Path Analysis Dissects Direct and Indirect Effects of Floret Morphological Traits on Seed Shattering in Naked Oat (Avena nuda)

Seed shattering is a key cause of yield loss in naked oat (Avena nuda) production, yet research specifically targeting this issue remains limited. This study phenotyped 316 diverse naked oat accessions for 14 floret morphological traits and shattering rate across six environments. Principal component analysis (PCA), K-Means clustering, and path analysis were employed for data mining. PCA identified three principal components representing morphological size, thickness-length trade-off, and differential thickness distribution between lemma and palea. K-Means clustering divided the accessions into two clusters differing significantly in morphological size and seed shattering resistance. Path analysis revealed that palea width showed the strongest negative direct effect on shattering, followed by lemma basal thickness and lemma basal ridge thickness, while seed area exhibited a significant positive direct effect. Indirect pathway decomposition further demonstrated that palea width and lemma basal thickness served as key negative indirect contributors, whereas seed area played a dual role with opposing direct and indirect contributions. The model explained 32.80% of shattering variation, with palea width contributing the largest relative share. These findings suggest that floret morphology is associated with naked oat seed shattering and may inform resistance breeding efforts.