Utilizing auxin dwarf genes to optimize seed yield and lodging resistance in rapeseed

Direct-seeding rapeseed production at high plant density raises the risk of lodging. We investigated the use of dwarf genes to improve rapeseed plant architecture to balance yield and lodging. Three genotypes with different plant architectures (dwarf sca^HS5, semi-dwarf +/sca^HS5, and tall HS5) were evaluated under varying nitrogen rates (N1, N2, and N3: 120, 240, and 360 kg N ha⁻¹) and plant densities (D1, D2, and D3: 15, 45, and 75 plants m⁻²) from 2019 to 2022. The results showed that increasing N rate positively influenced yield while decreasing lodging resistance in all genotypes. Increasing plant density (D2–D3) enhanced lodging resistance and yield in sca^HS5 and +/sca^HS5, but reduced yield in HS5. Compared to the two parents, +/sca^HS5 exhibited moderate expressions of IAA3, GH3.15, and SAUR30 in stems under N2D3, resulting in reduced plant height and increased compactness. Additionally, +/sca^HS5 had a thicker silique layer than HS5 by 14.7%, and it had a significant correlation between branch height/angle and yield. Increasing N rate led to increased lignin and pectin contents, while cellulose content decreased. Increasing plant density resulted in greater stem cellulose content and CSLA3/7 expression in sca^HS5 and +/sca^HS5, but decreased in HS5. Compared to HS5, +/sca^HS5 exhibited higher expressions of ARAD1 and GAUT4, along with a 51.1% increase in pectin content, leading to improved lodging resistance under N2D3. Consequently, +/sca^HS5 showed a 46.4% higher yield and 38.9% lodging resistance than HS5 under N2D3, while sca^HS5 demonstrated strong lodging resistance but lower yield potential. Overall, this study underscores the potential of utilizing auxin dwarf genes to optimize the trade-off between yield and lodging resistance in rapeseed and the possibility of maximizing yield potential by optimizing the plant architecture of +/sca^HS5 through nitrogen reduction and dense planting.