Blueberry (Vaccinium spp.) is becoming increasingly popular in China as a nutritional berry crop. With the expansion of blueberry production, many diseases have become widespread in different regions of China. In August of 2012, stem and leaf spots symptomatic of anthracnose were sporadically observed on highbush blueberries in a field located in Liaoning, China, where approximately 15% of plants were diseased. Symptoms first appeared as yellow to reddish, irregularly-shaped lesions on leaves and stems. The lesions then expanded, becoming dark brown in the center and surrounded by a reddish halo. Leaf and stem tissues (5 × 5 mm) were cut from the lesion margins and surface-disinfected in 70% ethanol for 30 s, followed by three rinses with sterile water before placing on potato dextrose agar (PDA). Plates were incubated at 28°C. Colonies were initially white, becoming grayish-white to gray with yellow spore masses. Conidia were one-celled, hyaline, and cylindrical with rounded ends, measuring 15.0 to 25.0 × 4.0 to 7.5 μm. No teleomorph was observed. The fungus was tentatively identified as Colletotrichum gloeosporioides (PenZ.) PenZ & Sacc. (teleomorph Glomerella cingulata (Stoneman) Spauld. & H. Schrenk) based on morphological characteristics of the colony and conidia (1). Genomic DNA was extracted from isolate XCG1 and the internal transcribed spacer (ITS) region of the ribosomal DNA (ITS1–5.8S-ITS2) was amplified with primer pairs ITS1 and ITS4. BLAST searches showed 99% identity with C. gloeosporioides isolates in GenBank (Accession No. AF272779). The sequence of isolate XCG1 (C. gloeosporioides) was deposited into GenBank (JX878503). Pathogenicity tests were conducted on 2-year-old potted blueberries, cv. Berkeley. Stems and leaves of 10 potted blueberry plants were wounded with a sterilized needle and sprayed with a suspension of 105 conidia per ml of sterilized water. Five healthy potted plants were inoculated with sterilized water as control. Dark brown lesions surrounded by reddish halos developed on all inoculated leaves and stems after 7 days, and the pathogen was reisolated from lesions of 50% of inoculated plants as described above. The colony and conidial morphology were identical to the original isolate XCG1. No symptoms developed on the control plants. The causal agent of anthracnose on blueberry was identified as C. gloeosporioides on the basis of morphological and molecular characteristics, and its pathogenicity was confirmed with Koch's postulates. Worldwide, it has been reported that blueberry anthracnose might be caused by C. acutatum and C. gloeosporioides (2). However, we did not isolate C. acutatum during this study. To our knowledge, this is the first report of stem and leaf anthracnose of blueberry caused by C. gloeosporioides in China. References: (1) J. M. E. Mourde. No 315. CMI Descriptions of Pathogenic Fungi and Bacteria. Kew, Surrey, UK, 1971. (2) N. Verma, et al. Plant Pathol. 55:442, 2006.
Wheat is an important staple food crop in sub-Saharan Africa. However, the current wheat consumption of 900 000 tons in Kenya outweighs the wheat production of 350 000 tons given the high population growth and inflation. The stem rust currently poses the greatest threat to wheat production due to the emergence of the virulent race of the Puccinia graminis f. sp tritici, Ug99 (TTKS) and its variants Ug99 + Sr24 (TTKSK) and Ug99 + Sr36 (TTKST) leading to about 70 to 100% yield losses. This study aimed at evaluating twenty-five wheat genotypes for both field and seedling resistance to stem rust. The genotypes were grown in an alpha lattice design and in two replicates both in the greenhouse and in the field at Kenya Agricultural Research Institute (KARI), Njoro. The seedling stage infection types were scored based on Stakman et al. (1962) scale. At the adult plant stages, the stem rust disease severity was based on modified Cobb's scale. The genotypes showed diverse seedling and adult plant resistance responses. The most resistant entries, KSL-2, KSL-3 and KSL-20 also exhibited the pseudo black chaff (PBC) trait implying they contain the Sr2 gene in their background; the basis of breeding for durable resistance to stem rust in wheat. These lines with high stem rust resistance could be backcrossed to the adapted and high yielding but susceptible Kenyan wheat varieties to avert further wheat yield declines.
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