The dynamic of plant-parasitic nematode populations in soil is closely related to soil microorganisms. Fungi from Heterodera zeae cysts were isolated to explore the phenomenon of decline in the H. zeae population in the soil. Phylogenetic study of partial ITS, BenA, CaM, and RPB2 gene sequences, in addition to morphological investigations, was utilized to identify a nematode-destroying fungus. The nematicidal activity of a novel strain GX1 against H. zeae was assessed in vitro and in the greenhouse. Our findings revealed that strain GX1 is a new species of Talaromyces, named Talaromyces cystophila. It has a strong parasitic and lethal effect on H. zeae cysts, with 91.11% parasitism on cysts at 3 days after treatment. The contents of second-stage juveniles (J2s) and eggs inside the cysts were degraded and formed dense vacuoles, and the damaged eggs could not hatch normally. The spore suspension exhibited high nematophagous activity against nematodes, and fermentation filtrate exhibited marked inhibition of egg hatching and nematicidal activities on J2s. The hatching inhibition rates of eggs exposed to 1 x 10(8) CFU/ml spore suspensions or 20% 1-week fermentation filtrate (1-WF) for 15 days were 98.56 and 100%, respectively. The mortality of J2s exposed to 1 x 10(8) CFU/ml spore suspension reached 100% at 24 h; exposure to 50% 2-WF was 98.65 and 100% at 24 and 48 h, respectively. Greenhouse experiments revealed that the spore suspension and fermentation broth considerably decreased H. zeae reproduction by 56.17 to 78.76%. T. cystophila is a potential biocontrol strain with nematophagous and nematicidal activity that deserves attention and application.

This study was conducted during 2021-2022 to detect and determine distribution and population of cyst nematodes, Heterodera spp. (Tylenchida: Heteroderidae) in black cabbage Brassica oleracea var. acephala L. (Brassicales: Brassicaceae) production areas of the Eastern Black Sea Region of T & uuml;rkiye. For it, a total of 77 samples were taken from 53 districts belonging to the Artvin, Giresun, Ordu, Rize, and Trabzon provinces in the region. Soil samples were taken from around the root of the kale plants. Nematodes were extracted by using the centrifugal flotation technique. The nematodes were identified using morphological features and molecular analysis based on Polymerase Chain Reaction (PCR) method. For molecular analysis, the ribosomal DNA region including the gene region of 28S ribosomal RNA (rRNA) (ITS1, 5.8S, ITS2) was amplified using primer sets TW81/AB28. Additionally, a species-specific primer set (Car-F/Car-R) covering the Cytochrome Oxidase I (cox1) region of mitochondrial DNA (mtDNA) was used. As a result of the analysis, cyst nematodes Heterodera cruciferae Franklin, 1945 , Heterodera carotae Jones, 1950 and Heterodera fici Kirjanova, 1954 species were identified in the kale production areas in the region. Heterodera carotae is the first record of the cyst nematode species in T & uuml;rkiye. Heterodera cruciferae, H. carotae, and H. fici were detected from the total collected soil samples at 16.9%, 3.9%, and 1.3% relative frequency, respectively. Among all, Giresun was the most infected province with 35.3% infection rate, followed by Trabzon with 26.3%, Ordu with 21.1% and Rize with 13.3%.