Suryanti

Survey of Egg- and Cyst-parasitic Fungi of Potato Cyst Nematode in Indonesia

Department of Agricultural Biotechnology, Seoul National University, Seoul 151-921, Korea(Received on October 19, 2009; Accepted on November 18, 2009)Twelve fungal isolates out of 123 isolates obtained fromcysts and soils of potato cyst nematode (PCN)-infestedfields in Central Java, Indonesia had parasitic abilitiesof over 50% on PCN eggs or females (cysts) in vitropathogenicity tests. Cultural and morphological charac-ters and DNA sequences of ribosomal genes in ITSregion revealed that they were four isolates of Gliocla-dium (Trichoderma) virens, three isolates of Fusariumoxysporum, one of F. lateritium, one of Penicilliumtritinum and two of Taralomyces spp. A hundred percentinfections occurred in eggs or cysts by three fungal iso-lates G. virens, F. oxysporum and P. oxalicum, suggestingthat these fungi may have a good potential for the PCNbiocontrol. Especially, G. virens isolates, which occurredmost frequently in the PCN-infested potato fields andare known to be highly adaptable to varying habitats,may be developed as reliable agents for controlling PCNwith both egg- and cyst-parasitic capabilities and withhigh ecological adaptabilities. Keywords : biological control, egg- and cyst- parasiticfungi, potato cyst nematode, species identificationPotato cyst nematode (PCN) Globodera sp. is the mostdestructive pest in potato-producing countries worldwide(Berg, 2006). Since PCN was firstly found at some potatoplantation areas in Indonesia (Indarti et al., 2004; Mulyadiet al., 2003), the number of potato fields infested with PCNhas increased continuously, building up the nematodepopulations especially in Banjarnegara, Central Java, whichaffects on both potato yield and quality. This nematode issubjected to stringent quarantine and/or regulatory proce-dures in all countries wherever this nematode is found(Berg, 2006). Cysts of PCN are easily spread by seed tubers,farming activities, transport of infested soil, especially cystcan be carried in soil adhering to seed tubers, bins andplants, particularly bulbs (Williams, 1982). PCN is difficult to control, especially at the cyst stage.Eggs and larvae inside the cysts are well protected fromdesiccation and chemicals, and remain dormant for severalyears in the absence of host plants (Williams, 1982). Thenematodes at this stage are highly resistant so that chemicalcontrol and cultural practices are reduced in their efficacies.Biological control techniques offer a good alternative optionfor the management strategy against PCN. The rhizosphere of host plants contains a number ofmicroorganisms which are considered useful for the develop-ment of biological control agents. However, presence ofpotential egg and cyst-parasitic fungi and their characteri-stics as biological agents for PCN have not been fullystudied so far. Therefore, the objectives of this study were1) to explore PCN egg- and cyst-parasitic fungi, 2) toexamine their PCN-pathogenic ability for evaluating theegg- and cyst-parasitic fungi as biocontrol agents, and 3) toidentily fungal species in potato areas infested with PCN.

Pengimbasan Ketahanan Pisang terhadap Penyakit Layu Fusarium dengan Asam Salisilat In Vitro

Salicylic acid (SA) is an important signal in plant defense. It is used as induced resistance agent against Fusarium wilt. An artificial induction was conducted by shaking the shoot groups of banana tissue culture in liquid medium of Murashige-Skoog (MS). MS medium was added with 0 ppm (as control), ⅛ LC50, ¼ LC50, ½ LC50, and LC50 concentration of SA. Alive shoot groups were subcultured for about three months and were acclimated. Resistance test had been conducted in glass house by inoculated six months old banana seedlings with Fusarium oxysporum f.sp. cubense (Foc). Leaves symptom were observed based on Leaf Symptom Index (LSI) and corm discoloration based on Rhizome Discoloration Index (RDI). The result of this research showed that induced banana seedlings had higher plant resistance to Fusarium wilt than control. Asam salisilat (SA) merupakan signal penting dalam ketahanan tanaman, digunakan sebagaisenyawa pengimbas ketahanan tanaman pisang terhadap penyakit layu Fusarium. Pengimbasan dilakukan pada kelompok tunas kultur jaringan pisang dalam medium kultur jaringan MS cair dengan konsentrasi SA 0 ppm (sebagai kontrol), ⅛ LC50, ¼ LC50,½LC50 danLC50.Tunas yang bertahan hidup ditumbuhkan sebagai bibit dan uji ketahanan dilakukan dirumah kaca dengan inokulasiFusariumoxysporumf.sp. cubense (Foc) pada bibit pisang umur enambulan pasca aklimatisasi. Pengamatan dilakukan terhadap gejala layu pada daun (Leaf Symptom Index = LSI) dan diskolorasi pada bonggol (Rhizome Discoloration Index=RDI). Hasil penelitianmenunjukkan bahwa bibit pisang hasil pengimbasanmemiliki ketahanan yang lebih tinggi dibandingkan dengan perlakuan kontrol.

PENGENDALIAN PENYAKIT LAYU PISANG DENGAN FUSARIUM NONPATOGENIK DAN FLUORESCENT PSEUDOMONADS

The study was aimed to know the ability of fluorescent pseudomonads and nonpathogenic Fusarium for controlling fusarium wilt of banan. The research was conducted both in the laboratory and glass ouse in the Faculty of Agriculture Gadjah Mada University. Laboratorial trial incuded the examining of antagonistic capacity in vitro and the population of these two antagonistic microorganism in compost medium. The examination of the effect of these two microorganisms in compost medium against fusarium wilt of banana Ambon Kuning cultivar was conducted in a glass house. The result showed that there was no antagonistic mechanism occured between fluorescent pseudomonads and nonpathogenic Fusarium. The treatment of compost with fluorescent pseudomonads or/and nonpathogenic Fusarium showed that there were differences on the optimum population of these two antagonistic microorganisms. Fluorescent pseudomonads attained its optimum population one week after inoculation while nonpathogenic Fusarium attained its optimum population two weeks after inoculation. The glass house trial showed taht compost enriched with two microorganisms with one week inocubation time reduced percentage of wilted leaves, although it was nonsignificant with control treatment. Field experiment should be conducted with higher population density of antagonist microorganisms.

Identifikasi Ras Fisiologis Fusarium oxysporum f.sp. cubense Berdasarkan Sifat Kompatibel Secara Vegetatif dan Pembentukan Bahan Volatil

Race characterization of F. oxysporum Schlecht. f.sp. cubense (E.F. Smith) Snyd. & Hans. by determining disease reaction is difficult because the result may be biased due to the variability of growing condition. This study is aimed to identify physiological races of F. oxysporum f.sp. cubense in banana plantation in the province of Daerah Istimewa Yogyakarta by examining the relation of the fungal pathogen isolates. The identification of physiological races of F. oxysporum f.sp. cubense was based on vegetative compatibility groups (VCGs). The research was conducted in The Laboratory of Mycology Faculty of Agriculture GMU on March to November 2000. Observation of heterokarion formed by the mutant of F. oxysporum f.sp. cubense on selective medium was carried out in order to identify the compatibility of two different fungal isolates. Nitrate non utilizing (nit) mutants obtained without mutagen were used as the label. Nit mutant obtained from the same wild type isolates could form heterokarion on minimal agar medium containing NaNO 3 as nitrogen source. Eleven isolates of F. oxysporum f.sp. cubense have been isolated from several cultivars of banana. Vegetative compatibility tests showed that of 11 eleven isolates, there were six different group VCGs where four of them formed volatile compound in rice medium whereas two of them did not. Key words: Fusarium wilt, F. oxysporum f.sp. cubense , vegetative compatibility groups (VCGs)