Viroids of the genus Pospiviroid are able to induce diseases in a wide range of host plants including important crop species. Although occasional disease outbreaks of Potato spindle tuber viroid (PSTVd) and closely related pospiviroids have been reported in potato and tomato, recent studies found an increase in number of latent infections in ornamental solanaceous species. In order to verify the presence of PSTVd and other pospiviroids in Croatia, a survey was conducted between 2009 and 2012. A total of 182 samples belonging to five ornamental species and two solanaceous crops were analyzed. Eight plants belonging to two different species (Solanum jasminodes and Lycianthes rantonnetii) were found infected by PSTVd and, in addition, one S. jasminoides plant infected by Tomato apical stunt viroid (TASVd). Viroid infection was confirmed by mechanical inoculation on tomato plants to observe symptom expression. Molecular characterization of the isolates was done and complete viroid sequences were submitted to the GenBank. This is the first evidence of the presence of PSTVd and TASVd and their variability in Croatia.

Potato is a globally important non-cereal crop in which infection with potato spindle tuber viroid (PSTVd) can cause stunted growth and significantly reduce tuber yield. We previously showed that PSTVd induces accumulation of the plant hormone jasmonic acid (JA) and alters antioxidant responses in potato plants. To clarify the role of JA in response to PSTVd, we analyzed disease development in transgenic JA-deficient opr3 and JA-insensitive coi1 lines compared to the wild-type. Transcriptomic analysis using RNA-Seq revealed that most genotype-specific differentially expressed genes (DEGs) in all comparisons were enriched in plant hormone signal transduction, plant-pathogen interaction, and MAPK signaling pathways, although the number of DEGs varied. These differences were confirmed by independent data from RT-qPCR, hormone, and hydrogen peroxide (H₂O₂) analyses. After PSTVd infection, opr3 plants showed enhanced JA signaling and increased abscisic acid (ABA) and auxin (AUX) content. In contrast, coi1 plants showed reduced ABA, AUX, and salicylic acid content. Both opr3 and coi1 plants showed reduced JA and H₂O₂ content and lower expression of defense-related genes, resulting in milder symptoms but increased viroid accumulation. In addition, treatment with methyl jasmonate alleviated symptoms in infected wild-type plants. Together, these results indicate a modulatory role for JA and JA signaling in basal immune responses and symptom development in the potato-PSTVd interaction.

Posljednjih nekoliko godina, virusne bolesti tikvica i tikvi u Hrvatskoj javljaju se u sve jačem intenzitetu i uzrokuju gubitke u proizvodnji. Cilj rada bio je utvrditi prisutnost virusa mozaika krastavca (CMV), virusa žutog mozaika tikvice (ZYMV) i virusa mozaika lubenice (WMV) na tim kulturama. Tijekom 2019. godine, na 18 lokacija (polja na otvorenom) u šest županija provedeni su vizualni pregledi te je ukupno sakupljeno 43 simptomatičnih uzorka tikvice i 39 uzoraka tikve u svrhu laboratorijske analize na prisutnost CMV, ZYMV i WMV. Analiza je provedena imunoenzimskim testom DAS-ELISA korištenjem komercijalnih seroloških kompleta. Od 82 uzorka, CMV je potvrđen u njih 55 (67%), ZYMV u 50 (61%), a WMV u 10 uzoraka (12%). Pojedinačna zaraza s jednim od tri istraživana virusa utvrđena je u ukupno 38 uzoraka (46%). Mješovite zaraze s dva virusa zabilježene su u 36 uzoraka (44%): 32 uzorka (39%) s kombinacijom CMV + ZYMV te četiri uzorka (5%) s kombinacijom CMV + WMV. Mješovita zaraza sa sva tri virusa (CMV + ZYMV + WMV) utvrđena je u dva uzorka. U šest uzoraka (7%) nije zabilježen niti jedan od tri istraživana virusa. U osam nasada utvrđena je prisutnost jednog virusa, u devet nasada prisutnost dva virusa, a u jednom od 18 pregledanih nasada utvrđena je prisutnost sva tri istraživana virusa.

Root-knot nematodes (RKNs) of the genus Meloidogyne spp., are among the most economically important groups of plant-parasitic nematodes worldwide, causing significant economic losses through yield reduction across a wide range of crops. In Croatia, although the presence of Meloidogyne spp. has been documented for decades, data at the species level was limited. As accurate identification is crucial for implementation of effective management strategies, we attempted to fill this gap. This study presents the results of a national survey of RKNs affecting potato crops as well as an early warning programme targeting vegetable crops, conducted across Croatia between 2022 and 2024. Nematodes were identified using morphological analyses (female perineal patterns and second-stage juveniles) and molecular methods (PCR with group-specific and species-specific primers, as well as DNA sequencing). Meloidogyne spp. were detected in 61 out of 210 samples, corresponding to an infestation rate of 29%. Four species were identified: M. incognita, M. hapla, M. arenaria, and M. javanica. Notably, M. incognita and M. javanica are reported here for the first time in Croatia. These results provide updated insights into the distribution and identity of RKNs in Croatia, thereby establishing a foundation for the implementation of sustainable management strategies.