Grain number in top, middle, and bottom parts of oat panicles: Relationships with endogenous ZR, ABA, IAA, and GA3

A comprehensive understanding of the variation in source-sink processes in different oat ( Avena sativa ) varieties might enhance successful breeding efforts to increase grain production. Distinguishing the sequential parts of oat panicles in relation to endogenous hormones remains a research gap that needs to be addressed to further elucidate the physiological mechanisms of yield formation. A two-year field experiment was conducted in Northwestern China with nine oat varieties to explore the interaction between yield traits and endogenous hormones in the top, middle, and bottom parts of the panicles. Tested varieties were grouped as high- and low-yielding, having grain yields ranging from 2.4 to 2.9 Mg ha −1 and 1.9–2.3 Mg ha −1 , respectively. Grain number rather than 1000-grain weight primarily regulated grain yield. Furthermore, in the high-yielding group, grain yield increased by 15 kg ha⁻¹ for each additional grain per panicle, which was three times the increase observed in the low-yielding group. In the high-yielding group, grain number was mainly regulated in the middle and bottom parts of the panicles, where it was 43 % and 52 % higher than in the low-yielding group, respectively. Notably, abscisic acid (ABA) levels in the middle parts of panicles were positively correlated with grain number, and its concentration in the high-yielding group was 63 % higher than the low-yielding group. However, the grain number of bottom parts of panicles was negatively related to gibberellin (GA 3 ), and its concentration in the high-yielding group was 25 % lower than in the low-yielding group. Overall, the grain number induced by oat variety was characterized by balanced endogenous ABA in the top and middle parts of panicles and lower GA 3 in the bottom parts, highlighting a potential guideline for yield increasing through hormonal regulation. • Oat grain yield was more contributed by grain number than 1000-grain weight. • In high-yielding varieties, grain number increased mainly in the middle and bottom parts of panicles. • ABA in the middle parts of panicles is positively associated with grain yield. • GA 3 in the bottom parts of panicles is negatively associated with grain number. • Balancing endogenous ABA and GA 3 in top, middle, and bottom parts of panicles can boost yield.