Root-knot nematodes are among the most economically important plant-parasitic nematodes affecting carrot production worldwide. Identification and utilization of resistant germplasm are important components of sustainable nematode management. This study evaluated the resistance and tolerance responses of 26 carrot genotypes to Meloidogyne javanica and characterized selected physiological responses following infection. Genotypes were screened under controlled conditions based on nematode reproduction, and plant growth traits were also evaluated. Physiological traits, including chlorophyll and carotenoid contents, relative water content (RWC), and membrane stability index (MSI), were assessed in the resistant genotype TN-99-129 and the susceptible genotype TN-99-62 at 35 days post inoculation. TN-99-129 was the only genotype consistently classified as resistant across the classification systems used, whereas several genotypes showed contrasting classifications depending on the criteria applied. Nematode infection had variable effects on plant growth among genotypes. Gall number was negatively correlated with changes in shoot fresh and dry weight, whereas nematode reproduction was not significantly correlated with shoot biomass changes. Infection significantly reduced chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid contents in TN-99-129, while RWC increased following infection. MSI also increased significantly in TN-99-62. These findings demonstrate substantial genotype-dependent variation in carrot responses to M. javanica and highlight the distinction between resistance and tolerance. TN-99-129 represents a promising source of resistance for carrot breeding, while the physiological responses provide complementary information for characterizing host responses to nematode infection.
Fusarium oxysporum Schltdl. is an economically important soil-borne fungal plant pathogen responsible for severe yield losses in greenhouse crops worldwide. The pathogen causes yellowing, wilting, stunting, crown and root rot in a wide range of economically important vegetable crops. In the present study, a total of 72 isolates of F. oxysporum were collected from greenhouse crops, including cucumber, tomato, eggplant, and strawberry, in southern Iran during 2017–2021. Based on primary pathogenicity assays, 24 representative isolates were selected for host-specificity and cross-pathogenicity analyses via artificial inoculation under greenhouse conditions. The results confirmed the presence of four formae speciales, including F. oxysporum f. sp. fragariae, f. sp. melongenae, f. sp. radicis-cucumerinum, and f. sp. radicis-lycopersici. Sixteen isolates were pathogenic only to their original host, whereas some isolates exhibited cross-pathogenicity on alternative hosts. Cross-host infections were observed among isolates obtained from strawberry, cucumber, tomato, and eggplant, particularly on bell pepper, tomato, cucumber, and eggplant hosts. Disease symptoms included yellowing, wilting, stunting, crown rot, and root rot. The findings demonstrate the potential for host-range among greenhouse-associated isolates of F. oxysporum and highlight potential risks associated with crop rotation and mixed-cultivation systems. To the best of our knowledge, several of the cross-pathogenic interactions observed in this study have not been previously reported among F. oxysporum isolates associated with greenhouse crops in Iran. These findings improve our understanding of host range diversity, the selection of proper crop rotation, and may contribute to integrated disease management strategies for greenhouse production systems.
In the humid tropics, soil waterlogging catalyzes a synergistic interaction between root hypoxia and the soil-borne Ralstonia solanacearum species complex (RSSC)–Meloidogyne spp. pathosystem, whose impact on tomato genetic resistance remains poorly documented. This study evaluated the phenotypic stability and cross-tolerance of seven tomato hybrids, including Chistera F1 and the regional standard Cobra 26, under this dual constraint. A single-season field trial conducted in Man (Côte d’Ivoire) during the rainy season utilized a natural topographic gradient to modulate the Soil Waterlogging Index (SWI: 0–3). Epidemic incidence and mortality were analyzed using generalized linear models with a binomial distribution. A Multifactorial Phytopathological Severity Index (MPSI) was developed to integrate bacterial wilt severity assessed by the area under the disease progress curve, root gall index, fruit fungal incidence, and economic damage. Severe soil waterlogging (persistent flooding > 24 h) resulted in a marked breakdown of resistance in intermediate genotypes and caused 100
