Population Genetic Structure of Meloidogyne javanica Recovered from Different Regions of Iran

Optimizing sustainable control of Meloidogyne javanica in tomato plants through gamma radiation-induced mutants of Trichoderma harzianum and Bacillus velezensis

This study investigates the efficacy of Trichoderma spp. and Bacillus spp., as well as their gamma radiation-induced mutants, as potential biological control agents against Meloidogyne javanica (Mj) in tomato plants. The research encompasses in vitro assays, greenhouse trials, and molecular identification methodologies to comprehensively evaluate the biocontrol potential of these agents. In vitro assessments reveal significant nematicidal activity, with Bacillus spp. demonstrating notable effectiveness in inhibiting nematode egg hatching (16-45%) and inducing second-stage juvenile (J2) mortality (30-46%). Greenhouse trials further confirm the efficacy of mutant isolates, particularly when combined with chitosan, in reducing nematode-induced damage to tomato plants. The combination of mutant isolates with chitosan reduces the reproduction factor (RF) of root-knot nematodes by 94%. By optimizing soil infection conditions with nematodes and modifying the application of the effective compound, the RF of nematodes decreases by 65-76%. Molecular identification identifies B. velezensis and T. harzianum as promising candidates, exhibiting significant nematicidal activity. Overall, the study underscores the potential of combined biocontrol approaches for nematode management in agricultural settings. However, further research is essential to evaluate practical applications and long-term efficacy. These findings contribute to the development of sustainable alternatives to chemical nematicides, with potential implications for agricultural practices and crop protection strategies.

Genetic diversity of the recovered populations of Mesocriconema xenoplax (Nematoda: Criconematidae) from orchards in Fars province, Southern Iran

In this survey, 14 populations of Mesocriconema xenoplax were collected from the rhizosphere of eight fruit and nut trees in Fars province, Southern Iran. The phylogenetic relationships of these populations with other representatives of the species were investigated using sequences of cytochrome c oxidase subunit 1 mitochondrial gene (COI) and D2-D3 expansion fragments of 28S rDNA. Phylogenetic studies indicated a close relationship of the currently sequenced populations with known haplotype groups (HG) in the COI tree and revealed two separate lineages in the 28S rDNA tree. Moreover, the genetic diversity of the populations was analyzed using seven ISSR primers as molecular markers. The estimated genetic diversity among populations regarding associated trees and geographic regions were low values of 3.3% and 5.9%, respectively, indicating high gene flow among the recovered nematode populations. On the other hand, the estimated fixation index (FST) was higher for associated plants than for geographic regions (0.611 vs 0.504) indicating that plant-based population segregation better explains genetic diversity in this species. This work expands our knowledge of the genetic structure of this cosmopolitan species of plant-parasitic nematodes.