Trichoderma harzianum IS005-12 promotes germination, seedling growth and seedborne fungi suppression in Italian ryegrass forage

Potential of Trichoderma harzianum IS005-12 (TH-IS005-12) to promote seed germination and seedling growth of Italian ryegrass (IRG) forage was evaluated in vitro. Non-desiccated seeds and those pre-harvestly desiccated with total herbicide were treated 25 days (freshly harvested) and 178 days after harvest (mature) with TH-IS005-12 spore suspensions at 0 (T0), 1.8 × 10⁷ (T1) and 1.2 × 10⁹ (T2) spore/mL. TH-IS005-12 promoted the early and final germination and seedling growth in all non-desiccated and desiccated, freshly harvested as well as mature IRG seeds. It was more effective in pre-harvestly desiccated freshly harvested seeds where T2 treatment increased final germination rate for 24%, root number per seedling 1.6-fold and seedling vigour 1.9-fold compared to the untreated control. Moreover, TH-IS005-12 showed an inhibitory activity against seedborne fungi Alternaria alternata and A. ventricosa suppressing their growth in vitro by 82% and 77%, respectively.

Antifungal Activity and Chemical Composition of Seven Essential Oils to Control the Main Seedborne Fungi of Cucurbits

Essential oils represent novel alternatives to application of synthetic fungicides to control against seedborne pathogens. This study investigated seven essential oils for in vitro growth inhibition of the main seedborne pathogens of cucurbits. Cymbopogon citratus essential oil completely inhibited mycelial growth of Stagonosporopsis cucurbitacearum and Alternaria alternata at 0.6 and 0.9 mg/mL, respectively. At 1 mg/mL, Lavandula dentata, Lavandula hybrida, Melaleuca alternifolia, Laurus nobilis, and two Origanum majorana essential oils inhibited mycelia growth of A. alternata by 54%, 71%, 68%, 36%, 90%, and 74%, respectively. S. cucurbitacearum mycelia growth was more sensitive to Lavandula essential oils, with inhibition of ~74% at 1 mg/mL. To determine the main compounds in these essential oils that might be responsible for this antifungal activity, they were analyzed by gas chromatography–mass spectrometry (GC-MS). C. citratus essential oil showed cirtal as its main constituent, while L. dentata and L. nobilis essential oils showed eucalyptol. The M. alternifolia and two O. majorana essential oils had terpinen-4-ol as the major constituent, while for L. hybrida essential oil, this was linalool. Thus, in vitro, these essential oils can inhibit the main seedborne fungi of cucurbits, with future in vivo studies now needed to confirm these activities.

Diversity of the Seedborne Fungi and Pathogenicity of Fusarium Species Associated with Intercropped Soybean

Maize/soybean relay strip intercropping has been widely practiced in Southwest China due to its high productivity and effective application of agricultural resources; however, several seedborne diseases such as seedling blight, pod and seed decay are frequently observed causing severe yield loss and low seed quality. So far, the population and pathogenicity of the seedborne fungi associated with intercropped soybean remain unexplored. In this study, seeds of 12 soybean cultivars screened for intercropping were collected from three growing regions in Sichuan Province of Southwest China, and the seedborne fungi were isolated from the surface-sterilized seeds. Based on sequence analysis of ribosomal DNA internal transcribed spacer (rDNA ITS), 148 isolates were identified into 13 fungal genera, among which Fusarium covered 55.0% as the biggest population followed by Colletotrichum. Furthermore, Fusarium isolates were classified into five distinct species comprising F. fujikuroi, F. proliferatum, F. verticillioides, F. asiaticum and F. incarnatum through sequence analysis of translation elongation factor 1 alpha (EF-1α) and DNA-directed RNA ploymerase II second largest subunit (RPB2). Among them, F. fujikuroi accounted for 51.22% (42/82) and was isolated from 91.7% (11/12) soybean varieties. Pathogenicity assay showed that five Fusarium species were able to infect the seeds of soybean cultivar “Nandou12” and caused water-soaked or rot symptoms, while F. fujikuroi and F. asiaticum had much higher aggressiveness than other species with significant reductions of seed fresh weight and germination percentage. Accordingly, this study indicates that Fusarium species are the dominant seedborne fungi in the intercropped soybean in Sichuan, China, and this provides some useful references for the effective management of seedborne fungal diseases as well as soybean resistance breeding in maize/soybean relay strip intercropping.

ISOLASI DAN IDENTIFIKASI CENDAWAN TERBAWA BENIH KAKAO HIBRIDA

<p>ABSTRAK<br />Benih merupakan komponen dasar dalam menentukan produktivitas<br />tanaman kakao. Benih yang sehat dapat merupakan faktor penting dalam<br />menentukan keberhasilan produktivitas kakao. Benih kakao mempunyai<br />kadar air cukup tinggi sehingga berpotensi terinfeksi cendawan, yang<br />dapat menurunkan mutu benih dan produksi kakao. Penelitian bertujuan<br />untuk mengisolasi dan mengidentifikasi beberapa cendawan terbawa benih<br />pada kakao hibrida. Penelitian dilakukan di Kebun Induk Benih Pusat<br />Penelitian Kopi dan Kakao Indonesia, Jember, Laboratorium Mikro-<br />biologi, Balai Penelitian Bioteknologi Perkebunan Indonesia, dan<br />Laboratorium Pengendalian Hayati IPB Bogor pada bulan Juni sampai<br />Oktober 2008. Penelitian menggunakan benih kakao hibrida dari hasil<br />persilangan buatan antar TSH 858 dengan Sca 6, dan percobaan disusun<br />dengan rancangan acak lengkap dengan 3 ulangan. Benih ditumbuhkan<br />pada 3 media, yaitu water agar (WA), potato dextrose agar (PDA), dan<br />kertas saring (KS). Tingkat infeksi pada benih diamati setiap hari dan<br />dianalisis dengan analisis sidik ragam dan dilanjutkan dengan uji selang<br />berganda Duncan. Cendawan diisolasi, dibiakkan, dimurnikan, dan<br />diidentifikasi dengan menggunakan buku kunci identifikasi. Tingkat<br />infeksi cendawan terbawa benih kakao hibrida tertinggi terdapat pada hari<br />keempat (35,00%) dan kelima (51,67%) pada media PDA. Sebanyak 13<br />spesies cendawan terbawa benih kakao hibrida berhasil diidentifikasi<br />dengan menggunakan media WA dan PDA, serta 8 spesies cendawan<br />dengan media KS. Ke-13 cendawan terbawa benih yang ditemukan sangat<br />berpotensi menurunkan mutu fisiologis benih dan produktivitas kakao.<br />Cendawan tersebut perlu diuji lebih lanjut karena masing-masing memiliki<br />sifat-sifat patogenik, saprofitik, atau antagonistis terhadap cendawan lain<br />pada benih kakao. Cendawan terbawa benih kakao hibrida paling dominan<br />adalah Aspergillus spp., Penicillium chrysogenium, Coletotrichum<br />acutatum, Curvularia geniculata, dan Fusarium spp. Cendawan-cendawan<br />yang diduga berbahaya adalah Aspergillus spp., Coletotrichum acutatum,<br />Curvularia geniculata, Fusarium spp., Phoma glomerata, dan<br />Macrophoma sp., dan yang diduga bersifat patogenik adalah Aspergillus<br />flavus, Aspergillus ochraceus, Cladosporium herbanum, Curvularia<br />geniculata, Fusarium oxysporum, Phoma glomerata, dan Macrophoma sp.</p><p>Kata kunci : Theobroma cacao, benih hibrida, infeksi cendawan, media<br />tanam</p><p>Isolation and Identification of Fungi on Hybrid Cacao Seeds</p><p>ABSTRACT<br />Seed is the basic component influencing the productivity of cacao<br />plantation. Healthy seed is the most important factor in determining the<br />success of cacao productivity. Moisture content of cacao seeds is quite<br />high potentially to cause fungi infection, which can further reduce seed<br />quality and cacao production. The research aimed at isolating and<br />identifying several seedborne fungi on hybrid cacao. The study was<br />conducted at main nursery of Indonesian Coffee and Cocoa Research<br />Institute Jember, Laboratory of Microbiology, Indonesian Biotechnology<br />Research Institute for Estate Crops, and the Laboratory for Biological<br />Control of IPB Bogor from June to October 2008. Research used hybrid<br />cacao seeds derived from crossing between TSH 858 x SCA 6, and the<br />experiment was arranged using completely randomized design with three<br />replicates. Cacao seeds were grown on three media, i.e. water agar (WA),<br />potato dextrose agar (PDA), and filter paper (KS). Infection rates on the<br />seedlings were observed every day and analyzed using ANOVA followed<br />by Duncan's multiple regression test (DMRT). Fungi were isolated,<br />cultured, purified, and identified using the identification keys. The highest<br />rate of seedborn fungal infection occured on fourth (35.00%) and fifth<br />(51.67%) days on PDA media. A total of 13 species of seedborn fungi on<br />hybrid cocoa were identified by using WA and PDA media, as well as 8<br />other species by using KS. The 13 seedborne fungi potentially reduce seed<br />physiological quality and cacao productivity. These fungi need to be<br />further tested because each has its own pathogenic, saprophytic, or<br />antagonistic properties towards other fungi on cacao seeds. Predominant<br />seedborn fungi on hybrid cacao were Aspergillus spp., Penicillium<br />chrysogenium, Coletotrichum acutatum, Curvularia geniculata, and<br />Fusarium spp. The fungi suspected harmful were Aspergillus spp.,<br />Coletotrichum acutatum, Curvularia geniculata, Fusarium spp., Phoma<br />glomerata, and Macrophoma sp., and those suspected pathogenic were<br />Aspergillus flavus, Aspergillus ochraceus, Cladosporium herbanum,<br />Curvularia geniculata, Fusarium oxysporum, Phoma glomerata, and<br />Macrophoma sp.<br />Key words : Theobroma cacao, fungi infection, hybrid seed, growing<br />media</p>

Morphological and Molecular Identification of Seedborne Fungi in Squash (Cucurbita maxima, Cucurbita moschata)

Squash is one of the most important crops of tropical and temperate regions, and it can be affected by several fungal pathogens. Most of these pathogens infect the seeds, which become an efficient vehicle to disperse seedborne pathogens over long distances, with consequent severe crop losses. The main objective of this study was the identification of the principal seedborne fungi in seeds extracted from 66 samples of asymptomatic and symptomatic squash fruit (Cucurbita maxima, Cucurbita moschata) collected in two countries, Tunisia and Italy. The symptoms of fruit decay were identified and classified according to lesion size. Following the blotter test, 14 fungal species were detected from the seeds. Seedborne fungi were identified in all fruit samples tested, including asymptomatic fruit. The most frequent fungi from Tunisian seeds were Alternaria alternata (25.1%), followed by Stagonosporopsis cucurbitacearum (24.6%), Fusarium solani (16.6%), Rhizopus stolonifer (13.3%), F. fujikuroi (7.8%), Albifimbria verrucaria (3.3%), and Stemphylium vesicarium (2.3%). For the fruits from Italy, the most frequently identified fungal species in seed samples were Alternaria alternata (40.0%), followed by F. fujikuroi (20.8%), Stemphylium vesicarium (3.0%), and Curvularia spicifera (2.1%). Morphological identification was confirmed by molecular diagnosis using the available species-specific primers. Furthermore, specific primers were designed to identify Albifimbria verrucaria, Paramyrothecium roridum, and Stemphylium vesicarium. Application of seed-health testing methods, including such conventional and molecular diagnostic tools, will help to improve seed quality and crop yields.

Seleksi Bakteri Endofit Penghasil Senyawa Metabolit untuk Pengendalian Cendawan Patogen Terbawa Benih Jagung

Endophytic bacteria have been reported to produce metabolite as antifungal compound. This study was aimed to obtain endophytic bacteria which are able to produce metabolite to control Fusarium sp., a potential seedborne fungi on maize. Endophytic bacteria were screened by hypersensitive test on tobacco leaves and antagonistic test. Endophytic bacteria isolates with high growth inhibitor activity were selected and examined for their metabolite compound. Thre isolates, i.e. Lactobacillus sp. isolate EF14III, Pseudomonas sp. isolate ER1I, dan Aeromonas sp. isolate ER10I has the potential to inhibit Fusarium sp.. Metabolite compound of Pseudomonas sp. isolates ER1I was able to decrease the infection Fusarium sp. by 65.0% in blotter test and decreased infection of Fusarium sp. up to 59.5% and 60.5% in growing on test using water agar and sterile soil, respectively. Cyclohexanone with concentration of 9.68% produced by Pseudomonas sp. isolat ERI1 may play a role as antifungal compound.