Brazil stands out in grain production, being the world's second-largest soya bean producer and the largest in Latin America. The area occupied by leguminous in the 2018/2019 harvest was 36 million hectares (CONAB, 2019). The Cerrado biome occupies about 44% of the country's agricultural area, which is responsible for 60% of total soya bean production (DICKIE, Magno, Giampietro, & Dolginow, 2016). The advance of agriculture in this biome is growing, which tends to further increase the percentage of crop production. In the Cerrado, the volume and frequency of rainfall is often fluctuating and insufficient, reducing the chances of adequate supply of the crop's water demand (Goes, Rodrigues, Arf, Arruda, & Vilela, 2011; Tardin et al., 2013). Therefore, it is common in Cerrado the soya bean crops to be subjected to drought stress conditions in their early stages, which can affect the germination process. The severity of the drought stress effect on soya bean depends on the

Resumo: Estudos recentes têm abordado o uso da prática da elevada densidade de semeadura na cultura da soja. Entretanto, os resultados práticos dessa técnica são divergentes. Assim, pesquisas nesse campo são importantes para elucidar os efeitos diretos dessa prática de manejo, como, por exemplo, a interferência no uso da radiação fotossinteticamente ativa (RFA). Portanto, objetivou-se com este estudo avaliar a dinâmica da RFA em diferentes densidades de cultivo na cultura da soja. Para tanto, conduziu-se um experimento a campo com delineamento em blocos casualizados com os tratamentos distribuídos em arranjo fatorial 3 × 5: três cultivares de soja RR® (P98Y12, TMG 132 e M-Soy 9056) e cinco densidades de semeadura (20, 30, 40, 50 e 60 plantas·m -2 ) com quatro repetições.Foram avaliados massa seca da parte aérea, radiação fotossinteticamente ativa no dossel inferior (RFA-I) e superior (RFA-S), intercepção da RFA, taxa de crescimento da cultura (TCC), taxa de crescimento relativo (TCR), taxa de assimilação líquida (TAL), eficiência de uso da radiação (EUR), coeficiente de extinção luminosa (k), índice de colheita de grãos (ICG), peso de 1.000 grãos e produtividade. Independentemente do cultivar, as densidades de 20 e 30 plantas·m -2 proporcionaram os maiores valores de TAL, TCR, k, ICG e produtividade. Apenas o uso dos parâmetros EUR, TCC e RFA interceptada não fornece informações sólidas para predizer a eficiência do cultivo adensado na cultura da soja. As densidades de cultivo tradicionalmente utilizadas se sobrepõem às demais quanto à qualidade da RFA no dossel e produtividade da soja. Palavras-chave:Glycine max (L.) Merrill, coeficiente de extinção luminosa, balanço radiométrico, qualidade da radiação.

Seeds of maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench.] were submitted to different osmotic potential levels induced by polyethylene glycol (PEG) with the objective of evaluating the effects of drought stress on seed germination and early seedling growth. Seeds were arranged in paper rolls and soaked in PEG solutions prepared with osmotic potentials 0.0 (control), -0.2, -0.4, and -0.8 MPa and kept into a seed germinator, at 25 °C for 18 days. A completely randomized design in a 2 × 4 factorial scheme with four replications of 50 seeds each was used. The results showed that by increasing of the osmotic potential level, germinated seed number, germination rate index, root and shoot length, shoot and root dry matter, and seedling vigor index (SVI) decreased, while mean germination time (MGT) and root: shoot ratio (RSR) increased in both crops. Additionally, the maize was more susceptible than sorghum to drought stress, with germination response declining more rapidly with decreasing osmotic potential. Sorghum crop tolerates water stress of up to -0.2 MPa, without reducing germination of the seeds; however, the growth of shoots and roots are inhibited. Drought stress limits the process of seed germination and early growth of maize seedlings.

No abstract

ABSTRACT. Soybean is one of the main sources of foreign exchange credits for Brazil in the agricultural sector. There is increasing interest in growing this leguminous crop, especially in the southern region of Minas Gerais, due to its importance as an alternative for crop rotation with maize. In this respect, the study of the adaptability of new cultivars to the region is indispensable so as to obtain high yields. Thus, the aim of this study was to evaluate the performance of 38 soybean cultivars for growing in the summer season in the municipality of Lavras, MG, Brazil, in the 2010/2011 and 2011/2012 crop years. The experiments were conducted in a randomized block design with 3 replications and the treatments consisted of 38 cultivars. At the time of harvest, the following assessments were made: grain yield (kg/ha), height of the lowest pod (cm), plant height (cm), and lodging. The data were subjected to individual and combined analysis of variance. The phenotypic mean values were clustered, adopting the Scott and Knott test. For simultaneous selection of multiple traits, the sum of rank index of Mulamba and Mock was adopted. The cultivar TMG 801 RR had the best yield performance; the cultivars Monsoy 8001, MGBR-46 8996 I.O. Soares et al. ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (3): 8995-9003 (2015) (Conquista), and BRSMG 68 (Vencedora) also stood out. Considering simultaneous selection for grain yield, plant height, height of the lowest pod, and lodging, the cultivar TMG 801 RR is recommended for growing in the summer season in the southern region of Minas Gerais.

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.

ABSTRACT. The aim of this study was to verify the adaptability and stability of soybean cultivars with regards to yield and oil content. Data of soybean yield and oil content were used from experiments set up in six environments in the 2011/12 and 2012/13 crop seasons in the municipalities of Patos de Minas, Uberaba, Lavras, and São Gotardo, Minas Gerais, Brazil, testing 36 commercial soybean cultivars of both conventional and transgenic varieties. The Wricke method and GGE biplot analysis were used to evaluate adaptability and stability of these cultivars. Large variations were observed in grain yield in relation to the different environments studied, showing that these materials are adaptable. The cultivars exhibited significant differences in oil content. The cultivars BRSGO204 (Goiânia) and BRSMG (Garantia) exhibited the greatest average grain yield in the different environments studied, and the cultivar BRSMG 760 SRR had the greatest oil content among the cultivars evaluated. Ecovalence was adopted to identify the 2 K.B. Silva et al. ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 15 (2): gmr.15026756 most stable cultivars, and the estimates were nearly uniform both for grain yield and oil content, showing a variation of 0.07 and 0.01%, respectively. The GGE biplot was efficient at identifying cultivars with high adaptability and phenotype stability.

RESUMO:O Estado do Piauí não apresenta por parte dos órgãos de pesquisa uma recomendação ofi cial de adubação nitrogenada para a cultura do milho no Cerrado piauiense. Objetivou-se avaliar a efi ciência de doses e épocas de aplicação de nitrogênio (N) no desenvolvimento e produtividade do milho no Cerrado piauiense. O delineamento experimental foi o de blocos ao acaso, com quatro repetições e 21 tratamentos, dispostos em esquema fatorial incompleto 4×5+1 tratamento adicional como controle (ausência aplicação de N). Os demais tratamentos constituíram-se da combinação de quatro doses de N (50; 100; 150 e 200 kg ha -1 ) e cinco formas de parcelamento do fertilizante: dose total na semeadura; dose total no estádio fenológico V6; 30% da dose na semeadura + 70% da dose no estádio fenológico V6; 50% da dose na semeadura + 50% da dose no estádio fenológico V6; 70% da dose na semeadura + 30% da dose no estádio fenológico V6. No período de pleno fl orescimento do milho, foram avaliados a concentração de N na folha, teor relativo de clorofi la, altura das plantas, fi tomassa seca da parte aérea e diâmetro do colmo das plantas. Na maturidade fi siológica, foi avaliada a altura de inserção, comprimento e número de fi leiras por espiga, massa de mil grãos, produtividade, efi ciência agronômica e índice de colheita de grãos. A maior produtividade foi verifi cada com a aplicação de 30% do N na semeadura e o restante em cobertura. A máxima produtividade de grãos foi de 6.520 kg ha -1 , utilizando a dose estimada de 134 kg ha -1 de N. Essa mesma forma de parcelamento do fertilizante (30% do N na semeadura e o restante em cobertura no Cerrado piauiense) também proporcionou maior efi ciência agronômica no uso do N. (50, 100, 150, and 200 ABSTRACT: There is no offi cial recommendation by research agencies regarding nitrogen fertilization for maize for the cerrado area of Piaui state. This study aimed to evaluate the nitrogen (N) rates and times of N application on the development and yield of maize in the cerrado of Piauí State, Brazil. The experiment was carried out in a randomized block design with four replicates and 21 treatments arranged in an incomplete 4 × 5 factorial scheme + 1 additional treatment as control (without N application). The other treatments were the combination of four N rates