Study on the relationship between physiological characteristics of superior and inferior grains with yield in different oat genotypes

To investigate the physiological characteristics of superior and inferior oat grains and their impact on yield, field experiments were conducted in 2021 and 2022 at the Modern Agricultural Science and Technology Park of Inner Mongolia Agricultural University, located in Tumd Right Banner, Baotou City, Inner Mongolia Autonomous Region. Nine oat varieties were used as experimental materials to determine the sucrose metabolism, starch content and related enzyme activities during the grain-filling period and the grain yield at maturity. Correlation and path analyses were performed to elucidate the relationships between physiological traits of superior and inferior grains and overall yield. The results showed that, based on grain yield at maturity, Bayou 1, Bayou 9, Bayou 18, and Caoyou 1 were classified as high-yielding varieties (2582.67-3341.29 kg hm-2), whereas Huabei 2, Baiyan 5, Baiyan 2, Dingyou 8, and Pin 5 were classified as low-yielding varieties (1894.05-2397.45 kg hm-2). Compared to the low-yielding varieties, the grain yield of the high-yielding varieties increased significantly by 5.39% to 76.41%. Notably, although the sucrose content in superior grains was lower than in inferior grains, sucrose synthase (SUS) activity was higher. Additionally, starch content, starch synthase (SSS), and ADP-glucose pyrophosphorylase (AGPase) activities were all higher in superior grains than in inferior ones, indicating a higher efficiency of sucrose cleavage and conversion into starch in superior grains. Grain yield showed positive correlations with starch content, SUS, SSS, and AGPase activities in the top, middle, and bottom portions of the panicle, and negative correlations with sucrose content. Moreover, yield was negatively correlated with sucrose phosphate synthase (SPS) activity specifically in the top part of the panicle. Path analysis revealed that SSS activity in superior grains had the greatest positive effect on yield, while SUS activity in inferior grains also contributed significantly. In conclusion, enhancing starch synthesis capacity in superior grains and improving sucrose metabolism in inferior grains can effectively increase oat yield.