Role of Ascorbate–Glutathione (AsA–GSH) Pathways in Phytophthora Leaf Blight Disease Resistance in Taro (Colocasia esculenta L. Schott)

Abstract

Taro (Colocasia esculenta L. Schott) is one of the important staple vegetable crops grown worldwide for its nutritious corms, leaves, and pseudostems. Taro invaded by leaf blight disease caused by Phytophthora colocasiae Racib. (Pc) resulted in 50% yield loss. On the other hand, inherent defense mechanisms of taro encounter the invaders to protect the plant from Pc invasion. The ascorbate–glutathione (AsA–GSH) pathways play an essential role in scavenging reactive oxygen species (ROS), a common phenomenon in plant–pathogen interaction. The present study focused on AsA–GSH regulations of thirty genotypes of taro under induced Pc infection. RCMC–5, among the tested taro genotypes, registered consistently higher induction of AsA, GSH, Ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), and dehydroascorbate reductase (DHAR) to encounter the Pc infection and overproduction of ROS. However, glutathione reductase (GR) was more prominent in DP–25, Jhankri, and TSL. AsA–GSH encounters the ROS overproduction, which was confirmed with lower H2O2 (0.20 µM g–1 FW) and malondialdehyde (MDA) content (20.10 nM g–1 FW) in resistant genotypes (RCMC–5) subsequently resulted in lower Pc infection (spot diameter, <2.0 cm and sporangia, <2). RCMC–5 could be one of the lines of interest in taro breeding programs for developing Pc resistant lines. AsA–GSH cycle could be a reliable parameter while selecting resistant lines for augmenting breeding strategies in taro against Phytophthora.