Gummy stem blight caused by Didymella bryoniae (anamorph Phoma cucurbitacearum) is a major fungal... more Gummy stem blight caused by Didymella bryoniae (anamorph Phoma cucurbitacearum) is a major fungal disease of watermelon (Citrullus lanatus) and other cucurbits. Thirty-five isolates of Didymella and Phoma spp. associated with symptoms of gummy stem blight on watermelon, Canary melon (Cucumis melo), muskmelon (C. melo), and winter squash (Cucurbita maxima) from Florida and Georgia were characterized based on morphology on agar media, pathogenicity on ‘Melody’ watermelon, the internal transcribed spacer (ITS) sequence of ribosomal DNA (rDNA), random amplified polymorphic DNA (RAPD) analysis, and polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) analysis. All of the isolates were pathogenic on watermelon but differed in virulence. RAPD and ITS sequence analysis indicated genetic variability among the isolates but PCR-RFLP analysis did not show any variability. ITS sequence phylogenetic analysis identified two isolates, DB-05 and DB-33, which had a greater ...
Preliminary screening of fungi and bacteria isolated from unmanaged mango trees in different ecol... more Preliminary screening of fungi and bacteria isolated from unmanaged mango trees in different ecologies of Ethiopia, yielded isolates antagonistic towards Colletotrichum gloeosporioides, the cause of mango anthracnose. Four isolates of bacteria, five yeasts and two ...
The occurrence of mycotoxins in barley, sorghum, teff (Eragrostis tef) and wheat from Ethiopia ha... more The occurrence of mycotoxins in barley, sorghum, teff (Eragrostis tef) and wheat from Ethiopia has been studied. Samples were analyzed for aflatoxin B(1) (AFB1), ochratoxin A (OTA), deoxynivalenol (DON), nivalenol (NIV) and zearalenone (ZEN) using high performance liquid chromatography (HPLC) and for fumonisins (FUM) using enzyme linked immunosorbent assay (ELISA). AFB1 and OTA were detected in samples of all the four crops. AFB1 was detected in 8.8% of the 352 samples analyzed at concentrations ranging from trace to 26 microg kg(-1). OTA occurred in 24.3% of 321 samples at a mean concentration of 54.1 microg kg(-1) and a maximum of 2106 microg kg(-1). DON occurred in barley, sorghum and wheat at 40-2340 microg kg(-1) with an overall incidence of 48.8% among the 84 mainly 'suspect' samples analyzed; NIV was co-analyzed with DON and was detected at 40 microg kg(-1) in a wheat sample and at 50, 380, and 490 microg kg(-1) in three sorghum samples. FUM and ZEN occurred only in sorghum samples with low frequencies at concentrations reaching 2117 and 32 microg kg(-1), respectively. The analytical results indicate higher mycotoxin contamination in sorghum, which could be related to the widespread storage of sorghum grain in underground pits leading to elevated seed moisture contents. This is the first report on the occurrence of OTA in teff.
ABSTRACT In this study, the sensitivity of Cadophora luteo-olivacea, Cylindrocarpon liriodendri, ... more ABSTRACT In this study, the sensitivity of Cadophora luteo-olivacea, Cylindrocarpon liriodendri, Cn. macrodidymum and eight species of the genus Phaeoacremonium to hot-water treatments (HWTs) in vitro was evaluated. Conidial suspensions and plugs of agar with mycelia were placed in Eppendorf vials and incubated for 30, 45 or 60 min in a hot-water bath at 41, 42, 43, 44, 45, 46, 47, 48 or 49°C for Cylindrocarpon spp. and at 49, 50, 51, 52, 53, 54 or 55°C for Ca. luteo-olivacea and Phaeoacremonium spp. In general, conidial germination and the colony growth rate of all pathogens decreased with increased temperature and time combinations. Cylindrocarpon spp. were more sensitive than Ca. luteo-olivacea and Phaeoacremonium spp. to HWT temperatures. Conidial germination of Ca. luteo-olivacea was inhibited by treatments above 51°C–30 min, while treatments up to 54°C–60 min were necessary to inhibit the mycelial growth. For Cylindrocarpon spp., conidial germination was inhibited by treatments above 45°C–45 min, while treatments above 48°C–45 min were necessary to inhibit the mycelial growth. Regarding Phaeoacremonium spp., treatments up to 54°C–60 min were necessary to completely inhibit both conidial germination and mycelial growth. These results suggest that current HWT protocols at 50°C for 30 min may be sufficient to control Cylindrocarpon spp. However, it would be necessary to develop HWT using higher temperatures to reduce the incidence of Ca. luteo-olivacea and Phaeoacremonium spp. infections.
Gummy stem blight caused by Didymella bryoniae (anamorph Phoma cucurbitacearum) is a major fungal... more Gummy stem blight caused by Didymella bryoniae (anamorph Phoma cucurbitacearum) is a major fungal disease of watermelon (Citrullus lanatus) and other cucurbits. Thirty-five isolates of Didymella and Phoma spp. associated with symptoms of gummy stem blight on watermelon, Canary melon (Cucumis melo), muskmelon (C. melo), and winter squash (Cucurbita maxima) from Florida and Georgia were characterized based on morphology on agar media, pathogenicity on ‘Melody’ watermelon, the internal transcribed spacer (ITS) sequence of ribosomal DNA (rDNA), random amplified polymorphic DNA (RAPD) analysis, and polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) analysis. All of the isolates were pathogenic on watermelon but differed in virulence. RAPD and ITS sequence analysis indicated genetic variability among the isolates but PCR-RFLP analysis did not show any variability. ITS sequence phylogenetic analysis identified two isolates, DB-05 and DB-33, which had a greater ...
Preliminary screening of fungi and bacteria isolated from unmanaged mango trees in different ecol... more Preliminary screening of fungi and bacteria isolated from unmanaged mango trees in different ecologies of Ethiopia, yielded isolates antagonistic towards Colletotrichum gloeosporioides, the cause of mango anthracnose. Four isolates of bacteria, five yeasts and two ...
The occurrence of mycotoxins in barley, sorghum, teff (Eragrostis tef) and wheat from Ethiopia ha... more The occurrence of mycotoxins in barley, sorghum, teff (Eragrostis tef) and wheat from Ethiopia has been studied. Samples were analyzed for aflatoxin B(1) (AFB1), ochratoxin A (OTA), deoxynivalenol (DON), nivalenol (NIV) and zearalenone (ZEN) using high performance liquid chromatography (HPLC) and for fumonisins (FUM) using enzyme linked immunosorbent assay (ELISA). AFB1 and OTA were detected in samples of all the four crops. AFB1 was detected in 8.8% of the 352 samples analyzed at concentrations ranging from trace to 26 microg kg(-1). OTA occurred in 24.3% of 321 samples at a mean concentration of 54.1 microg kg(-1) and a maximum of 2106 microg kg(-1). DON occurred in barley, sorghum and wheat at 40-2340 microg kg(-1) with an overall incidence of 48.8% among the 84 mainly 'suspect' samples analyzed; NIV was co-analyzed with DON and was detected at 40 microg kg(-1) in a wheat sample and at 50, 380, and 490 microg kg(-1) in three sorghum samples. FUM and ZEN occurred only in sorghum samples with low frequencies at concentrations reaching 2117 and 32 microg kg(-1), respectively. The analytical results indicate higher mycotoxin contamination in sorghum, which could be related to the widespread storage of sorghum grain in underground pits leading to elevated seed moisture contents. This is the first report on the occurrence of OTA in teff.
ABSTRACT In this study, the sensitivity of Cadophora luteo-olivacea, Cylindrocarpon liriodendri, ... more ABSTRACT In this study, the sensitivity of Cadophora luteo-olivacea, Cylindrocarpon liriodendri, Cn. macrodidymum and eight species of the genus Phaeoacremonium to hot-water treatments (HWTs) in vitro was evaluated. Conidial suspensions and plugs of agar with mycelia were placed in Eppendorf vials and incubated for 30, 45 or 60 min in a hot-water bath at 41, 42, 43, 44, 45, 46, 47, 48 or 49°C for Cylindrocarpon spp. and at 49, 50, 51, 52, 53, 54 or 55°C for Ca. luteo-olivacea and Phaeoacremonium spp. In general, conidial germination and the colony growth rate of all pathogens decreased with increased temperature and time combinations. Cylindrocarpon spp. were more sensitive than Ca. luteo-olivacea and Phaeoacremonium spp. to HWT temperatures. Conidial germination of Ca. luteo-olivacea was inhibited by treatments above 51°C–30 min, while treatments up to 54°C–60 min were necessary to inhibit the mycelial growth. For Cylindrocarpon spp., conidial germination was inhibited by treatments above 45°C–45 min, while treatments above 48°C–45 min were necessary to inhibit the mycelial growth. Regarding Phaeoacremonium spp., treatments up to 54°C–60 min were necessary to completely inhibit both conidial germination and mycelial growth. These results suggest that current HWT protocols at 50°C for 30 min may be sufficient to control Cylindrocarpon spp. However, it would be necessary to develop HWT using higher temperatures to reduce the incidence of Ca. luteo-olivacea and Phaeoacremonium spp. infections.
Uploads
Papers by Amare Ayalew