Blueberry (Vaccinium spp.) production in northeast China has grown remarkably in the last twenty years due to its highly nutritional and economic value. As blueberry acreage increases, the diversity of diseases and challenges for control are gaining more attention. In August 2009, unusual leaf spots were observed on one-year-old potted lowbush blueberry (V. angustifolium) in the blueberry testing grounds of Jilin Agricultural University in Changchun city, China. Disease incidence ranged from 40% to 100% in some poorly-ventilated areas of the nursery garden. The infection began as small brown dots on the leaves. These dots enlarged to a diameter of 3-4 mm and progressed to form deep brown, circular, elliptical or irregular spots with a dark red halo around the margin (Fig. 1). In a humid environment, black, sessile and discoid conidiomata developed on the spots and exuded a pink spore mass that turned brown with age. Leaves eventually dropped off with the disease.Infected leaves were surface-sterilized and plated onto potato dextrose agar (PDA). The plates were incubated at 25°C for 5-10 days. The fungal colonies on PDA showed white mycelia covered with black globular acervuli. Microscopic observation revealed typical conidia of Pestalotiopsis sp. These were five-celled mature conidia (three darker median and two hyaline end cells) with dimensions 21.0-26.0 x 6.5-7.8 μm, with two to four (mostly three) apical appendages 21-32 μm long, and one basal appendage 3.5-5.8 µm long. Based on these morphological characteristics, the fungus was identified as Pestalotiopsis photiniae (Guba EF, 1961). Pathogenicity was tested by spraying a suspension of conidia (1 x 10 5 conidia/ ml) on the leaves of healthy blueberry plants, distilled water serving as control. After 7-10 days, the symptoms described above were observed on the leaves of all the inoculated plants, whereas these symptoms did not develop on the control plants. The same fungus was re-isolated from diseased leaves, confirming Koch's postulates. The ITS sequence (GenBank Accession No. GU395992) obtained from this strain (Pp.jlnd09) was 99% identical to that of P. photiniae KUC5019 (GenBank Accession No. GQ241287). The morphological and molecular data corresponded to those of P. photiniae. Although a leaf spot disease caused by P. clavispora in China was reported in 2008 (Luan et al., 2008), the pathogens and symptoms of these two leaf spot diseases on blueberry are different according to a comparison of the present study with that of Luan et al. (2008). Firstly, the species on which leaf spot disease was observed in our study was lowbush blueberry (V. angustifolium);in Luan et al. (2008) it was half-high blueberry (V. corymbosum). Secondly, the size of leaf spots (3-4 mm) observed in our study was smaller than those (4-8 mm) reported earlier and we also observed a clear dark red halo around the margin of lesions, not previously reported (Luan et al., 2008). Thirdly, there were differences in the characteristics of the mature conidia between the two Pestalotiopsi...
Thirty isolates of Apiosporina morbosa, which were isolated from wild chokecherry (Prunus virginiana), an ornamental cultivar of chokecherry with purple foliage (P. virginiana 'Shubert Select'), and domestic plum (Prunus domestica), were compared for morphological and molecular characteristics, using culture techniques and data from internal transcribed spacers (ITS) I and II, restriction fragment length polymorphisms (RFLP), and sequence-related amplified polymorphism (SRAP) analyses. Strains of A. morbosa grew as olive-green colonies that changed in about 2 weeks to a dark-brown colour. Cultures produced single-or two-celled and cylindrical conidia with tapering ends. Conidia had a mean size of 4.51 µm × 10.97 µm. The overall colony and conidial morphology in cultures of the A. morbosa isolates was generally similar to that of an isolate of Cladosporium herbarum. Pseudothecia were globose and produced clavate asci with unequally two-celled and club-shaped ascospores having mean sizes of 6.68-7.37 µm × 16.42-16.78 µm. RFLP markers produced by endonucleases DdeI, Bst98I, and VspI in the ITS region differentiated the pathogen isolates from other gall-associated fungi, but no difference was observed among the A. morbosa isolates, using these markers. The sequences of the ITS region had >99% similarity among 30 isolates of A. morbosa, and a total of eight unique genotypes were found, based on ITS sequence alignment. The most common genotype was manifested in 21 of 30 A. morbosa isolates, based on the ITS sequences. Three A. morbosa isolates had an identical sequence to that of an isolate of C. herbarum. A comparison with an isolate of Cladosporium cladosporioides showed that A. morbosa differed from C. cladosporioides by 3%, based on ITS sequences. SRAP analysis detected 18 unique genotypes and a high genetic diversity (H = 0.256) among 25 isolates of A. morbosa. The pathogen population isolated from wild chokecherry produced more unique genotypes and higher genetic diversity (H = 0.283) than the population from 'Shubert Select' (H = 0.165). However, an exact test indicated no differentiation between these two populations (P = 0.334) with a gene flow rate of 4.28. Most of the isolates from 'Shubert Select' were clustered in a subgroup in a phylogenetic dendrogram. Phylogenetic analysis of ITS sequences of the A. morbosa isolates in our study and related taxa extracted from GenBank revealed that A. morbosa had the closest genetic distance with Cladosporium spp.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.