Sensitivity of Two Next Generation Dryland Rice Varieties to Pretilachlor and Acetochlor during the Germination Stage

Purpose This study aimed to investigate the differences in dose- and tissue-specific sensitivity to soil-applied herbicides between two next generation dryland rice (NGDR) varieties Dianheyou 918 and Dianheyou 615 during the germination stage.

Methods Petri dish experiments were conducted to compare the effects of pretilachlor and acetochlor solutions on radicle and plumule growth when exposed via the seed coat, radicle, and coleoptile.

Results When the application rate of pretilachlor (active ingredient) reached 0.22 kg/hm² or above, after the herbicide was absorbed through the seed coat, it significantly inhibited the growth of radicle and plumules in both NGDR varieties. When the herbicide was absorbed via the radicle, the sensitivity threshold for radicle growth decreased to 0.11 kg/hm², while the sensitivity thresholds for plumule growth were 0.45 kg/hm² for Dianheyou 918 and 0.22 kg/hm² for Dianheyou 615. When the herbicide was absorbed via the coleoptile, the tolerance of both radicle and plumule growth to pretilachlor could reach 0.90 kg/hm². However, for acetochlor, regardless of absorption via the seed coat, radicle, or coleoptile, both radicle and plumule growth exhibited high sensitivity to acetochlor: a dose of 0.34 kg/hm² was sufficient to significantly inhibit radicle and plumule growth in both varieties. Therefore, acetochlor might need to be combined with deep-sowing techniques to avoid phytotoxicity at the germination stage.

Conclusion These findings provide a theoretical basis and field management strategies for the precise spatiotemporal application of pretilachlor and acetochlor in NGDR paddies in Yunnan Province.