Physiological and Biochemical Changes in Lucerne (Medicago sativa) Plants Infected with ‘Candidatus Phytoplasma australasia’-Related Strain (16SrII-D Subgroup)

Abstract

Changes in physiological and biochemical patterns in lucerne plants caused by the presence of ‘Candidatus Phytoplasma australasia’, which is one of the significant pathogens causing yield losses in lucerne plants, were investigated. Significant differences were evident in total chlorophyll, chlorophyll a, chlorophyll b, and protein amounts between ‘Ca. Phytoplasma australasia’-positive and negative lucerne plants. Stress-related metabolites such as phenol, malondialdehyde, and proline accumulations in ‘Ca. Phytoplasma australasia’-positive plants were remarkably higher than those of phytoplasma-negative plants. As a response to disease attack, phytoplasma-positive plants exhibited higher antioxidant enzymes (peroxidase and catalase) and non-enzymatic metabolite responses such as jasmonic and salicylic acids. We state that partial disease responses were revealed for the first time to breed resistant lucerne lines infected by ‘Ca. Phytoplasma australasia’.

Molecular characterization of ‘Candidatus Phytoplasma phoenicium’ infecting almond (Prunus dulcis) and evaluation of biochemical defenses produced in the plants

“…Similarly, the increases in total phenolic contents followed by phytoplasma infection were evident in pepper and alfalfa plants (Ayvaci et al, 2022;Reveles-Torres et al, 2018). Increases in proline and phenol contents in almond leaves are strong parameters that the plant reacts to the pathogen attack and goes on defensive stages.…”

“…There are quite a few studies containing CAT and POD enzyme activities in phytoplasma infections in pistachio trees (Akkurak et al, 2021), and alfalfa (Ayvaci et al, 2022), corn (Junqueira et al, 2004), lime (Zafari et al, 2012), mungbean (Hameed et al, 2017) plants. In addition to these studies, Ranjbar et al (2022) reported increased CAT and POD enzyme activities in almond trees exposed to drought stress.…”

“…Determination of phenol content was carried out according to Shetty et al (1995) with some modifications (Ayvaci et al, 2022).…”

“…SA content was performed according to prepared by Rainsford (2004) with some modifications (Ayvaci et al, 2022).…”

“…They stated that CAT, POD and proline levels in leaves increased while protein and total chlorophyll contents decreased as compared to those of healthy plants. Ayvaci et al (2022) also reported that increases in stress-related metabolites such as proline, malondialdehyde (MDA) and phenol in lucerne plants infected with Ca. P. australasia compared to control plants.…”