OCCURRENCE AND INTENSITY OF FOLIAR DISEASES AND PHENOLOGY IN SIX SOYBEAN CULTIVARS DURING TWO SOWING TIMES

Abstract

The aim of this study was to evaluate the occurrence and intensity of leaf diseases and crop cycle in six soybean cultivars in Passo Fundo, RS, Brazil, during two times of sowing in 2007-08 season. Cultivars A 4910 RG, BMX Apolo RR, A 6001 RR, CD 214 RR, FUNDACEP 55 RR and CD 219 RR were used,  because they represent large area of cultivation in Brazilian state. A randomized complete block design (DBCA) with six treatments and four replications was used, and the data obtained were submitted to variance analysis. Subsequently, a comparison of media by Tukey (p≤0.05) was carried out for each season, and for the comparison between the seasons test T (p≤0.05) was used. The intensity of leaf diseases present in the aerial part of crop was evaluated weekly in a period of five weeks. Severity values (except cercospora blight and soybean rust) were integrated in the area under the relative disease progress curve (AACPDr). Cultivars A 4910 RG and BMX Apolo RR had lower severity of downy mildew and blight cercospora, as well as of the number of lesions cm^-2 of Asian rust. Cultivars CD 219 RR and FUNDACEP 55 RR showed less bacterial blight, downy mildew and powdery mildew severity. Genotype A 4910 RG behaved as very early, BMX Apolo RR, A 6001 RR and CD 214 RR as precocious, FUNDACEP RR 55 as medium and CD 219 RR as late.