Synergistic action of Trichoderma koningiopsis and T. asperellum mitigates salt stress in paddy

Abstract

Intensive cultivation increases the salinity and alkalinity of soil leading to its degradation. Such soil lead to abiotic stress conditions in plants causing ROS-mediated cellular damage. Microbes constitute an important group of bio-stimulants, which are promising alternatives to reduce ROS-mediated abiotic stresses and improve plant growth. In the present study synergistic activity of stress-tolerant Trichoderma koningiopsis NBRI-PR5 (MTCC 25372) and T. asperellum NBRI-K14 (MTCC 25373) (TrichoMix) was assessed in paddy crop under salt stress conditions. Improved soil microbial biomass carbon (MBC), total organic carbon (TOC), and available nutrients N/P/K by 2-3 folds was observed in the pot experiment using the TrichoMix. It restored the heterogeneous microbial population of the paddy rhizosphere during salt stress and modulated the soil enzyme activities. The anatomical distortions in rice roots due to salt stress were stabilized in presence of the TrichoMix. Different stress marker genes (OsMAPK5, OsAPX, OsGST, OsUSP, OsBADH, OsLYSO, OsNRAMP6, and OsBz8) were differentially modulated by the TrichoMix in presence of salt stress as compared to the control. The TrichoMix increased the yield by 10% in marginally stressed fields; however, it enhanced the yield by approximately 60% when used with the 50% recommended dose of NPK. In the integrated treatment, Fe and Zn were fortified by approximately 40% and 29% respectively in the grains. From the present study, it was concluded that the TrichoMix stimulated the rice plants to accumulate osmoprotectants, improved the anatomical features, modulated the plant defense system, and improved the grain yield and quality. Therefore, the NBRI-PR5 and NBRI-K14 mixture may be used as a bio-stimulant to increase productivity in the rapidly deteriorating soil and reduce the NPK inputs.

Supplementary information: The online version contains supplementary material available at 10.1007/s12298-022-01192-6.

Keywords: Biostimulants; Paddy; Salt tolerance; Synergistic; T. asperellum; T. koningiopsis; TrichoMix.

Fig. 1

Effect of TrichoMix (T. koningiopsis and T. asperellum) on plant growth under salt stress conditions. A Without salt control set, B set with salt treatment (100 mM), c sodic field trial, D yield and mineral content of the rice grain obtained from field trial. Cont: Control, S + Cont: Salt + Control, S + TrichoMix: Salt + TrichoMix, FP: Farmer’s practice (NPK), TrichoMix: Trichoderma mixture

Fig. 2

Biochemical status of rice plants treated with T.koningiopsis and T. asperellum under salt stress conditions. A Carotenoid, B total chlorophyll, C proline, D TSS (Total soluble sugar), E GB (Glycine betaine), F LPX (Lipid peroxidation). Values are means of 3 replicates. Different letters indicate significance among the treatments (DMRT, P value ≤ 0.05)

Fig. 3

Antioxidant enzymes status of rice plants after 30 days of salt stress treatment. SOD: Superoxide dismutase, APX: Ascorbate peroxidase, PPO: Phenol peroxidase, CAT: Catalase, GPX: Guaiacol peroxidase All the values are means of 3 replicates with S.E. bars. Different letters indicate significance among the treatments (DMRT, P value ≤ 0.05)

Fig. 4

Differential expression of stress responsive genes in rice treated with TrichoMix grown under salt stress conditions in net house. The graphs show fold—change values in treatment as compared to the control. All the values are means of 3 replicates with S.E. bars. Different letters indicate significance among the treatments (DMRT, P value ≤ 0.05)

Fig.5

Effect of TrichoMix on enzyme activities of rhizosphere soil of paddy grown under salt stress conditions. A DHA (dehydrogenase), B alkaline phosphatase, C protease D β-glucosidase, E fluorescein diacetate hydrolysis (FDA) and F urease, G Aryl sulphatase

Fig. 6

Transverse section of rice roots treated with TrichoMix in salt stress conditions showing differences in the lignification of exodermis and endodermis. A, B Show details of the cellular structure of the exodermis region in control (A) and stress (B) condition. C, D The panels show the details of the steler region in control (C) and stress (D) condition. The figures are enlarged portion of the pictures shown in the inset having a scale bar of 200 μm. EVOS digital inverted microscope was used to capture the root images of rice at 20X magnification. Ep(epidermis), Ex (exodermis), Sc (sclerenchyma layer), Me (Mesodermis) Ae (aerenchyma lacunae), En (Endodermis), Pe (Pericycle), Mx (Metaxylem), Mx (Central meta xylem), Px (Protophloem), Pcc (Pith companion cells), Pc (Passage cell), Ph (Phloem complex)

Fig. 7

A model summarizing the physiological, molecular and anatomical changes in the salt stressed and Salt + TrichoMix treated plants