Phylogenetic, Morphological, and Pathogenic Characterization of Alternaria Species Associated with Fruit rot of Mandarin in California

Alternaria rot caused by Alternaria species is one of the major postharvest diseases of mandarin fruit in California. The aims of this study were to identify these Alternaria species using phylogenetic analyses and morphological characteristics and test their pathogenicity to mandarin. Decayed mandarin fruit exhibiting Alternaria rot symptoms were collected from three citrus fruit packinghouses in the Central Valley of California. In total, 177 Alternaria isolates were obtained from decayed fruit and preliminarily separated into three groups representing three species (A. alternata, A. tenuissima and A. arborescens) based on the colony characterization and sporulation patterns. To further identify these isolates, phylogenetic analysis was conducted based on DNA sequences of the second largest subunit of RNA polymerase II (RPB2), plasma membrane ATPase (ATPase) and Calmodulin gene regions in combination with morphological characters. Of the 177 isolates, 124 isolates (70.1%) were identified as A. alternata and 53 isolates (29.9 %) were A. arborescens. The isolates initially identified as A. tenuissima based on the morphological characteristics could not be separated from those of A. alternata in phylogenetic analysis and thus considered A. alternata. Pathogenicity tests showed that both Alternaria species were pathogenic on mandarin fruit at both 5°C and 20°C. Our results indicated that two Alternaria species, A. alternata and A. arborescens, were responsible for Alternaria rot of mandarin fruit in California with A. arborescens causing fruit rot on mandarin being reported for the first time.

Download Full-text

Phylogenetic, Morphological, and Pathogenic Characterization of Alternaria Species Associated with Fruit Rot of Blueberry in California

Phytopathology ◽

10.1094/phyto-05-15-0122-r ◽

2015 ◽

Vol 105 (12) ◽

pp. 1555-1567 ◽

Cited By ~ 22

Author(s):

X. Q. Zhu ◽

C. L. Xiao

Keyword(s):

Dna Sequences ◽

Central Valley ◽

Morphological Characters ◽

Fruit Rot ◽

Postharvest Quality ◽

Plasma Membrane Atpase ◽

Factors Affecting ◽

Molecular Approaches ◽

Alternaria Species ◽

Pathogenicity Tests

Fruit rot caused by Alternaria spp. is one of the most important factors affecting the postharvest quality and shelf life of blueberry fruit. The aims of this study were to characterize Alternaria isolates using morphological and molecular approaches and test their pathogenicity to blueberry fruit. Alternaria spp. isolates were collected from decayed blueberry fruit in the Central Valley of California during 2012 and 2013. In total, 283 isolates were obtained and five species of Alternaria, including Alternaria alternata, A. tenuissima, A. arborescens, A. infectoria, and A. rosae, were identified based on DNA sequences of the plasma membrane ATPase, Alt a1 and Calmodulin gene regions in combination with morphological characters of the culture and sporulation. Of the 283 isolates, 61.5% were identified as A. alternata, 32.9% were A. arborescens, 5.0% were A. tenuissima, and only one isolate of A. infectoria and one isolate of A. rosae were found. These fungi were able to grow at temperatures from 0 to 35°C, and mycelial growth was arrested at 40°C. Optimal radial growth occurred between 20 to 30°C. Pathogenicity tests showed that all five Alternaria spp. were pathogenic on blueberry fruit at 0, 4, and 20°C, with A. alternata, A. arborescens, and A. tenuissima being the most virulent species, followed by A. infectoria and A. rosae. Previously A. tenuissima has been reported to be the primary cause of Alternaria fruit rot of blueberry worldwide. Our results indicated that the species composition of Alternaria responsible for Alternaria fruit rot in blueberry can be dependent on geographical region. A. alternata, A. arborescens, A. infectoria, and A. rosae are reported for the first time on blueberry in California. This is also the first report of A. infectoria and A. rosae infecting blueberry fruit.

Download Full-text

Identification of Lasiodiplodia pseudotheobromae Causing Fruit Rot of Citrus in China

Plants ◽

10.3390/plants10020202 ◽

2021 ◽

Vol 10 (2) ◽

pp. 202

Author(s):

Jianghua Chen ◽

Zihang Zhu ◽

Yanping Fu ◽

Jiasen Cheng ◽

Jiatao Xie ◽

...

Keyword(s):

Phylogenetic Analyses ◽

Elongation Factor ◽

Morphological Characteristics ◽

Citrus Fruit ◽

Economic Loss ◽

Fruit Rot ◽

Post Inoculation ◽

Citrus Reticulata ◽

Postharvest Diseases ◽

Citrus Reticulata Blanco

Considering the huge economic loss caused by postharvest diseases, the identification and prevention of citrus postharvest diseases is vital to the citrus industry. In 2018, 16 decayed citrus fruit from four citrus varieties—Satsuma mandarin (Citrus unshiu), Ponkan (Citrus reticulata Blanco cv. Ponkan), Nanfeng mandarin (Citrus reticulata cv. nanfengmiju), and Sugar orange (Citrus reticulata Blanco)—showing soft rot and sogginess on their surfaces and covered with white mycelia were collected from storage rooms in seven provinces. The pathogens were isolated and the pathogenicity of the isolates was tested. The fungal strains were identified as Lasiodiplodia pseudotheobromae based on their morphological characteristics and phylogenetic analyses using the internal transcribed spacer regions (ITS), translation elongation factor 1-α gene (TEF), and beta-tubulin (TUB) gene sequences. The strains could infect wounded citrus fruit and cause decay within two days post inoculation, but could not infect unwounded fruit. To our knowledge, this is the first report of citrus fruit decay caused by L. pseudotheobromae in China.

Download Full-text

First Report of Fruit Rot of Sweet Cultivars of Japanese Plum caused by Alternaria alternata, A. arborescens, and A. tenuissima in Chile

Plant Disease ◽

10.1094/pdis-03-21-0465-pdn ◽

2021 ◽

Author(s):

Danae Riquelme ◽

Carolina Zúñiga ◽

Eduardo Tapia

Keyword(s):

Rna Polymerase Ii ◽

Central Valley ◽

Fruit Rot ◽

Conidial Suspension ◽

Plasma Membrane Atpase ◽

First Report ◽

Japanese Plum ◽

Leaf Spots ◽

Prunus Salicina ◽

Sterile Needle

During the last two seasons, an unusual fruit rot was observed in four orchards of sweet Japanese plum (Prunus salicina) cultivars located in the Chilean Central Valley (30°00ʼS, 70°42ʼW). The incidence was 5% in Black Majesty, 4% in Red Lyon, and 6% in Sweet Mary cultivars in 2020. Fruits in the field showed a firm, dehydrated, and slightly sunken rot on the blossom end, along with rough and irregular epidermis in the affected area. Internally, the fruit flesh appeared light to dark-brown or olive-green. Symptomatic fruits (n=119) were superficially disinfected (75% ethanol) and, pieces of the pericarp (3 x 3 mm) were removed and placed on potato dextrose agar (PDA). Isolates of Alternaria spp. were obtained and 9 of these were selected for identification. Colonies were dark olive to gray-brown with white margins, small, catenulate and muriform conidia, produced in single or branched conidiophores. Isolates produced brown to golden-brown, ovoid, ellipsoidal to obclavate conidia with dimensions of 19.7 to 26.7 × 10.0 to 11.9 μm with two to four transverse and zero to three longitudinal septa on 0.05× PDA (Pryor and Michailides 2002) after 7 d at 20°C under 10/14 h light/dark cycles. A molecular analysis was performed by sequencing the nuclear genes RNA polymerase II subunit (RPB2), plasma membrane ATPase (ATP), and the calmodulin (Cal) gene using primers RPB2-5F2/fRPB2-7cR, ATPDF1/ATPDR1, and CALDF1/CALDR1, respectively (Lawrence et al. 2013; Woudenberg et al. 2013). A BLAST search revealed the presence of Alternaria spp. with a 99% to 100% identity with the reference sequences of A. alternata (JQ905182, JQ671874, JQ646208), A. arborescens (JQ646487, JQ671880, JQ646214), and A. tenuissima (JQ811961, JQ811989, JQ646209). Maximum parsimony phylogenetic analysis confirmed the identifications. Sequences were deposited in GenBank as numbers MW514249 to MW514257, MT872324 to MT872332, and MT872314 to MT872322 for RPB2, ATP, and Cal sequences, respectively. All these Alternaria isolates were deposited in the Colección Chilena de Recursos Genéticos Microbianos – INIA, Chillán Chile (RGM3069 to RGM3077). Pathogenicity of A. alternata (n=4), A. arborescens (n=3) and, A. tenuissima (n=2) was tested in Red Lyon plum fruits. Plums were disinfected in 1% sodium hypochlorite for 2 min, rinsed in sterile distilled water for 1 min and dried on absorbent towels in a laminar flow hood. Then, the plums were wounded on the blossom end with a sterile needle (1 x 0.5 mm), inoculated with 10 µl of a conidial suspension (106 conidia/ml), wrapped with Parafilm and maintained in a humid chamber (>95% relative humidity). An equal number of fruits wounded and inoculated with sterile water were used as a control. After 7 days at 20°C, all inoculated fruits developed a dark-brown firm rot with lesion lengths of 24.4 (±3.0) mm, 19.6 (±0.7) mm, and 16.8 (±2.4) mm for A. alternata, A. arborescens and A. tenuissima, respectively. A. alternata was the most aggressive species (P < 0.001). Control fruits remained asymptomatic. Koch’s postulates were fulfilled after the re-isolating the causal agent from the border of the lesions. Leaf spots and fruit rots caused by Alternaria isolates have been reported in stone fruits, including plums (Kim et al. 2005; Long et al. 2021; Moosa et al., 2019; Yang et al. 2014). To our knowledge, this is the first report of A. alternata, A. arborescens, and A. tenuissima associated with fruit rot in sweet Japanese plum cultivars in the field, in Chile.

Download Full-text

A New Accurate Genotyping HRM Method for Alternaria Species Related to Fruit Rot Diseases of Apple and Pomegranate

International Journal of Phytopathology ◽

10.33687/phytopath.004.03.1531 ◽

2016 ◽

Vol 4 (3) ◽

pp. 159-165 ◽

Cited By ~ 1

Author(s):

Antonios Zambounis ◽

Aliki Xanthopoulou ◽

George Karaoglanidis ◽

Athanasios Tsaftaris ◽

Panagiotis Madesis

Keyword(s):

Morphological Characteristics ◽

Curve Analysis ◽

Fruit Rot ◽

Nucleotide Polymorphisms ◽

Postharvest Diseases ◽

Accurate Identification ◽

Complex Species ◽

Alternaria Species ◽

Species Specific ◽

Pomegranate Fruit

Alternaria core rot and Alternaria black heart rot of apple and pomegranate fruit, respectively, are major pre- and postharvest diseases worldwide. However, it is very difficult to differentiate the rot related Alternaria species in the Alternaria complex as they are not always correlate to species-groups based upon morphological characteristics and due to the limited genetic variation these species exhibit among each other. Therefore, it is crucial to exploit novel assays towards the accurate identification and differentiation of these Alternaria species. We have developed, a real-time PCR assay [using species specific primers targeting the endopolygalacturonase (EndoPG) gene] combined with a high-resolution melting (HRM) curve analysis for discrimination of the 14 single nucleotide polymorphisms (SNPs)-based Alternaria haplotypes, which were assigned based on the aligned sequence profiles of 138 Alternaria spp. strains previously isolated from apple and pomegranate rotted fruit. This analysis specifically generated 14 unique HRM curve haplotype profiles among the Alternaria complex species tested. The results showed that HRM curve analysis allows the rapid and adequate identification and genotyping of the three Alternaria species (A. alternata, A. tenuissima and A. arborescens) responsible mostly for the apple and pomegranate fruit rot diseases.

Download Full-text

A New Postharvest Fruit Rot in Apple and Pear Caused by Phacidium lacerum

Plant Disease ◽

10.1094/pdis-02-15-0158-re ◽

2016 ◽

Vol 100 (1) ◽

pp. 32-39 ◽

Cited By ~ 11

Author(s):

M. S. Wiseman ◽

Y. K. Kim ◽

F. M. Dugan ◽

J. D. Rogers ◽

C. L. Xiao

Keyword(s):

Phylogenetic Analysis ◽

Ribosomal Subunit ◽

Morphological Characteristics ◽

Apple Fruit ◽

Fruit Rot ◽

Morphological Data ◽

Postharvest Diseases ◽

Pear Fruit ◽

Diseased Fruit ◽

Molecular Phylogenetic

During surveys for postharvest diseases of apple and pear, an unknown postharvest fruit rot was observed in Washington State. The disease appeared to originate from infection of the stem and calyx tissue of the fruit or wounds on the fruit. An unknown pycnidial fungus was consistently isolated from the decayed fruit. Isolates from apple and pear were characterized and identified by molecular phylogenetic analysis and morphology. Pathogenicity of representative isolates on apple and pear fruit was tested under laboratory or field conditions. A BLAST search in GenBank showed that isolates differed from Phacidium lacerum and its synonym, Ceuthospora pinastri, by only 0 to 4 bp in sequences within part of the combined large ribosomal subunit + internal transcribed spacer + small ribosomal subunit regions. The phylogenetic analysis confirmed the taxonomic placement of the unknown fungus in the genus Phacidium, with the highest match being C. pinastri (formerly anamorphic P. lacerum) and with closely related taxa from GenBank forming congeneric clades. The fungus grew at 0 to 30°C and formed unilocular to multilocular pycnidial conidiomata on artificial media after approximately 5 to 7 days at room temperature. On potato dextrose agar incubated for a 12-h photoperiod, semi-immersed globose to subglobose pycnidial conidiomata were 250 to 1,000 μm in diameter (mean = 350), with 1 to 3 nonpapillate to slightly papillate ostioles and a buff conidial matrix. Conidia produced on phialides were 8 to 13 by 1.5 to 2.5 μm, hyaline, aseptate, cylindrical, with an abruptly tapered, typically slightly protuberant base, 2 to 3 guttules, and sometimes with a mucilaginous, flexuous, unbranched appendage which is attached to the apex of the conidium and disappears with age. Conidiogenous cells were flask shaped and 6 to 15 ×1.5 to 3 μm. Colony characteristics included felt-like aerial white mycelium, gray olivaceous at the center becoming greenish to colorless toward the margin, in concentric rings, with pycnidia forming in 5 to 7 days originating from the center of the plate. Morphological characteristics of the fungus had the greatest conformity with the description for C. pinastri. Based on molecular and morphological data, the fungus is identified as P. lacerum. ‘Fuji’ apple fruit and ‘d’Anjou’ pear fruit that were wounded, inoculated with representative isolates, and incubated at 0°C yielded the same symptoms as seen on decayed fruit collected from commercial fruit packinghouses. Stem-end rot, calyx-end rot, and wound-associated rot developed on fruit inoculated in the orchard after 3 months of cold storage. The fungus was reisolated from the diseased fruit. This is the first report of a fruit rot in apple and pear caused by P. lacerum. We propose Phacidium rot as the name of this disease.

Download Full-text

Outbreak of Leaf Spot and Fruit Rot in Florida Strawberry Caused by Neopestalotiopsis spp.

Plant Disease ◽

10.1094/pdis-06-20-1290-re ◽

2021 ◽

pp. PDIS-06-20-1290

Author(s):

Juliana S. Baggio ◽

Bruna B. Forcelini ◽

Nan-Yi Wang ◽

Rafaela G. Ruschel ◽

James C. Mertely ◽

...

Keyword(s):

Internal Transcribed Spacer ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Taxonomic Status ◽

Spore Production ◽

Potato Dextrose Agar ◽

Fruit Rot ◽

Low Genetic Diversity ◽

Pathogenicity Tests ◽

A New Species

Pestalotiopsis-like species have been reported affecting strawberry worldwide. Recently, severe and unprecedented outbreaks have been reported in Florida commercial fields where leaf, fruit, petiole, crown, and root symptoms were observed, and yield was severely affected. The taxonomic status of the fungus is confusing because it has gone through multiple reclassifications over the years. Morphological characteristics, phylogenetic analyses, and pathogenicity tests were evaluated for strawberry isolates recovered from diseased plants in Florida. Phylogenetic analyses derived from the combined internal transcribed spacer, β-tub, and tef1 regions demonstrated that although there was low genetic diversity among the strawberry isolates, there was a clear separation of the isolates in two groups. The first group included isolates recovered over a period of several years, which was identified as Neopestalotiopsis rosae. Most isolates recovered during the recent outbreaks were genetically different and may belong to a new species. On potato dextrose agar, both groups produced white, circular, and cottony colonies. From the bottom, colonies were white to pale yellow for Neopestalotiopsis sp. and pale luteous to orange for N. rosae. Spores for both groups were five-celled with three median versicolored cells. Mycelial growth and spore production were higher for the new Neopestalotiopsis sp. isolates. Isolates from both groups were pathogenic to strawberry roots and crowns. However, the new Neopestalotiopsis sp. proved more aggressive in fruit and leaf inoculation tests, confirming observations from the recent outbreaks in commercial strawberry fields in Florida.

Download Full-text

Morphometry and Phylogeny of the Different Populations of Selaginella tamariscina (P. Beauv.) Spring and S. pulvinata (Hook. & Grev.) Maxim. in Northern Thailand

Chiang Mai University Journal of Natural Sciences ◽

10.12982/cmujns.2021.077 ◽

2021 ◽

Vol 20 (4) ◽

Author(s):

Udon Pongkawong ◽

◽

Jatupol Kampuansai ◽

Rossarin Pollawatn ◽

Arunothai Jampeetong ◽

...

Keyword(s):

Phylogenetic Analysis ◽

Southern China ◽

Phylogenetic Analyses ◽

Dna Barcode ◽

Morphological Characteristics ◽

Taxonomic Status ◽

Morphological Characters ◽

The Philippines ◽

Northern Thailand ◽

Selaginella Tamariscina

Abstract “Dok Hin” is the Thai local name for Selaginella species that form rosettes. They commonly distributes in Siberia, Manchuria, southern China, Japan, the Philippines and Thailand. Morphology of Dok Hin is very resemble leading to misidentification. So, exactly number of species of Dok Hin in Thailand and their differences in morphological characteristics is not well understood. Thus, revision of morphological characters and phylogenetic confirmation of the taxonomic identification are needed. This study aims to examine morphological charateristics and phylogenetic patterns in eight populations of the Dok Hin in Northern Thailand. Morphology of Dok Hin from each populations was quantitatively examined using 15 vegetative and 6 reproductive characters meanwhile phylogenetic analyses was explored by DNA barcode ITS2. The results of the phylogenetic analysis revealed the existence of two species of Dok Hin, S. tamariscina and S. pulvinata. Selaginella tamariscina can be distinguished from S. pulvinata by its presence of a pseudotrunk above ground and ridges of dorsal leaves. On the other hand, the results of phylogenetic analysis indicated the differences among populations of S. pulvinata as well. Chiang Mai populations of S. pulvinata was characterized by peculiar set of characters long leaves and leaf apices look like caudate, while the rest of their populations have shorter leaves and leaf apices look like aristate. It indicates that S. pulvinata has genetic and phenotypic divergence among populations. However, additional studies of Dok Hin populations in other parts of Thailand and studies on different genetic markers are necessary to confirm the taxonomic status of S. pulvinata. Keywords: Dok Hin, Morphometric, Phylogeny, Pseudotrunk, Resurrection plant

Download Full-text

First Report of Fusarium pernambucanum Causing Fruit Rot of Muskmelon in China

Plant Disease ◽

10.1094/pdis-07-21-1520-pdn ◽

2021 ◽

Author(s):

Xianping Zhang ◽

Jiwen Xia ◽

Jiakui Liu ◽

Dan Zhao ◽

Lingguang Kong ◽

...

Keyword(s):

Phylogenetic Analyses ◽

Apical Cell ◽

Morphological Characteristics ◽

Fruit Rot ◽

Likelihood Method ◽

Correct Identification ◽

Pathogenicity Test ◽

First Report ◽

The Core ◽

Representative Isolate

Muskmelon (Cucumis melo L.) is one of the most widely cultivated and economically important fruit crops in the world. However, many pathogens can cause decay of muskmelons; among them, Fusarium spp. is the most important pathogen, affecting fruit yield and quality (Wang et al. 2011). In May 2017, fruit rot symptoms were observed on ripening muskmelons (cv. Jipin Zaoxue) in several fields in Liaocheng of Shandong Province, China. Symptoms appeared as brown, water-soaked lesions, irregularly circular in shape, with the lesion size ranging from a small spot (1 to 2 cm) to the decay of the entire fruit. The core and the surface of the infected fruit were covered with white to rose-reddish mycelium. Two infected muskmelons were collected from each of two fields, 10 km apart. Tissues from the inside of the infected fruit were surface disinfected with 75% ethanol for 30 s, and cultured on potato dextrose agar (PDA) at 25 °C in the dark for 5 days. Four purified cultures were obtained using the single spore method. On carnation leaf agar (CLA), macroconidia had a pronounced dorsiventral curvature, falcate, 3 to 5 septa, with tapered apical cell, and foot-shaped basal cell, measuring 19 to 36 × 4 to 6 μm. Chlamydospores were abundant, 5.5–7.5 μm wide, and 5.5–10.5 μm long, ellipsoidal or subglobose. No microconidia were observed. These morphological characteristics were consistent with the descriptions of F. pernambucanum (Santos et al. 2019). Because these isolates had similar morphology, one representative isolate was selected for multilocus phylogenetic analyses. DNA was extracted from the representative isolate using the CTAB method. The nucleotide sequences of the internal transcribed spacers (ITS) (White et al. 1990), translation elongation factor 1-α gene (TEF1), RNA polymerase II second largest subunit gene (RPB2), calmodulin (CAM) (Xia et al. 2019) were amplified using specific primers, sequenced, and deposited in GenBank (MN822926, MN856619, MN856620, and MN865126). Based on the combined dataset of ITS, TEF1, RPB2, CAM, alignments were made using MAFFT v. 7, and phylogenetic analyses were processed in MEGA v. 7.0 using the maximum likelihood method. The studied isolate (XP1) clustered together with F. pernambucanum reference strain URM 7559 (99% bootstrap). To perform pathogenicity test, 10 μl of spore suspensions (1 × 106 conidia/ml) were injected into each muskmelon fruit using a syringe, and the control fruit was inoculated with 10 μl of sterile distilled water. There were ten replicated fruits for each treatment. The test was repeated three times. After 7 days at 25 °C, the interior of the inoculated muskmelons begun to rot, and the rot lesion was expanded from the core towards the surface of the fruit, then white mycelium produced on the surface. The same fungus was re-isolated from the infected tissues and confirmed to fulfill the Koch’s postulates. No symptoms were observed on the control muskmelons. To our knowledge, this is the first report of F. pernambucanum causing of fruit rot of muskmelon in China. Considering the economic value of the muskmelon crop, correct identification can help farmers select appropriate field management measures for control of this disease.

Download Full-text

Descriptions of four new dextral land snails of the genus Camaena (Gastropoda, Eupulmonata, Camaenidae) from south China

ZooKeys ◽

10.3897/zookeys.996.54187 ◽

2020 ◽

Vol 996 ◽

pp. 37-58

Author(s):

Pei Wang ◽

Mei-Ling Hu ◽

Jun-Hong Lin ◽

Hai-Fang Yang ◽

Xiao-Jing Li ◽

...

Keyword(s):

New Species ◽

South China ◽

Dna Sequences ◽

Reproductive System ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Land Snails ◽

Shell Morphology ◽

Molecular Phylogenetic ◽

Living Environments

In this study, four new dextral camaenid from China are reported, based on shell morphology, reproductive system anatomy, and molecular phylogenetic analyses: Camaena funingensis Zhou, Wang & Lin, sp. nov., Camaena gaolongensis Zhou, Wang & Lin, sp. nov., Camaena maguanensis Zhou, Wang & Hu, sp. nov., and Camaena yulinensis Zhou, Wang & Hu, sp. nov. Detailed descriptions of the morphological characteristics including shells and genitalia, DNA sequences, and living environments of the four new species are provided, with further comparisons with congeners.

Download Full-text

Alternaria spp. associated with leaf blight of maize in Heilongjiang Province, China

Plant Disease ◽

10.1094/pdis-06-21-1151-re ◽

2021 ◽

Author(s):

Xi Xu ◽

Li Zhang ◽

Xilang Yang ◽

Hanshui Cao ◽

Jingjing Li ◽

...

Keyword(s):

Rna Polymerase Ii ◽

Disease Incidence ◽

Morphological Characteristics ◽

Population Expansion ◽

Leaf Blight ◽

Economic Losses ◽

Heilongjiang Province ◽

Maize Leaves ◽

Alternaria Species ◽

Alternaria Sp

Maize is a major economic crop worldwide. Maize can be infected by Alternaria species causing leaf blight that can result in significant economic losses. In this study, 168 Alternaria isolates recovered from symptomatic maize leaves were identified based on morphological characteristics, pathogenicity, and multi-locus sequence analyses of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), the internal transcribed spacer of ribosomal DNA (rDNA ITS), the RNA polymerase II second largest subunit (RPB2), and histone 3 (HIS3). Maize isolates grouped to four Alternaria species including Alternaria tenuissima, A. alternata, A. burnsii, and Alternaria sp. Notably, A. tenuissima (71.4%) was the most prevalent of the four isolated species, followed by A. alternata (21.5%), Alternaria sp. (4.1%), and A. burnsii (3.0%). Pathogenicity tests showed that all four Alternaria species could produce elliptic to nearly round, or strip lesions on leaves of maize, gray white to dry white in the lesions center and reddish brown in the edge. The average disease incidence (58.47%) and average disease index (63.55) of maize leaves inoculated with A. alternata were significantly higher than levels resulting from A. tenuissima (55.28% and 58.49), Alternaria sp. (55.34% and 58.75), and A. burnsii (56% and 55). Haplotype analyses indicated that there were 14 haplotypes of A. tenuissima and 5 haplotypes of A. alternata in Heilongjiang province and suggested the occurrence of a population expansion. Results of the study showed that Alternaria species associated with maize leaf blight in Heilongjiang province are more diverse than those have been previously reported. This is the first report globally of A. tenuissima, A. burnsii, and an unclassified Alternaria species as causal agents of leaf blight on maize.

Download Full-text