Growth and symbiosis of plants with arbuscular mycorrhizal fungi in soil submitted to biochar application.

Arbuscular mycorrhizal fungi (AMF), which is intrinsically present or may be introduced in soils by inoculation, is an example of natural and renewable resource to increase plant nutrient uptake. This kind of fungi produces structures (hyphae, arbuscles and sometimes vesicles) inside the plant root cortex. This mutualistic relationship promotes plant gains in terms of water and nutrient absorption (mainly phosphorus). Biochar can benefit plant interaction with AMF, however, it can contain potentially toxic compounds such as heavy metals and organic compounds (e.g. dioxins, furans and polycyclic aromatic hydrocarbons), depending on the feedstock and pyrolysis conditions, which may damage organisms. For these reasons, the present work will approach the impacts of biochar application on soil attributes, AMF-plant symbiosis and its responses in plant growth and phosphorus uptake. Eucalyptus biochar produced at high temperatures increases sorghum growth; symbiosis with AMF; and enhances spore germination. Enhanced plant growth in the presence of high temperature biochar and AMF is a response of root branching stimulated by an additive effect between biochar characteristics and root colonization. Biochar obtained at low temperature reduces AMF spore germination; however it does not affect plant growth and symbiosis in soil.

Evaluation of the reaction of watermelon parent and F1 plants to Meloidogyne enterolobii.

The aim of this study was to evaluate the performance of progenies from Citrullus lanatus var. lanatus (cultivated watermelons) when crossed with progenies from C. lanatus var. citroides (fodder watermelon with a historic of resistance to the nematode Meloidogyne enterolobii). The parents and their F1s were evaluated for resistance to this nematode. In the initial stages of eleven treatments, watermelon seedlings plantlets were transplanted to plastic bags of six kilograms once the first leaves developed. Ten inoculated plants with 5,200 eggs in the soil near the stem of the plant and four non-inoculated ones were used in each treatment, in a complete block design. Sixty-two days after sowing, the following characteristics were evaluated: the length of the aerial part of the plant (LAP, in m), fresh mass of the aerial part (FMAP, in g), root fresh mass (RFM, in g), egg number (EN) and reproduction factor (RF). A comparison between the averages of inoculated and non-inoculated plants was performed using Scott-Knott test at 5% and the diallelic analysis was performed using the GENES program. The morphological characteristics did not allow for the identification of the parent plants or the F1s with respect to nematode resistance, but the variables EN and RF were useful for such identification. The analyses of the general and specific combining abilities indicate highly significant effects with respect to this resistance, showing additive gene effects as well as dominance and epistatic gene effects, allowing for identification of parents and F1s that can be used in watermelon breeding programs to improve resistance to the M. enterolobii.

Biological characteristics of black armyworm Spodoptera cosmioides on genetically modified soybean and corn crops that express insecticide Cry proteins.

This study aimed to evaluate the development and reproduction of the black armyworm, Spodoptera cosmioides when larvae fed on leaves of Bt-corn hybrids, expressing a single Cry1F and also Cry1F, Cry1A.105 and Cry2Ab2 in pyramided corn and their non-Bt-isoline (hybrid 2B688), as well as on leaves of two soybean isolines expressing the Cry1Ac protein and its non-Bt isoline (A5547-227). We also assessed the effect of these Bt and non-Bt plants on the leaf consumption rate of S. cosmioides larvae. This pest was unable to develop when fed on any of the corn isolines (Bt and non-Bt). When both 1st and 3rd instar larvae were fed on corn leaf, mortality was 100% in both Bt and non-Bt corn. In contrast, when corn leaves were offered to 5th instar larvae, there were survivors. Defoliation and leaf consumption was higher with non-Bt corn than with both of the Bt corn isolines. There was no negative effect of Bt soybean leaves on the development and reproduction of S. cosmioides with respect to all evaluated parameters. Our study indicates that both Bt and non-Bt corn adversely affect the development of S. cosmioides while Bt soybean did not affect its biology, suggesting that this lepidopteran has major potential to become an important pest in Bt soybean crops.