No abstract

This study aimed to identify phenotypic plasticity in populations of Jatropha curcas. The experiment was conducted with a completely randomized design with eleven treatments and four replications. Morphophysiological variables were analyzed in the agricultural year, 2014-2015. Positive correlations were only observed between crown diameter and seed production, and canopy diameter and stomatal density in adaxial epidermis, indicating that canopy diameter can be used as a descriptor in plant breeding programs. Cluster analysis confirmed the existence of diversity among populations of J. curcas, with the formation of two groups, demonstrating the narrow genetic basis of Jatropha found in different regions of Brazil. The analysis of phenotypic plasticity demonstrated that morphological variables had a higher coefficient of plasticity in relation to physiological and productive variables. The morphological and physiological variables can be used in J. curcas breeding programs to study diversity and phenotypic plasticity.

Soybean is one of the most important cultures harvested in the world, and Brazil is ranked the second major producer and the top exporter of this oilseed. Brazil presents good edaphoclimatic conditions for soybean cropping, it has a strong research structure and has capacity to enhance its cropping area, and however, the faulty infrastructure in its own terrain hinders logistic operations for soybean flow and exportation. Brazil has a huge deficit in grain storing, forcing producers to flow their production right after harvesting. Brazilian transportation is centered on a road system, and it is not viable once road conditions are precarious and also there are long distances to run. Soybean should then be transported by water or railway, but these means of transportation are not enough in the country due to low exploitation of existing waterways and the short railway system. Besides, Brazilian ports are inefficient, when the soybean harvest flow is at its peak for exportation; there are long lines of trucks and ships. This series of internal barriers increase the costs of Brazilian soybean and reduces its competition in the foreign market. Thus, it is of pivotal importance that the Brazilian government performs investments in building warehouses. It is also vital to invest in the improvement of the road network, extend railways and waterways and enhance ports, so that the costs with soybean logistics drop and producers should be able to increase their profits and competitiveness in the overseas market.

Indirect somatic embryogenesis (ISE) is a morphogenetic pathway in which somatic cells form callus and, later, somatic embryos (SE). 2,4-dichlorophenoxyacetic acid (2,4-D) is a synthetic auxin that promotes the proliferation and dedifferentiation of somatic cells, inducing the ISE. However, 2,4-D can cause genetic, epigenetic, physiological and morphological disorders, preventing the regeneration and/or resulting abnormal somatic embryos (ASE). We aimed to evaluate the toxic 2,4-D effect during the Coffea arabica and C. canephora ISE, assessing the SE morphology, global 5-methylcytosine levels (5-mC%) and DNA damage. Leaf explants were inoculated in media with different 2,4-D concentrations. After 90 days, the friable calli were transferred to the regeneration medium, and the number of normal and abnormal SE was monthly counted. The increase of the 2,4-D concentration increased the number of responsive explants in both Coffea. At 9.06, 18.08 and 36.24 μM 2,4-D, C. arabica presented the highest values of responsive explants, differing from C. canephora. Normal and abnormal SE regeneration increased in relation to the time and 2,4-D concentration. Global 5-mC% varied at different stages of the ISE in both Coffea. Furthermore, the 2,4-D concentration positively correlated with global 5-mC%, and with the mean number of ASE. All ASE of C. arabica and C. canephora exhibited DNA damage and showed higher global 5-mC%. The allotetraploid C. arabica exhibited greater tolerance to the toxic effect of 2,4-D than the diploid C. canephora. We conclude that synthetic 2,4-D auxin promotes genotoxic and phytotoxic disorders and promotes epigenetic changes during Coffea ISE.

Cover crop residue left on the soil surface as organic mulch in no-tillage crop production provides several environmental benefits, including weed suppression. Thus, many farmers who use cover crops attempt to reduce the use of agricultural inputs, especially herbicides. Therefore, our objectives were to study the potential of different cover crop species to suppress weeds and produce an in situ organic mulch, and evaluate the effect of the organic mulch with and without spraying glyphosate on weed suppression for vegetable (tomato (Solanum lycopersicum L. and broccoli (Brassica oleracea L. var. botrytis) growth and yield. Five cover crop treatments (sunn hemp (Crotalaria juncea L.), jack bean [Canavalia ensiformis (L.) DC.], pearl millet [Pennisetum glaucum (L.) R. Br.], grain sorghum [Sorghum bicolor (L.) Moench ssp. bicolor] and a no-cover crop (control)) were used in the main plots; and spraying or no spraying glyphosate on the flattened cover crop in the sub plots of split-plot experimental design. Organic mulch from pearl millet, sorghum and sunn hemp resulted in lower weed biomass during the early season of both tomato and broccoli than jack bean and no-cover crop (control). Spraying glyphosate after roller crimping reduced weed biomass by 103 g m−2 and 20 g m−2 by 45 and 60 days after transplanting (DAT) of tomato, respectively and resulted in a better tomato yield compared to non spraying. Glyphosate reduced weed biomass by 110 g m−2 in the early season of broccoli (30 DAT), but did not affect yield. Terminating high biomass cover crops with a roller crimper is a promising technique for weed management in vegetable crops, which has the potential to reduce or even eliminate the need for herbicide.