Kiwifruit (Actinidia deliciosa) is a crop of high economic importance, with Italy ranking as the third-largest global producer. In recent years, Italian kiwifruit orchards have been severely affected by kiwifruit vine decline syndrome (KVDS), a disease characterized by root rot, leaf chlorosis, phylloptosis, and progressive vine decline. To investigate the potential involvement of soilborne oomycetes in KVDS, a survey of symptomatic plants was conducted in Latina Province (Lazio, Italy). Two oomycete species, Pythium dissotocum and Globisporangium sylvaticum, were consistently isolated from diseased roots. Pathogenicity tests on A. deliciosa cultivar Hayward revealed that both species induced severe symptoms under waterlogged conditions, whereas only mild or no symptoms developed under regular irrigation. These results provide the first evidence that P. dissotocum and G. sylvaticum can contribute to KVDS symptomatology in Italy. These findings offer new insight into KVDS dynamics, highlighting the variability of pathogenic species involved. Similar oomycetes with comparable pathogenic traits have been previously reported, reinforcing the multifactorial nature of the disease and the influence of environmental stress, particularly waterlogging, on its expression.
Peacock eye disease, caused by the hemibiotrophic fungus Venturia oleaginea, is the most destructive and widespread disease of olive in Israel. In a national project to develop an environmentally friendly peacock eye disease-management protocol for the local olive industry, it was found that one or a few fungicide applications in the autumn effectively suppressed disease development in the concurrent season. Since fungicide application timing should be based on environmental criteria rather than a predefined seasonal schedule, the goal of the current study was to define criteria for predicting the occurrence of infection events. It was observed that peacock eye severity and leaf abscission were significantly lower in tree canopies facing sunrise between October and December, the presumed period of autumn infection events, than in those facing other directions. Accordingly, we used the uneven distribution of the disease with varying canopy orientation as a tool to ascertain the relative importance of the respective weather variables to infection. Duration of leaf wetness caused by dew was the most salient ambient condition showing consistent, albeit short-duration (≤2 h) differences between canopy sides. In vitro experiments were conducted to examine how this small difference leads to marked differences in disease severity and to define conditions promoting conidial germination, germ tube elongation, and sporulation. Based on these and our previous results, we defined criteria for predicting the occurrence of infection events in highly susceptible olive cultivars: a rain event of 15 mm or more (for 1 day or accumulated over several consecutive days), wetness duration of at least 6 h, and temperatures between 12 and 18°C during the wetting period. These criteria could serve to time fungicide applications.
In recent years, widespread epidemics of eggplant stem blight were observed in eggplant fields of Tongdao County, Hunan Province, China (26°24′ N, 109°54′ E), with a mean disease incidence of approximately 60%. Infected plants initially develop water-soaked brown lesions on stems, which gradually expand to girdle the stems, ultimately resulting in plant wilting. Tissue pieces from lesion margins were surface-sterilized 90 s in 2% NaClO, 30 s in 75% ethanol, then rinsed three times with sterile distilled water. Tissues were dried with sterile filter paper, plated on PDA, and incubated at 28℃ for 4 days in the dark. A fungus was consistently recovered from diseased samples, and six isolates exhibiting identical morphological characteristics were obtained. Hyphal tips of these isolates were transferred onto fresh PDA plates and incubated for 30 days to produce spores. Single spore isolates were then obtained by dilution plating. After 7 day incubation on PDA, the colony produced sparse white mycelium that expanded outward, forming concentric rings. When the fungus was cultured on sterilized eggplant stems, black stromata were formed. Pycnidia were borne on the surface of stromata, and numerous β-conidia and a small number of α-conidia were observed. The unicellular α-conidia are fusiform to elliptical with rounded apices and bases, usually containing two oil globules, and measure 5.52 to 12.48 × 1.73 to 3.32 µm (n = 50). The filiform and aseptate β-conidia are curved at the apex, with dimensions of 20.62 to 34.48 × 1.06 to 1.74 µm (n = 50). Based on the above morphological characteristics, the fungus was preliminarily identified as Diaporthe (Phukhamsakda et al., 2025). Two representative isolates (TDQZ01 and TDQZ02) were subjected to molecular identification based on ITS, TEF1, HIS3, CAL and TUB2 sequences amplified with primers ITS4/ITS5(White et al., 1990), EF1-728F/EF1-986R (Carbone and Kohn, 1999), CYLH3F/H3-1b (Crous et al., 2006; Glass and Donaldson, 1995), CAL228F/CAL737R (Carbone and Kohn, 1999), and T1/Bt-2b (Glass and Donaldson, 1995) respectively. Sequences were deposited in GenBank under accession numbers ITS (PZ159274,PZ798684), TEF1 (PZ278281, PZ822606), HIS3 (PZ278283, PZ822605), CAL (PZ278282, PZ815256) and TUB2 (PZ278284, PZ815257), and showed >99%, >94%, >99%, >98% and >99% sequence identity, respectively, to Diaporthe melonis strain CBS 435.87 (accession numbers KC343141, KC343867, KC344109, KC343383, KC343625) based on BLASTn analysis. Furthermore, Maximum likelihood analyses based on concatenated multilocus sequences placed isolates TDQZ01 and TDQZ02 within the clade of Diaporthe melonis. Eggplants were grown at 28 °C with a 12 h light/12 h dark photoperiod to the six true leaf stage for inoculation assays. Mycelial discs (6 mm in diameter) of TDQZ01 and TDQZ02 were inoculated onto the stem wounding eggplant (5*5 mm), whereas PDA discs served as the control. All treated stems were wrapped with parafilm for moisturized incubation. Six days after inoculation, dark-brown lesions formed on the stems inoculated with the pathogen. The inoculated plants gradually wilted and died by 15 days after inoculation, followed by the formation of black stromata on stem tissues, whereas PDA controls remained healthy. D. melonis was reisolated only from symptomatic tissues and confirmed by morphology and sequencing, fulfilling Koch’s postulates. Collectively, these results demonstrate that Diaporthe melonis is the causal pathogen of eggplant stem blight. To our knowledge, this is the first report of eggplant stem blight caused by Diaporthe melonis in China. The present findings provide references for breeding resistant cultivars and integrated management of eggplant stem blight.
Groundnut (Arachis hypogaea L.) is an important oilseed crop cultivated on approximately 5.8 million hectares, producing 10.4 million tonnes with an average productivity of 1.8 tonnes per hectare in India (GOI, Department of Agriculture, Cooperation and Farmers Welfare, 2025). Late leaf spot (LLS) of groundnut has been reported in India for several decades based on symptomatology and morphological characteristics. The causal agent has undergone several taxonomic revisions and has been successively classified under the genera Mycosphaerella, Cercosporidium/Cercospora, and Phaeoisariopsis, in earlier literature (Jenkins, 1938; McDonald et al., 1985 and Subrahmanyam et al., 1995) before being reclassified as Nothopassalora personata based on molecular phylogenetic evidence. Therefore, molecular confirmation, together with morphological characterization, has become essential for accurate identification and consistent diagnosis of the pathogen across groundnut-growing regions. During a July 2024 survey of a groundnut field at ICRISAT (17.5115°N, 78.2751°E), Patancheru, Hyderabad, Telangana, India, severe small, circular to irregular dark brown to black spots were observed mainly on the abaxial surfaces of older leaves, occasionally with a yellow halo on the TMV-2 variety, consistent with late leaf spot symptoms. The severity of the disease was assessed using the scale developed by Subramanyam et al. (1995) and reached up to 60%. Severely infected leaves turned yellow, desiccated, and dropped prematurely, resulting in complete defoliation. Similar late leaf spot symptoms have been reported from Iran (Bakhshi and Zare,2020) and Argentina (Monguillot et al.,2023), where the pathogen was confirmed through molecular characterization. The detached leaf assay was performed to confirm the pathogenicity (Deshmukh et al., 2018). Conidia were collected freshly from field-infected leaves using ROCKYVAC™ oil-free piston vacuum pump (Tarsons Products Ltd., Kolkata, India). A suspension of 3 x 107 spores/ml was prepared by suspending the spores in distilled water and used for inoculation on the leaf surface, and placed in a growth chamber at 25 ± 1℃ for 30 days. The leaves developed symptoms at 15-20 days after inoculation and pathogen was confirmed based on symptomology and microscopic observation of conidia. Conidia were elongate, cylindrical to slightly obclavate (club-shaped), hyaline with 3-7 septa, with 43.8-47.5 X 4.8-5.6 µm in size. The molecular confirmation of the pathogen was performed using the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA and the partial RNA polymerase II second largest subunit (rpb2) gene. Total DNA was extracted from conidia collected from fresh, naturally infected field-grown groundnut leaves using the DNeasy Plant Mini Kit (QIAGEN Hilden, Germany) according to the manufacturer's instructions. PCR amplification was performed in a thermocycler (Eppendorf-Vapo.Protect) using ITS1 and ITS4 primers for amplification of the ITS region and fRPB2-5F and fRPB2-7cR primers (IDT, Singapore) for amplification of the partial rpb2 region and the obtained amplicons were purified using PCR clean-up kit (Duren, Germany) as per the manufacturer’s protocol and sequenced by sanger’s dideoxy chain-termination method. The ITS and rpb2 sequences were edited in BioEdit (https://bioedit.software.informer.com/7.2/) and aligned in CLUSTALW, and the phylogenetic tree of both regions was constructed in MEGA 11 software (Tamura et al., 2021) by using the neighbor-joining method. The sequence was deposited in NCBI (rpb2 accession number PZ495589) and (ITS accession number PZ809112). Based on the symptoms, morphology, pathogenicity test and rpb2 gene sequence, the causal organism was identified as Nothopassalora personata, the pathogen causing late leaf spot of groundnut. To our knowledge, this is the first report of molecular confirmation of Nothopassalora personata causing late leaf spot of groundnut in India. These molecular baseline data will support future late leaf spot resistance screening and fungicide efficacy trials in Indian groundnut-growing regions.
