Accessions Nos Research Articles

First Report of Colletotrichum chrysophilum Causing Anthracnose on Nance (Byrsonima crassifolia) in Mexico.

Nance fruit [Byrsonima crassifolia (L.) HBK] is a native crop widely distributed in Mexico and South America (Medina-Torres et al. 2018). It has been reported that nance is a good source of active compounds with anti-inflammatory, neuropharmacological and antioxidant effects. In 2022, the annual production of nance fruit in Mexico was of 7,713.13 tons and average yield of 5.64 t/ha with economic value of 51,952.66 million pesos (SIAP, 2022). This production generated significant economic income for the communities at a local, regional, and national level. In January 2023, irregular necrotic spots were observed on leaves and fruit of nance in an orchard of 50 nance trees located in San Sebastián Nopalera (16°54'52.73"N; 97°47'50.35"W), Oaxaca, Mexico. The incidence of the disease ranged from 50 to 60% of the trees. Infected fruit first showed dark-brown lesions with defined borders that coalesced to form large necrotic area. Isolates were purified by single spore isolation method (Choi et al. 1999).Colletotrichum strains were grown in PDA medium and five monoconidial isolates were obtained. A representative sample was selected (CNC-NP3) and deposited in the Culture Collection of Phytopathogenic Fungi of Plant Pathology Laboratory of the CIIDIR-Oaxaca of the Instituto Politécnico Nacional. Colony on PDA was white with sparse aerial mycelium, and the center was dark grey with abundant acervuli. Conidia (n = 100) were hyaline, aseptate, cylindrical with rounded apex, 13.5 to 15.2 × 4.3 to 5.1 μm. Appressoria (n = 20) were terminal or lateral, obovoid to clavate and some with slightly lobed, 9.9 to 11.6 × 5.3 to 6.6 μm. Based on the morphology, the isolate was identified as belonging to the Colletotrichum gloeosporioides species complex (Jayawardena et al. 2016). The representative isolate CNC-NP3 was identified by multilocus phylogenetic analysis using nucleotide sequences of internal transcribed spacer (ITS), actin (ACT), β-tubulin (TUB2), and glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) (Jayawardena et al. 2016). The sequences were deposited in GenBank (accessions nos. OQ861102 (ITS), OQ870548 (ACT), OQ870549 (TUB2), OQ870550 (GAPDH). The phylogenetic analysis was carried out by Maximum likelihood method using concatenated sequences of ITS, ACT, TUB2 and GAPDH genes (Kozlov et al. 2019). The multilocus phylogenetic analysis revelated clearly the isolate CNC-NP3 as Colletotrichum chrysophilum. To confirm pathogenicity of CNC-NP3, 30 healthy fruits were inoculated. Fifteen disinfected nance with wounds and fifteen nance without wounds were inoculate with 10 µL of conidial suspension (1×105 spores/mL) from 7-day old culture. And controls were inoculated using sterile distilled water. Fruits were placed in a moist chamber covered with plastic bag at 25 °C for 48 h to maintain high humidity. After 4 days the inoculation sites development symptoms that were identical to those initially observed in the field, whereas the control group remained symptomless. The pathogenicity test was performed twice, with the same results. The pathogen was re-isolated from the lesion to fulfill Koch's postulates. Currently, Colletotrichum chrysophilum has been reported causing anthracnose disease in several crops: apple in New York (Khodadadi et al. 2020), papaya in Mexico (Pacheco- Esteva et al.2022), Blueberry (Soares et al. 2022) and banana in Brazil (Astolfi et al. 2022). To our knowledge, this is the first report of anthracnose in Byrsonima crassifolia caused by Colletotrichum chrysophilum in Oaxaca, Mexico.

First Report of Anthracnose Caused by Colletotrichum siamense on Hydrangea macrophylla in China.

Hydrangea macrophylla (Thunb.) Ser. (Hydrangeaceae), a shrubby perennial plant, is widely used as an ornamental flowering plant because of its showy inflorescences and colorful sepals. In October 2022, leaf spot symptom was observed on H. macrophylla in Meiling Scenic Spot, which covers an area of about 143.58 km2 in Nanchang, Jiangxi Province, China (28.78°N, 115.83°E). An investigation was carried out in a 500 m2 mountain area with 60 H. macrophylla plants in a residential garden, the incidence of disease observed was 28~35%. The symptoms were visible as nearly round dark brown spots on the leaves in the early stages of infection. At later stages, the spots gradually developed grayish white center with dark brown margins. To isolate the pathogen, seven leaves randomly selected from 30 infected leaves were cut into 4-mm2 pieces, surface disinfected with 75% ethanol for 30s followed by 5% NaClO for 1 min, rinsed in sterile water three times, placed on potato dextrose agar (PDA), and cultured at 25 °C in the dark for 7 days, and four strains with similar morphological characteristics were obtained from 7 diseased samples. Conidia were aseptate, cylindrical, hyaline, obtuse at both ends, and measured 13.31 to 17.53 × 4.43 to 7.45 µm (15.47 ± 0.83 × 5.91 ± 0.62 µm, n = 60). Morphological characteristics matched Colletotrichum siamense (Weir et al. 2012; Sharma et al. 2013). For molecular identification, two representative isolates (HJAUP CH003 and HJAUP CH004) were used for genomic DNA extraction, and the internal transcribed spacer (ITS), partial sequences of actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), β-tubulin (TUB2) and partial calmodulin (CAL) were amplified, using primer pairs ITS4/ITS5 (White et al. 1990), ACT-512F/ACT-783R, GDF1/GDR1, Bt2a/Bt2b and CL1C/CL2C (Weir et al. 2012), respectively. The sequences were deposited in GenBank (accessions nos. ITS: OQ449415, OQ449416; ACT: OQ455197, OQ455198; GAPDH: OQ455203, OQ455204; TUB2: OQ455199, OQ455200; CAL: OQ455201, OQ455202). Concatenated sequences of the five genes were used to conduct phylogenetic analyses using the maximum-likelihood method in MEGA7.0 (Sudhir et al. 2016) and Bayesian inference analysis in MrBayes 3.2 (Ronquist et al. 2012). Our two isolates cluster together with four strains of C. siamense with 93%ML/1.00BI bootstrap support. The isolates were identified as C. siamense based on the morpho-molecular approach. Pathogenicity of HJAUP CH003 was tested indoors by inoculating detached wounded leaves of six healthy H. macrophylla plants. Three healthy plants with three leaves were punctured with flamed needles and sprayed with a 1 × 106 spores/ml spores suspension, and another three healthy plants were wounded inoculated with mycelial plugs (5 × 5 mm3). Mock inoculations were used as controls with sterile water and PDA plugs on three leaves each. Treated plant tissue were incubated in an artificial climate box at 25°C, 90% relative humidity and a photoperiod of 12 h. After 4 days, symptoms similar to those of natural infection were observed on all wounded inoculated leaves, while no symptoms appeared on mock-inoculated leaves. The fungus isolated from inoculated leaves was identical to the original pathogen based on morphological and molecular data, confirming Koch's hypothesis. It has been reported that C. siamense can cause anthracnose on numerous plants (Rong et al. 2021; Tang et al. 2021; Farr and Rossman 2023). This is the first report of C. siamense causing anthracnose on H. macrophylla in China. The disease is of major concern to the horticultural community as it seriously affects the aesthetic value of ornamentals.

First Report of Myrtle Rust Caused by Austropuccinia psidii in Campomanesia guazumifolia (Camb.) Berg in Brazil.

Campomanesia guazumifolia is a Brazilian fruit tree that has ecological importance and the potential to be explored by the food and medical industries (Lima et al., 2011). In February 2019, in the experimental orchard at the Universidade Tecnológica Federal do Paraná, Dois Vizinhos city, Paraná State - Brazil, disease symptoms were observed on leaves, stems, and fruits of 22 C. guazumifolia trees. Yellow uredinia were observed on upper side of the leaves, stems, and flowers, which resembled typical uredinia of Myrtaceae rust. The pustules occurred mainly on young shoots, and on flowers, they infected their sepals. Over time, tissues colonized by the pathogen exhibited deformations and mummification occurred in infected fruits. In the orchard, the fungus affected 80% yield. Twenty diseased plant parts (from each of the eleven trees) were collected at different positions in the orchard. One strain were selected as a representative for morphological characterization, multilocus phylogenetic analysis, and pathogenicity tests. The structures observed were epiphyllous uredinia (leaves), united in small groups with hyaline and obovoid or obpyriform urediniospores, which presented echinulate ornaments, germinated pores in the subequatorial and inordinate positions (Cummins; Hiratsuka, 2003) (n = 30, 14.84 x 21.12 μm). The morphology of uredinia and urediniospores was similar to the morphological characteristics of the genus Austropuccinia previously described in Young (2019). For molecular identification, genomic DNA was extracted and the internal transcribed spacer (ITS) region (White et al. 1990), β-tubulin (TUB2) and translation elongation factor 1-alpha (TEF) (Machado et al. 2012) were amplified by PCR, and sequenced. Bayesian inference was used to reconstruct a phylogenetic tree, using MrBayes v. 3.2.1 (Ronquist et al., 2012). The multilocus phylogenetic analysis clearly distinguished the isolate APCG001 as Austropuccinia psidii separating it from all other species. The sequences were deposited in GenBank (accessions nos. ITS: ON003418, TUB2: ON568196, and TEF: ON437601). For pathogenicity tests, four healthy branches (20 leaves each) were sprayed with 2.5 mL of (APCG001) uredospore suspension (105 mL-1) and covered with a plastic bag in the orchard. The air temperature ranged from 16ºC to 25ºC. Sterile distilled water was used as a control. Three replications (pathogen and control) were performed on different trees. After 6 days, symptoms of rust appeared on the plants. Control branches did not show fungal growth. The inoculation test was repeated again, confirming the initial results. This is the first report of infection by A. psidii in C. guazumifolia trees in Brazil, causing rust, necrosis, and early senescence in fruits, leaves, and stems. Myrtaceae rust reduces the C. guazumifolia leaf area, affecting photosynthetic production and reducing fruit quality.

First Report of Colletotrichum chrysophilum Causing Papaya Anthracnose in Mexico.

Anthracnose, caused by Colletotrichum spp., is the most important fungal disease of papaya (Carica papaya L.) worldwide. In March 2020, mature papaya fruit (cv. Maradol) showing typical symptoms of anthracnose were observed in an orchard located in Pinotepa Nacional, Oaxaca, Mexico. Disease incidence of 100 papaya plants surveyed in the orchard was estimated at about 45%. Initially, small and water-soaked lesions appeared on the fruit surface, which later enlarged to circular sunken lesions with translucent light brown margins. On advanced infections, salmon-pink masses of spores were observed on the lesions. Twenty Colletotrichum-like colonies were consistently isolated on potato dextrose agar (PDA) medium at 25°C in the dark for 6 days and 10 monoconidial isolates were obtained. An isolate was selected as representative for further characterization. The isolate was deposited as CPM-H4 in the Culture Collection of Phytopathogenic Fungi of Plant Pathology Laboratory of the CIIDIR-Oaxaca of the Instituto Politécnico Nacional. On PDA, the colonies were initially light grey then later became dark grey with orange conidial masses after incubation for 7 days. Conidia (n= 50) were hyaline, aseptate, cylindrical with rounded ends, and measured 10.2 to 13.6 × 4.1 to 5.3 μm. Appressoria (n= 20) were mostly simple, solitary and smooth-walled, dark brown, and clavate, measuring 6.8 to 14.8 × 5.5 to 7.7 μm. Based on morphology, the isolate was tentatively identified as belonging to the Colletotrichum gloeosporioides species complex (Weir et al. 2012). For molecular identification, total DNA was extracted, and the internal transcribed spacer (ITS) region (White et al. 1990), and partial sequences of actin (ACT), β-tubulin (TUB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and chitin synthase (CHS-1) genes were amplified (Weir et al. 2012), and sequenced. The sequences were deposited in GenBank (accessions nos. OM965612 (ITS), OM959540 (ACT), ON065005 (TUB2), ON065003 (CHS-1), ON065004 (GAPDH). A phylogenetic tree based on Bayesian inference and including published ITS, ACT, TUB2, GAPDH, and CHS-1 sequence dataset for Colletotrichum spp. was constructed. The multilocus phylogenetic analysis clearly distinguished the isolate CPM-H4 as Colletotrichum chrysophilum. Pathogenicity of the fungus was verified on 10 healthy papaya fruits (cv. Maradol) without wounds. A drop of a conidial suspension (1 × 105 spores/ml) was placed on three locations on each fruit. Ten control fruit were treated in the same way but with sterilized water. The fruits were kept in a moist plastic chamber at 25°C and 12 h light/dark for 8 days. The pathogenicity test was repeated twice. All inoculated papaya fruits developed sunken necrotic lesions 6 days after inoculation, whereas no symptoms were observed on the control fruits. The fungus was consistently re-isolated only from the diseased fruits and found to be morphologically identical to the isolate used for inoculation, fulfilling Koch´s postulates. Colletotrichum chrysophilum has been previously reported to cause anthracnose on mango (Fuentes-Aragón et al. 2020a), avocado (Fuentes-Aragón et al. 2020b), and banana (Fuentes-Aragón et al. 2021) in Mexico; however, to our knowledge, this is the first report of C. chrysophilum causing papaya anthracnose in Mexico. Therefore, it is necessary to explore the diversity of Colletotrichum species associated with papaya in Mexico through subsequent phylogenetic studies as well as to monitor the possible movement and distribution of this pathogen into other Mexican regions.

First Report of Colletotrichum siamense Causing Anthracnose of Guava (Psidium guajava) in Mexico.

Guava (Psidium guajava L.) is a small tree belonging to the Myrtaceae family and it is distributed worldwide in the tropical and subtropical areas. During the summer of 2019, symptoms of fruit anthracnose were observed on approx. 90% of 250 guava trees located in backyards in Juan Jose Rios, Sinaloa, Mexico. Lesions on guava fruit were irregular, necrotic, and sunken. On advanced infections, acervuli containing salmon-pink masses of spores were observed on the lesions. Twenty fruits were collected from 10 trees (2 fruits per tree). Colletotrichum-like colonies were consistently isolated on PDA medium and 20 monoconidial isolates were obtained. Four isolates were selected as representatives for morphological characterization, multilocus phylogenetic analysis, and pathogenicity tests. The isolates were deposited in the Culture Collection of Phytopathogenic Fungi of the Faculty of Agriculture of El Fuerte Valley at the Sinaloa Autonomous University (Accession nos. FAVF205-FAVF208). Colonies on PDA medium were flat with an entire margin, with abundant felty and white aerial mycelium, with pink conidial masses. Conidia (n= 100) were cylindrical, hyaline, aseptate, with ends rounded, and measuring 14.8 to 18.1 × 4.4 to 5.3 μm. Based on morphological features, the isolates were tentatively allocated in the C. gloeosporioides species complex (Weir et al. 2012). For molecular identification, genomic DNA was extracted, and the internal transcribed spacer (ITS) region (White et al. 1990), as well as partial sequences of actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), β-tubulin (TUB2), chitin synthase (CHS-1) and glutamine synthetase (GS) genes were amplified by PCR (Weir et al. 2012), and sequenced. A phylogenetic tree based on Bayesian inference and including published ITS, GAPDH, TUB2, ACT, CHS-1, and GS data for Colletotrichum species was constructed. The multilocus phylogenetic analysis clearly distinguished the four isolates FAVF205-FAVF208 as C. siamense separating it from all other species within the C. gloeosporioides species complex. The sequences were deposited in GenBank (accessions nos. ITS: MW598512-MW598515; GAPDH: MW595216-MW595219; TUB2: MW618012-MW618015; ACT: MW595208-MW595211; CHS-1: MW595212-MW595215; and GS: MW618008-MW618011). Pathogenicity of the four isolates was verified on 40 healthy guava fruits. Twenty fruits were wounded with a sterile toothpick (2 mm in depth) and a mycelial plug (6 mm of diameter) was placed on each wound. Ten fruits inoculated with a PDA plug without mycelial growth served as controls. The fruit was kept in a moist plastic chamber at 25°C for 7 days. Pathogenicity of each isolate was tested with both non-wound and wound inoculation methods. The experiments were repeated twice with similar results. All inoculated fruits developed sunken necrotic lesions 4 days after inoculation, whereas no symptoms were observed on the control fruits. The fungi were consistently re-isolated only from the diseased fruits, fulfilling Koch´s postulates. Colletotrichum siamense has been previously reported on guava fruit in India (Sharma et al. 2015). However, to our best knowledge, this is the first report of C. siamense causing fruit anthracnose on guava in Mexico. Therefore, it is necessary to explore the diversity of Colletotrichum species on guava in detail through subsequent phylogenetic studies as well as to monitor the distribution of this pathogen into other Mexican regions.

First Report of Penicillium ulaiense Causing Postharvest Whisker Mold of Oranges (Citrus sinensis) in Spain

In a survey of postharvest losses in citrus packinghouses located in Valencia province (Spain) conducted during the 2017 to 2018 citrus season, mold symptoms distinctive from those of the most frequent and well-known citrus green and blue molds (caused by Penicillium digitatum [Pers.] Sacc. and Penicillium italicum Wehmer, respectively) were observed in about 1 to 2% of the sampled molded orange fruits (Citrus sinensis L.). Distinctive symptoms on sporulated soft lesions were the grayish blue color of the conidial masses and the presence of whisker-like coremia with tall whitish stalks. This whisker mold was often found in mixed infections with green and/or blue molds in the same fruit. The potential causal agent (isolate IVIA NAV-1) was transferred to potato dextrose agar (PDA) plates and purified by consecutive replating after 7 days of incubation at 25°C. At this time, colonies were mostly circular, compact, 30 to 40 mm in diameter, with dense velvety grayish mycelium and abundant bluish conidia. Conidiophores were sinoid, mostly terverticillate, and conidia were cylindrical to ellipsoidal, smooth, and thin walled, measuring 4.8 to 8.4 × 2.0 to 3.2 μm. Based on these morphological characteristics, the isolate IVIA NAV-1 was tentatively identified as Penicillium ulaiense H.M. Hsieh, H.J. Su & Tzean (Frisvad and Samson 2004). To confirm the identity, molecular identification was performed in a specialized laboratory. The rDNA internal transcribed spacer regions ITS 1 and ITS 2 and the β-tubulin gene were amplified, sequenced, and deposited in GenBank (accessions nos. MH477872 and MH477873, respectively). A BLAST search for ITS showed 100% identity and 100% query coverage with P. ulaiense strain CBS 210.92 (accession no. KC411695.1). A BLAST search for the β-tubulin gene showed 99% identity and 100% query coverage with P. ulaiense isolate 1399 (accession no. LT629297.1). Selected healthy oranges of cultivar Valencia were surface disinfected by dipping in 0.5% sodium hypochlorite for 2 min followed by thorough rinsing in deionized water. Pathogenicity was tested by pipetting 30 µl of a spore suspension (1 × 10⁶ conidia/ml), prepared from 7- to 10-day-old PDA cultures, onto fresh rind wounds, which were made on the equatorial area of disinfected fruit using a sterile, stainless steel rod with a probe tip of 1 mm in width × 2 mm in length (one wound per fruit, total of 20 oranges). Additionally, 10 disinfected, wounded, noninoculated oranges were used as controls. The same procedure was repeated 15 days later with another lot of Valencia oranges. In both tests, disease symptoms were observed on all inoculated fruit after 7 days of incubation at 25°C, and P. ulaiense was consistently reisolated, thereby fulfilling Koch’s postulates. No decay was observed on any of the control fruit. To our knowledge, this is the first report of P. ulaiense causing whisker mold of citrus fruit in Spain. The disease has been previously reported in important citrus-producing areas such as California (Holmes et al. 1993), Egypt (Youssef et al. 2010), Pakistan (Khan et al. 2017), and Korea (Park et al. 2018).

First Report of Cadophora luteo-olivacea Causing Side Rot on Kiwifruit in Chile

HomePlant DiseaseVol. 102, No. 3First Report of Cadophora luteo-olivacea Causing Side Rot on Kiwifruit in Chile PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Cadophora luteo-olivacea Causing Side Rot on Kiwifruit in ChileJ. Auger, I. Pérez, C. Osorio-Navarro, and M. EsterioJ. Auger†Corresponding author: J. Auger; E-mail: E-mail Address: jauger@uchile.clSearch for more papers by this author, I. PérezSearch for more papers by this author, C. Osorio-NavarroSearch for more papers by this author, and M. EsterioSearch for more papers by this authorAffiliationsAuthors and Affiliations J. Auger † I. Pérez C. Osorio-Navarro M. Esterio , Laboratorio de Fitopatología Frutal y Molecular, Facultad de Ciencias Agronómicas, Universidad de Chile, C.P. 8820808, La Pintana, Santiago, Chile. Published Online:9 Jan 2018https://doi.org/10.1094/PDIS-09-17-1349-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Kiwifruit (Actinidia deliciosa [Chev] Ling et Ferguson cv. ‘Hayward’) can be stored for over 6 months at 0 ± 1°C. However, in recent years a postharvest disease of kiwifruit, characterized by a side rot appearing during harvest or after 3 to 6 months postharvest cold storage period, has been observed in several packinghouses in central Chile. Symptoms on kiwifruit were depressed and elliptical areas, associated with brown-violet skin and brown pulp. Symptomatic kiwifruit samples from different packinghouses were sterilized with 75% (v/v) ethanol, and infected tissue was placed onto potato dextrose agar (PDA) at 24°C in the dark for a 7-day period. Single spore colonies were flat, felty, and cottony in the middle, with smooth margins, with an even edge and varying in color from white turning to gray/black-olivaceous. Microscopically, straight, septate, short conidiophores had mostly cylindrical monophialides with hyaline collarettes. Conidia (n = 50) from four representative isolates recovered from naturally infected kiwifruit (2VCBC, 2VCBD, 2VCBF, and 2VCCD) were hyaline, unicellular, oblong elliptical or ovoid, and mostly biguttulated, measured 3.8 to 5.8 × 2.2 to 3.5 µm (mean, 2.9 × 4.8 µm). Cultural and morphological pathogen characteristics were similar to those described for Cadophora sp. (Gramaje et al. 2011). Three loci (ITS, β-tubulin, and EF1-α) of the four representative isolates were sequenced using the primers ITS1/ITS4, Bt2a/Bt2b, and EF1-728F/EF1-986R (Travadon et al. 2015). BLAST analysis revealed ITS, β-tubulin, and EF1-α sequences (accessions nos. MF464553, MF464555, MF464558, and MF464562) to share 99 to 100% identity with Cadophora luteo-olivacea isolates in GenBank (accession nos. KT350592, KT350591, and KU720079); the sequences (accession nos. MF464554, MF464556, MF464559, and MF464563) were compared with those of C. luteo-olivacea in the NCBI GenBank database and had 99% nucleotide sequence identity (accession nos. KF764682, KF764648, and KF764647), and the sequences (accession nos. MF772484, MF772481, MF772482, and MF772480) were 100% identical to C. luteo-olivacea sequences in GenBank (accession nos. KT350599, KT350598, and KT350597), respectively. Twenty ‘Hayward’ kiwifruits (per representative isolates) were wounded-inoculated in the fruit equatorial region with 20 μl of a spore suspension (106 conidia/ml) prepared from a 15-day-old PDA culture and incubated at 24°C in darkness. Typical symptoms appeared between 8 and 12 days. Kiwifruits inoculated with sterile distilled water remained symptomless. Fungi isolated from the lesions had morphological characteristics that resembled the original isolates from infected fruits. The identity of the reisolations was confirmed as C. luteo-olivacea by sequencing, thus completing Koch’s postulates. C. luteo-olivacea has been identified associated with a similar symptom (skin pitting) on kiwifruit stored long-term in Italy (Piano at al. 2001; Spadaro et al. 2010). In kiwifruit orchards, C. luteo-olivacea is normally a soil-borne microorganism and may be transported into packing houses on fruit skins or in harvest bins (Gilardi et al. 2007). Side rot caused by C. luteo-olivacea represents an economically significant problem for the kiwifruit packinghouses in Chile, owing to the lack of effective postharvest fungicides and the limited knowledge of the pathogen and disease epidemiology. To our knowledge, this is the first report of side rot of kiwifruit caused by C. luteo-olivacea in Chile.

First Report of Phytopythium helicoides Causing Rhizome Rot of Asian Lotus in China

HomePlant DiseaseVol. 100, No. 2First Report of Phytopythium helicoides Causing Rhizome Rot of Asian Lotus in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Phytopythium helicoides Causing Rhizome Rot of Asian Lotus in ChinaX. Yin, X. Z. Li, J. J. Yin, and X. WuX. YinSearch for more papers by this author, X. Z. LiSearch for more papers by this author, J. J. YinSearch for more papers by this author, and X. WuSearch for more papers by this authorAffiliationsAuthors and Affiliations X. Yin X. Z. Li J. J. Yin X. Wu , Shandong Rice Research Institute/Hydrobiology Research Center, Shandong Academy of Agricultural Sciences, Jinan, Shandong, 250100, China. Published Online:17 Dec 2015https://doi.org/10.1094/PDIS-07-15-0833-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Asian lotus (Nelumbo nucifera Gaertn. ssp. nucifera), also called sacred lotus, is an economically important aquatic plant in China. It is a well known and popular vegetable for its nutritious rhizomes and seeds. Rhizome rot is a prevalent disease threatening lotus production and can cause yield loss of up to 80%, or even total loss (Li et al. 2013; Ding et al. 2002). The diseased lotus showed root necrosis, rhizome rotting, and leaf wilting. To determine the pathogen present, six symptomatic rhizomes of No. 4 variety Hubei Lotus were collected from Yaoqiang Town, Jinan City (36°40′ N; 117°00′ E), in December 2013. The collected rhizomes were excised, surface-sterilized, and placed on potato dextrose agar (PDA) medium. After incubation at 28°C for one day, white fungal colonies were isolated. To confirm the pathogenicity, 2-week-old lotus seedling plants and 1-month-old asexual plants were inoculated with mycelial agar disks of the isolates. Three seedling plants and eight asexual plants’ rhizomes were inoculated. The fungus-free agar disks were used as the negative control. Inoculated seedling plants were placed in the growth chamber, and small water tanks with inoculated rhizomes in soil were placed outdoors in the summer months in Jinan. One week postinoculation, the inoculated seedling plants showed root necrosis and rhizomes showed symptoms of rot. The same fungus was recovered from symptomatic roots and rhizomes. The inoculation experiments were repeated twice and showed the same results. The roots and rhizomes inoculated with the control agar disks remained symptomless, and no fungi were recovered. The pathogenic fungal isolates were identified based on morphological characteristics and DNA sequence analysis. After incubation at 28°C for one day on PDA, colonies were cottony to felty in texture and always white in color with average diameters of 90 ± 3 mm. Hypha can grow at a temperature range from 15°C to 40°C. In the typical isolate, Jnyq1, sporangia were ellipsoidal, papillate, proliferating, and 20.2 to 31.2 × 22.8 to 34.6 µm in diameter. Zoospores were formed in vesicles. Oogonia were terminal, smooth, and 23.3 to 28 μm in diameter. Antheridia were lobulate, elongate, monoclinous or diclinous, and 1 to 3 per oogonium. Oospores were aplerotic and spherical. Jnyq1 was further classified by sequencing the ITS1-5.8S rRNA-ITS2 region (the rDNA of the internal transcribed spacer regions 1 and 2 and the 5.8S gene, GenBank Accession No. KT258905), co I (the cytochrome oxydase I gene, Accession No. KT258906), and co II (the cytochrome oxydase II gene, Accession No. KT258907) using primer pairs ITS1/ITS4 (White et al. 1990), FM35/FM59, and FM66/FM58 (Martin 2000), respectively. BLAST results revealed that the ITS1-5.8S rRNA-ITS2 region, co I, and co II from Jnyq1 shared nucleotide identities of 97%, 99%, and 99% with corresponding segments of Phytopythium helicoides (Accessions Nos. HQ643382, FR774199, and AB108014), respectively. To our knowledge, this is the first report of P. helicoides causing rhizome rot of lotus in China. Rhizome rot of lotus caused by Fusarium oxysporum is well known in China (Liu 1992).

First Report of Stemphylium vesicarium as Causal Agent of Wilting and Root Rotting of Radish Sprouts in Italy.

A consistent contamination from a Stemphylium sp. was detected on radish (Raphanus sativus) seeds by a seed blotter test. Twenty-five percent of seed lots were contaminated. Stemphylium vesicarium (teleomorph Pleospora allii) was identified on the basis of morphological characters of conidia and conidiophores (4). Conidia were golden brown to dark drown, oblong to oval with one to four transverse and one to three longitudinal septa, constricted at one to three of the major transverse septa. Conidia dimensions ranged from 12 to 22 × 30 to 40 μm. Conidiophores were straight or occasionally one-branched with a swollen apex and one to four septate. Pseudothecia with asci and ascopores were observed on radish seeds. Asci were cylindrical to clavate with eight ascospores with up to six transverse septa and numerous longitudinal septa. Species identification was also confirmed after comparing the sequences of the internal transcribed spacer (ITS) region of rDNA and gpd (glyceraldehyde-3-phosphate dehydrogenase) (3) of four isolates with those of Stemphylium species already present in the NCBI database. Accessions Nos. AM 746020 to AM746023 and AM883174 to AM883177 were deposited for ITS and gpd, respectively. Artificial inoculations were carried out on radish seeds previously disinfected with 1% sodium hypochlorite for 10 min and then plated on S. vesicarium sporulating colonies grown on potato dextrose agar (PDA). The four sequenced isolates were tested for pathogenicity. Disinfected seeds were plated onto PDA only and used as a control. After 48 h of incubation, seeds were sown in sterilized soil in plastic plates. The emerging and the eventually dead plants were counted. Stem necrosis and root rotting developed on sprouts within the first week after sowing. On the surviving infected plantlets, wilting and death occurred on more than 70% of the plants within 4 weeks after sowing. Control plantlets obtained from disinfected seeds remained healthy. The fungus reisolated from wilted and dead plants was morphologically identical to the original isolates, thus confirming S. vesicarium as the causal agent. In Italy, this pathogen is common on asparagus (1), but it has also been reported on Allium spp., tomato, and pear. On European pear it is the causal agent of brown spot (2), a destructive disease in the Mediterranean area but also in the Netherlands and other continental European countries. On the basis of these results, seed contamination with S. vesicarium can represent a threat for the production of radish for sprout consumption. To our knowledge, this is the first report of S. vesicarium on radish plantlets in Italy.