Cassava (Manihot esculenta) shows high phenotypic plasticity, acclimatization, wide adaptability, and resilience to adverse edaphoclimatic conditions. In this context, this systematic review aims to identify what were the factors that determined the production of cassava in Brazil in the last three decades, and to direct what are the possible perspectives of the crop in the country. The methodology to produce this review was based on studies that which integrate the academic information produced in different situations (1990-2020), environments, states, groups of researchers and existing scientific evidence for this theme. Based on the information, a binary matrix of information was assembled based on the following characters, plant density per hectare, soil type, city, state, average air temperature, planting line spacing, plant spacing on the planting line, implantation date, implantation station, harvesting station, productivity per hectare, days for harvest, liming, fertilization, precipitation and climate. It is evident that in the last 30 years the productivity of cassava in Brazil has been increased, mainly in low-income populations and those located in rural areas. There are prospects for increasing cassava production for fresh sale and industry. The crop is characterized as rustic, highly adaptive, tolerant of water stress and acidic soils, being highly influenced by the climate, rainfall, air temperature, and incident solar radiation. Productivity is determined by the time of implantation, liming, fertilization, density, and plant arrangement.
The study had the purpose to evidence the agronomic performance, inter-relations of characters and the multivariate differentiation of soybean genotypes cultivated in the preferential season, in the state of Rio Grande do Sul, Brazil. In the crops season of 2017/2018, The experimental design was the completely randomized blocks, being 25 genotypes with three replicates. The data obtained was submitted to presuppositions based on normality and homogeneity of residual variances, variance analysis, Tocher method, Euclidian algorithm, linear correlations, relative contribution of characters by Singh and artificial neural networks. The agronomic performance of the genotypes presents superior seeds yield per plant through the elevated magnitude of reproductive nodes, legumes and seeds per plant. The plant height of the soybean is positively associated with the number of total nodes and reproductive nodes in the main stem and branches, where they are directly linked with the soybean productive potential. The most polymorphic characters correspond to the number and mass of thousand seeds, being possible to differentiate in a multivariate way the soybean genotypes though the similarity profiles.
The objective of this work was to evaluate the interference of physical, nutritional, sanitary, and genetic aspects in the quality of soybean seeds. The experimental design used was randomized blocks, using 55 soybean F6 genotypes, with 4 replications. In this study, thousand seeds mass, germinated seeds, accelerated aging, tetrazolium, phytosanitary indicators (Aspergillus flavus, Cercospora kikuchii, Fusarium graminearum, Fusarium semisectum, and Bacteriosis), seed nutritional indicators (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, copper, iron, manganese, zinc, sodium, and molybdenum). The physiological quality of the seeds is negatively affected by the health aspects of Cercospora kikuchii, Aspergillus flavus, Fusarium semisectum and Bacteriosis. In addition, nutritional aspects also act negatively due to the presence of salts, and positively due to the levels of P. Likewise, Zn, Mo and K are correlated as strong indicators of seed vigor levels. The developed genotypes have excellent behavior towards pathogens and seed nutrition, contributing to high quality seed production.
Molybdenum is the micronutrient required in less quantity by plants and found in lower concentrations in Brazilian soils. The study aimed to study the influence of the application of molybdenum (Mo) and potassium (K) via foliar feeding, at different phenological stages, on the quality of soybean seeds. The work was conducted in the field in the county of Coronel Bicaco, RS under the condition of a typical dystropheric red Latosol (Oxisol) soil, in the 2017/2018 season crop. The experimental design was randomized blocks in a factorial scheme phenological stages x cultivars. Analysis of variance revealed significance for the interaction between phenological stages x cultivars for the variables composed by germination, abnormal, hard, dead, as well as field emergence, plant length and root length. There is influence of foliar feeding of molybdenum (Mo) and potassium (K) in different phenological stages of soybean. It was found that there was no significant difference for the yield of soybean cultivars under foliar feeding of Mo and K in the different treatments to which they were submitted.
The climate unpredictability causes long periods of drought, becoming the main risk factor in soybeans production fields and consequent losses to farmers in Brazil and worldwide. As sessile organisms, plants are constantly challenged by a wide range of environmental stresses, including drought. Growth constraints and stress due to these environmental changes result in reduced yield and significant harvesting losses. The response to abiotic stresses is a very complex phenomenon, since several stages of plant development can be affected by a particular stress and often several stresses affect the plant simultaneously. In order to mitigate the damages caused by the climate, new soybean cultivars adapted to the drought and the diversified climate are necessary, as well as technological advances in the production of soybeans that must advance with the increase of cultivated area. Therefore, the mechanisms underlying tolerance and adaptation to stress have been the focus of intensive research. In this sense, the objective of this review is to provide an overview of the evolution of genetic improvement regarding the search for more drought-tolerant cultivars, as well as to verify which strategies are used in the genetic improvement of soybean in the search of these genotypes.
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