Flavonoids and amino acid regulation in Capsicum annuum L. by endophytic fungi under different heat stress regimes

• Endophyte Penicillium resedanum LK6 improved Capsicum annuum growth under heat stress.
• Endophyte-infestation decreased leaf damage and lipid peroxidation than control.
• P. resedanum plant's roots had high macro and micro nutrients as compared to control.
• P. resedanum inoculated plants had proline and ammonia than control.
• P. resedanum infested plants had significantly regulated flavonoid biosynthesis.

We investigated the effects of gibberellins producing endophytic fungus Penicillium resedanum LK6 on Capsicum annuum L. plant growth during 7 and 15 days of heat (40 °C) stress. The results showed that endophyte-associated plants had higher number of leaves per plant and biomass as compared to non-inoculated control plants. The survival rate and leaf damage was significantly lower in endophyte-treated plants than control under stress. Control plants had significantly higher leaf damage which also coupled with increased level of electrolytes and lipid peroxidation under heat stress. Conversely, these effects were lower in P. resedanum-associated plants. The endophyte-inoculated plants had higher nutrients contents as compared to control plants. P. resedanum-infestation also modulated amino acid metabolism. Proline accumulation was significant in endophyte-inoculated plant than control under stress. Flavonoids (daidzin, daidzein and m-glycitin) were synthesized in higher quantities to reduce the negative impacts of heat stress in P. resedanum plants than control. In conclusion, the findings showed an ameliorative effect of P. resedanum-association with pepper plants under heat stress, which can be a useful symbiotic strategy for expanding agriculture production with changing global temperature regimes.