Field screening ofPisum accessions to evaluate their susceptibility to the pea weevil (Coleoptera: Bruchidae)

Summary Seventeen unreplicated field trials over nine sites and four years were used to classifyPisum germplasm (P. sativum L. &P. fulvum Sibth. & Sm) as potential sources of resistance to the pea weevil,Bruchus pisorum (L.). The emergence of adult weevils from <10% of harvested seed was used as the selection criterion to indicate possible resistance. A total of 1900Pisum accessions were assessed using the field trials and 1754 of theP. sativum accessions were eliminated. However in the 18P. fulvum accessions screened, the level of infestation by pea weevil was always below the arbitrary resistance threshold selected. This suggests thatP. fulvum accessions could be a valuable source of resistance to the pea weevil.     

MecaNiCAL, a supply–demand model of carbon and nitrogen partitioning applied to defoliated grass: 2. Parameter estimation and model evaluation

The MecaNiCAL model of carbon and nitrogen partitioning over a period of regrowth for a mean grass plant as described in Part 1 was fitted and evaluated against data from an experiment under controlled conditions with contrasting light and nitrogen nutrition. In the first investigation, the rate of nitrogen uptake was imposed to limit the compensation of errors between process. The root:shoot ratio was simulated well, with a good estimation of the nitrogen allocation to shoots. Some underestimation of the root weight after the cut and the final shoot weight under the low nitrogen treatment were consequences of both the lack of remobilisation and the high priority given to shoots. The good agreement obtained with the expected trend in simulations conducted with the simple nitrogen aborption submodel in extended conditions (contrasting initial content of nitrogen substrate and temperature change in regrowth) ensures the general consistency of the model in the limit of its area of validity. Partitioning to shoots and forage production seem to be sensitive mainly to the size of the carbohydrate substrate pool and its availibility, particularly under conditions of low light. Estimating the initial carbohydrate substrate pool by biochemical analysis may improve the accuracy of the model. Compared with more simple assumptions of partitioning, MecaNiCAL shows a higher level of agreement with the partitioning response to a wide range of environmental conditions. A simple assumption relating partitioning to plant nitrogen content does not seem to be sufficient to simulate the decrease in the root:shoot ratio observed under conditions of low light. Nevertheless, more data from experiments conducted under a wider range of contrasting conditions are required to estimate the validity of MecaNiCAL attached to the nitrogen absorption submodel and the advantage of its more complex assumptions with even greater accuracy.     

Saline soil microbiome: A rich source of halotolerant PGPR

Twenty halotolerant free-living, nitrogen-fixing bacterial strains were isolated from the Lonar Soda Lake and screened for growth at different NaCl concentrations. Out of 20, only Four isolates DL2, DL3, and DL6 showed optimum growth at 4% NaCl, and DL11 showed optimum growth at 6% NaCl concentration and tolerated 10% NaCl concentration. Biochemical and 16S rRNA sequencing identified DL2 as P. mendocina, DL3 as A. beijerinckii, DL6 as P. stutzeri, and DL11 as B. subtilis. Further, these four isolates were characterized for plant growth-promoting traits and all are indole acetic acid and ammonia producers and they also solubilize the phosphate under 4% NaCl concentration. The salt tolerance of these isolates was also increased from 10 to 14% by using a physical mutagen like UV and mutant strains were also screened for PGP traits. To determine the efficacy of these isolates as plant growth-promoting bacteria, Bioinoculum I (mixed culture of wild strains) and Bioinoculum II (mixed culture of mutant strains) were prepared and tested on Catharanthus roseus at 4% NaCl concentration. Plants treated with Bioinoculum II showed 12.61 and 82.35% increase in shoot and root length, respectively, and 71.42% increase in number of flowers as compared to control plants under saline conditions. These results indicate that halotolerant bacteria isolated from saline environments have the potential to enhance plant growth under saline stress through direct or indirect mechanisms and would be most appropriate as bioinoculants under such conditions.     

A gene action model to explain gametophytic self-incompatibility

Gametophytic self-incompatibility in flowering plants can be explained in terms of recent concepts of gene action. The S alleles may be assumed to be regulators which produce monomers of a dimer repressor controlling a high rate of growth operon in the pollen tube. Similarity between monomers in the style and pollen tube produce a functional dimer repressor which inhibits this operon. A low velocity growth operon yielding pollen tube growth typical of incompatible pollen tubes would function when the high velocity operon is inactive.     

Comparison of different pollen viability assays to evaluate pollen fertility of potato dihaploids

Summary The main obstacle in breeding potato (Solanum tuberosum L.) dihaploids is the severe limitation of male fertility. To determine pollen viability assays that correlate well to fertility in crosses, results of five different pollen viability assays were compared by correlation analysis with fruit and seed set characters in test crosses, and to pollen tube growth in situ (PL-test). The methods used were: staining the pollen cells with carmino acetic acid (CAA-test); in vitro pollen germination (PG-test); and detection of pollen staining rates after incubation with fluoresceine diacetate (FDA-test), 2-3-5-triphenyle tetrazolium chloride (TTC-test), and 5-bromo-4-chloro-3-indolyle--galactoside (X-Gal-test).The results of test crosses and pollen tube growth in situ correlated with the results of all other assays with the following ranking, from highest to lowest: enzyme activity assays (X-Gal-test, FDA-test, TTC-test), in vitro pollen germination (PG-test), and pollen staining by CAA. The newly developed X-Gal-test for monitoring -galactosidase activity showed the least variation of all assays investigated. Thus, this highly reproducible simple procedure is recommended for male fertility screening.Abbreviations B/F Berries obtained per 100 flowers - CAA Carmino acetic acid - FDA Fluoresceine diacetate - PG Pollen germination rate in vitro - PL Pollen tube growth in situ - S/B Seeds per berry - S/F Seeds per pollinated flower - TTC 2-3-5-triphenyle tetrazolium chloride - X-Gal 5-bromo-4-chloro-3-indolyle--galactoside     

MecaNiCAL, a supply–demand model of carbon and nitrogen partitioning applied to defoliated grass: 1. Model description and analysis

A model for the dynamic simulation of dry matter distribution between shoots and roots of a grass forage plant is presented. The objective of this work was to develop a relatively simple mechanistic model of grass growth to simulate the response of assimilate partitioning to variations in light and nitrogen supply based on an original theoretical scheme [Gillet, M., Lemaire, G., Gosse, G., 1984. Essai d'élaboration d'un schéma global de la croissance des gramineés forragères. Agronomie 4 (1), 75–82]. In the model, called MecaNiCAL, C and N assimilates are partitioned between shoots and roots according to the availability of carbohydrate substrate, organ demands and a fixed priority between each demand. Demand related to organ synthesis is described as a function of the plant concentration in the organic nitrogen substrate and temperature. To stay within an acceptable range of complexity, the model is applied only in one vegetative regrowth performed on a hydroponic system with different light and nitrogen nutrition. Carbon and nitrogen acquisition per day are computed by independent submodels, which makes it possible to connect simple and robust functions of carbon assimilation and nitrogen uptake to the partitioning model. Carbon assimilation is simulated for a plant in a canopy, and nitrogen uptake is simulated by a function which depends on nitrogen plant requirements directly related to plant net photosynthesis and the amount of nitrogen available in the nutritive solution. All the assumptions used to describe assimilate partitioning are discussed in relation to knowledge of physiological processes in order to examine closely the limits of the model.     

Long-term effects of crop rotation,manure and mineral fertilisation on carbon sequestration and soil fertility

Carbon sequestration, recently advocated to mitigate climate change, needs a thorough knowledge of the dynamics of soil organic carbon (SOC), whose study requires long-term experiments. A field trial started in 1967 is still in progress in the Southeast Po valley (Italy). It compares a 9-year rotation (corn–wheat–corn–wheat–corn–wheat–alfalfa–alfalfa–alfalfa), two 2-year successions (corn–wheat and sugarbeet–wheat), continuous corn and continuous wheat. During the first 18 years (up to 1984) wheat crops were always followed by catch crops of silage corn. Within each rotation, three rates of cattle manure have been factorially combined with three mineral NP rates. In 1984 the highest manure application was stopped. Wheat straw and corn stalks have always been removed from the field. Since 1972 up to now every year we have determined the organic C and total N contents in soil samples collected from 0.40-m depth. During the first 18 years (in the presence of the catch crop) SOC exponentially declined, probably as a consequence of the intensification of tillage depth and crop succession with respect to the previous conventional agriculture. The intensification regarded ploughing, which became deeper, the number of cropped species that in most treatments was reduced, and mineral N application, which, on average, increased. The drop was faster in the sugarbeet–wheat succession than in the 9-yr rotation and continuous wheat. After 1985, without the catch crop, SOC linearly increased, faster in the 9-yr rotation and continuous wheat than in sugarbeet–wheat. The results can be ascribed to the amount and C/N ratio of debris remaining in the field after each crop, even after having taken away wheat straw and corn stalks. The debris consisted of sugarbeet tops, with a low C/N ratio, and of roots and basal culms of the two cereal crops with higher C/N ratio. Mineral fertilizers significantly increased SOC, probably for the greater amount of cereal roots and sugarbeet tops in more fertilized plots. The influence of manure was less intense, but its benefits lasted longer than 18 years after its interruption. Soil N content was more related to accumulated organic matter than to mineral N fertilisation. In conclusion the highest C sequestration was obtained with manure addition, with the highest rate of mineral fertilizers, and in the rotation containing the alfalfa ley. The effects of these factors were not additive.     

A simple method for evaluation of sprout characters in soybean

Soybean sprouts are an important year-round vegetable in Asia. Currently, testing of soybean lines for sprout traits is labor intensive and amount of seed required have dictated that testing generally begins after lines have been composited from a plant row in the F₄ or later generations. Sprout testing requires germination of more than 150 seeds, precise watering over several days and movement of seedlings from water baths to growth chambers limiting the number of entries which can be evaluated. The objective of this study was to determine if germinating fewer seeds (10, 20 or 40) on an agar medium is comparable to sprouting over 150 seeds in the traditional method for evaluating soybean genotypes for sprout traits. Sprout growth characteristics were compared for Pungsannamulkong, a known sprout soybean, germinated on 1.0, 1.2, and 1.4% agar medium. Sprout traits 5 days after seeding 20 or 40 seeds on a 1.4% agar medium were very similar to the traditional method. There was no advantage for germinating soaked seeds over dry seeds on the agar medium to determine sprout characteristics. Evaluation of 20 dry seeds on a 1.4% agar medium of eight known sprout cultivars was comparable to the traditional method for measuring sprout characteristics for each cultivar. The agar method requires less labor, fewer seeds, no watering schedules or water baths and less growth chamber space than the traditional method to test genotypes for sprout characteristics. This allows more lines from soybean breeding populations in earlier generations to be evaluated. The agar method will improve the efficiency for evaluating soybean breeding lines for sprout traits.     

Effects of soil scraping on the reclamation of tsunami-damaged paddy soil

We investigated the possibility of tsunami-damaged paddy soil remediation in Japan using a scraping method. We collected undisturbed soil blocks to maintain the soil structure from paddy damaged by salt from the tsunami. Scraping treatments to remove the top 2 cm of the soil surface were conducted once, twice, and thrice after drying naturally in a greenhouse environment, as well as a noscraping control. Electrical conductivity (EC) of the soil dramatically decreased to < 1.36 dS m^?1 in the residual soils after scraping. The EC values of the residual soils were significantly lower after being scraped twice or thrice compared with a single scraping. Similarly, the mean NaCl removal rates were significantly higher with two (91%) or three scrapings (97.2%) compared with a single scraping (73.3%). The growth of rice plants was almost normal in the residual soils based on a visual score (approximately 3 on average) using a standard evaluation system at 4 weeks after transplantation. There were no significant differences in the grain yields from the residual soils with different scraping frequencies, and the EC values of all the residual soils were < 1.36 dS m^?1. This study clearly indicates that there were reductions in the EC and good plant growth performance in the residual soils after scraping, and there was also a high rate of NaCl removal. Therefore, scraping may be a useful method for the remediation of salt-damaged paddy soils when irrigation or culvert systems are affected severely by tsunamis and earthquakes.     

SOILPAR 2.00: software to estimate soil hydrological parameters and functions

2 is a program for estimating soil parameters. It allows: (1) storing soil data in a georeferenced database, (2) computing estimates of soil hydrological parameters using 15 procedures, (3) comparing the estimates against measured data using both statistical indices and graphics, and (4) creating maps using the ESRI format. An interface to/from Excel and CropSyst is provided. Eleven methods estimate one or more of the following characteristics: soil water content at predefined soil matrix tension, saturated hydraulic conductivity, and bulk density. Three methods estimate the parameters of well-known soil water retention functions (Brooks-Corey, Hutson-Cass, van Genuchten), and one estimates both saturated soil hydraulic conductivity and the soil water retention curve parameters (Campbell). The software runs under Windows 98/NT/2000/XP and is freely downloadable via internet.     

SPN: A model for the study of soil-plant nitrogen fluxes in silage maize cultivation

The aim of this study was to adapt the Soil-Plant-Nitrogen (SPN) model to silage maize, as an explorative tool for evaluating the possibility of expanding maize cultivation to regions which historically have been too cold for maize production, and for estimating the effects of management practices as fertiliser and manure application on C and N fluxes. The model was validated using data from a 5-year maize experiment conducted in northern Germany. Available observations included shoot biomass and N yield, soil mineral N (0–90 cm) sampled in spring and autumn, and nitrate in the soil solution during winter; occasionally also the soil water content and ground water level were recorded. The SPN crop module, originally developed for barley production in Norway, was successfully adapted to maize. The strategy adopted was to assess the maize-specific algorithms for the radiation use efficiency (RUE) and the leaf area index (LAI) by statistical analysis of selected subsets of the available observations. In addition, parameters were modified with respect to crops characteristics. The baseline mineralisation of the SPN soil module was inspected with respect to the ability to predict both the observed plant N uptake and soil mineral N of the unfertilised plots. In order to predict the time course of plant N uptake it was necessary to incorporate a ploughing effect, as a transient mineralisation burst. The modified SPN was evaluated with respect to the whole range of mineral N and cattle slurry treatments. Nitrogen and biomass yields were successfully predicted. The dynamicity of the soil mineral N prediction was reasonable, but a statistical analysis of the model performance was hampered by the selective timing of the soil samples. The good fit of the time course of the plant N uptake under contrasting fertiliser treatments suggests that the predictions of soil N immobilisation and losses can also be assumed to be reasonable. The SPN model seems a suitable tool for the prediction of the effects of climate and management on the yield and on the soil-plant N economy of silage maize. However, under extreme combination of high radiation and low temperature or vice-versa, RUE estimation may be a source of uncertainty and more empirical studies are recommended.     

Sirius: a mechanistic model of wheat response to environmental variation

Sirius is a wheat simulation model that calculates biomass production from intercepted photosynthetically active radiation (PAR) and grain growth from simple partitioning rules. Leaf area index (LAI) is developed from a thermal time sub-model. Phenological development is calculated from the mainstem leaf appearance rate and final leaf number, with the latter determined by responses to daylength and vernalisation. Effects of water and N deficits are calculated through their influences on LAI development and radiation-use efficiency. This paper describes the model and its validation using data from independent and near independent experiments at Lincoln, New Zealand, and Rothamsted, UK. Despite there being no calculation of tiller dynamics or grain number, the model accurately simulated the behaviour of crops exposed to a wide range of conditions. We conclude that the accurate prediction of phenological development and LAI is much more important for grain yield prediction than are the components of yield. Although grain population is not a necessary step in yield calculation in Sirius, the model proved useful in investigating the effects of stress in setting grain number. The analysis showed that the influence of stress on partitioning of biomass to the ear during pre-anthesis ear growth was much more important in determining grain number than was the effect on biomass accumulation during the same phase.     

A model for simulating the height of rice plants

A reliable approach for modelling rice plant height would allow the simulation of processes with a significant impact on yields, e.g., lodging, floodwater effect on leaves temperature, crop–weeds competition for radiation interception. In this paper we present a new model for the simulation of rice plant height based on the integral of the percentage of biomass partitioned to stems. The model was compared with four alternative approaches using data collected during eight experiments carried out in Russia, Japan and US between 1991 and 2000, proving to be the most accurate in reproducing plant height during the whole crop cycle. RRMSE ranged between 8.02% and 20.87%, modelling efficiency was always close to one and the absolute value of coefficient of residual mass never exceeded 0.16. It resulted also the most robust and the less complex (according to the Akaike's Information Criterion) among those compared. The model presents a lower level of empiricism with respect to the other approaches found in the literature, deriving plant height from the allocation of biomass to stems, which are the plant organs most involved in determining canopy height. This model represents a suitable base for further developments aiming at including the effect of management practices (e.g., fluctuating water depth) and environmental factors (e.g., crop–weeds competition for radiation interception). Moreover, the low input requirements favour its inclusion in operational cropping systems models.     

灰色关联分析对国外马铃薯新品种引种鉴定的评估

用灰色关联度分析方法，对从白俄罗斯引进的四个马铃薯新品种2000－2001年多点试验鉴定的性状表现进行综合评价。结果表明：BEPAC（编号白引3号）和CИHTE3（编号白引4号）表现突出，关联度排序为第一位和第二位，高于对照，有很好的应用价值；OPBИTA（编号白引1号）和ЯXAHT（编号白引5号）综合评判不如对照，关联度低于对照，排序为第四和第五位，不宜在生产上推广。     

Sunflower response to a range of soil water contents

The objective of the study was to investigate the effect of different water stress intensities on the fraction of carbon partitioned to the head. Water consumption, yield and its components, leaf area, and net photosynthesis were also measured. Plants were grown in plastic pots in a greenhouse. At the eight-leaf stage, water stress was imposed and held until physiological maturity. Three levels of stress intensity, defined by pre-dawn leaf water potential, were studied. Water stress resulted in an increase in harvest index and water-use efficiency. In stressed treatments, leaf area decreased through a drop in leaf expansion and net photosynthesis declined linearly with leaf water potential. At anthesis, water stress induced an increase in the fraction of assimilates partitioned to the head. The relationship between net photosynthesis and leaf water potential was not affected by the level of stress intensity and the allocation of photosynthates to the head was similar in all stressed treatments. Thus, in this study it is concluded that sunflower responded to water stress in the same way at all stress intensities.     

Rpest—An indicator linked to a crop model to assess the dynamics of the risk of pesticide water pollution: Application to banana-based cropping systems

Like many intensive monocultures, some features of banana-based cropping systems may be detrimental to the environment. Pesticide use is a major cause of surface water and groundwater pollution. The risk of water pollution due to pesticides is very high in the insular areas of the French West Indies (FWI). In order to assess these risks and help design more sustainable cropping systems, we propose using an indicator to assess the risk of pesticide pollution over time (Rpest). Rpest provides dynamic assessments through a linkage with a cropping system model that simulates environmental factors and agricultural practices. An expert validation check was conducted and demonstrated that Rpest can rank cropping systems by risk as well as experts. A sensitivity analysis highlighted that the indicator can take the properties of active ingredients and pedoclimatic data into account in assessments. Rpest helps to pinpoint high pollution risk periods. It can also be used to test alternatives and compare systems. This tool can be integrated into a model-based, global, prototyping methodology used for more sustainable cropping systems.     

The importance of soil microbial activity for the supply of iron to sorghum and rape

It is generally accepted that soil microorganisms play an important role in producing siderophores which enhance the availability of soil Fe to higher plants. There is not much direct experimental evidence to support this supposition, however, because it is difficult to grow plants under sterile conditions over long periods. The object of this investigation was to test whether a sterile soil medium impairs Fe translocation from the soil to plant roots. The plant species selected are of agronomical importance, namely rape (Brassica napus L.) and sorghum (Sorghum bicolor L.). The latter a graminaceous species which is able to excrete phytosiderophores from the roots into the soil which allows Fe to be mobilized and transported to plant roots. Sorghum and rape were grown for 18 and 21 days, respectively, in a non-sterile soil (control) and in the same soil which was sterilized before plant cultivation. In a further treatment, the sterile grown rape plants were supplied with Fe EDDHA 1 week before harvest in order to test whether a poor growth of plants grown in the sterile soil was caused by an insufficient Fe supply. Plants cultivated on the sterile soil were significantly retarded in root and shoot growth. This was especially true for rape which produced very small leaves. Plants responded immediately to the Fe addition which induced a vigorous growth. This clearly shows that the poor growth in the sterile soil was caused at least in part by an insufficient Fe supply. In neither plant species was yellowing of young leaves observed as a symptom typical of insufficient Fe supply. From this follows that retardation of plant growth is a more sensitive indicator of an insufficient Fe supply than is yellowing of young leaves at least for rape and sorghum. This finding is of agronomical importance since a reduced growth because of insufficient Fe supply is much more difficult to identify as Fe deficieny than Fe chlorosis (yellow leaves). Iron concentrations in roots and leaves of the sterile grown plants were significantly lower than the corresponding concentrations in the non-sterile grown plants. From these findings it can be concluded that soil microbial activity is essential for Fe acquisition by soil-grown rape. Similarily, sorghum which is able to release siderophores from the roots, requires soil microbial activity to ensure satisfactory Fe supply.     

A mixed model analysis of 10 years of oat evaluation data: use of agronomic information to explain genotype by environment interaction

The versatility of mixed model procedures in investigating large, unbalanced sets of genotype by environment data is illustrated on an historic set of yields from a South Australian oat evaluation program. Information on specific genotypic traits is included in the analysis in order to isolate unexplained genotype by environment interaction.