Biochar amendment changes jasmonic acid levels in two rice varieties and alters their resistance to herbivory

Muhammad Waqas,Muhammad Hamayun,Sajjad Asaf,Kyung-Min Kim,Sopheap Yun,Raheem Shahzad,Abdul Latif Khan,Sang-Mo Kang,In-Jung Lee,Jorge Paz-Ferreiro

doi:10.1371/journal.pone.0191296

Abstract

Biochar addition to soil not only sequesters carbon for the long-term but enhances agricultural productivity. Several well-known benefits arise from biochar amendment, including constant provision of nutrients, increased soil moisture retention, decreased soil bulk density, and sometimes the induction of systemic resistance against foliar and soil borne plant pathogens. However, no research has investigated the potential of biochar to increase resistance against herbivory. The white-backed plant hopper (WBPH) (Sogatella furcifera Horváth) is a serious agricultural pest that targets rice (Oryza sativa L.), a staple crop that feeds half of the world’s human population. Therefore, we investigated the (1) optimization of biochar amendment levels for two rice varieties (‘Cheongcheong’ and ‘Nagdong’) and (2) subsequent effects of different biochar amendments on resistance and susceptibility of these two varieties to WBPH infestation. Initial screening results for the optimization level revealed that the application of biochar 10% (w/w) to the rooting media significantly improved plant physiological characteristics of both rice varieties. However, levels of biochar amendment, mainly 1, 2, 3, and 20%, resulted in negative effects on plant growth characteristics. Cheongcheong and Nagdong rice plants grown with the optimum biochar level showed contrasting reactions to WBPH infestation. Specifically, biochar application significantly increased plant growth characteristics of Nagdong when exposed to WBPH infestation and significantly decreased these characteristics in Cheongcheong. The amount of WBPH-induced damage to plants was significantly lower and higher in Nagdong and Cheongcheong, respectively, compared to that in the controls. Higher levels of jasmonic acid caused by the biochar priming effect could have accumulated in response to WBPH infestation, resulting in a maladaptive response to stress, negatively affecting growth and resistance to WBPH in Cheongcheong. This study highlights the importance of investigating the effects of biochar on different rice varieties before application on a commercial scale to avoid potential crop losses.

Highlights

Rice is at the top of globally important agronomic crops (Oryza sativa L.) and is a major dietary staple for half of the human population
We found an optimum level of biochar (10%, w/w) that promotes plant physiological characteristics of both Cheongcheong and Nagdong rice varieties
The decrease in jasmonic acid levels under normal conditions and slight increase under white-backed plant hopper (WBPH) infestation could indicate a regulated response to stress in Nagdong, which might explain the observed increase in resistance and plant growth parameters

Summary

Introduction

Rice is at the top of globally important agronomic crops (Oryza sativa L.) and is a major dietary staple for half of the human population. Nymphs and adults damage the rice plants by feeding on the phloem They turn the crop into a meaningful source of transmitting major viral diseases, such as southern rice black-streaked dwarf virus. Important crop factors such as plant vigor, height, number of productive tillers, filled grains, and yield are subsequently negatively affected [5]. The management of WBPH infestation largely relies on chemical pesticides This method has economic and environmental consequences, such as killing WBPH predators, and pesticide resistance in insects cannot be avoided. Various genes delivering resistance against sap-sucking insects have been sorted out in the rice germplasm itself; the development of resistant varieties is a slow process [9]

Methods

Results

Conclusion