Cultural and morphological characterisations of Fusicoccum sp., the causal agent of rubber (Hevea brasiliensis) leaf blight in Malaysia

Leaf blight caused by Fusicoccum sp. is becoming a serious canopy disease of rubber trees in Malaysia. Despite its increasing significance, information regarding the biology of the causal fungus is scarce. This study provides morphological data useful for its characterisation. Fungal isolates obtained from leaf samples collected from several rubber plantations in Selangor, Johor and Perak were compared in terms of their behaviour in various cultural media potato dextrose agar (PDA), Czapex-dox agar (CDA), corn meal agar (CMA) and malt extract agar (MEA). Furthermore, their incidence on rubber leaves was assessed. In all media and different pH tested, significant differences were observed in spore production, dimension of conidiomata and growth rates among isolates. On PDA, pH 6 supported the best growth compared to other media used. The growth rate was 16.8 mm/day on PDA and MEA, against 14.4 mm /day on CDA and 11.4 mm/day on CMA. The highest spore production (161.33 X 10 6 spores /mh) was obtained on PDA. The optimum temperature for spore germination in water agar was 24 °C 28 °C within a period of eight hours. AU fungal isolates tested were pathogenic to H. brasiliensis but showed variation in symptoms

Neofusicoccum ribis associated with leaf blight on rubber (Hevea brasiliensis) in Peninsular Malaysia

Hevea brasiliensis is a natural source of rubber and an important plantation tree species in Malaysia. Leaf blight disease caused by Fusicoccum substantially reduces the growth and performance of H. brasiliensis. The aim of this study was to use a combination of both morphological characteristics and molecular data to clarify the taxonomic position of the fungus associated with leaf blight disease. Fusicoccum species were isolated from infected leaves collected from plantations at 3 widely separated locations - Selangor, Perak, and Johor states - in Peninsular Malaysia in 2010. All the isolates were identified according to their conidial patterns and DNA sequences generated from internal transcribed spacers (ITS1 and ITS2), the 5.8S rRNA, and an unknown locus (BotF15) containing microsatellite repeats. Based on taxonomic and sequence data, Neofusicoccum ribis was identified as the main cause of leaf blight disease in H. brasiliensis in commercial plantations in Malaysia. A pathogenicity trial on detached leaves further confirmed that N. ribis causes leaf blight disease. N. ribis is an important leaf pathogen, and its detection in Malaysia has important implications for future planting of H. brasiliensis

Identification of Pithomyces chartarum causing leaf spot of cabbage in Malaysia

A leaf spot disease was observed on cabbage (Brassica oleracea L. var. capitata) affecting 80% of plants growing in greenhouses and fields in Serdang, Selangor, Malaysia. Symptomatic leaf samples were collected from infected plants and isolations made on agar medium. Single-spore isolates from resulting colonies were identified based on cultural and morphological characteristics as Pithomyces chartarum. Morphological identification was confirmed by sequence analysis of the internal transcribed spacer (ITS) regions 1 and 2, including 5.8S rDNA (ITS1-5.8S-ITS2). Pathogenicity tests indicated that P. chartarum causes leaf spot on cabbage. This is the first report of leaf spot caused by P. chartarum on cabbage in Malaysia

Transcriptional expression of three putative pathogenesis-related proteins in leaves of rubber tree (Hevea brasiliensis) inoculated with Neofusicoccum ribis

Pathogenesis related-proteins (PR-proteins) and enzymes are important tools for understanding the molecular markers of plant response to external factors. In this study, semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was optimized to detect the expressions of two PR-proteins and one enzyme extracted from the leaf RNA of two rubber clones (PB 350 and RRIM200) at four-period intervals. The expression patterns of enzymes β-1,3-glucanase (Glu), chitinase (Chit), and phenylalanine ammonia lyase (PAL) in the leaf tissues of the clones RRIM 2002 and PB 350 to Neofusicoccum ribis were expressed by up and down regulations and varied with time. The trial inoculation indicated that the gene expressions were significantly higher in tolerant clones (RRIM 2002) than in the susceptible clones (PB 350). Gene expression analysis of the biomarkers revealed that the earlier detection markers in infections occurred within 5–10 days post infection and showed significant correlation with disease development, ranging from 1.67–3% in the RRIM 2002 clone and approximately 8.33% in the PB 350 clone. This is the first study on the infection and up-regulation of gene expression in rubber leaves infected with N. ribis isolate SK10 (ICMP 20078). This study showed the importance of exploring the SK10 isolate as an indicator of infection ability and positive fungal–host interaction

Susceptibility of rubber (Hevea brasiliensis) clones to Neofusicoccum ribis

The aim of this study was to evaluate the ability of Neofusicoccum ribis to infect leaf surfaces of different rubber (Hevea brasiliensis) clones. Neofusicoccum ribis isolates previously identified on the basis of morphological characteristics and DNA sequence analysis were used to inoculate rubber leaves and seedlings in vitro and in vivo respectively. Neofusicoccum ribis isolates were demonstrated to cause lesions on rubber clones examined in this study. There was variation in susceptibility of the rubber clones to the pathogen. This study provides useful information that could be exploited to better manage the disease

Neofusicoccum ribis Associated with Leaf Blight on Rubber (Hevea brasiliensis) in Peninsular Malaysia

Hevea brasiliensis is a natural source of rubber and an important plantation tree species in Malaysia. Leaf blight disease caused by Fusicoccum substantially reduces the growth and performance of H. brasiliensis. The aim of this study was to use a combination of both morphological characteristics and molecular data to clarify the taxonomic position of the fungus associated with leaf blight disease. Fusicoccum species were isolated from infected leaves collected from plantations at 3 widely separated locations – Selangor, Perak, and Johor states – in Peninsular Malaysia in 2010. All the isolates were identified according to their conidial patterns and DNA sequences generated from internal transcribed spacers (ITS1 and ITS2), the 5.8S rRNA, and an unknown locus (BotF15) containing microsatellite repeats. Based on taxonomic and sequence data, Neofusicoccum ribis was identified as the main cause of leaf blight disease in H. brasiliensis in commercial plantations in Malaysia. A pathogenicity trial on detached leaves further confirmed that N. ribis causes leaf blight disease. N. ribis is an important leaf pathogen, and its detection in Malaysia has important implications for future planting of H. brasiliensis

Fungi associated with the blighted leaf symptoms of Hevea brasiliensis

This article describes the fungi isolated from the blighted leaf of rubber (Hevea brasiliensis) tree in Malaysia. Previously, Neofusicoccum ribis (Family Botryosphaeriaceae) was reported as the causal agent of rubber leaf blight in Malaysia. To date, there are limited studies on this particular disease in Malaysia and worldwide. The current study was carried out on rubber leaves displaying leaf blight symptoms caused by N. ribis from different locations to discover the fungi that reside in the blighted leaves. Rubber leaf samples with blight symptoms were collected from two different locations in Malaysia. The fungal isolates were isolated following the agar plate method and subjected to cultural and morphological characterization. Based on the cultural and morphological characterization, eight fungal isolates were further subjected to molecular identification. Five fungal isolates namely SBI, SB2, SB3, SB6 and SPKT1 were identified as N. ribis, one fungus (SB4) as Diaporthe drenthii, and another two fungi namely SB5 and SPKT2 were identified as Lasiodiplodia pseudotheobromae. Based on the morphological and molecular identification, all the N. ribis isolates demonstrated similar characteristics of the rubber leaf blight pathogen as documented in a previous study