Comparative biological activity of abamectin formulations on root-knot nematodes (Meloidogyne spp.) infecting cucumber plants: in vivo and in vitro.

The root-knot nematodes (Meloidogyne spp.) are considered one of the most destructive diseases in the world. In Egypt, farmers primarily rely on chemical nematicides, which have become costly to control. Currently, abamectin is a bio-based pesticide used as an alternative tool against Meloidogyne spp. on cucumber plants (Cucumis sativus L.). During the current research, four tested abamectin formulations were DIVA (1.8% EW), RIOMECTIN (5% ME), AGRIMEC GOLD (8.4% SC) and ZORO (3.6% EC) compared with two reference nematicides namely, CROP NEMA (5% CS) and TERVIGO (2% SC). The main results showed that, in vitro study elucidated that the most effective formulations of abamectin as a larvicidal were EW with LC50 value of 21.66 µg ml-1. However, in the egg hatching test, the formulations of abamectin SC (2%) and EW were the most effective in reducing egg hatching, with LC50 values of 12.83 and 13.57 µg ml-1. The calculated relative potency values showed diversity depending on the two referenced nematicides. On the other hand, in vivo study, the results indicated that, all tested formulations of abamectin recorded general mean reductions in root galls (23.05-75.23%), egg masses (14.46-65.63%). Moreover, the total population density declined by 39.24-87.08%. Furthermore, the influence of abamectin formulations, in the presence of root-knot nematodes, on the growth of cucumber plants parameters, such as root dry weight, root length, root radius, root surface area, shoot dry weight and shoot height, as well as the content of macro-elements (N, P and K) exhibited varying levels of response.

Trichoderma pubescens Elicit Induced Systemic Resistance in Tomato Challenged by Rhizoctonia solani.

Rhizoctonia solani causes severe diseases in many plant species, particularly root rot in tomato plants. For the first time, Trichoderma pubescens effectively controls R. solani in vitro and in vivo. R. solani strain R11 was identified using the ITS region (OP456527); meanwhile, T. pubescens strain Tp21 was characterized by the ITS region (OP456528) and two genes (tef-1 and rpb2). The antagonistic dual culture method revealed that T. pubescens had a high activity of 76.93% in vitro. A substantial increase in root length, plant height, shoot fresh and dry, and root fresh and dry weight was indicated after applying T. pubescens to tomato plants in vivo. Additionally, it significantly increased the chlorophyll content and total phenolic compounds. The treatment with T. pubescens exhibited a low disease index (DI, 16.00%) without significant differences with Uniform® fungicide at a concentration of 1 ppm (14.67%), while the R. solani-infected plants showed a DI of 78.67%. At 15 days after inoculation, promising increases in the relative expression levels of three defense-related genes (PAL, CHS, and HQT) were observed in all T. pubescens treated plants compared with the non-treated plants. Plants treated with T. pubescens alone showed the highest expression value, with relative transcriptional levels of PAL, CHS, and HQT that were 2.72-, 4.44-, and 3.72-fold higher in comparison with control plants, respectively. The two treatments of T. pubescens exhibited increasing antioxidant enzyme production (POX, SOD, PPO, and CAT), while high MDA and H2O2 levels were observed in the infected plants. The HPLC results of the leaf extract showed a fluctuation in polyphenolic compound content. T. pubescens application alone or for treating plant pathogen infection showed elevated phenolic acids such as chlorogenic and coumaric acids. Therefore, the ability of T. pubescens to inhibit the growth of R. solani, enhance the development of tomato plants, and induce systemic resistance supports the application of T. pubescens as a potential bioagent for managing root rot disease and productivity increase of crops.