Evaluation and selection of early-maturing winter rape (Brassica napus L.) varieties for “rice-rice-rape” cropping system in Guangdong

Objective  To evaluate and select the early-maturing, high-yield and high-quality rape varieties suitable for the triple-cropping mode of “rice-rice-rape” in Guangdong Province, solve the outstanding problem of non-alignment of crop rotation at present, and promote the improvement of grain and oil production capacity in Guangdong Province.

Method The experiment was carried out in the winter idle field of double-cropping rice. The 25 early-maturing winter rape (Brassica napus L.) varieties were selected as evaluation materials, their growth duration time, yield and quality traits were assessed, and their correlations with meteorological factors were analyzed as well.

Result The whole growth duration of 25 winter rape varieties ranged from 136 to 151 d. The days from sowing stage to initial flowering stage, from initial flowering stage to full flowering stage, from full flowering stage to final flowering stage, and from final flowering stage to maturity were on average 88.0, 7.2, 21.1 and 30.0 d; The accumulative effective temperatures above 0 ℃ were on average 1 648.4, 98.3, 360.3 and 525.3 ℃ respectively. Their average yield was 1 832.1 kg·hm⁻², ranging from 1 279.0 to 2 288.1 kg·hm⁻². The average daily yield was 12.5 kg·hm⁻², ranging from 8.6 to 15.5 kg·hm⁻². The seed yield was positively and significantly correlated with seeds per pod (P<0.01). The seed oil content averaged at 44.5%, varying from 40.4% to 48.4%. The protein content was 22.4% on average, with a range between 19.2% and 25.4%. Additionally, the average oleic acid content was 58.5%, with a range between 19.6% and 73.3%. According to correlation analysis, from sowing stage to initial flowering stage, yield has extremely significant positive correlation with average temperature and photosynthetically active radiation, oil content has significant positive correlation with average temperature(P<0.05), and extremely significant positive correlation with photosynthetically active radiation. Cluster analysis discoverd 11 high-yield-type varieties with various growth durations, and their daily yield, seeds per pod, number of primary branches and effective pods per plant were higher or greater.

Conclusion Early-maturing winter rape varieties displays significantly different adaptability in Guangdong. The varieties with high daily yield, high seed number per pod, high primary branch number, and high effective pod number per plant can fully utilize the light and temperature resources in the early growth stages, leading to the formation of high-yield and high-oil traits. They are suitable for “rice-rice-rape” production in rice-growing region of central Guangdong and hilly area.