Potassium fertilization and sowing seasons on protein yield in soybean cultivars

ABSTRACT The present study was conducted in order to determine the effects of potassium (K) fertilizer doses on the protein yield of different soybean cultivars, sown in two seasons, in the agricultural year 2013/14 (12/05/13 and 01/23/14), in Palmas-TO, Brazil. The experimental design, in each sowing season, was randomized blocks with 60 treatments and three replicates. The treatments were arranged in a 10 × 6 factorial scheme, represented by ten cultivars (BRS 325RR, M 9144RR, BRS 33871RR, TMG 1288RR, BRS 333RR, P 98Y70RR, TMG 1180RR, BRS 9090RR, M 8766RR and BRS 8990RR) and six doses of K fertilizer (0, 40, 80, 120, 160 and 200 kg ha-1 K2O). The late sowing decreased the protein yield. K fertilization increased the protein yield in soybean cultivars. The BRS 9090RR, BRS 33871RR and BRS 333RR cultivars, at high and low K doses, were the most promising for the protein yield, and their cultivation is strategic from the economic and environmental point of view

Reaction of melon genotypes to the gummy stem blight and the downy mildew Reação de genótipos de melão ao crestamento gomoso e ao míldio

The gummy stem blight (Didymella bryoniae) and the downy mildew (Pseudoperonospora cubensis) are two foremost melon (Cucumis melo) diseases, considering their effects on yield and fruit quality. Despite the importance of such diseases, relatively few studies have been done so far on the identification of resistance sources to D. bryoniae and P. cubensis in Brazil. This work aimed at evaluating the resistance of commercial melon genotypes to the gummy stem blight and the downy mildew. Firstly, the most aggressive and representative D. bryoniae isolate was selected. Subsequently, the resistance of 86 melon genotypes to stem infection was studied upon greenhouse conditions by inoculating with the previously selected isolate. Afterwards, the resistance to mildew and leaf infection by D. bryoniae of 28 melon genotypes was evaluated in the field, under natural infection. In the greenhouse, all 86 melon genotypes were infected and showed stem infection symptoms caused by D. bryoniae four days after inoculation. Nevertheless, a significant variation on the resistance levels of the melon genotypes was found. Under field conditions and natural inoculation, genotypes Taslaki and Sary Juliabi were the most susceptible to leaf infection by D. bryoniae, significantly differing from the other genotypes. The lowest levels of susceptibility were identified in genotypes Perlita Busle S1, Valenciano Elíptico, Glaver, MR1, and 2526. All genotypes were susceptible to the downy mildew, albeit differing in susceptibility levels.<br>O crestamento gomoso do caule (Didymella bryoniae) e o míldio (Pseudoperonospora cubensis) estão entre as principais doenças do meloeiro (Cucumis melo) ocasionando redução da produtividade e da qualidade dos frutos. Apesar da importância dessas doenças, são poucos os trabalhos envolvendo a identificação de fontes de resistência a D. bryoniae e a P. cubensis no Brasil. O objetivo deste trabalho foi avaliar a resistência de genótipos comerciais de melão a essas doenças. A partir da seleção de um isolado mais agressivo, foi estudada, em condições de casa de vegetação, a resistência de 86 genótipos de meloeiro à infecção por D. bryoniae no caule. Posteriormente, em condições de campo, foi avaliada a resistência conjunta de 28 genótipos ao crestamento gomoso e ao míldio. Em casa de vegetação, todos os 86 genótipos de meloeiro avaliados foram infectados e mostraram sintomas de crestamento no caule, quatro dias após a inoculação. Houve variação significativa nos níveis de resistência entre os genótipos avaliados. No campo, sob inóculo natural, os genótipos Taslaki e Sary Juliabi mostraram-se mais suscetíveis à infecção por D. bryoniae nas folhas, diferindo significativamente dos demais genótipos. Os menores níveis de suscetibilidade foram verificados nos genótipos Perlita Busle S1, Valenciano Elíptico, Glaver, MR1 e 2526. Na avaliação da resistência ao míldio, todos os genótipos foram considerados suscetíveis, embora tenham sido encontradas diferenças nos níveis de suscetibilidade