Combined effect of salt stress and Xanthomonas axonopodis pv citri on citrus (Citrus aurantifolia)

M Salahuddin M Chowdhury,Md Shahedur Rahman,Gazi Ziaul Haque Masum,Nazneen Sultana,Shahran Ahmed Nayem,Mohammad Abu Hena Mostofa Jamal

doi:10.1016/j.heliyon.2020.e03403

Abstract

Xanthomonas axonopodis pv citri (Xac) and salt stress are two crucial hindrances to citrus production. The effect of continuous salt application and Xac infection in citrus has been investigated. Citrus plants were exposed to salt stress by irrigating with 50 mM, 100 mM, 150 mM, and 200 mM NaCl solution on weekly basis and challenged by Xac. Salt stress affected the defense response of Citrus plants to Xac and therefore lesion diameter and disease severity were gradually increased at higher salt concentration. Meanwhile, accumulation of Na+ and Cl− in the leaves were also increased with the increase of salt concentration. Besides, physiological performance (PP) of plants was estimated based on the parameters such as net assimilation rate, chlorophyll content, stomatal conductance, transpiration rate and intercellular CO2 concentration. The PP of sole Xac treated plants was gradually increased and maintained up to end of the experiment, whereas plants treated with Xac+50 mM and Xac+100 mM NaCl showed the highest PP up to 30 days after inoculation and then decreased. However, the PP of Xac+150 mM and Xac+200 mM NaCl treated plants gradually decreased till the end of experiment. Similarly, the PP of 200 mM NaCl treated plants declined continuously. Interestingly, the PP in 50 mM and 100 mM NaCl treated plants was higher initially and then decreased at 30 DAI to 40 DAI. This study revealed that citrus canker disease development was enhanced by salt stress. In addition, the physiological performance of the plants was enhanced by Xac and Xac + moderate salt stress but then demolished under severe salt stress.

Highlights

Plants need to confront with a wide sort of stress to survive in natural condition
Initially we found that salt treatment enhanced canker disease development which was undoubtedly manifested by the higher disease severity and lesion diameter
Salinity has positive effect on disease development caused by Oidium and Phytophthora fungi in tomato plant (Kissoudis et al, 2014)

Summary

Introduction

Plants need to confront with a wide sort of stress to survive in natural condition. Salinity, an abiotic stress and pathogen, a biotic stress are largely two prominent factors that plants need to deal with for survival. Salt stress could increase the prevalence of many citrus diseases (Afek and Sztejnberg, 1993; Dann et al, 1998), but no information is available about the effect of salinity on citrus canker disease. Xac is the only known bacteria yet that can produce XacPNP gene which is mobile protein signaling molecules and secreted into the apoplast to regulate plant homeostasis (Wang et al, 2011). The effect of single stressor like salinity, drought and pathogen infection have been copiously investigated, very meager information is available about how a combination of different stresses affects plants. Salinity have negative effect on citrus physiology (Balal et al, 2012) It affects net assimilation rate through reducing stomatal conductance and water uptake which led to an increase of intercellular CO2 concentration. To understand the combined effect of a biotic and abiotic stress on citrus plant we determined the impact of simultaneously applied salt stress and Xac infection on citrus plant

Methods

Results

Conclusion