Aldo Ferrero

Allelopathy, a chance for sustainable weed management.

The exploitation of crop allelopathy against weeds may be useful to reduce issues related to the use of herbicides. Several crops, such as alfalfa, barley, black mustard, buckwheat, rice, sorghum, sunflower and wheat, demonstrate strong weed suppression ability, either by exuding allelochemical compounds from living plant parts or from decomposing residues. As well as the positive effect on weed reduction, the introduction in agronomic rotations of allelopathic crops, their use as a mulch to smother crops or as a green manure may also be helpful in reduction of other agricultural problems, such as environmental pollution, use of unsafe products and human health concerns, through a reduction in chemical inputs. Knowledge of allelopathic properties of crops may also be advantageous in mitigation of soil sickness. Moreover, information on weed allelopathy may be profitable in preventing serious crop damage if the weed biomass is buried in the soil, and a crop susceptible to allellochemicals is planned for the following year. The use of allelopathic traits from crops or cultivars with important weed inhibition qualities, together with common weed control strategies, can play an important role in the establishment of sustainable agriculture.

Cross-Resistance to Herbicides of Five ALS-Inhibiting Groups and Sequencing of the ALS Gene in Cyperus difformis L.

Resistance to ALS-inhibiting herbicides in Cyperus difformis has evolved rapidly in many rice areas worldwide. This study identified the mechanism of resistance, assessed cross-resistance patterns to all five chemical groups of ALS-inhibiting herbicides in four C. difformis biotypes, and attempted to sequence the ALS gene. Whole-plant and ALS enzyme activity dose-response assays indicated that the WA biotype was resistant to all ALS-inhibiting herbicides evaluated. The IR biotype was resistant to bensulfuron-methyl, orthosulfamuron, imazethapyr, and propoxycarbazone-sodium and less resistant to bispyribac-sodium and halosulfuron-methyl, and susceptible to penoxsulam. ALS enzyme activity assays indicated that resistance is due to an altered target site yet mutations previously found to endow target-site resistance in weeds were not detected in the sequences obtained. The inability to detect resistance mutations in C. difformis may result from the presence of additional ALS genes, which were not amplified by the primers used. This study reports the first ALS gene sequence from Cyperus difformis. Certain ALS-inhibiting herbicides can still be used to control some resistant C. difformis biotypes. However, because cross-resistance to all five classes of ALS-inhibitors was detected in other resistant biotypes, these herbicides should only be used within an integrated weed management program designed to delay the evolution of herbicide resistance.

Common Ragweed (Ambrosia artemisiifolia) Growth as Affected by Plant Density and Clipping

Abstract During the past century, common ragweed has spread from its native eastern North America to Europe, where it has become an increasing problem from both an agricultural and a human health perspective. Two field experiments were performed over a 2-yr period in a naturally infested fallow field in northern Italy to evaluate the effects of common ragweed plant density on its growth dynamics and to study its response to clipping. In the first experiment, three plant densities were tested (4, 12.5, and 25 plants m−2) and plant height, aboveground biomass, and leaf area were assessed. Intraspecific competition had a substantial negative effect on leaf area and aboveground biomass on a per plant basis in both years, but did not affect plant height. However, the high-density (25 plants m−2) treatment resulted in the highest total aboveground biomass (1,428 and 4,377 g m−2) and leaf area index (5.6 and 12.6 m2 m−2) in 2006 and 2007, respectively. In the second experiment, common ragweed plants were clipped at reaching 20 cm (four clippings during the season), 50 cm (three clippings), or 80 cm (two clippings) plant height. Number of surviving plants, flowering plants, and aboveground biomass were assessed before each clipping. Clipping resulted in a partial reduction in the surviving plants and did not prevent flowering. Under the most stressing condition (clipping at 20 cm height), more than 67% of plants survived to the last clipping and, among these, more than 97% flowered, whereas before the last clipping at reaching 80 cm height from 50 to 100% of plants survived and 100% of them flowered. These findings in northern Italy confirm that common ragweed is a fast-growing annual species, capable of producing considerable aboveground biomass at various pure stand densities and that plants can still flower from plants clipped at various frequencies. Nomenclature: Common ragweed, Ambrosia artemisiifolia L. AMBEL

Application of the ricewq—vadoft model for simulating the environmental fate of pretilachlor in rice paddies

No validated models in Europe are capable of simulating the environmental fate of pesticides under the specific conditions of rice fields. Rice water quality--vadose zone flow and transport (RICEWQ-VADOFT) is a model developed from the coupling of a surface runoff model (RICEWQ) and a vadose zone flow and transport model (VADOFT) for determining predicted environmental concentrations in paddy water and sediment, runoff, and groundwater. This study is intended to evaluate the capability of this model to simulate effectively the environmental fate of the herbicide pretilachlor in the paddy environment. A two-year field study conducted in a representative rice-cultivated area of northern Italy provided measured concentrations of pretilachlor in paddy water and sediment and also a limited number of observations on runoff losses. The model successfully predicted the water balance in the paddy field in both years. After limited calibration, the model predicted the fate of pretilachlor in paddy water and sediment with high accuracy. Agreement between predicted and measured concentrations of pretilachlor in both years was assessed statistically using several statistical indicators. For example, modeling efficiency (EF) values of 0.867 to 0.935 and 0.702 to 0.718 in paddy water and sediment, respectively, document the strong agreement between predicted and measured pesticide concentrations. The model predictions showed high agreement with the limited amount of measured runoff data in 2002. The model predicted that no significant amounts of pretilachlor would leach below the top 25 cm of the soil, although no measured data were available to evaluate the predicted results. A sensitivity analysis of the model to variables controlling pesticide partitioning to paddy sediment (VBIND, depth for direct partitioning of pesticide to bed sediment; VMIX, mixing velocity by molecular diffusion) revealed that the predictions of pesticide leaching were influenced strongly by those variables. Generally the RICEWQ-VADOFT model is a useful modeling tool for pesticide risk assessment in rice paddies.

Germination of Weedy Rice in Response to Field Conditions during Winter

Abstract Weedy rice is a problematic weed that infests paddy fields worldwide. Differing populations, with varying physiological and morphological traits, characterize this weed. In particular, seed dormancy makes its control difficult. The objective of this study was to evaluate the germination behavior of five Italian weedy rice populations (two awnless, two awned, and one mucronate) after exposure of seeds to different field storage conditions (flooding, burial, and dry soil surface) during winter in two sites (Grugliasco and Vercelli, Italy). Seed samples were taken from each population, storage condition, and site, every 15 d for petri dish germinability testing. The two sites displayed slightly different germination patterns, which were probably due to the differing climatic conditions. One of the awned populations showed the highest (always exceeding 80%) and fastest germination percentage in all field conditions and sites, compared with the other four populations. Although flooding promoted germination in one awnless population, it delayed germination in two others (one awned and one awnless), attaining only 20% germination after more than 100 d. In all populations, burial delayed germination, whereas seed placement on the dry soil surface enhanced it. Our study indicated that autumn tillage that promotes weedy rice seed burial should be discouraged; spring tillage that exposes seeds to the soil surface and cause their depletion should be encouraged. The tested technique of winter flooding can also improve weedy rice control, despite its varying efficacy among populations. Cycles of flooding and drying followed by spring tillage might improve weedy rice seed control. Nomenclature: Weedy rice, Oryza sativa L

Patterns Of Resistance To Als Herbicides In Smallflower Umbrella Sedge (Cyperus Difformis) And Ricefield Bulrush (Schoenoplectus Mucronatus)1

Biotypes of smallflower umbrella sedge and ricefield bulrush resistant to acetolactate synthase (ALS)-inhibiting herbicides have been reported in several rice areas of the world. Here, we present results of a study conducted on whole plants of seven smallflower umbrella sedge and four ricefield bulrush biotypes collected in Italian, Spanish, and Californian rice fields to evaluate cross-resistance to ALS herbicides in these important weeds of temperate rice. The following herbicides were tested: bensulfuron-methyl, halosulfuron, cinosulfuron, imazamox, and bispyribac-sodium. The smallflower umbrella sedge and ricefield bulrush biotypes studied exhibited different cross-resistance patterns, some of which have not been previously reported. The Italian smallflower umbrella sedge biotype was cross-resistant to bensulfuron-methyl, cinosulfuron, imazamox, and bispyribac-sodium, but was susceptible to halosulfuron. One smallflower umbrella sedge biotype from California was also resistant to bensulfuron-methyl, imazamox, and bispyribac-sodium, but had a lower level of resistance to halosulfuron. In contrast, the second smallflower umbrella sedge biotype from California was strongly resistant to halosulfuron and was also resistant to bensulfuron-methyl and bispyribac-sodium, but moderately resistant to imazamox. The Spanish smallflower biotype was resistant to the sulfonylurea herbicides bensulfuron-methyl and halosulfuron. Different responses were observed in ricefield bulrush. The Italian biotype was resistant to the sulfonylureas only, whereas the biotype from California exhibited broad cross-resistance to all the ALS herbicides tested. Knowledge on cross-resistance is needed to formulate herbicide use and weed management strategies for delaying the evolution of resistance to ALS herbicides in rice systems. Nomenclature: Bensulfuron-methyl, halosulfuron, cinosulfuron, imazamox, bispyribac-sodium, smallflower umbrella sedge, Cyperus difformis L. #3 CYPDI, ricefield bulrush, Schoenoplectus mucronatus (L.) Palla (syn. Scirpus mucronatus L.) # SCMPU. Additional index words: ALS herbicides, herbicide resistance, cross-resistance, weed management, temperate rice, rice production systems. Abbreviations: SU, sulfonylureas; IMI, imidazolinones; TP, triazolopyrimidines; PB, pyrimidinylbenzoates; SCT, sulfonylaminocarbonyltriazolinones; FW, fresh weight; GR50, herbicide dose necessary to cause 50% growth reduction; I50, herbicide dose necessary to cause 50% inhibition; LD50, herbicide dose necessary to cause 50% mortality; R, resistant; RI, resistance index; S, susceptible.

Rice Cultivation in the E.U. Ecological Conditions and Agronomical Practices

Publisher Summary This chapter discusses the rice cultivation in the EU ecological conditions and agronomical practices. The rice production originated from all these countries together accounts for more than three quarters of the total world production. Rice is grown in at least 114 countries with a total production of about 610 million metric tonnes. It has been estimated that rice has fed more people over a longer period than any other crop. One-half of the world population and virtually all of East and Southeast Asia are entirely dependent upon rice. The introduction of rice in the Mediterranean European countries has long been debated. This plant came first in the North African regions from the East through an unusual series of leaps and bounds, thanks to its incredible capacity to adapt itself to different and variable environmental conditions. In the European Union rice is at present cultivated in about 410,000 ha, mostly located in the Mediterranean countries. The top two rice producers that together contribute more than 80% of the total rice production in Europe are Italy and Spain. Rice is not a staple food for most of the European population; nevertheless, rice consumption in the continent has increased in the last few years due to immigration and diversification of the diet of the Europeans.

Microsatellite markers reveal multiple origins for Italian weedy rice

Weedy rice (Oryza sativa L.) is one of the major issues of rice cultivation worldwide. In Italy, it infests about 70% of the total rice area. Different Weedy Rice populations can be distinguished based on variable morphological and physiological traits; however, little is known about genetic differentiation and origin of Italian weedy rice populations. The objective of this study was to genetically and morphologically characterize and compare different Italian weedy rice populations selected on the basis of different phenotypes. The main Italian rice territory was divided into 10 geographical areas in which 40 weedy rice populations were collected and grouped according to the awn traits. All the individuals of the populations were morphologically characterized according to plant and seed traits. Genetic characterization was performed using 19 SSR markers on all the collected accessions, and several rice cultivars, including some very old (late 19th century), nowadays are no longer cultivated. ANOVA showed that morphological plant and seed traits were significantly affected by the collection area and awnedness group. The importance of the awn morphology was also reflected in the Bayesian clustering where, despite a relatively low genetic diversity, the clusters displayed different awn types. An UPGMA dendrogram confirmed the clusters detected in STRUCTURE analysis and also revealed a grouping of certain old cultivars with the weedy rice, suggesting a common origin.

Potential allelopathic effects of Jerusalem artichoke (Helianthus tuberosus) leaf tissues.

Abstract Jerusalem artichoke has been reported to colonize several ecological niches and agronomic crops in southern Europe. This plant is also of interest because of its high biomass production and its potential to produce ethanol for biofuel. Allelopathy may be an advantageous trait in Jerusalem artichoke under cultivation, as it potentially reduces weed interference with the crop, theoretically allowing a reduction of mechanical or chemical input required for weed management. However, this trait may also be unfavorable if other crops are cultivated in rotation with Jerusalem artichoke or in areas infested by this species. The aim of this study was to investigate the sensitivity of selected diverse crops (wheat, lettuce, corn, tomato, rice, and zucchini) and weeds (barnyardgrass, black nightshade, common lambsquarters, common purslane, large crabgrass, and pigweed) to the presence of Jerusalem artichoke dried leaf tissues in laboratory experiments performed under controlled conditions. The simulated soil incorporation of different Jerusalem artichoke residues (four cultivars and a weedy population) was carried out in a series of laboratory and greenhouse experiments. Jerusalem artichoke reduced the radicle growth of seedling lettuce (60%), tomato (30%), large crabgrass (70%), and barnyardgrass (30%), whereas total germination of these species was less affected. Sensitivity to Jerusalem artichoke residues was species dependent; germination and initial growth of corn were not affected, whereas winter wheat, lettuce, tomato, rice, and zucchini seedlings were more sensitive to residue presence. Our experiments show that both wild and cultivated decomposing Jerusalem artichoke residues, particularly leaves and stems, possess phytotoxic potential. Additional field experimentation remains to be conducted to determine if allelopathy in the field contributes to its invasibility. Nomenclature: Jerusalem artichoke, Helianthus tuberosus L.; barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG; black nightshade, Solanum nigrum L. SOLNI; common lambsquarters, Chenopodium album L. CHEAL; common purslane, Portulaca oleracea POROL; corn, Zea mays L.; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; lettuce, Lactuca sativa L.; pea, Pisum sativum L.; redroot pigweed, Amaranthus retroflexus L. AMARE; rice, Oryza sativa L.; tomato, Lycopersicon esculentum Mill.; wheat, Triticum aestivum L.; zucchini, Cucurbita pepo L.

Phototransformation of the Herbicide Propanil in Paddy Field Water

When irradiated in paddy-field water, propanil (PRP) undergoes photodegradation by direct photolysis, by reactions with •OH and CO3•-, and possibly also with the triplet states of chromophoric dissolved organic matter. Irradiation also inhibits the nonphotochemical (probably biological) degradation of PRP. The dark- and light-induced pathways can be easily distinguished because 3,4-dichloroaniline (34DCA, a transformation intermediate of considerable environmental concern) is produced with almost 100% yield in the dark but not at all through photochemical pathways. This issue allows an easy assessment of the dark process(es) under irradiation. In the natural environment, we expect PRP photodegradation to be important only in the presence of elevated nitrate and/or nitrite levels, e.g., [NO3-] approaching 1 mmol L-1 (corresponding to approximately 60 mg L-1). Under these circumstances, •OH and CO3•- would play a major role in PRP phototransformation. Because flooded paddy fields are efficient denitrification bioreactors that can achieve decontamination of nitrate-rich water used for irrigation, irrigation with such water would both enhance PRP photodegradation and divert PRP dissipation processes away from the production of 34DCA, at least in the daylight hours.