Canonical correlations of light and temperature with yield and agronomic traits of semi-winter rapeseed (Brassica napus L.) sowed in spring

To improve the utilization value of semi-winter rapeseed in Tibet, canonical correlations were used to analyze canonical correlations of light and temperature with yield and agronomic characters of semi-winter rapeseed (Brassica napus L.) sowed in spring. The aim of the study was to effectively solve the shortage of rapeseed germplasm resources in Tibet. In this paper, light and temperature indicators, including accumulated temperature, daily extreme temperature difference and total sunshine length, were investigated during vegetative growth period, bud and flowering period and silique mature period, respectively. The agronomic and yield characters for 18 semi-winter rapeseed varieties were also investigated in different growth period, which included four stem characters, two branch characters and four yield characters. The results showed that the yield and agronomic characters of semi-winter rapeseed were significantly correlated with accumulated temperature, extreme temperature difference and sunshine length during different growth periods of semi-winter rapeseed. However, in different growth periods, the dominant light and temperature indicators were different. During vegetative growth period, light and temperature were significantly correlated with branch characters. The dominantly driving light and temperature indicator of branches number was accumulated temperature. During bud and flower period, extreme temperature difference and sunshine length played a determinative role, which had better promotion effect on stem and main inflorescence. During silique mature period, light and temperature were significantly correlated with stem, branch and yield characters. Extreme temperature differences were the key driving factor for the effects on the effective silique number and 1000-grain weight. Longer sunshine length decreased primary branch height and increased length of main inflorescence and yield per plant. In conclusion, it was suggested to pay attention to rapeseed varieties that were tolerant to extreme differences in temperature and sufficient light when introducing and breeding semi-winter rapeseed for early maturity and ‘double low’ quality in Tibet. The first focus of the selection of agronomic traits was on the length of main inflorescence, followed by effective branch number, effective silique number and then 1000-grain weight.