Summary1. Arbuscular mycorrhizal fungi (AMF) can influence plant community composition and diversity. Previous research has shown that the addition of nutrients reduces the effectiveness of AMF. However, the ways in which soil nutrient availability and AMF interact and affect plant community productivity and ecosystem stability are still poorly understood. 2. We examined the impact of AMF suppression and phosphorus (P) addition on plant diversity, community productivity and temporal stability (TS) in a field experiment. AMF root colonization and the concentration of an AMF-specific phospholipid fatty acid were significantly reduced after application of the fungicide benomyl as a soil drench. 3. The TS of the plant community was higher in communities without benomyl application compared with communities with benomyl application indicating that AMF contribute to the TS of plant communities. AMF suppression increased productivity at the plant species, functional group and community levels under high P addition rates. At the zero P addition rate, AMF did not affect plant community productivity, as the dominant species Artemisia frigida was more abundant in control plots with AMF, while the subdominant species Stipa krylovii was more abundant in the benomyltreated plots with reduced AMF abundance. Compensatory effects between C 3 grasses and non-N 2 -fixing forbs were observed in the control plots with AMF along the gradient of P addition rates, but these effects were not detected among plant species in the benomyl-treated plots under AMF suppression above an addition rate of 4.76 P 2 O 5 m À2 year À1 . Although AMF suppression did not influence the diversity of the plant communities, it did decrease the diversity of N 2 -fixing forbs at the zero P addition rate and above an addition rate of 18.90 g P 2 O 5 m À2 year À1 , indicating that AMF play key roles in the maintenance of N 2 -fixing forbs at these P addition rates. P addition led to biodiversity losses at application rates below 2.36 g P 2 O 5 m À2 year À1 at the community level.4. Synthesis. Arbuscular mycorrhizal fungi and soil P availability interact to influence the productivity and TS of a plant community by mediating compensatory effects among plant species and functional groups.

Understanding the drivers that account for plant production allows for a better understanding of plant communities and the transitions within ecological sites and can assist managers in making informed decisions about stocking rates and timing of grazing. We compared climatic drivers of herbage production for 3 plant communities of the Clayey ecological site in southwestern South Dakota: the midgrass community dominated by western wheatgrass (Pascopyrum smithii [Rybd.] A. Love); the mixed-grass community codominated by western wheatgrass, blue grama (Bouteloua gracilis [H.B.K.] Lag. Ex Griffiths), and buffalograss (Buchloe dactyloides [Nutt.] Engelm.); and the shortgrass community dominated by blue grama and buffalograss. We used herbage yield and weather data for the period 1945-1960 collected at the South Dakota State University Range and Livestock Research Station near Cottonwood, South Dakota, to develop stepwise regression models for each plant community. Midgrass herbage production was best predicted by current-year spring (April-June) precipitation, number of calendar days until the last spring day with minimum temperature À18C, and previous-year spring precipitation (R 2 ¼ 0.81). Mixed-grass herbage production was best predicted by current-year spring precipitation and days until the last spring freeze (R 2 ¼ 0.69). Shortgrass herbage production was best predicted by current-year spring precipitation (R 2 ¼ 0.52). Midgrass plant communities were, overall, 650 kg ha À1 (SE ¼ 92 kg ha À1) more productive (P , 0.01) than mixed-or shortgrass plant communities given the same climatic inputs. Our study enables managers to make timely informed decisions regarding stocking rates and timing of grazing on this ecological site in western South Dakota. Resumen Entender los factores que participan en la producció n vegetal permite una mejor comprensió n de las comunidades vegetales y las transiciones dentro de los sitios ecoló gicos y puede ayudar a los manejadores de pastizales a tomar decisiones fundamentadas respecto a la carga animal y época de apacentamiento. Comparamos factores climá ticos que influyen en la producció n de forraje de 3 comunidades vegetales del sitio ecoló gico Arcilloso en el suroeste de South Dakota: la comunidad de zacates medios, dominada por ''western wheatgrass'' (Pascopyrum smithii [Rybd.] A. Love); la comunidad de zacates mixtos co-dominada por ''western wheatgrass,'' ''blue grama'' (Bouteloua gracilis [H.B.K.] Lag. Ex Griffiths), y ''buffalograss'' (Buchloe dactyloides [Nutt.] Engelm.); y la comunidad de zacates cortos dominada por ''blue grama'' y ''buffalograss.'' Utilizamos datos climá ticos y de producció n de forraje del periodo 1945-1960 colectados en la Estació n

Aims:  To understand the diversity, taxonomy and antagonistic potential of rice‐associated bacteria, and to discover new bacteria for biocontrol of rice foliar pathogens. Methods and Results:  Amplified ribosomal DNA restriction analysis (ARDRA), BOX‐PCR and 16S rRNA gene sequence analysis were used to identify the diversity of 203 rice‐associated antagonistic bacteria. Eleven potential biocontrol bacteria were used to test their biological control of rice blast in a natural field experiment. Eleven different genera were encountered in five divisions, including Bacilli, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Deinococci. The most prominent genus in all microenvironments was Bacillus (68·5%). The efficacy of rice leaf blast biocontrol was 64·35% for strain 1Pe2, 57·86% for strain 2R37 and 56·44% for strain 1Re14. Conclusions:  Biocontrol data from the field experiments demonstrated no positive correlation between antagonism, physiological characteristics and biocontrol efficacy. There was significant diversity among the rice‐associated bacteria isolated from different microenvironments. The most prominent genus of all microenvironments was Bacillus. Brevibacillus brevis strain 1Pe2 and Deinococcus aquaticus strain 1Re14 have good potential for field application and commercial use. Significance and Impact of the Study:  This is the first attempt to study the diversity and identification of rice‐associated antagonistic bacteria from different microenvironments, and endophytic bacteria Deinococcus aquaticus strain 1Re14, Acidovorax sp. isolate 3Re21 and Brevibacillus brevis strain 1Pe2 are first reported as rice‐associated bacteria.

Alfalfa (Medicago sativa L.) production is negatively affected by drought stress. This is particularly true for alfalfa grown on non-irrigated rangelands. Thus, the development of drought-tolerant alfalfa cultivars is of great significance. A greenhouse study was conducted to evaluate 11 alfalfa accessions including several that are adapted to rangeland conditions and two commercial accessions, for their performance under drought condition. Water supply was adjusted based on the transpiration rate of individual plants to compensate for 100, 75, 50 or 25 % of transpirational water loss. We found that RS, a naturalized alfalfa collected from the Grand River National Grassland in South Dakota, showed the best resistance to drought condition. It showed the smallest reduction in stem elongation (36 %), relative growth rate (14 %), and shoot dry mass (40 %) production under the severest drought tested in this study relative to the non-drought treatment. While RS showed less biomass production under well-watered conditions, it produced similar or more shoot biomass under drought conditions compared to other accessions. Associated with the drought resistance or less sensitivity to drought, RS showed greater capability to maintain root growth, shoot relative water content, and leaf chlorophyll content compared to other accessions. Different from other accessions, RS showed increasing water use efficiency (WUE) as water deficit became severe, reaching the greatest WUE among 11 accessions. Our results suggest that RS is a valuable genetic resource that can be used to elucidate physiological and molecular mechanisms that determine drought resistance in alfalfa and to develop alfalfa with improved WUE.

Key messageThis article used seven characters from the 2D image analysis to dissect the genetic architecture underlying rice grain shape in onejaponica × indicapopulation consisting of 215 recombinant inbred lines.AbstractTwo-dimensional (2D) digital image analysis is efficient for investigating the rice grain shape characters in large genetic and breeding populations. In this study, we used 2D image analysis to investigate seven characters, i.e., grain length (GL), grain width (GW), length-to-width ratio (LW), grain area (GA), grain circumference (GC), grain diameter (GD), and grain roundness (GR), in one japonica × indica genetic population consisting of 215 recombinant inbred lines. GL and GW can be recorded manually as well, and have been extensively used together with LW (i.e., GL/GW) in genetic studies on grain shape. GC and GA can be hardly measured manually, and have not been used together with GD and GR. Results indicated that the seven characters could be precisely measured by 2D image analysis, genotype by environment interaction was low, and heritability was high. Each character was controlled by a few major stable genes and multiple minor additive genes. A total of 51 QTL were detected for the seven characters across four diverse environments, 22 from GL, GW, and LW, the three traditional characters, and 29 from the other four characters. The 51 QTL were clustered in eighteen marker intervals. Comparing with previous studies and analyzing the stability of identified QTL, we found six non-reported marker intervals, one each on chromosomes 2 and 3, and two each on chromosomes 6 and 8. The newly identified loci and the large-scale phenotyping system would greatly improve our knowledge about the genetic architecture and the future rice breeding on grain shape.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-015-2560-7) contains supplementary material, which is available to authorized users.