Molecular Identification of Sweet potato virus C on Sweetpotato in Bali, Indonesia

A survey was conducted in several sweet potato cultivations in Bali Province. Survey found that many plants exhibited potyvirus symptom, such as chlorosis blotches. This study was to determine disease incidence, detection and identification of the virus causing these symptoms on sweet potato plants in Bali. Samples were collected by purposive sampling of 10 plants from each location in Bali (Denpasar, Gianyar, Badung, Buleleng, Tabanan, Klungkung, Karangasem, Jembrana, Bangli). Disease insidence was observed based on viral symptoms in the field. Identification of nucleic acids was done using Potyvirus universal primer and DNA sequencing. Disease incidence in Bangli, Buleleng, and Denpasar Regencies was > 50%. RT-PCR and CiFor/CiRev Potyvirus universal primers successfully amplified ± 700 bp of CI genes from all samples from Bangli, while samples from 8 other districts were not amplified using the same primers. The SPVC isolate of sweet potato showed nucleotide and amino acid homology similarities with the sweet potato isolate from East Timor (MF572066), 96.8% and 97.4%, respectively and these were referred to the "Asian" strain. This indicates that SPVC has spread in East Java and Bali.

Susceptibility of Weedy Hosts from Pacific Northwest Potato Production Systems to Crop-Aggressive Isolates of Verticillium dahliae

Verticillium wilt, caused by Verticillium dahliae, is a disease of dicotyledonous crops such as potato and has a wide host range and persistent, long-term survival structures called microsclerotia that can persist in soil for up to 14 years. Some V. dahliae isolates are particularly aggressive on a specific plant host while retaining the ability to infect a wide range of other hosts. Weeds can serve as hosts for V. dahliae but whether they serve as sources of inoculum for aggressive isolates of V. dahliae to crop hosts is unknown. The goal of this research was to quantify V. dahliae microsclerotia obtained from 16 weeds which were grown in the greenhouse. Potting medium was infested with one of eight V. dahliae isolates from potato, mint, sugar beet, sunflower, tomato, and watermelon. The isolates from mint and potato were aggressive on the host from which they were originally isolated. All 16 weeds were infected by at least one V. dahliae isolate, although the number of microsclerotia produced from some infections was relatively low (≤5 microsclerotia/g of dry plant). Black nightshade yielded greater numbers of microsclerotia of the V. dahliae potato isolate than any other isolate in three of four trials in the greenhouse (second trial false discovery rate, adjusted P ≤ 0.0158; third trial, P ≤ 0.0264; and fourth trial, P ≤ 0.0193). Litchi tomato yielded greater numbers of microsclerotia of the V. dahliae potato isolate than any other isolate in one of four trials (first trial, P ≤ 0.0149). A V. dahliae isolate from tomato yielded greater numbers of microsclerotia in large crabgrass and wild oat in a second trial (P ≤ 0.0158). Weeds, depending on the species, grown during and between potato crop rotations may increase the number of microsclerotia of the potato-aggressive isolates of V. dahliae.

First Report of Tomato yellow ring virus (Tospovirus, Bunyaviridae) Infecting Tomato in Kenya

Tomato (Lycoperscion esculentum) is one of the most popular vegetables and a major source of nutrition and income for smallholders in Africa. Thrips-transmitted tospoviruses are among the economically important pathogens of tomatoes that cause significant crop losses worldwide (3). In surveys for Tomato spotted wilt virus (TSWV) in the major tomato production areas of Kenya between March 2010 and January 2012, tomato fruits with chlorotic ring spots on fruits with stem and leaf necrosis were observed frequently. The symptoms were more evident in the dry seasons and disease incidence ranged from 28 to 42%. The pathogen did not react with antiserum specific to TSWV (Agdia Biofords, Ervy, France) in double-antibody sandwich (DAS)-ELISA. Furthermore, the pathogen did not react with antiserum specific to Capsicum chlorosis virus (CaCV), Chrysanthemum stem necrosis virus (CSNV), Groundnut ring spot virus (GRSV), Impatiens necrotic spot virus (INSV), Iris yellow spot virus (IYSV), and Watermelon silver mottle virus (WSMoV) (Agdia Biofords and DSMZ, Germany) in DAS-ELISA, but reacted positively to antiserum specific to Tomato yellow fruit ring virus (TYFRV) (DSMZ, AS0526). The nucleocapsid (N) gene specific primers (TFfor: 5′-ACTCATTAAAATGCATCGTTCT-3′ and TFrev: 5′-CTAAGTAAACACCATGGCTACC-3′ as forward and reverse primers, respectively) were designed by choosing six conserved regions of the N gene sequences of known TYFRV and Tomato yellow ring virus (TYRV) sequences available from GenBank. Using these primers, TYRV infection of tomatoes collected from Loitokitok, Kenya (2.73°S, 37.51°E) was confirmed by reverse transcription (RT)-PCR. PCR products of approximately 912-bp were obtained from six out of 11 symptomatic tomato samples tested, but not from healthy and water controls. Amplicons were gel-purified using QuickClean II Gel Extraction Kit (GenScript, UK) and sequenced using TFfor and TFrev primers. A consensus sequence was generated using Geneious Pro 5.5.6 Software (Biomatters Ltd., Auckland, NZ). The BLAST revealed that the N-gene sequence of the Kenyan tomato isolate (GenBank Accession No. JQ955615) had sequence identity with the Cineraria isolate (98.5%) (Accession No. DQ788693.1) and the Anemone isolate (98.1%) (Accession No. DQ788694.1) of TYRV (4) from Fars Province, Iran; an Alstroemeria isolate (98.4%) (Accession No. HQ154130.1) and two tomato isolates (98.3%) (Accession Nos. HQ154131.1 and AY686718.1) of TYRV from northern Khorasan Province, Iran, and a tomato isolate (98.1%) (Accession No. AJ493270.1) of TYFRV from Varamin, Iran. The Kenyan tomato isolate differed from a TYFRV potato isolate (87.5%) from Iran (Accession No. EU126931.1) (1), a TYRV potato isolate (87.5%) from Iran (Accession No. JF836812.1); a soybean isolate of TYRV (87.4%) from Iran (Accession No. DQ462163.1) (2), and showed significant divergence from that of Polygonum ringspot virus from Italy (81%) (Accession No. EF445397.1). To our knowledge, this is the first report of TYRV infecting tomatoes in Kenya. Further surveys and monitoring of TYRV incidence and distribution in the region, vector competence of thrips species, and impact on the crop yield are in progress. References: (1) A. R. Golnaraghi et al. Plant Dis. 92:1280, 2008. (2) A. Hassani-Mehraban et al. Arch. Virol. 152:85, 2007. (3) H. R. Pappu et al. Virus Res. 141:219, 2009. (4) R. Rasoulpour and K. Izadpanah, Austral. Plant Pathol. 36:285, 2007.

PEMANFAATAN BEBERAPA ISOLAT Trichoderma harzianum SEBAGAI AGENSIA PENGENDALI HAYATI PENYAKIT LAYU FUSARIUM PADA BAWANG MERAH IN PLANTA

ABSTRACT The green house research aimed to know the best isolate of T. harzianum in controlling Fusarium wilt , shallot production, and the effect of T. harzianum application time in suppressing the disease. Randomized block design was used with twelve treatments. Each treatment was replicated three times. The treatments were negative control, positive control as wel as extract of ginger isolate, banana isolate, shallot isolate, potato isolate, and ginseng isolates. The treatments were applied a week before or after inoculation of the pathogen. The result showed that the antagonist extract of ginger isolate applied a week before inoculation decreased the disease intensity by 43.854%. The antagonist extract application applied before or after inoculation were not significant difference . The antagonist of potato isolate extract was the best in increasing number of plants per clump and tuber fresh weight resulting 9.7503 and 13.133 g, respectively. The best extract in increasing root growth was shallot extract. The ginger isolate extract increased root length by 17.672%. Keywords: Trichoderma harzianum isolates, biological control, Fusarium wilt, shallot ABSTRAK Penelitian rumah kasa ini bertujuan untuk mengetahui isolat T. harzianum yang paling baik dalam mengendalikan penyakit moler dan meningkatkan hasil bawang merah, serta pengaruh waktu pemberian T. harzianum dalam menekan penyakit moler. Rancangan yang digunakan adalah Rancangan Acak Kelompok (RAK), yang terdiri atas 12 perlakuan dengan 3 ulangan. Perlakuan yang dicoba adalah kontrol negatif (tanpa perlakuan T. harzianum dan Fusarium oxysporum) dan kontrol positif (hanya dengan inokulasi F. oxysporum), serta ekstrak isolat jahe, pisang, bawang merah, kentang, dan ginseng yang diberikan 1 minggu sebelum atau sesudah inokulasi. Hasil penelitian menunjukkan bahwa ekstrak T. harzianum isolat jahe yang disiram sebelum inokulasi Fusarium oxysporum, mampu menurunkan intensitas penyakit sebesar 43,854%. Belum terlihat jelas pengaruh nyata pemberian ekstrak antagonis sebelum maupun sesudah inokulasi patogen. Ekstrak T. harzianum isolat kentang adalah isolat terbaik dalam meningkatkan jumlah anakan per rumpun dan bobot basah umbi, yaitu masing-masing 9,7503 dan 13,133 g, sedangkan ekstrak terbaik dalam pertumbuhan akar yaitu isolat bawang merah yang meningkatkan jumlah akar sebesar 57,452% dan ekstrak isolat jahe menunjukkan pengaruh terbaik meningkatkan panjang akar sebesar 17,672%. Eugenia Volume 17 No. 2 Agustus 2011 Kata Kunci: Isolat Trichoderma harzianum, pengendalian hayati, penyakit layu Fusarium, bawang merah

Aggressiveness and Competitive Fitness of Phytophthora infestans Isolates Collected from Potato and Tomato in France

To test the hypothesis that host-related differences in the genotypic composition of populations of the late blight pathogen Phytophthora infestans can be explained by differential pathogenicity, the aggressiveness of isolates of the pathogen collected in France from potato and tomato was measured on detached leaflets of potato (cv. Bintje) and tomato (cv. Marmande). A preliminary trial with four isolates (two each from potato and tomato) showed that lesion appearance and development were similar for each isolate in detached leaflets and in whole plant tests in growth cabinets. Isolates collected from tomato were more pathogenic to tomato than isolates collected from potato. This was particularly the case for isolates belonging to the A2 mating type. Isolates originating from potato had a higher infection efficiency and a higher sporulation capacity on this host, but they induced lesions that generally spread more slowly than those caused by isolates from tomato. Extensive variation for components of aggressiveness on potato, and to a lesser extent on tomato, was observed in collections of isolates from each of the two hosts. Competition experiments between one potato isolate and one tomato isolate in field plots of the susceptible potato cv. Bintje clearly demonstrated the higher competitive fitness of the potato isolate on its host of origin. Therefore, differential pathogenicity to potato and tomato certainly contributes to the differentiation between P. infestans populations present on potato and tomato in France; however, additional factors, possibly related to survival ability or random genetic drift, are probably also involved and may explain the persistence of weakly pathogenic isolates in these populations.

Verticillium Wilt of Paprika Caused by a Highly Virulent Isolate of Verticillium dahliae

Verticillium dahliae caused wilting, stunting and early dying of paprika plants in Israel, resulting in a 22% reduction in yield. A V. dahliae isolate from diseased paprika plants was slower growing on agar medium than V. dahliae isolates from potato, tomato, watermelon, and Dodonaea, but formed microsclerotia earlier. The paprika isolate of V. dahliae was highly virulent to paprika in pathogenicity tests. Disease severity indices obtained from three paprika cultivars ranged from 3.7 to 4.9 (on a scale of 0 to 5). The disease caused height reductions of 43 to 62% in the three inoculated paprika cultivars, and pathogen colonization levels were 10- to 35-fold higher in stems than in leaves. The potato isolate of V. dahliae did not produce symptoms or cause stunting of paprika, and could not be detected in stems or leaves. The tomato, watermelon, and Dodonaea isolates did not cause disease symptoms in paprika, although they colonized the plant tissue. In potato and eggplant, the paprika isolate caused a higher incidence of disease with more severe symptoms and a higher level of tissue colonization than did the potato isolate.