Table of contents: 2020
The amount of absorbed phosphorus directly impacts on the growth and grain yield of common bean plants. We evaluated dry matter production at different growth stages and grain yield of common bean genotypes in response to phosphorus availability in a nutrient solution and examined possible associations between these characters. The experiment was carried out in a greenhouse, using a completely randomized design in sub-sub-divided plots. The main plots consisted of five phosphorus concentrations (0.5; 0.9; 1.3; 1.9 and 2.3 mmol.L-1) supplied to plants in a nutrient solution in the growth medium. The sub-plots were composed of two common bean genotypes (Pérola and IPR88 Uirapurú, which are commonly used in Rio Grande do Sul state) and the sub-sub-plots by two growing seasons (fall-winter and spring-summer). In the initial stages, at the first trifoliate leaf and flowering stages, the highest dry mass production occurred in the leaves. As the plants developed, they produced more dry matter in the pods during the pod filling stage, and later in grains, at the maturation stage. Phosphorus concentrations in the nutrient solution between 1.33 and 1.84 mmol.L-1 provided the greatest mass of beans at podfilling and at maturation, the largest number of grains and the greatest grain yield in the two genotypes. The characters dry mass of the leaves, stems and pods in pod filling, dry mass of grains at maturity, number of grains and number of pods are promising for indirect selection criteria.
Recently, carbon nanotubes (CNTs) are gaining attention in the field of agriculture as advanced approaches to minimize toxicity of mycotoxins for crop plants. We examined whether MWCNTs can be used to alleviate genotoxicity and DNA damage induced by ochratoxin A (OTA) in the common bean (Phaseolus vulgaris) by comparing the action of three OTA doses, prior and post-adsorption of OTA on the surface of MWCNTs. The phenotypic parameters, ultrastructure of chloroplasts and nuclei using transmission electron microscopy, and status of nuclear DNA (nDNA) using flow cytometry, comet assay and random amplified polymorphic DNA (RAPD) were used as bioassays. Exposure time was 48 hours. The most effective MWCNT dose (optimal) was 50µg/mL; it enhanced the phenotypic parameters (seed germination and seedling growth, tolerance, and vigor indices), induced unexpected modification of size, shape, external and internal ultrastructure of chloroplasts and nuclei, increased the content of nDNA and genome size, reduced the extent of nDNA damage, and produced a larger number of amplified DNA products and new DNA bands more than the control. Lower and higher MWCNT doses had reductions in these parameters. On the other hand, increases in doses in OTA treatments induced major toxicity in the common bean, leading to strong reductions in all parameters of the bioassays. The MWCNTs served as an adsorbent for OTA and led to alleviation of its toxicity. We conclude that optimal and adsorbent MWCNTs dose could be used as nanocarbon-fertilizer and nanocarbon-mycotoxin to protect crop plants in order to increase crop quality and productivity.