Mônica Cagnin Martins

Épocas de semeadura e densidade de plantas de soja: I. Componentes da produção e rendimento de grãos

Yield of three soybean cultivars and of three maturation dates, sowed on typical, late and autumn sowing dates was evaluated. Three individual and independent experiments, one for each sowing date, were carried out in a randomized block factorial design 3 x 3 with three replications (3 cultivars: IAC-12, IAC-17 and IAC-19; three planting densities: 10, 20, and 30 plants.m1). The yield components used for evaluation were: total number of pods and total number of grains, determined for 10 randomly choosen plants per plot. The weight 1,000 grains and grain yield were determined for each plot. Yield components showed differences among themselves, with a compensating effect among cultivars, densities, and sowing dates, providing a uniform grain yield. Cultivar IAC-19 showed the best grain yield performance in the autumn sowing date, independently of plant densities. Sowing date mostly affects grain yield.

Avaliação da tolerância de cultivares de soja à ferrugem asiática no oeste da Bahia

Tolerance assessment of soybean cultivars to Asian rust caused by Phakopsora pachyrhizi in western Bahia The use of tolerance as a form of control for soybean rust can be a viable alternative, since qualitative resistance has been shown to be unstable in function of fungal variability. This trial was carried out at in western Bahia in 2003/04, with the objective of assessing the tolerance of the main soybean (Glycine max) cultivars used in the area. Four early maturity cultivars [MG/BR 46 (Conquista), Emgopa 315, BRS Corisco and M-SOY 8411] and four cultivars of late maturity (BRS Barreiras, M-SOY 9350, FT 106 and BRS Sambaiba) were assessed. Tolerance was quantified by determining the difference of yield in subplots treated and untreated with fungicide. The cultivars MG/BR 46 (Conquista) and M-SOY 8411 did not present significant yield differences; however, this could not be attributed to tolerance in function of the low severity observed in this trial. This difference could be attributed to escape, since when the rust obtained higher values of severity, the two cultivars were already in the final stages of development. Although the maximum severity observed in this trial has been low (30.5% for BRS Barreiras), except MG/BR 46 (Conquista) and MSOY 8411, the others cultivars assessed presented significant differences among the subplots treated and untreated with fungicide. This shows an absence of tolerance in the main cultivars commercially planted in western Bahia. It was observed that early maturity cultivars had inferior yield reductions than late maturity cultivars. Additional keywords: resistance, control, Glycine max.

Épocas de semeadura, densidades de plantas e desempenho vegetativo de cultivares de soja

The present research was carried out in Piracicaba, SP, Brazil, to evaluate vegetative performance of three soybean cultivars at two sowing dates, at five plant densities. The cultivars used were: IAC-17, IAC-12 and IAC-19, with early, semi-early and medium maturation, respectively, sown at the typical planting date and late date. Each cultivar was sown at densities of 10, 15, 20, 25, and 30 plants.m-1. Experimental plots with five rows spaced 0.50 m and 5.0 m long were randomized in blocks, using a factorial design (3 cultivars x 5 plant densities), with three replications. Plant final height, main stem diameter, number of nodes, and number of branches per plant were evaluated. Reduction of cultivars cycle for the late sowing date occurred mainly during the reproductive phase. Independently of the planting date, the increase in plant density, implyed in an increased final plant height and in decreasing main stem diameter and number of branches per plant. Number of nodes in the main stem was reduced with the delay of the planting date.

Perdas causadas pela ferrugem-asiática em cultivares de soja semeadas em diferentes épocas, no Oeste da Bahia

Yield loss caused by rust in soybean cultivars sown in different periods in the western region of Bahia, Brazil The objective of this work was to quantify the yield loss caused by Asian soybean rust in three cultivars sown in different periods in the western region of Bahia. The experiments were installed in Sao Desiderio, BA, in the growing seasons 2007/2008 and 2008/2009. The experimental design was carried out in random blocks with four replicates and subdivided plot scheme in time. The plot was represented by the rust control treatments (with and without chemical control) and the subplots represented by cultivars (Monsoy 8411, BRS Corisco and BRS Barreiras). The severity, number of leaves throughout the cycle and yield were evaluated. The logistic model was the one that better fitted the severity data whereas the polynominal exponential function Ln (y) = a + bx 1, 5