Agriculture accounts for ~ 70% of all water use and the world population is increasing annually; soon more people will need to be fed, while also using less water. The use of plant-associated bacteria (PAB) is an eco-friendly alternative that can increase crop water use efficiency. This work aimed to study the effect of some PAB on increasing soybean tolerance to drought stress, the mechanisms of the drought tolerance process, and the effect of the PAB on promoting plant growth and on the biocontrol of Sclerotinia sclerotiorum. PAB were isolated from soybean rhizosphere and S. sclerotiorum sclerotia. The strains identified as UFGS1 (Bacillus subtilis), UFGS2 (Bacillus thuringiensis), UFGRB2 and UFGRB3 (Bacillus cereus) were selected on their ability to grow in media with reduced water activity. Soybean plants were inoculated with the PAB and evaluated for growth promotion, physiological and molecular parameters, after drought stress. Under drought stress, UFGS2 and UFGRB2 sustained potential quantum efficiency of PSII (Fv/Fm), while a decrease was found in the control plants. Moreover, UFGS2 and UFGRB3 maintained the photosynthetic rates in non-stressed conditions compared to the control. UFGS2-treated plants showed a higher stomatal conductance and higher transpiration than the control, after drought stress. Some PAB-treated plants also had other beneficial phenotypes, such as increases in fresh and dried biomass relative to the control. Differential gene expression analysis of genes involved in plant stress pathways shows changes in expression in PAB-treated plants. Results from this study suggest that PAB can mitigate drought stress in soybean and may improve water efficiency under certain conditions.
Aiming to provide a global diagnosis of the actual threat of pollution to the most important aquifers of the State of São Paulo, Brasil, due to its intensive industrialization and agriculture, three government institutions -the Instituto Geologico (Geological Institute), the CETESB (Environmental Sanitary Technology Company) and the DAEE (Water and Eleotrical Energy Department) - carried out a regional survey to define the aquifers' vulnerability to pollution and for recording and ranking the potential contaminant sources.
This paper describes the results of this survey, excluding the metropolitan area of the city of São Paulo. More than 500 industries were recorded and ranked according to their low, moderate or high potential contaminant load for impacting groundwater. Thirty - one aquifer units were defined and a 1:500.000 scale vulnerability map was produced.
Critical areas were defined and recommended as being priority sites for the adoption of control measures.
ABSTRACT. The goal of this study was to study resistance inheritance in the soybean (Glycine max L.) accession PI 594767-A to the Phakopsora pachyrhizi isolate PPUFV02, and map the resistance gene(s) identified using microsatellite markers. Crosses between PI 594767-A and the susceptible cultivar 'Conquista' gave rise to the segregating subpopulations 26C-2 and 26C-5, which in the F 2 generation were evaluated for their reactions to PPUFV02. In addition, analyses with microsatellite markers linked to the Rpp1-Rpp5 loci were also performed. The segregation pattern obtained in 26C-2 revealed that resistance was governed by a recessive gene; a 1:2:1 segregation pattern was observed in 26C-5, indicating control by a gene with partial dominance. This variability may have been caused because environmental conditions, particularly temperature, when 26C-5 was assessed were unfavorable for pathogen development, allowing the phenotypic expression of heterozygous alleles in PI 594767-A. A resistance gene was located in the soybean linkage group G, in the genomic region between Sct_187r2 and Sat_064 that contains the Rpp1 locus. Resistance in PI 594767-A is probably conferred by a new Rpp1 gene allele, because this accession has a haplotype for Sct_187r2 and Sat_064, which differs from haplotypes of accessions that also contain resistance alleles that map the Rpp1 locus. The use of Sct_187r2 and Sat_064 will facilitate the introgression of the resistance allele from PI 594767-A and its pyramiding with other resistance genes into genotypes with superior agronomic characteristics, in order to obtain cultivars with broad-spectrum resistance to P. pachyrhizi.
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