ABSTRACT The cocoa tree, Theobroma cacao L., suffers large yield losses in Aceh Indonesia due to ... more ABSTRACT The cocoa tree, Theobroma cacao L., suffers large yield losses in Aceh Indonesia due to the disease black pod rot, caused by Phytophthora spp. Despite having the largest area under cacao production in Sumatra, farmers in the Aceh region have low overall production because of losses to insect pests and black pod rot. Trichoderma spp. were isolated from the roots and leaves of cacao trees and screened as potential biological control agents. Isolates used in the study were T. asperellum isolates T2 and T4, T. longibrachiatum isolates T15 and T16, and T. virens isolates T1 and Tv. T1, T2, T4, and Tv completely colonized and destroyed Phythophthora tropicalis and Phytophthora palmivora mycelium in precolonized plate assays. All six isolates reduced P. tropicalis, but none reduced the growth of P. palmivora in dual plate assays. Phytophthora growth was suppressed on MIN media amended with sterile heat inactivated Trichoderma culture filtrates, with Tv best suppressing growth of both Phytophthora spp. T. virens isolate Tv was the only isolate observed coiling around P. tropicalis mycelium and disrupted the formation of P. palmivora sporangia. Of all six isolates, only Tv reduced P. palmivora lesion expansion in a detached pod assay, reducing severity by 71%. Tv also reduced P. palmivora infection on seedlings when applied aerially at 1x106 and 1x108 conidia/ml, by 19% and 59% respectively. T. virens isolate Tv is a mycoparasite, antagonizes Phytophthora in a dual plate assay, and shows antibiosis against Phytophthora spp., suggesting that multiple modes of action contribute to its ability to limit Phytophthora lesion expansion on cacao pods and seedlings.
Theobroma cacao (cacao) is a tropical understory tree with sensitivity to drought. Cacao responds... more Theobroma cacao (cacao) is a tropical understory tree with sensitivity to drought. Cacao responds to drought by decreases in net photosynthesis, PS II efficiency, stomatal conductance, water potential and changes in leaf florescence. Drought also alters cacao gene expression as well as leaf glucose and free amino acid content. In recent years an incredible diversity of fungal endophytes has been
ABSTRACT Bacterial endophytes have long been investigated for their beneficial effects on plants,... more ABSTRACT Bacterial endophytes have long been investigated for their beneficial effects on plants, such as plant growth promotion, increased mineral uptake, providing biologically fixed nitrogen, suppressing plant diseases, and induction of plant defense cascades. While the use of beneficial endophytes to mange plant diseases of annual and biannual crops has been researched and reviewed for some time now, far less work has focused on utilizing bacterial endophytes in perennial crops. Recent studies on the microbial communities of cacao, citrus, apple, spruce, and popular trees, among others, have demonstrated that perennial crops are home to a diverse community of endophytic bacteria. We summarize the present knowledge of biological control modes of action and use of bacterial endophytes for management of diseases in perennial crops. We also summarize the use of new molecular technologies, such as pyrosequencing and QPCR, to gain a better understanding on the interaction between plant hosts, pathogens, and bacterial endophytes.
ABSTRACT The cocoa tree, Theobroma cacao L., suffers large yield losses in Aceh Indonesia due to ... more ABSTRACT The cocoa tree, Theobroma cacao L., suffers large yield losses in Aceh Indonesia due to the disease black pod rot, caused by Phytophthora spp. Despite having the largest area under cacao production in Sumatra, farmers in the Aceh region have low overall production because of losses to insect pests and black pod rot. Trichoderma spp. were isolated from the roots and leaves of cacao trees and screened as potential biological control agents. Isolates used in the study were T. asperellum isolates T2 and T4, T. longibrachiatum isolates T15 and T16, and T. virens isolates T1 and Tv. T1, T2, T4, and Tv completely colonized and destroyed Phythophthora tropicalis and Phytophthora palmivora mycelium in precolonized plate assays. All six isolates reduced P. tropicalis, but none reduced the growth of P. palmivora in dual plate assays. Phytophthora growth was suppressed on MIN media amended with sterile heat inactivated Trichoderma culture filtrates, with Tv best suppressing growth of both Phytophthora spp. T. virens isolate Tv was the only isolate observed coiling around P. tropicalis mycelium and disrupted the formation of P. palmivora sporangia. Of all six isolates, only Tv reduced P. palmivora lesion expansion in a detached pod assay, reducing severity by 71%. Tv also reduced P. palmivora infection on seedlings when applied aerially at 1x106 and 1x108 conidia/ml, by 19% and 59% respectively. T. virens isolate Tv is a mycoparasite, antagonizes Phytophthora in a dual plate assay, and shows antibiosis against Phytophthora spp., suggesting that multiple modes of action contribute to its ability to limit Phytophthora lesion expansion on cacao pods and seedlings.
Theobroma cacao (cacao) is a tropical understory tree with sensitivity to drought. Cacao responds... more Theobroma cacao (cacao) is a tropical understory tree with sensitivity to drought. Cacao responds to drought by decreases in net photosynthesis, PS II efficiency, stomatal conductance, water potential and changes in leaf florescence. Drought also alters cacao gene expression as well as leaf glucose and free amino acid content. In recent years an incredible diversity of fungal endophytes has been
ABSTRACT Bacterial endophytes have long been investigated for their beneficial effects on plants,... more ABSTRACT Bacterial endophytes have long been investigated for their beneficial effects on plants, such as plant growth promotion, increased mineral uptake, providing biologically fixed nitrogen, suppressing plant diseases, and induction of plant defense cascades. While the use of beneficial endophytes to mange plant diseases of annual and biannual crops has been researched and reviewed for some time now, far less work has focused on utilizing bacterial endophytes in perennial crops. Recent studies on the microbial communities of cacao, citrus, apple, spruce, and popular trees, among others, have demonstrated that perennial crops are home to a diverse community of endophytic bacteria. We summarize the present knowledge of biological control modes of action and use of bacterial endophytes for management of diseases in perennial crops. We also summarize the use of new molecular technologies, such as pyrosequencing and QPCR, to gain a better understanding on the interaction between plant hosts, pathogens, and bacterial endophytes.
Uploads
Papers by Rachel Melnick