Changes in soybean cultivars released over the past 50 years in southern Brazil

On-farm soybean yield has increased considerably in the last 50 years in southern Brazil, but there is still little information about how selection and breeding for yield increase has changed the agronomic attributes of cultivars. The objectives of this study were to evaluate the changes in soybean yield, seed oil and protein concentration, and changes in plant attributes that might be associated with yield improvement of 26 soybean cultivars released over the past 50 years in southern Brazil, sown simultaneously in a common field environment for two growing seasons. The average rate of yield gain was 45.9 kg ha(-1) yr(-1) (2.1% ha(-1) yr(-1)), mainly due increased seed number per area and harvest index. Over year of cultivar release, cultivars became less susceptible to lodging, as well as plant mortality reduced. Meanwhile, the seed oil concentration increased, and seed protein concentration decreased, which could have negative consequences for soybeans use and requires further attention for breeding of future cultivars. Breeders have successfully contributed to the annual rate of soybean yield increase in southern Brazil. By our results, as well as the official on-farm production data, there is no evidence of soybean yield reaching a plateau in the near future in southern Brazil.

Automated summary

On-farm soybean yield has significantly increased in southern Brazil over the past 50 years. This study evaluated the changes in yield improvement and associated agronomic attributes of soybean cultivars released in the region. The results showed that increased seed number per area and harvest index were the main factors contributing to yield increase. Meanwhile, cultivars became less susceptible to lodging and plant mortality reduced. Seed oil concentration increased, while seed protein concentration decreased. These findings have important implications for soybean utilization and future breeding efforts.