Role of lignin metabolism and associated metabolites for lodging resistance in oat (Avena sativa L.)

Lodging refers to permanent dislocation of plants from upright position restricting the growth and development of plants. It is influenced by the morphological, biochemical and molecular traits. In our study, the importance of phenylpropanoid pathway enzymes and related defensive secondary metabolites influencing lodging resistance has been studied in oat. Field experiment was conducted in Rabi season of 2020-21 and 2021-22 in randomized block design by using ten recently released oat varieties/ advanced breeding lines. Phenylalanine ammonia lyase (PAL) activity was upregulated in RO-11-1 while downregulated in OL-15. Correlation analysis depicted that PAL was positively associated with tyrosine ammonia lyase (TAL; 0.758*). In order to regain upright position, variety OL-15 recorded higher 4-coumarate CoA ligase, cinnamyl alcohol dehydrogenase and peroxidase (POX) activity than RO-11-1 in lodged conditions. The increased lignin biosynthesis enzymes with lodging resulted in significantly higher lignin accumulation in lodged plants of OL-15 than non-lodged plants. In RO-11-1, pathway diverted more toward flavonoid biosynthesis due to already higher lignin accumulation in non-lodged conditions. Innate ability to accumulate more lignin in RO-11-1 may be the reason for higher mechanical strength and filling degree followed by lowest lodging rate. Further, RO-11-1 maintained homeostasis and sustain lodging stress due to accumulation of non-enzymatic antioxidants were enhanced in this variety under lodged conditions. In conclusion, our study provides information regarding modulation in phenylpropanoid pathway underlying lodging stress response in order to identify tolerant variety for further functional and genetic engineering.