Browsing by Author "Melnick, Rachel L."

Now showing 1 - 11 of 11
  • Bacterial endophytes of perennial crops for management of plant disease
    Melnick, Rachel L.; Bailey, B. A.; Backman, Paul A. (Springer, 2013)
    Bacterial endophytes, microorganisms which inhabit the internal tissues of plants, can suppress disease and are often used as a biological control in annual crops. Less research, however, has been applied to the use of bacterial endophytes to prevent disease in perennial crops, which presents a more complex challenge. However, exploration of their potential as a biological control in perennial crops has been limited. This chapter assembles current knowledge on the subject, providing case studies on bacterial endophytes for cacao pod diseases and citrus tree diseases.
  • Bacterial endophytes: Bacillus spp. from annual crops as potential biological control agents of black pod rot of cacao
    Melnick, Rachel L.; Zidack, N. K.; Bailey, B. A.; Maximova, S. N.; Guiltinan, M.; Backman, Paul A. (Netherlands: Elsevier, 2008)
    This study examines methods to reduce black pod rot in cacao plants.
  • Detection and expression of enterotoxin genes in endophytic strains of Bacillus cereus
    Melnick, Rachel L.; Testen, Anna L.; Poleatewich, A. M.; Backman, Paul A.; Bailey, B. A. (Society for Applied Microbiology, 2012-03-06)
    The aim of this study was to determine whether endophytic Bacillus cereus isolates from agronomic crops possessed genes for the nonhaemolytic enterotoxin (Nhe) and haemolysin BL (HBL) and, therefore, have the potential to cause diarrheal illness in humans.
  • Endophytes and plant/microbe interactions
    Bailey, B. A.; Melnick, Rachel L. (2010)
    This presentation details work done in SANREM CRSP phase III on biological control of fungal and other diseases in cacao.
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    Endophytic Bacillus Spp. of Theobroma cacao: Ecology and potential for biological control of cacao diseases
    Melnick, Rachel L. (2010)
    In South America, there are three key diseases that affect the yield of Theobroma cacao: black pod, caused by Phytophthora spp.; frosty pod, caused by Moniliophthora roreri; and witches' broom, caused by Moniliophthora perniciosa. Although chemical control options exist, farmers typically only use cultural disease management such as phytosanitary pruning. Agrochemical use can be problematic in the developing countries where cacao is grown due to large risks to human health and the environment. As a result, there has been increased interest in the use of biological control for management of cacao diseases due to problems associated with pesticide use as well as consumer desire for organic chocolate. Fungal species have been the main focus for research on biological control of cacao diseases, while cacao-associated bacteria have been nearly ignored. The research in this dissertation focuses on obtaining and screening endospore-forming cacao bacterial endophytes for their ability to suppress diseases. In addition to research on suppression of witches' broom, four bacterial isolates were tested for their ability to suppress cacao pod disease and cherelle wilt in two cacao genotypes. None of the four tested isolates reduced diseases on cacao pods, but application of B. pumilus ET increased the overall number of healthy pods in the first two months of the four month experiment. These successful field results indicate the positive potential for the use of native endophytic bacteria to manage cacao diseases. In conclusion, the results reported here indicate that B. pumilus ET would likely make an excellent biological control agent, due to its multiple modes of action and ability to be combined with endophytic Trichoderma spp.
  • Enfermedades de cacao y control biológico con endófitas
    Melnick, Rachel L. (Cohabamba, Bolivia: Promoción e Investigación de Productos Andinos and USAID, 2009)
    Presentation on biological suppression of cacao diseases from Ph.D. dissertation.
  • Field evaluation of endophytes for management of witches' broom on cacao
    Melnick, Rachel L.; Poleatewich, A. M. (2008)
    This Penn State study examines the effectiveness of endophytic bacteria on cacoa trees as a biocontrol agent for witches' broom. The study involved field trials on seedlings with various levels of susceptibility. The application of bacteria was found to be most effective for tolerant genotype seedlings, but was not statistically significant for highly resistant strains.
  • Field evaluation of endophytic endospore-forming bacteria with cacao varieties for management of witches' broom during the dry season
    Melnick, Rachel L. (St. Paul, MN.: The American Phytopathological Society, 2007)
    Technical paper on biocontrol of cacao disease
  • Impact of application of endophytic Bacillus spp. for biocontrol of cacao diseases on native microbial communities
    Melnick, Rachel L. (2009)
    "Interest in ecologically-based management of cacao diseases has lead to research on biocontrol. Sixty-nine endophytic Bacillus spp. were isolated from cacao trees escaping disease near Quevedo, Ecuador and screened as potential biological control agents. Four elite Bacillus spp. are currently being field evaluated to determine their ability to suppress witches' broom disease, caused by Moniliophthora perniciosa. Research was conducted to determine how applications of biocontrol agents impacts diversity and abundance of native microbial communities. Since most endophytes are likely neutral in terms of plant health, it is hypothesized that application of beneficial bacteria will displace neutral endophytes to positively impact overall plant health. Each isolate was applied to runoff at log 8.0 CFU/ml with 0.20% Silwet L-77 adjuvant to 4 branches each of 3 replicate nacional trees per treatment. Controls consisted of application of adjuvant alone. Three months after both the application and reapplication of the bacteria, leaf discs were excised from 2 sprayed leaves per branch. Leaf discs from one tree were combined and placed in RNALater for preservation during shipment. Genomic DNA was extracted from the sample and Automated Ribosomal Intergenic Spacer Analysis (ARISA) was utilized to determine ecological shifts in both bacterial and fungal communities. Data will be presented on effects of application of these biocontrol agents on native microbial communities." (Abstract from meeting website: http://www.apsnet.org/meetings/2009/abstracts/a09ma495.htm)
  • Isolation of endophytic endospore-forming bacteria from Theobroma cacao as potential biological control agents of cacao diseases
    Melnick, Rachel L.; Suárez, C.; Bailey, B. A.; Backman, Paul A. (Elsevier, Inc., 2011)
    This article describes research on the effectiveness of biological controls of cacao fungal diseases. The study was conducted using endophytes from Ecuador, and treatments were shown to be effective.
  • Studies on the suppression of cacao diseases with Ecuadorian endophytic Bacillus spp.
    Melnick, Rachel L. (State College, PA.: Pennsylvania State University, 2008)
    Powerpoint presentation on cacao disease supression research in Ecuador