Salicylic acid (SA) induces the mechanism of the plant defence and plays a role in plant -pathogen interactions. Following the nematode infection, effects of SA treatment on plant weights and the expression of pathogen related gene have not been fully understood. The present study was aimed to determine the effects of SA treatment on the expression Pathogenesis related 1 gene (PR1 gene) and alteration on plant parameters in tomatoes (Solanum lycopersicum). Plant seedlings were dripped within the SA solution. The expression of PR1 gene achieved using RT-PCR at 1, 3, 7, 14, 21-days post infection (dpi) with Meloidogyne incognita. Upregulation of PR1 gene was determined in early (1 dpi) and late (21 dpi). SA treatment and nematode infection altered plant parameters. SA treatment increased the plant defence mechanisms in tomato against Meloidogyne incognita.

Background: Entomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae) and their symbiotic bacteria are pathogenic for a wide range of insect pests and have been used successfully as a biological control agent. Although EPNs are well studied against many agricultural insect pests, the efficacy of their symbiotic bacteria still remains unclear for many insect pests of agricultural importance. In the present study, the virulence of native EPN isolates and their cell-free supernatants of symbiotic bacteria were tested against the 3rd and 4th larval instars of Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae) under laboratory conditions (25 ± 1 °C and R.H. 60%). Results: The 4th instar larvae were more susceptible to infective juveniles (IJs) and mortalities over (95%) were achieved by all tested EPN isolates at the concentration of 100 IJs/cm² after 72 hrs of exposure. The cell-free supernatants were more effective against the 3rd instar larvae and the highest mortalities were recorded as 42 and 60% in the contact and leaf disc bioassays, respectively. Conclusion: The results indicated that the cell-free supernatants can be an ideal application for young larval stages of A. segetum. However, further studies are required to test the effectiveness of both EPNs and the cell-free supernatants of their symbiotic bacteria in field conditions.

Several nematode species can be found in different densities in almost any soil ecosystem, and their diversity in those ecosystems depends on numerous reasons, such as climatic conditions and host presence. Cereals are one of the main hosts of plant-parasitic nematodes (PPN), chiefly root-lesion nematodes (RLN, Pratylenchus spp.) and cereal cyst nematodes (CCN, Heterodera spp.). These nematodes are known as major parasites of the cereal crops; however, agricultural areas accommodate various nematodes showing biological variation. The diversity of parasitic nematodes on cereals in the Sakarya provinces of Türkiye, where cereals are intensively grown and located in the middle of two climatic zones, has not been well studied. Therefore, in this study, we aimed to determine the diversity, identification, and molecular phylogeny of PPNs in wheat-growing ecosystems in the Hendek, Pamukova, Geyve, Akyazı, and Central districts of Sakarya. The diversity of PPNs was calculated using the Shannon diversity index. Thirteen PPN genera were detected in 92% of soil samples. Heterodera filipjevi was identified in 24% of the soil samples using morphological, morphometrical, and molecular tools. In the morphological and molecular analyses, intraspecific polymorphism was observed in H. filipjevi populations. The result indicated that the high infestation rate of H. filipjevi was recorded from Geyve and Pamukova, followed by Hendek and Akyazı; however, a low infestation rate was detected in the Central district. The moderate value of the Shannon index of migratory nematode species was obtained in wheat fields as 2.31, whereas the value of evenness was 0.93, implying moderate diversity and high evenness of nematodes. This study is the first comprehensive report on H. filipjevi from wheat cropping areas in the Sakarya province. Intensified cereal cropping systems with/without non-cereal rotations increased the risk of plant-parasitic nematodes, especially RLNs and H. filipjevi infection of wheat production areas in the province.

The plant parasitic nematode genus Meloidogyne parasitize almost all flowering crops. Plants respond with a variety of morphological and molecular mechanisms to reduce the effects of pathogens. Proteinase inhibitors (PI), a special group of plant proteins which are small proteins, involve in protective role in the plants attacked by microorganisms. Still, the plant response using PI against nematodes has not been well understood. Therefore, this study was aimed to determine the expression of proteinase inhibitor I (PI-I) gene subsequent the infection of M. incognita, M. javanica, and M. chitwoodi in tomato plants post nematode infections. Molecular methods were used to determine the PI gene expressions at different days post nematode infections in host tissues. Results revealed that the population of M. incognita species reached the highest level of nematode population followed by M. javanica and M. chitwoodi, respectively. All Meloidogyne species induced expression of PI-I gene reached at the utmost level at 3 days post infection (dpi) in host tissues. Relative gene expression level was sharply dropped at 7 dpi, 14 dpi, and 21 dpi in M. incognita induced gene expression in host tissues. Similar results were observed in host tissues after infection of M. javanica and M. chitwoodi. The commonalities of plant response across a diverse Meloidogyne species interaction and the expression of PI gene may be related to plant defense system. Increased level of PI gene expressions in early infection days in host tissues induced by parasitic nematodes may share resemblances to the mechanisms of resistance on biotrophic interactions.

Several pathogens and pests damage tomato plants, and only one and/or more pathogens and pests can coexist in the same plant at the same time. As several numerous pathogens are found in the same plant, the damage to the tomato plants is higher. Pathogens such as nematodes, viruses, viroids, bacteria, and insects adversely affect the growth and development of tomato plants. They may infect roots or upper part of the plant and can cause not only slow down the growth of plants, but also crop losses and their death. Damaging of plant caused by pathogens and pests reduces the market value of plant products. Those pathogens and pests are also called biotic stress agents. The damage, mode of infection, and the mechanism of infection in each tomato plant and pathogens might be different. This situation is crucially important to understand plant pathogen relationship in detail in terms of controlling pests and pathogen. The effect of each pest/pathogen on tomato plants during the cultivation, the type of damage, and new developments and perspectives on morphological and molecular aspects in tomato-pathogen interactions will be discussed in this chapter.