Insecticidal property of Ocimum essential oil embedded polylactic acid packaging films for control of Sitophilus oryzae and Callosobruchus chinensis.

Naturally derived essential oils (EOs) from Ocimum basilicum (OB) and Ocimum gratissimum (OG) were incorporated in polylactic acid (PLA) matrix with concentration of 2.5 % and 5 % respectively by solvent casting method, with an aim to develop insecticidal polymer pouches (insect proof polymer pouches). The major components following GC-MS analysis revealed the presence of EOs as estragole (69.998 %) in OB and thymol (29.843 %) in OG. The developed films with EOs showed remarkable insecticidal activity with 100 % and 80 % mortality rate for OB and OG respectively at 2.5 % concentration against rice weevil (Sitophilus oryzae). While, both OB and OG EOs observed 100 % mortality against pulse beetle (Callosobruchus chinensis) after 96 h exposure in presence of grain conditions and the insecticidal efficacy was equivalent to the commercial hermetic bags (CSB). The physical property of film showed increase in the film thickness in EO-PLA films whereas the mechanical properties of EO-PLA films matrix have increased the polymer flexibility with decreasing tensile strength (TS) and Youngs modulus (EM) as TS OB 5 %, OG 5 % - 15.64 MPa, 17.66 MPa respectively. While, water vapour transmission rate (WVTR) was reduced to 0.015 g/m2.hr, optical characteristics showed slight significant change in colour and FTIR spectra exhibited a change in -OH stretching compared to blank PLA matrix. The surface morphology of the blank and EO embedded PLA films visualized by SEM depicted a complete homogenization of essential oils in the PLA matrix.

Molecular insights of fungal endophyte co-inoculation with Trichoderma viride for the augmentation of forskolin biosynthesis in Coleus forskohlii.

To understand the compatibility of three native endophytic fungi Phialemoniopsis cornearis (SF1), Macrophomina pseudophaseolina (SF2) and Fusarium redolens (RF1) with Trichoderma viride (TV1) on Coleus forskohlii in enhancing plant growth and forskolin content, field experiments were conducted. Co-inoculation of RF1+TV1 showed significant improvement in plant growth (52%), root biomass (67%), and in-planta forskolin content (94%), followed by treatment with SF2+TV1 and SF1+TV1. qRT-PCR was carried out to quantify expression of five key forskolin biosynthetic pathway genes (CfTPS2, CfTPS3, CfTPS4, CfCYP76AH15, and CfACT1-8) in RF1+TV1 treated C. forskohlii plants. Elevated expression of CfTPS2, CfTPS4, CfCYP76AH15 and CfACT1-8 genes was observed with RF1+TV1 combination as compared to uninoculated C. forskohlii plants. Besides, RF1+TV1 treatment considerably reduced the severity of nematode infection of C. forskohlii plants under field conditions. Thus, congruent properties of F. redolens (RF1) were witnessed with co-inoculation of T. viride (TV1) under field conditions which resulted in enhanced forskolin content, root biomass, and reduced nematode infections in C. forskohlii. Overall, this approach could be an economical and sustainable step towards cultivation of commercially important medicinal plants.

Development of low-cost plant probiotic formulations of functional endophytes for sustainable cultivation of Coleus forskohlii.

Deployment of plant endophytes at field level is reported to make an impact on agricultural crop productivity; development and deployment of suitable crop specific plant probiotics in a suitable delivery matrix is a value-added task. In our study, we attempted to develop bioformulations of native, fungal endophytes of Coleus forskohlii to improve plant yield using two different carrier-based materials (talc and wheat bran). Initially, fungal endophytes (RF1, SF1, and SF2) were grown on sterilized wheat bran under solid state condition and their growth kinetics and pattern were analyzed by ergosterol content and scanning electron microscope, respectively. 10-day-grown fungal endophytic cultures were used for the development of two types of formulations (wheat bran and talc-based formulations) and tested for their efficacy on host plant, C. forskohlii under field conditions. Interestingly, application of wheat bran-based endophytic formulations significantly (p < 0.01) enhanced plant height (12-29%), number of branches (51-63%), root biomass (26-33%), photosynthetic pigments (32-101%), and forskolin content (35-56%) compared to talc-based formulations under field conditions. Shelf life of endophytes (RF1, SF1, and SF2) in both formulations revealed spore viability in wheat bran-based formulations for 6 months storage period as compared to talc-based formulations. Overall, the present investigation envisages developing plant probiotic bioformulations of functional endophytes of C. forskohlii to enhance root biomass and in planta forskolin content.