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In Southeast Asia, upland rice (Oryza sativa L.) is farmed extensively on hilly slopes without terraces or flooded paddies, raising concerns about soil erosion and degradation of watersheds. If perennial rice cultivars were developed, they could help reduce soil erosion from upland rice fields. In a two-part series, Sacks et al. (p. 120–128 and 129–134) evaluated perennial growth and agronomic traits for interspecific progeny derived from cultivated rice x two perennial wild relatives (O. rufipogon Griff. and O. longistaminata A. Chev. et Roehr.). Unlike the upland cultivars, some interspecific progeny were strongly perennial. Progenies derived from O. rufipogon were generally fully fertile but progenies of O. longistaminata were usually partly sterile. It should be possible to develop cultivars of perennial upland rice but it will likely take 5 to 10 more years.
Inheritance of Increased Oleic Acid Concentration in Mustard
Several sources of zero-erucic acid Ethiopian mustard (Brassica carinata A. Braun) have been developed, but in all cases the seed oil was characterized by a high degree of polyunsaturation. This problem could be solved by transferring the increased oleic acid trait, currently available in mutants with high erucic acid content, to zero erucic acid backgrounds. In this research, Velasco et al. (p. 106–109) investigated the inheritance of increased oleic acid concentration in the high erucic acid Ethiopian mustard mutant N2-3591. Results revealed that increased oleic acid concentration in N2-3591 was the result of a mutation at a single locus. This simple, monogenic inheritance will facilitate the transference of the trait to zero-erucic acid Ethiopian mustard.
Assessment of Alfalfa during Fall Harvest
The underlying causes of the adverse effect of a fall harvest on alfalfa (Medicago sativa L.) persistence and yields are unclear. Dhont and coworkers (p. 181–194) assessed changes in root N reserves in response to the timing of the fall harvest. Fall accumulation (concentrations and amounts) of the specific amino acids proline, arginine, and histidine was depressed by harvesting early in the fall. The abundance of the major soluble protein of 32 kDa was also reduced by an early fall harvest. Results highlight the determinant contribution of specific N reserves to spring regrowth of alfalfa.
Carbon Isotype Discrimination and Yield in Durum Wheat
Measurement of carbon isotope discrimination (
) in plant material is a promising method for improving transpiration efficiency and, consequently, crop yield in water-limited conditions. Durum wheat (Triticum turgidum L. var. durum) is mostly cultivated in Mediterranean conditions, where crop growth is most dependent on ground moisture stored during the crop season. Araus et al. (p. 170–180) studied the effect of environment on the relationship between grain and yield for durum wheat in the Mediterranean. Water input was responsible for the strong positive relationship observed between and yield across trials during grain filling. No correlation was found between and yield across genotypes for trials with a mean yield up to about 2000 kg ha-1, but for yields of 2500 kg ha-1 and above, the correlation was steady and positive, with an r value around 0.5. Breeding to raise durum yield in Mediterranean conditions could take advantage of selecting for higher only in relatively wet years, or under supplementary irrigation.
Condensed Tanin Concentration of Birdsfoot Trefoil
Condensed tannins are compounds that affect livestock performance. At moderate concentrations, tannins improve the ruminant animal's absorption of soluble proteins. In this research, Wen et al. (p. 302–306) show that the new type of birdsfoot trefoil (containing rhizomes) contains at least twice the condensed tannins as the standard type of birdsfoot trefoil. Further, as birdsfoot trefoil is grown in a mixed pasture and then grazed, condensed tannin concentration is higher than in pure stands of ungrazed plants.
Development of Species-Specific SCAR Markers in Bentgrass
Bentgrass species (Agrostis spp) are cool season turfgrasses tolerant of close mowing heights and commonly used on golf courses and lawns. Some bentgrass species are difficult to distinguish because of similar morphological characteristics and genetic compatibility. Scheef and coworkers (p. 345–349) designed sequence characterized amplified region (SCAR) markers from RAPD bands to identify specifically creeping and colonial bentgrass species. These SCAR markers are useful for screening clones collected from naturalized populations and have potential for identifying progenies derived from artificial interspecific hybridizations among bentgrass species.
Bacterial Brown Spot Resistance in Common Bean
Bacterial brown spot (BBS), incited by Pseudomonas syringae pv. syringae (Pss), is an important bacterial disease of common bean (Phaseolus vulgaris L.). Using F8:9 recombinant inbred lines derived from the Mesoamerican cross of Belneb RR-1 (susceptible to BBS) x A 55 (resistant to BBS), Jung and coworkers (p. 350–357), on the basis of three assays, found one genomic region on linkage group (LG) 2 significantly associated with QTLs for BBS resistance. Pss population size on field grown plants was effectively assessed by a leaflet freezing assay that could be utilized to screen progenies, even when no distinct phenotypic disease symptoms are present on the plants. Marker assisted selection for resistance to BBS may improve selection efficiency for resistance because of the low heritability of the reaction to BBS.
Partial Resistance to White Mold in a Transgenic Soybean Line
Oxalate oxidase (OxO) in transgenic soybean [Glycine max (L.) Merr.] has reduced white mold fungus [Sclerotinia sclerotiorum (Lib.) de Bary] growth in indoor seedling studies. Cober et al. (p. 92–95) characterized the response of an OxO transgenic line to white mold under field conditions. Across 3 yr in an infested field at Sainte-Foy, the transgenic line had a disease severity index (DSI) of 7 compared with the nontransgenic sib line with a DSI of 46. In noninfested trials, no significant differences were found between the transgenic, the negative sib, and the parental lines for seed yield. The transgene provided white mold resistance equivalent to the best commercial cultivars in a white mold susceptible background.
Nitrate Levels under Fairways and Inherent Risks to Water Quality
A 2-yr study was conducted by Lee et al. (p. 247–257) to measure nitrate levels under golf course fairways in situ and evaluate the potential for ground water pollution. Nitrate levels were consistently low (1 to 4 mg kg-1 soil), being uniform with depth and across landscape positions, and similar to adjacent, nonfertilized areas. Nitrogen release from mineralization was substantial and supplied amounts 30 to 100% of that applied as fertilizer. Because of temperature responses, however, N release from mineralization appeared to be synchronized with bermudagrass growth. The results gave no indication that N fertilization or ecology of the bermudagrass system posed inherent risks to water quality.
Estimating Yield Depression Caused by Nonuniformity of Spatial Plant Patterns
On the basis of a nonlinear relationship between single plant yield and individual area per plant (estimated by the area of Thiessen polygons), yield can be decomposed into two additive terms. The first term depends on the mean of individual plant areas. The second term is negative, depends on the mean and variance simultaneously, is proportional to the variance of individual plant areas, and can be interpreted as the effect of variable individual plant areas on yield. This provides the amount of yield depression caused by nonuniformity of spatial distribution of plants across the area. Theoretical concepts and results were applied by Hühn (p. 421–425) to an experimental yield data set of winter oilseed rape. The amount of yield depression was 5.3%.
Sunflower Seed Weight and Oil Concentration Determined by Solar Radiation during Seed Filling
A reduction in intercepted photosynthetically active radiation (PAR) during a short period of seed filling could affect weight per seed and oil concentration in sunflower (Helianthus annuus L.) depending when the reduction occurs. Aguirrezábal et al. (p. 152–161) investigated the effects of intercepted PAR reductions during different periods of seed filling. A reduction in intercepted PAR during 7 to 10 d of seed filling affected weight per seed and oil concentration. Final weight per seed and oil concentration were largely determined by intercepted radiation from 250 to 450°C d after flowering. Changes in intercepted radiation during the established critical period explained differences in weight per seed and oil concentration of sunflower crops. These results could be useful to improve sunflower crop modeling and management.
Distal Grains Have Lower Element Concentration in Wheat
Little is known about the distribution of element concentration in the wheat [Triticum aestivum (L.)] spike. Calderini and Ortiz-Monasterio (p. 141–151) investigated (i) dry weight and macro- and micronutrient concentrations of grains and (ii) their dynamics during grain filling in cultivars and a synthetic line of wheat at different positions of the spike. Element concentrations decreased as much as 30% with increasing floret position away from the rachis. The difference between grains, however, varied with each element (e.g., Zn = -18%; K = +1%). There is potential to alter element concentration of grains with appropriate plant breeding strategies.
Ice Initiation and Propagation in Turfgrass
An infrared thermal imaging radiometer (camera) was used by Stier et al. (p. 415–420) to view ice initiation and propagation in whole turfgrass plants in real time. Freezing always originated in roots, spreading acropetally and basipetally throughout connecting root tissues until it contacted the crown, eventually progressing upwards into shoots and leaves. Ice-nucleating bacteria did not incite freezing of turf tissues. The project demonstrated the utility of infrared imaging for detecting freezing events in whole turfgrass plants. Results suggest that root tissue in the vicinity of the crown is the source of ice which propagates into the crown and kills the plant.
Stem Rust Resistance and Seed Yield Correlation in Tall Fescue
Tall fescue is an important grass used for forage and turf in temperate regions of the world. Economic impact of stem rust, first reported in Oregon tall fescue seed production fields in 1987, has increased in recent years. Fungicide applications are needed to control the disease, but genetic resistance would provide a more environmentally sound approach. Barker et al. (p. 75–79) increased tenfold the frequency of resistant plants in two tall fescue populations after two cycles of recurrent selection. In years with heavy stem rust infection, populations with resistance had higher seed yields than susceptible cultivars. Utilizing genetic resistance would reduce fungicide use by seed growers without sacrificing seed yield.
Extractable Soil Phosphorus Concentrations and Creeping Bentgrass Response
Few studies have directly related turfgrass growth and quality responses to extractable soil P concentrations in sand greens. Guillard and Dest (p. 272–281) determined creeping bentgrass (Agrostis stolonifera L.) growth and quality responses to extractable soil P from a sand putting green using the modified-Morgan, Bray-1, and Mehlich-1 extractants. Critical extractable P concentrations (above which there is a low probability of response to increasing soil P concentrations) for shoot counts, thatch thickness, relative clipping yields, quality ratings, P deficiency ratings, tissue P concentrations, and root weights were determined using Cate-Nelson and Quadratic Response and Plateau models. The results can be used to revise or update existing P fertilization recommendations for bentgrass grown on sand-based media.
Corn Belt Dent Diversity
Open-pollinated cultivars of Corn-Belt Dent corn (Zea mays L.) being maintained in germplasm repositories represent the ancestral gene pool of modern commercial hybrids. Labate et al. (p. 80–91) estimated genetic variation in 57 open-pollinated cultivars and 12 inbred lines using microsatellite loci. They found evidence for a large degree of past admixture among the open-pollinated cultivars, as they shared 85% of their genetic variation. The genetic structure of this germplasm revealed a strong influence of pedigree, even though past selection was intense. Such knowledge of genetic structure can aid end users wishing to utilize genetic variation from open-pollinated cultivars.
Fruiting Site Competition and Yield in Cotton
Yield in cotton is limited because fruiting branches commonly produce mature bolls at only one of three fruiting sites (FS) on a fruiting branch, possibly because competition among FS for sustenance contributes to fruit shed and smaller bolls. Boquet and Moser (p. 195–201) found dependent relationships among FS that were both beneficial and negative for yield. Competition between FS 1 and FS 2 decreased boll weight at FS 2. Boll set at FS 1, however, increased the probability of boll set at FS 2 and boll set at FS 2 increased boll weight at FS 1. These dependent relationships among FS that affect boll set and size are important to the understanding of yield potential in cotton.
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  J. Argyris, D. TeKrony, D. Hershman, D. VanSanford, M. Hall, B. Kennedy, M. Rucker, and C. Edge Fusarium Head Blight Infection following Point Inoculation in the Greenhouse Compared with Movement of Fusarium graminearum in Seed and Floral Components Crop Sci., February 23, 2005; 45(2): 626 - 634. [Abstract] [Full Text] [PDF]
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