Adaptability and stability study of soybean lines developed for high yield in Paraná State using four methodologies

An adaptability and stability study was carried out using soybean yield data from several locations in Parana State, obtained from 1990 to 1999. The main objectives were: a) to check the efficiency of the Embrapa Soja breeding program for selecting the highest yielding lines with specific (regional) or broad adaptation; b) to analyze the performance of the control cultivars under favorable and unfavorable conditions; c) to identify the best stability methodology for inbred line evaluation. The evaluated lines were classified into early (L), semiearly (M) and medium (N) maturity groups. A randomized complete block design with four replications was used in each location and all analyses were carried out by maturity group. The number of M maturity lines that scored higher than the controls BR-16 and Embrapa 4 increased along the years, especially in unfavorable environments. On the other hand, the number of L and N maturity groups scoring higher than the controls either remained constant or fluctuated (increasing or decreasing) with time. The controls FT-Guaira, Embrapa 4, BR16 and FT-10 and the great majority of the tested lines showed broad adaptation. IAS 5 and FT-Abyara showed adaptation to poor environments and also broad adaptation. The analysis of the means in favorable and unfavorable environments was the most efficient method for soybean line evaluation. A methodology to classify soybean genotypes was proposed, based on these means.