broken stalks, and two associated selection indices. Partitioning of the entry sums of squares from diallel matings of the original (C0) and advanced (CA) cycle populations using Gardner and Eberhart's Analysis II and Analysis III indicated genetic improvement occurred for the per se and cross performance of most populations. Accompanying the favorable changes in population performance were less favorable shifts from predominantly additive genetic effects in C0 to greater nonadditive genetic effects in CA This shift did not substantially change the general combining ability estimates (gi) of most populations. However, for grain yield, the underlying components of gi effects were altered in their relative importance. General combining ability (GCA) effects in the C0 were caused primarily by the population per se effects (vi), while in CA the GCA effects were caused predominately by parental heterotic effects (hi).
Contributions of Leaf Rust Resistance and Awns to Agronomic and Grain Quality Performance in Winter Wheat
Authors: Martin J. N. , Carver B. F. , Hunger R. M. , Cox T. S.
Published: July 2010

Wheat (Triticum aestivum L.) cultivars grown in the Great Plains usually bear awned spikes for their putative value to grain yield and quality. Awnletted cultivars are generally limited to forage‐only systems. We hypothesized that an awnletted type would be more acceptable to grain producers if flag leaf senescence is delayed by protection against leaf rust (caused by Puccinia triticina Erikss.), the principal foliar disease affecting wheat production in the southern Great Plains. In field experiments under moderate levels of leaf rust infection, our objective was to estimate the effects of awns and leaf rust resistance according to the action and interaction of genes controlling these traits. Our analysis focused on agronomic and quality attributes previously shown to be influenced by these genes. Experimental lines were developed from crosses between leaf rust‐susceptible (awnletted or awned) near‐isolines of ‘Century’ and two leaf rust‐resistant, awned backcrossed‐derived lines with Lr41 or Lr42 from Triticum tauschii (Coss.) Schmal. For most attributes, genes controlling awns and rust resistance acted additively but with unequal effects. For the average effects of Lr41 and Lr42, grain yield increased by 63 and 26%, test weight increased by 5 and 3%, and kernel weight increased by 14 and 9%. Averaged across resistant and susceptible types for each gene, awns increased yield by 6.2 and 0%, increased test weight by 1.7% (either Lr gene source), and increased kernel weight by 6 and 4%. Rust resistance was more effective in compensating for the absence of awns than awns were in compensating for the lack of rust resistance. Leaf rust resistance improved milling quality by increasing flour yield and kernel diameter, independent of the presence or absence of awns. The development of awnletted cultivars with acceptable grain yield potential and quality appears achievable, but their utility in a grain‐only production system will be limited without leaf rust resistance.
Enhanced Soybean Plant Growth Resulting from Coinoculation of Bacillus Strains with Bradyrhizobium japonicum
Authors: Bai Yuming , Zhou Xiaomin , Smith Donald L.
Published: July 2010

Nodulation and subsequent nitrogen fixation by soybean [Glycine max (L.) Merr.] plants are inhibited by low root zone temperatures (RZTs). Plant growth promoting bacteria can help overcome these deleterious effects. Three Bacillus strains, B. subtilis NEB4 and NEB5 and B. thuringiensis NEB17, were isolated from inside the nodules of vigorous field‐grown soybean plants in 1998, and were shown to have plant growth promoting activity on pouch‐grown soybean plants under greenhouse conditions. To test their ability to improve soybean nodulation and growth under low RZTs, these strains were coinoculated onto soybean plants, with Bradyrhizobium japonicum, under greenhouse conditions at RZTs of 25, 17, and 15°C, and under field conditions in a short growing season area. In all cases, the experiments were conducted with soybean cultivar OAC Bayfield. All the three Bacillus strains enhanced soybean nodulation and growth in greenhouse and field experiments. Coinoculation with NEB17 provided the largest and most consistent increases in nodule number, nodule weight, shoot weight, root weight, total biomass, total nitrogen, and grain yield. The other two strains provided positive responses in only 1 of the 2 yr of field‐testing. Thus, B. thuringiensis NEB17 would be suitable for use as a plant growth promoting bacterial strain in soybean production systems in short growing season regions.
Fusarium graminearum Infection during Wheat Seed Development and Its Effect on Seed Quality
Authors: Argyris Jason , van Sanford David , TeKrony Dennis
Published: July 2010

Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe causes losses in wheat (Triticum aestivum L.) seed quality and yield. Field studies were conducted in 2000 and 2001 to investigate F. graminearum seed infection (SI) and its relationship to seed germination and vigor and the production of the mycotoxin deoxynivalenol (DON). Seeds from four soft red winter wheat cultivars having different levels of Type II resistance to F. graminearum were harvested at frequent intervals during development and maturity. Low levels of SI occurred late in seed development in 2000, which resulted in high seed quality. In 2001, under heavy disease pressure, F. graminearum increased from <20% at 10 d after anthesis (DAA) to >98% at maturity in both resistant and susceptible cultivars, resulting in unacceptable standard germination (SG) (<80%) and seed vigor [<70% accelerated aging (AA) germination] early in seed development. Although fungicide seed treatment improved the SG of all cultivars, it still remained below acceptable commercial seed quality (80%). Deoxynivalenol was present at significant levels (5 to 25 mg kg−1) throughout seed development and maturation in all cultivars in 2001. Although the resistant cultivar P25R18 had reduced levels of DON and lower seed damage compared with susceptible P2552, resistance had no effect on SI and seed quality. Therefore, under severe disease pressure, Type II resistance offers little advantage to seed producers in reducing SI and improving seed quality during severe FHB epidemics.
Genetic Diversity of Soybean Cultivars from China, Japan, North America, and North American Ancestral Lines Determined by Amplified Fragment Length Polymorphism
Authors: Ude George N. , Kenworthy William J. , Costa Jose M. , Cregan Perry B. , Alvernaz Jennie
Published: July 2010

Asian soybean [Glycine max (L.) Merr.] improvement programs have been conducted for many years almost completely independent of U.S. breeding programs. Productive, modern Asian cultivars may be a promising source of new yield genes for U.S. breeding programs. However, this hypothesis has not been tested. The objectives of this study were to determine the level of genetic diversity within and between Asian and North American soybean cultivars (NASC) by amplified fragment length polymorphism (AFLP) analysis and to identify Asian cultivars with significant genetic difference from NASC. The genetic diversity and relationships were assessed among 35 North American soybean ancestors (NASA), 66 high yielding NASC, 59 modern Chinese cultivars, and 30 modern Japanese cultivars. Five AFLP primer‐pairs produced 90 polymorphic (27%) and 242 monomorphic AFLP fragments. Polymorphic information content (PIC) scores ranged from zero to 0.50. Only 53 of the 332 AFLP fragments provided PIC scores ≥0.30. Genetic distance (GD) between pairs of genotypes was calculated on the basis of the similarity indices determined by the 332 AFLP fragments. Within each of the cultivar groups, the average GD between pairs of genotypes was 6.3% among the Japanese cultivars, 7.1% among the NASC, 7.3% among the NASA, and 7.5% among the Chinese cultivars. The average GD between the NASC and the Chinese cultivars was 8.5% and between the NASC and the Japanese cultivars was 8.9%. Although these distances were not significantly different, they were greater than the average GD between all pairs of NASC (7.1%). Clustering and principal coordinate analysis using all 332 fragments showed a separation of the cultivars into three major groups according to their geographic origin. North American soybean ancestors overlapped with all three cultivar groups. The Japanese cultivars were more removed from NASA and NASC than the Chinese cultivars and may constitute a genetically distinct source of useful genes for yield improvement of NASC.
Cultural Management of Weeds in Turfgrass
Authors: Busey Philip
Published: July 2010

Cultural management of weeds in turfgrass is the use of mowing, fertilization, irrigation, cultivation, planting, and turfgrass selection to affect weed populations. There is consensus in the literature on a few cultural factors influencing some weeds in cool‐season turfgrasses. Taller mowing height, 4 to 8 cm, depending on turfgrass, reduces populations of crabgrasses (Digitaria spp.) in Kentucky bluegrass (Poa pratensis L.) and fescues (Festuca spp.). A high rate of N fertilization (100–300 kg N ha−1 yr−1) reduces populations of crabgrasses, dandelion (Taraxacum officinale G.H. Weber ex Wiggers), and other broadleaf weeds in cool‐season turfgrasses. Annual bluegrass (Poa annua L.) may be favored by this high rate of fertilization. Fertilization of turfgrasses when they are not actively growing increases weeds. Slow‐growing grasses such as zoysiagrasses (Zoysia spp.) have more weeds at high N fertilization rate. Environmental stresses including drought injury, unnecessary aeration or vertical mowing, biotic stress such as nematode and insect herbivory, and diseases contribute to weed colonization. Adapted cultivars and species of turfgrasses that are genetically resistant to biotic and environmental stresses have the fewest weed problems. Adapted turfgrasses can sometimes be effectively managed in the absence of herbicides, especially if they are well established. The generalized mechanisms for cultural management of weeds are poorly understood. Research is needed on optimizing the choices of herbicide and/or cultural practices as part of an integrated management system for turfgrass.
Additive Main Effects and Multiplicative Interaction Model
Authors: Moreno‐González J. , Crossa J. , Cornelius P. L.
Published: July 2010

Many studies have shown the practical advantages of applying the additive main effects and multiplicative interaction (AMMI) model to multienvironment trials; however, a theory about the contributions of error and genotype × environment interaction (GEI) variance components to interaction principal components (PCs) in AMMI models is needed. The objectives of this work were to (i) develop an eigenvalue partition (EVP) method for separating variation attributable to each AMMI interaction PC into interaction variance and error variance components: (ii) develop root mean square predictive difference (RMSPD) on the basis of the EVP theory (RMSPEVP), for selecting the best truncated AMMI model; (iii) apply the RMSPDEVPcriterion to three multienvironment cultivar trials and to simulation data generated for selecting the best truncated AMMI model; and (iv) validate the EVP method by comparing results of the RMSPDEVPcriterion with those obtained with the criterion conventionally used to choose a truncated AMMI model by cross validation (RMSPDCV). A data resampling method was devised to estimate the contribution of error variance to the eigenvalues. The coefficients of the structural GEI variance component were always larger than those of the error variance component for the earlier PC axes. As the error associated with the cell means decreased and the number of replications increased, the portion of the cumulative GEI explained by the earlier AMMI PC axes generally increased, whereas the portion of the error sum of squares (SS) explained by the earlier AMMI PC axes decreased. The RMSPDEVPand RMSPDCVmethods selected similar truncated AMMI models. The RMSPDEVPcriterion is useful for selecting the best truncated AMMI models with the advantage that it can be applied to all trial replications.
Additive Main Effects and Multiplicative Interaction Model
Authors: Moreno‐González J. , Crossa J. , Cornelius P. L.
Published: July 2010

A shrinkage estimation method, herein named the CCC method, for multiplicative models has been shown to improve predictions of cell means in multienvironment cultivar trials; however, better estimations of shrinkage factors are needed. Objectives of this study were (i) to develop shrinkage factors for AMMI (Additive Main effect and Multiplicative Interaction) multiplicative terms based on the eigenvalue partition (EVP) method and (ii) to compare AMMI models fitted by EVP and CCC shrinkage methods, unshrunken AMMI models chosen by cross validation, and best linear unbiased prediction (BLUP) based on a fixed main effects and random genotype × environment interaction (GEI) model. The prediction methods were applied to three multienvironment cultivar trials, and also to simulated data. The four alternative prediction methods were compared by cross validation with the root mean squared predictive difference (RMSPD). According to the RMSPD cross validation criterion, the EVP shrinkage estimation method produced the most accurate predictions in almost all cases. When error variance was of a small to moderately large magnitude, results for EVP and CCC methods were in close agreement, CCC being slightly worse; EVP became better as error variance became very large, probably because of the unreliability of Gollob́s degrees of freedom as a measure of error variance absorption by the principal components (PC) when data are extremely noisy. Shrunken EVP models were generally more predictively accurate than truncated least squares‐fitted AMMI models and BLUPs, which was also true for CCC except when error variance was large. The EVP shrinkage method appears to be promising for obtaining improved predictions of cultivar performance in multienvironment cultivar trials.
Allelic Diversity Changes in 96 Canadian Oat Cultivars Released from 1886 to 2001
Authors: Fu Yong‐Bi , Peterson Gregory W. , Scoles Graham , Rossnagel Brian , Schoen Daniel J. , Richards Ken W.
Published: July 2010

There is longstanding concern that modern plant breeding reduces crop genetic diversity. Such reduction may have consequences both for the vulnerability of crops to changes in their pests and diseases and for their ability to respond to changes in climate and agricultural practices. This concern, however, has not been well validated in recent molecular studies of genetic diversity of several crop species. The objective of this study was to assess allelic diversity changes in 96 Canadian oat (Avena sativa L.) cultivars released from 1886 to 2001 by means of 30 simple sequence repeats (SSRs). A total of 62 alleles were found from 11 informative SSR loci. Thirty‐nine alleles were detected infrequently (frequency ≤ 0.15) among the cultivars and only two alleles were observed frequently (frequency ≥ 0.95). Analyses of the dynamics of SSR alleles over time in these oat cultivars revealed random patterns of allelic change at three loci, shifting patterns of change at one locus, increasing patterns of change at two loci, and decreasing patterns of change at five loci. Significant decrease of alleles was detected in cultivars released after 1970 and also in some specific breeding programs. Three different band‐sharing analyses of the genetic diversity of the grouped cultivars, however, failed to detect significant diversity changes among cultivars released from different breeding periods or programs. These findings indicate that allelic diversity at particular loci, rather than average genetic diversity, is sensitive to oat breeding practices. They also indicate the need for attention to be paid to oat germplasm conservation.
Genetic Components of Yield Stability in Maize Breeding Populations
Authors: Lee E. A. , Doerksen T. K. , Kannenberg L. W.
Published: July 2010

Phenotypic stability has long been recognized as an important target in plant breeding. Stability is influenced in part by the genetic structure, i.e., level of heterogeneity and heterozygosity, of the cultivar. Yet, very little is known about the genetic components underlying stability, and how population improvement strategies influence stability. We examined 12 maize (Zea mays L.) breeding populations selected via reciprocal recurrent selection (RRS), selfed progeny recurrent selection (S), or a method combining RRS and S (COM), to examine changes in the genetic structure of the phenotypic stability of three traits (grain yield, grain moisture, and broken stalks), and two associated selection indices. Partitioning of the genotype × environment sums of squares from diallel matings of the original (C0) and advanced (CA) cycle populations into linear trends indicated that only grain yield and the unadjusted performance index (UPI) followed a predictable linear response. Grain yield and UPI linear trends were further partitioned by Gardner and Eberhart Analysis III to examine the genetic components of stability. We found that recurrent selection (RS) improved grain yield stability, and that this trait is heritable, predictable, and mostly controlled through additive gene action. Improvement in grain yield stability was observed both in cross and per se performance and was accompanied by significant improvement in the mean performance of the populations. However, the improvement in grain yield stability did not result in substantial changes in the general combining ability (gi) estimates of most populations. Our results indicate that grain yield stability can be improved through RS by selecting solely for mean performance across multiple environments.
Divergent Selection for Resistance to Maize Weevil in Six Maize Populations
Authors: Dhliwayo Thanda , Pixley Kevin V.
Published: July 2010

Maize weevil (Sitophilus zeamais Motschulsky) is an important pest of maize (Zea mays L.) in the tropics, causing serious losses for many resource‐poor farmers who store grain on‐farm for use as food and seed. This study evaluated whether weevil resistance of six maize populations could be divergently changed by S1 and S2 selection, and assessed the importance of replicating grain samples when screening for resistance. Weevil resistance was evaluated for unreplicated S1 and for replicated and unreplicated S2 lines by infesting 50‐g grain samples with 32 young adult weevils, and then incubating the samples in a controlled temperature and relative humidity (CTH) laboratory. Divergent synthetics were formed by recombining the most resistant 10% and the most susceptible 10% of at least 100 lines screened for weevil resistance for each maize population. Replicated S2 selection was successful for both populations where it was applied, resulting in an average of 16% (P < 0.01), 49% (P < 0.05), and 20% (P < 0.01) difference between divergent synthetics for weevil progeny emerged, grain weight loss, and the Dobie index of susceptibility, respectively. S1 unreplicated selection was successful for two of the six populations, while S2 unreplicated selection was not successful. Reciprocal effects were significant (P < 0.01) for weevil resistance of F1 varietal crosses among the divergently selected synthetics, indicating the influence of maternal effects. Nevertheless, the most resistant crosses were those among the most resistant synthetics, confirming that additive gene action for weevil resistance was important. Our results provide practical insights regarding methodologies and demonstrate that it is possible to improve weevil resistance of maize populations.
Development of Sequence Tagged Site and Cleaved Amplified Polymorphic Sequence Markers for Wheat Stripe Rust Resistance Gene Yr5
Authors: Chen Xianming , Soria Marcelo A. , Yan Guiping , Sun Jun , Dubcovsky Jorge
Published: July 2010

The Yr5 gene confers resistance to all races of the wheat stripe rust pathogen [Puccinia striiformis Westend. f. sp. tritici Eriks. (P. s. tritici)] identified so far in the USA. Cosegregating resistance gene analog polymorphism (RGAP) markers for Yr5 are available but their use requires skills in polyacrylamide gel electrophoresis and may not be polymorphic across various varieties. To develop better markers to be used in marker‐assisted selection for the Yr5 resistance, sequence tagged site (STS) primers were designed on the basis of the sequences of RGAP markers Xwgp‐18 (AY167598) from the spring wheat (Triticum aestivum L.) ‘Avocet Susceptible’ (AVS) and Xwgp‐17 (AY167597) from the Yr5 near isogenic line (NIL) in the AVS background carrying the Yr5 gene from T. aestivum subsp. spelta (L.) Thell. cv. Album (TSA). Three sets of STS markers (two codominant and one dominant) were developed to amplify a region including a polymorphic 6‐base pairs (bp) insertion–deletion (indel). The cosegregation of the STS markers with Yr5 was confirmed with 114 BC7:F3 lines developed from the cross between AVS and TSA. The STS markers worked well in five out of 17 non‐Yr5 wheat varieties, but the remaining varieties had a similar size of fragment to the Yr5 marker. Because the codominant STS markers were based on a 6‐bp indel, they could not be separated by agarose gel electrophoresis. Cleaved amplified polymorphic sequence (CAPS) markers were then developed on the basis of a DpnII restriction site that is present in all non‐Yr5 varieties and absent in the Yr5 NIL. The CAPS markers for the Yr5 NIL and non‐Yr5 varieties can be separated by agarose gel electrophoresis. The codominant STS markers are easier to score than the original RGAP markers. The CAPS markers are not only easier to score, but also can be used in crosses of an Yr5 donor with a much wider range of wheat germplasms. These markers should be valuable tools to accelerate the introgression of Yr5 into commercial cultivars and to combine Yr5 with other genes for durable resistance to stripe rust.
Increased Soybean Pubescence Density
Authors: Pfeiffer Todd W. , Peyyala Rebecca , Ren Quanxing , Ghabrial Said A.
Published: July 2010

Soybean mosaic virus (SMV) infection of double‐cropped soybean [Glycine max (L.) Merr.] is likely to reduce yield due to soybean flowering date occurring after the start of aphid (Aphis spp.) movement that spreads the virus. Increased pubescence density provides a mechanical barrier to aphid probing that may delay SMV infection until after flowering, a strain‐nonspecific resistance mechanism. The objectives of this study were to (i) evaluate the resistance benefit derived from increased pubescence density and the resulting reduction in incidence of SMV infection in soybean double‐cropping systems, and (ii) compare the yield of soybean having increased pubescence density with the yield of genetically resistant genotypes of normal pubescence. Thirty soybean lines in three maturity sets with combinations of normal, dense, and extra‐dense pubescence and SMV‐resistant and ‐susceptible alleles were grown for 3 yr in late‐planted tests at Lexington, KY. Inoculated border rows provided the virus source for natural aphid transmission of SMV. Extra‐dense pubescence significantly reduced the incidence of SMV infection at R1 and R6 and produced a delay parameter on disease progress curves where the maximum disease increase was after flowering. In the late maturity set where the incidence of SMV infection on normal‐pubescence SMV‐susceptible genotypes was greater than 20%, extra‐dense pubescence provided the same SMV resistance yield benefit as the Rsv1y resistance allele. The mean yield of extra‐dense pubescence genotypes, however, was less than that of normal‐ and dense‐pubescence genotypes.
Photosynthesis and Productivity of Old and Modern Durum Wheats in a Mediterranean Environment
Authors: Koç Müjde , Barutçular Celaleddin , Genç Ibrahim
Published: July 2010

Genetic variability of leaf net photosynthesis rate (An) and its relation to productivity in durum wheat (Triticum turgidum L. var. durum) is not well defined. Two field experiments were conducted at the experimental area of the Faculty of Agriculture, in the University of Çukurova, Turkey, to evaluate the differences between old and modern cultivars in An and productivity. Experiments with sowing dates in November 1996 and February 1997 were performed under rainfed and irrigated conditions, respectively. Measurements included leaf gas exchange and agronomic traits. Old cultivars (OC) were later flowering and taller than modern cultivars (MC) and their harvest indexes were lower. Before the onset of leaf senescence, most of the OC exhibited higher An values than most of the MC, but the extent of variability was not great. High An was correlated with high stomatal conductance (gs), but no overall correlation between An and the ratio of internal [CO2] to [CO2] in the air was observed. In spite of higher An, OC showed no superiority in grain yield. The results indicate that mesophyll conductance rather than gs has an effect on variation in An, and that preanthesis dry matter distribution and total flag leaf photosynthesis and its duration appear to be more relevant than An for grain yield, especially under drought.
Antioxidative Enzymes Offer Protection from Chilling Damage in Rice Plants
Authors: Kuk Yong In , Shin Ji San , Burgos Nilda R. , Hwang Tay Eak , Han Oksoo , Cho Baik Ho , Jung Sunyo , Guh Ja Ock
Published: July 2010

Rice (Oryza sativa L.) is a tropical crop, but is also grown in temperate regions in late spring to summer. Cold temperature damage is a common problem for early‐planted rice in temperate countries. Physiological responses to chilling, including antioxidative enzyme activity, were investigated in rice to identify mechanisms of chilling tolerance. Plants were exposed to 15°C (cold‐acclimated) or 25°C (nonacclimated) for 3 d, under 250 μmol m−2 s−1 photosynthetically active radiation (PAR). All plants were then exposed to chilling temperature at 5°C for 3 d and allowed to recover at 25°C for 5 d. Leaf fresh weight, relative water content, lipid peroxidation, chlorophyll a fluorescence, and quantum yield showed that cold‐acclimated leaves were less affected by chilling compared to nonacclimated leaves. Cold‐acclimated leaves also recovered faster from chilling injury than nonacclimated leaves. We analyzed the isozyme profile and activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR). Significant induction of expression and activity of antioxidative enzymes CAT and APX in leaves and SOD, CAT, APX, and GR in roots were observed. We deduced that CAT and APX are most important for cold acclimation and chilling tolerance. Increased activity of antioxidants in roots is more important for cold tolerance than increased activity in shoots. Chilling‐sensitive rice plants can be made tolerant by cold acclimation.