Establishment of the “Valsa pyri metabolites (VpM)-suspension cell”-based system to study the response of pears to VpM

Abstract

Valsa canker, caused by Valsa pyri (Vp), is a necrotrophic fungal disease that seriously damaged the pear industry in the world. Investigations on resistant mechanisms are helpful for resistance breeding and effective control methods. The current study obtained suspension cells of a resistant rootstock ‘Duli-G03’ (Pyrus betulifolia bunge) and a susceptible species ‘Yuluxiang’ (Pyrus bretschneideri Rehd.). Furthermore, the study explored the culture methods of callus and suspension cells of both varieties. Murashige and Skoog (MS) medium supplemented with 0.5 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg/L 6-benzylaminopurine (6-BA) was suitable for callus induction and suspension cell proliferation of ‘Yuluxiang’, while Nitsch & Nitsch Medium (NN69) with 5 mg/L 6-BA and 0.4 mg/L 1-naphthlcetic acid (NAA) was suitable for ‘Duli-G03’. After suspension cells treated with Vp metabolites (VpM), differentially expressed genes (DEGs) were mainly involved in “signal transduction”, “plant-pathogen interaction”, “plant hormone signal transduction”. Among these, disease resistance protein- and tobacco mosaic virus (TMV) resistance protein-related genes, such as GWHGAAYT037865, GWHGAAYT031455, GWHGAAYT037851, were only promptly induced in ‘Duli-G03’. On the contrary, DEGs related to Hypersensitive response (HR) (gene4043), ethylene (ET) (gene26613) and brassinosteroid (BR) (gene33208) were aroused only in ‘Yuluxiang’. The results supplied important implications for understanding the molecular mechanisms of pear resistance to Valsa canker. Some of the screened genes can be further investigated for disease resistance effects and pave the ground for the mining of disease resistance genes.