Comparative evaluation of physiological and biochemical changes in black pepper plants infected by Colletotrichum siamense in response to Trichoderma viride and T. harzianum application

Abstract

Black pepper (Piper nigrum L.) holds a prominent position as a globally renowned spice. Pepper vines are susceptible to various diseases, among which anthracnose stands out as a highly detrimental disease capable of severely affecting both foliage and berries. The current study was carried out to find out the effectiveness of Trichoderma viride and T. harzianum to manage the anthracnose disease of black pepper and to assess the plant innate defense response to these biocontrol agents application. Results demonstrated that foliar application of T. viride and T. harzianum, either individually or in combination, resulted in a significant reduction of disease incidence by 59.3, 67.2, and 69.8% respectively, compared to untreated infected plants. Additionally, disease severity was lowered to 71.1, 75.6, and 77.8% respectively in the treated groups. Simultaneously, these treatments exhibited a substantial promotion of black pepper growth, as indicated by increased leaf area index, number of leaves, shoot length and root length compared to the control. Physiological and biochemical analyses revealed a notable increase in chlorophyll (Chl a, Chl b, Total chl) and flavonoid content, coupled with reductions in hydrogen peroxide (H2O2), and Malondialdehyde concentrations at 48 and 96 h after treatment. Furthermore, evaluation of the superoxide dismutase (SOD) revealed a significant increase in SOD enzymatic activity following the application of the fungi, whether applied individually or in combination. Consequently, it was inferred that both T. viride and T. harzianum effectively protected black pepper plants from anthracnose by suppressing disease incidence, enhancing chlorophyll content, improving overall plant health, and inducing the innate defense system. These findings highlight the multifaceted advantages offered by T. viride and T. harzianum in terms of plant protection and growth promotion.