Interaction between Soybean Cultivars and Seed Density

Plant, environmental conditions and management type will determine final crop yield. Enhanced yield can be reached by using well-adapted and potentially productive genotypes;all of them ally to crop cultural practices and management. Among these, seed density stands out, once it interferes with plant morphology and competition for water and nutrients. Thus, this study aimed to evaluate the effect of varied seed densities on agronomic traits in soybean, besides identifying cultivars with wide adaptability to different environments and seed densities. Six soybean cultivars were assessed under four seed densities (100, 200, 300 and 400 thousand plants·ha-1), in nine different environments from Minas Gerais State, Brazil. The experimental design was a completely randomized block design with three replications. The BRSMG 760SRR and BRSMG 820RR cultivars had the best average performance independent of the environments and seed densities. The seed density of 300 thousand plants per hectare showed to be as the most adequate for soybean cultivation on the evaluated environments. Furthermore, seed density interacted with the agronomic traits in soybean.

Agronomic and Energetic Potential of Biomass Sorghum Genotypes

The biomass sorghum [Sorghum bicolor (L.) Moench], is an interesting crop considering the necessity to invest in alternative sources to generate renewable energy. The objective of this experiment was to identify sorghum biomass genotypes with greatest agronomic and energetic potential, and verify if there is phenotypic association between agronomic and technological properties in the hybrids. The study was conducted in three cities of the Minas Gerais State, Brazil (Lavras, Uberlandia and Sete Lagoas). It was evaluated 16 genotypes of sorghum biomass, being 14 of them sensitive hybrids to photoperiod and two cultivars, as control, insensitive to photoperiod. The experimental design was a triple lattice 4 × 4, with plots formed by four linear rows of 5.0 m. The morphoagronomic characteristics evaluated for the three environments were: days to flowering (FLOW), plant height (PH), number of stems (NS) and green matter production (GMP). In the experiment conducted in Lavras, also it was evaluated the agronomic traits: stem diameter (SD) and dry matter production (DMP) besides the technological traits: higher heating value (HHV), crude fiber (CF), neutral detergent fiber (NDF) and acid detergent fiber (ADF). The genotype × environment interaction was significant for all traits. The hybrids had superior performance compared to the control genotypes. Biomass sorghum hybrids, sensitive to photoperiod, when compared with commercial hybrids of forage sorghum, insensitive to photoperiod, had an average production of 34 t ha-1 dry matter with 62% humidity and higher heating value of 4.400 Kcal/Kg. There was no phenotypic correlation between agronomic and technological characters evaluated.

<i>Sitophilus</i>Weevil Reaction in Upland Rice Elite Lines

Insects of the genus Sitophilus are among the most destructive pests in rice storage, and the best strategy to control it is to use resistant genotypes. In this study, 26 upland rice elite lines were evaluated for Sitophilus weevil reaction on grain weight. The seeds were placed in plastic recipients stored in a room with temperature and lightning simulating a warehouse environment. The number of living weevils and the grain weight were obtained in two evaluations, one 35 days after storage, and the other 35 days after infestation. The lines differed statistically for number of living weevils and for grain weight in both evaluations. The correlations between these two characters were -?0.99 and -?0.47 for the first and the second evaluation (P < 0.05), respectively. The lines BRS Pepita, AB 112089 and AB 112090 were the most susceptible. Seventeen of the twenty-six elite lines were resistant in both evaluations and could be successfully used in upland rice breeding programs.

Performance of Conventional and Transgenic Soybean Cultivars in the South and Alto Paranaiba Regions of Minas Gerais, Brazil

The aim of this study was to compare transgenic and conventional soybean cultivars in regard to yield performance and agronomic traits. Six soybean cultivars were tested: three conventional cultivars and their three isogenic transgenic derivatives, in two locations, Lavras and Patos de Minas in Minas Gerais, Brazil, in the 2012/13 crop season. Data on yield (kg&middotha-1), plant height (cm), and tolerance to lodging were collected. The cultivars had different responses. The cultivar BRS/MG46 Conquista had lower yields than its isogenic derivative BRS Valiosa RR, but this was not seen with the conventional cultivar M-SOY 6101, which produced more than its isogenic derivative M-SOY 7211 RR. Between the isogenic cultivars BRS/MG68 Vencedora and BRS Favorita RR, there were no significant differences. Nevertheless, the contrast between the mean values of the transgenic and conventional cultivars shows that the conventional cultivars had mean values greater than the transgenic cultivars.

Genetic Parameters Estimates Associated to Conversion of Nicotine to Nornicotine in Burley Tobacco

Nicotine represents the predominant alkaloid in cultivated tobacco. In burley varieties, during senescence and curing of leaves, nicotine can be converted to nornicotine, which is highly undesirable because of its relationship with the tobacco specific nitrosamines formation. Thus, an alternative for producing varieties with low or null nornicotine content would be to select plants or progenies for traits related to nicotine conversion. Therefore, understanding genetic control and inheritance underlying this process is important to chooseappropriate strategies in breeding programs. Two contrasting inbred lines for nicotine conversion to nornicotine, TN 90 and BY 37, have been crossed to obtain the segregating generations (F2 and BCs). Genetic parameters of mean and variance, as well as the average degree of dominance and heritability were estimated. It has been found that nicotine conversion has predominantly additive effects, and in addition, narrow sense heritabilities at the individual level were higher than 65%. Both are desirable conditions for conducting a selection program of burley tobacco aiming at development of inbred lines associating yield and other traits with low or null nicotine conversion.

Potassium Fertilization and Physiological Soybean Seed Quality

The purpose of this study was to evaluate the influence of increased application rates of potassium on the physiological quality of seeds from different soybean cultivars. Seeds from two locations (S?o Gotardo, MG and Lavras, MG, Brazil) were used. After harvest, the seeds were sent to the Central Seed Analysis Laboratory of the Federal University of Lavras. We used a randomized design in a 4 × 6 factorial arrangement of four cultivars and six doses of potassium. All tests were performed with two replicates of 50 seeds (300 seeds per treatment). Germination, emergence under controlled conditions, accelerated aging, electrical conductivity, and tetrazolium tests were performed. Data were subjected to analysis of variance. In soybean seed production fields with high potassium content in the soil, higher application rates of potassium do not increase the physiological quality of seeds.