Prevalence of Fusarium wilt disease of cucumber (Cucumis sativus Linn) in Peninsular Malaysia Caused By Fusarium oxysporum and F. solani

Fusarium wilt disease is one of the most problematic and destructive disease in cucumber production. The causative agents are Fusarium oxysporum and F. solani. These pathogens are soil borne and transmitted through infested soil and water. A field survey was conducted to study the disease prevalence in the major growing areas of cucumber in Peninsular Malaysia. Field study revealed that the disease was highly prevalence in the field with the disease incidence was in the range of 10%–60%. The morphological properties of F. oxysporum are microconidia (3.8–15.7 µm × 2.9–4.9 µm), macroconidia (14.8–38.5 µm × 2.4–5.7 µm) and number of septate was 1–4. While for F. solani are microconidia (3.39–14.63 µm × 2.36–4.44 µm), macroconidia (7.22–50.46 µm × 2.43–6.14 µm) and number of septate was 1–5. Based on molecular identification had confirmed that the disease is caused by F. oxysporum and F. solani with similarity index of 99%–100% based on internal transcribed spacer (ITS) gene sequences. The pathogenicity test showed that the symptoms of Fusarium wilt disease was firstly appeared as yellowing of old leaves. Progressively, the infected plant will be wilted and finally died. The outputs of this study are highly important to establish an effective disease management programme to reduce disease prevalence and yield loss in the field

Control of gray mold disease of tomato caused by Botrytis cinerea using bacterial secondary metabolites

Gray mold disease is caused by Botrytis cinerea and it is the most significant and devastating disease affecting tomato cultivation worldwide. This disease was recently reported infecting tomato fruits in Cameroon Highland, Pahang. Biocontrol agents have been proven to be effective towards many phytopathogens. In this study, 43 bacterial isolates were screened against B. cinerea in-vitro. Five isolates with more than 65% inhibition of radial growth (PIRG) were selected for the subsequent experiments. Findings in dual culture assay revealed that BM11 and BC4 were the most effective biocontrol agent, with PIRG of 82.5% and 71.8%, respectively. BM11 and BC4 isolates were identified using the 16S rDNA gene. The identification results found that BM11 and BC4 were Pseudomonas protegens and Brevibacterium casei, respectively. Ten major bioactive compounds were successfully identified by Gas chromatography-mass spectrometry (GC-MS) from the culture filtrate of both biological control agent (BCA) isolates. These bioactive compounds may responsible for antifungal activity. In vivo study revealed that culture filtrate extract manages to suppress disease lesions on the treated tomato fruit from 0.86 -1.03 cM, 30 days after inoculation. Based on overall findings suggested that P. protegens and B. casei were the promising BCA in controlling gray mold disease of tomato fruit

Characterization and pathogenicity of Rhizoctonia spp isolated from various crop species in different agroecosystems in Malaysia

Rhizoctonia species is well known as a necrotrophic soilborne fungus prevalent in different agro-ecosystem worldwide. It has been reported as a destructive fungal pathogen that caused various types of diseases on a wide variety of crops. This study investigated Rhizoctonia isolates obtained from different crops and locations based on morphological traits, pathogenicity, molecular identification and genetic diversity characterization. Morphological traits revealed that majority of the isolates were multinucleated (MNR) except for two isolates were binucleated (BNR). Radial growth rate showed that all the isolates could cover the plate within 2-3 days and few isolates covered the plate within four days. Mycelium width ranged between 3.60 -7.33μm, while most of the culture texture appeared oppressed. Nevertheless, some were raised and fluffy. The culture colors were varied from white to light yellowish white or light brown to brown. Sclerotia color was light brown to dark brown and sclerotia distribution pattern was centered and rim concentrated to scatter while the intensity of sclerotia was high to low and some isolates did not produce. Based on identification of the ITS rDNA and tef-1 α genes different taxonomic groups were determined. Twenty-seven isolates were identified as R. solani AG-1 IA, four isolates as R. solani AG-1 ID, two isolates as R. solani AG-4 HG-I and one isolates as R. solani AG-2-2 IV. Two isolates were identified as binucleate Rhizoctonia AG-Fa and AG-A. Phylogenetic analysis using different algorithms separated Rhizoctonia spp. to the distinct clades. Binucleate Rhizoctonia AG-Fa clustered with R. solani isolates indicating close relationship with some taxonomic groups of R. solani. Variation was detected for ITS rDNA and tef-1 α gene sequences at 0.25 variation and 30% homopolymer level. This led to the identification of 50 SNPs and Indels for ITS while 28 SNPs and Indels were found for tef-1 α which indicated that ITS rDNA variation is greater than tef-1 α. Species-specific primer of ITS rDNA region has confirmed the identity of each anastomosis groups. The virulence among isolates of AG-1 IA was varied where strains of rice were more virulent than the strains of corn. Similarly, the virulent among various anastomosis groups in this study showed that AG-1 IA, AG-4 GH-I and AG-2-2 IV were more virulent than AG-1 ID, AG-Fa and AG-A. Genetic variability was detected using RAPD, iPBS and ISSR markers. All molecular markers were able to show reasonable polymorphisms. There was no relationship between morphological traits, pathogenicity, geographical origin and genetic diversity. However, the clustering tree and PCA plot supported the separation based on taxonomic groups indicating that there are other factors which could play a significant role on genetic variation. The knowledge gathered in this study would be useful for developing crops that are resistant to Rhizoctonia diseases. This will assist in planning for the right crop rotation and proper disease management programs

Prevalence of Fusarium Wilt Disease of Cucumber (Cucumis sativus Linn) in Peninsular Malaysia Caused by Fusarium oxysporum and F. solani

Fusarium wilt disease is one of the most problematic and destructive disease in cucumber production. The causative agents are Fusarium oxysporum and F. solani. These pathogens are soil borne and transmitted through infested soil and water. A field survey was conducted to study the disease prevalence in the major growing areas of cucumber in Peninsular Malaysia. Field study revealed that the disease was highly prevalence in the field with the disease incidence was in the range of 10%–60%. The morphological properties of F. oxysporum are microconidia (3.8–15.7 μm × 2.9–4.9 μm), macroconidia (14.8–38.5 μm × 2.4–5.7 μm) and number of septate was 1–4. While for F. solani are microconidia (3.39–14.63 μm × 2.36–4.44 μm), macroconidia (7.22–50.46 μm × 2.43–6.14 μm) and number of septate was 1–5. Based on molecular identification had confirmed that the disease is caused by F. oxysporum and F. solani with similarity index of 99%–100% based on internal transcribed spacer (ITS) gene sequences. The pathogenicity test showed that the symptoms of Fusarium wilt disease was firstly appeared as yellowing of old leaves. Progressively, the infected plant will be wilted and finally died. The outputs of this study are highly important to establish an effective disease management programme to reduce disease prevalence and yield loss in the field.</jats:p

Control of gray mold disease of tomato caused by Botrytis cinerea using bacterial secondary metabolites

Gray mold disease is caused by Botrytis cinerea and it is the most significant and devastating disease affecting tomato cultivation worldwide. This disease was recently reported infecting tomato fruits in Cameroon Highland, Pahang. Biocontrol agents have been proven to be effective towards many phytopathogens. In this study, 43 bacterial isolates were screened against B. cinerea in-vitro. Five isolates with more than 65% inhibition of radial growth (PIRG) were selected for the subsequent experiments. Findings in dual culture assay revealed that BM11 and BC4 were the most effective biocontrol agent, with PIRG of 82.5% and 71.8%, respectively. BM11 and BC4 isolates were identified using the 16S rDNA gene. The identification results found that BM11 and BC4 were Pseudomonas protegens and Brevibacterium casei, respectively. Ten major bioactive compounds were successfully identified by Gas chromatography-mass spectrometry (GC-MS) from the culture filtrate of both biological control agent (BCA) isolates. These bioactive compounds may responsible for antifungal activity. In vivo study revealed that culture filtrate extract manages to suppress disease lesions on the treated tomato fruit from 0.86 -1.03 cM, 30 days after inoculation. Based on overall findings suggested that P. protegens and B. casei were the promising BCA in controlling gray mold disease of tomato fruit

CONTROL OF GRAY MOLD DISEASE OF TOMATO CAUSED BY Botrytis cinerea USING BACTERIAL SECONDARY METABOLITES

Gray mold disease is caused by Botrytis cinerea and it is the most significant and devastating disease affecting tomato cultivation worldwide. This disease was recently reported infecting tomato fruits in Cameroon Highland, Pahang. Biocontrol agents have been proven to be effective towards many phytopathogens. In this study, 43 bacterial isolates were screened against B. cinerea in-vitro. Five isolates with more than 65% inhibition of radial growth (PIRG) were selected for the subsequent experiments. Findings in dual culture assay revealed that BM11 and BC4 were the most effective biocontrol agent, with PIRG of 82.5% and 71.8%, respectively. BM11 and BC4 isolates were identified using the 16S rDNA gene. The identification results found that BM11 and BC4 were Pseudomonas protegens and Brevibacterium casei, respectively. Ten major bioactive compounds were successfully identified by Gas chromatography-mass spectrometry (GC-MS) from the culture filtrate of both biological control agent (BCA) isolates. These bioactive compounds may responsible for antifungal activity. In vivo study revealed that culture filtrate extract manages to suppress disease lesions on the treated tomato fruit from 0.86 -1.03 cM, 30 days after inoculation. Based on overall findings suggested that P. protegens and B. casei were the promising BCA in controlling gray mold disease of tomato fruit.</jats:p

Genetic variability of Rhizoctonia spp. isolated from different hosts and locations

Rhizoctonia species is well known as a destructive fungal pathogen in various agro-ecosystems globally. The current study attempted to investigate the genetic diversity among various anastomosis groups of Rhizoctonia species obtained from different locations and crops. Two types of markers were used to detect the genetic variability among isolates. The results showed that all the molecular markers were able to show reasonable polymorphisms. The clustering tree and PCA plot analysis supported the separation based on taxonomic groups more than the separation according to geographical origin and host. This indicates that there are other important factors that contribute to the genetic variation among Rhizoctonia isolates. The knowledge gathered in this study would be useful for developing crops that are resistant to Rhizoctonia diseases. This will assist in planning for the right crop rotation and proper disease management programs