Variability and interrelationships of grain quantity and quality characteristics in soybean

Grain yield is the most important quantitative character in breeding of soybean (Glycine max (L.) Merrill), depending on both the genotypic potential and environmental conditions of soybean growing. Essentially, all of the genetic gains in soybean yield have been achieved by traditional breeding methods, involving hybridisation and phenotypic selection (CORYELL et al., 1999). Grain yield is a complex trait and consists of components of quantitative nature, whose expression is determined by genetic and environmental factors as well as their interactions. Therefore, variability of quantitative trait is caused by genetic variability, environmental variability and variability of their interaction (BURTON, 1987; BOS and CALIGARI, 1995; SOLDATI, 1995). According to BOARD et al. (1997) soybean yield is basically determined by seed size (grams per 100 seed) and seed number (number per square meter). Seed number is determined by seed per pod (number) and pod number (number per square meter) and pod number can be influenced by pod