Soybean In Argentina Research Articles

Cowpea mild mottle virus infecting soybean crops in northwestern Argentina

Argentina is one of the leading soybean producing and exporting countries in the world. During the 2004/2005 cropping season, soybean production reached a record �8.� million tons. Although soybean is grown mainly in the central Pampas, it is also cultivated in the northwest of the country, where it plays a significant role in the local economy. Among the biotic factors affecting soybean yields in this region, fungal diseases account for the major economic losses (Wrather et al., Plant Dis. 81:107. 1��7). Nevertheless, diseases of viral etiology have also been recorded. Six different virus species have been detected infecting soybean in Argentina: Soybean mosaic virus (SMV), Alfalfa mosaic virus (AMV), Tobacco streak virus (TSV), Cucumber mosaic virus (CMV), Peanut mottle virus (PMV) and a geminivirus which has not been characterized yet. A survey conducted in Salta Province (NW Argentina) during late summer 2005 revealed the presence of soybean plants with systemic leaf chlorosis, distortion and stunting, which were negative in serological or hybridization tests to the viruses mentioned above. This work reports on the identification of the disease’s causal agent. Leaf dip preparations were made from leaves of symptomatic and asymptomatic (presumably healthy) soybean plants. Samples were ground in phosphate buffer pH 7 + 0.01% (w/v) sodium sulphite, stained with 2% uranyl acetate and examined under a JEOL 1220 electron microscope. Straight filamentous particles of about 6�0-650 nm, which resembled those of carlavirus, were consistently associated with the diseased plants, while no particles were observed in samples from asymptomatic soybeans. On this basis, plants were tested for Cowpea mild mottle virus (CPMMV, genus Carlavirus) by DAS-ELISA. Leaf samples were ground in extraction buffer (PBS pH 6.8 + 0.05% Tween 20 + 2% polyvinyl pyrrolidone) at a 1:5 (w/v) dilution. Specific polyclonal antisera (DSMZ GmbH, Germany) were used. Positive (supplied by DSMZ) and negative (healthy soybean) controls were included on each microtitre plate. After incubation with p-nitrophenyl phosphate at room temperature for 1 h, A405nm values greater than 0.�00 were obtained for the infected samples, compared with less than 0.100 for the healthy controls. CPMMV, a virus serologically unrelated to any other member of the genus, was first reported infecting Vigna unguiculata (L.) Walp. in Ghana (Brunt & Kenten, Ann. Appl. Biol. 74:67. 1�7�). Natural hosts of CPMMV include several species in the family Fabaceae. Its occurrence on soybean has been reported in southeast Asia, India and west Africa (Suryawanshi et al., Indian J. Virol. 5:12�. 1�8�). More recently, a disease causing stem necrosis of soybean in Brazil has also been attributed to CPMMV or a related carlavirus (Almeida et al., Fitopatol. Bras. �0:1�1. 2005). In Argentina, CPMMV has already been found on common bean (Phaseolus vulgaris L.) in Salta Province (RodriguezPardina et al., Australas. Plant Pathol. ��:12�. 2004), where large populations of the whitefly vector Bemisia tabaci Genn. may be responsible for the transmission of the pathogen to other crops. The possible spread of CPMMV to different soybean production regions, as well as its economic impact, still has to be determined.

Roundup Ready soybeans in Argentina: farm level and aggregate welfare effects

AbstractAlthough adoption rates of genetically modified crops have been staggering in some countries, there is still comparatively little evidence about biotechnology impacts under diverse agroecological and institutional conditions. These knowledge gaps lead to an overly precautious attitude among policy makers and the public. This article analyzes the effects of Roundup Ready (RR) soybeans in Argentina, the country with the second biggest transgenic area worldwide. Based on recent survey data, it is shown that the technology increases total factor productivity by 10% on average, with cost savings being somewhat more pronounced for smaller than for larger farms. The reduction in use of toxic herbicides and of tillage operations entails positive environmental repercussions. Aggregate welfare effects are computed over the 1996–2001 period with a three‐region, partial equilibrium model, comprising Argentina, the United States, and the rest of the world. In 2001, RR soybeans created more than US$1.2 billion of economic surplus at the global level. The largest share went to consumers (53%), followed by seed and biotechnology firms (34%), and agricultural producers (13%). Due to comparatively weak intellectual property protection, and thus only small technology mark‐ups in seed prices and widespread adoption, Argentine soybean growers receive 90% of the benefits in that country. This demonstrates that farmers in developing countries can gain considerably when they obtain access to suitable foreign innovations through technology spill‐overs.

Roundup Ready soybeans in Argentina: farm level and aggregate welfare effects

Roundup Ready soybeans in Argentina: farm level and aggregate welfare effects

Widespread use of glyphosate tolerant soybean and weed community richness in Argentina

Trends in weed richness responses to widespread use of glyphosate tolerant soybean in Argentina are presented. An experiment was carried out since 1997 to analyse weed community changes associated with the continuous and exclusive use of glyphosate. Sampling results showed that weed richness in soybean decreased or remained stable early in the season before glyphosate application but increased at harvest. A survey of crop advisers indicated that 37 species were of increasing, 18 species of decreasing importance. It is suggested that successional changes are taking place in the cropping systems in response to changes in weed control practices.

First Report of Koch's Postulates Completion of Sudden Death Syndrome of Soybean in Argentina.

Foliage symptoms on soybean resembling those of sudden death syndrome were detected in Argentina during 1991 and 1992 in the Pampas Region and during 1992 and 1993 in the Northwest Region. Isolations were made in 1999, 2000, and 2001 from soybean plants (Glycine max (L.) Merr.) showing these symptoms. Five isolates of fungi obtained from taproot tissue and blue sporulation on taproot exteriors were selected for further evaluation. These isolates were plated on potato dextrose agar supplemented with streptomycin (PDAS). Based on the spore morphology, colony growth rate, morphology and pigmentation on PDAS, and lack of microconidia (1) five isolates were identified as Fusarium solani f. sp. glycines. Soybean cvs. Ripley, Spencer, Pioneer 9492RR, and A6445 RG were inoculated in greenhouse tests with each of the isolates using toothpick and soil infestation methods for a total of six experiments. Isolate 171 provided by J. Rupe (University of Arkansas, Fayetteville) was tested as a positive control. Foliar symptoms typical of sudden death syndrome and similar to those in the field were observed 14 and 25 days, respectively, after inoculations using the toothpick and soil infestation methods. Lesions produced on leaves averaged 3.6 for all five isolates and 4 for the reference strain using a disease severity scale where: 1 = no symptoms; 2 = slight symptom development with mottling and mosaic on leaves (1 to 20% foliage affected); 3 = moderate symptom development with interveinal chlorosis and necrosis on foliage (21 to 50% foliage affected); 4 = heavy symptom development with interveinal chlorosis and necrosis (51 to 80% foliage affected); and 5 = severe interveinal chlorosis and necrosis (81 to 100% foliage affected). Noninoculated controls were symptomless. Differences in virulence were observed among the isolates. Based on disease symptoms in the greenhouse and cultural morphology on PDAS, the isolates were classified as Fusarium solani f. sp. glycines. Isolates recovered from symptomatic plants resembled Fusarium solani f. sp. glycines on PDAS and peptone/p-chloro-nitrobenzene agar amended with streptomycin, confirming Koch's postulates. Fusarium solani f. sp. glycines was recovered from 60% of inoculated plants. Reference: (1) K. W. Roy et al. Plant Dis. 81:1100,1997.

Effects of the Epap granulovirus on its host, Epinotia aporema (Lepidoptera: Tortricidae).

The bean shoot borer, Epinotia aporema, is a major pest of soybeans in Argentina. Larvae of this pest are attacked by a granulovirus (EpapGV) that is the most important cause of sporadic epizootics in E. aporema populations. We studied the pathology of this virus in last-instar larvae using light and electron microscopy, and evaluated the effect of the disease on larval growth and development. EpapGV caused a polyorganotropic infection. No nucleocapsids were observed in the nuclei of infected cells prior to nuclear membrane disruption. Nevertheless, granulin was detected in the nucleus by immuno-gold staining, indicating that late gene expression occurred prior to nuclear membrane disruption. Establishment of the virogenic stroma led to complexes of continuous parallel convoluted membranous sheets. Nucleocapsids were enveloped in these areas to form virions, which were then occluded. Apparently as part of the cell-to-cell spread of infection, nucleocapsids were observed enclosed in large numbers within membrane-bound vesicles located between the cells and basal lamina. Larvae infected by EpapGV suffered a retardation of development and typically failed to pupate, but exhibited a weight increase greater than that of healthy E. aporema.

Presence of the nematode Heterodera glycines (Nematoda: Tylenchida) associated with soybean in Argentina

Presence of the nematode Heterodera glycines (Nematoda: Tylenchida) associated with soybean in Argentina

Difficulties in recommending phosphorus fertilizers for soybeans in Argentina

Abstract In Argentina, soybean has been cropped without fertilization, although soil phosphorus (P) contents have decreased. Areas earlier considered well supplied are at present P‐deficient. Our objective was to determine the native and fertilizer P uptake and its relationship with yields. A trial was carried out using soils with different P content. The fertilizer efficiency was quantified using 32P. The results of biomass, yield and P uptake by the crop indicated that fertilization did not match the different native P availability. From this behavior the placement of the fertilizer appeared to us as a possibility to be taken into account. The fertilized band is near the roots in the first growth stages; in the stages of higher P uptake rate, the roots are in contact with a soil mass with lower P availability. The placement and depth of fertilization is suggested to be considered together with the soil analysis, to avoid difficulties in fertilizer recommendations.