Doctor of Philosophy (PhD)


Plant Pathology and Crop Physiology

Document Type



Peppers (Capsicum spp.) are native plants to the Americas. They are cultivated worldwide for direct human consumption and industrial purposes. Peppers can be infected by acute plant viruses, which cause a variety of diseases and crop losses. Many Capsicum species can also be infected by persistent viruses, which do not cause apparent disease and are transmitted only vertically.

The presence of persistent viruses in cultivated and non-cultivated Capsicum spp. was investigated and the genome sequences of persistent viruses belonging to the family Endornaviridae were determined and analyzed. An endornavirus species closely related to bell pepper endornavirus (BPEV) was found infecting C. frutescens, C. baccatum, and C. chinense.

The transcriptome of two near-isogenic lines (NILs) of bell pepper cv. Marengo, one infected with BPEV and the other BPEV-free was characterized before and after inoculation with the acute virus pepper mild mottle virus (PMMoV). Genes involved in plant defense response to external biotic and abiotic stimulus and interspecies interactions between organisms where differentially expressed between the two NILs.

Using the two NILs, some biological and molecular interactions between BPEV and the acute viruses, PMMoV and tobacco mild green mosaic virus (TMGMV) were evaluated. BPEV was associated with systemic symptom reduction in pepper plants infected with single and mixed infections of PMMoV and TMGMV.

Biological and molecular interaction(s) between BPEV and fungi (Colletotrichum sp.), bacteria (Pseudomonas sp.) and nematodes (Meloidogyne incognita) were evaluated using the two bell pepper NILs. The titers of BPEV increased after infections with either Colletotrichum sp. or Pseudomonas sp.

The overall results of these investigations suggest that in the genus Capsicum, endornaviruses are not host-specific; the continuous infection of BPEV may trigger the plant immune response; and that mixed infections between BPEV and Colletotrichum sp., or Pseudomonas sp., increased the titers of BPEV.



Committee Chair

Valverde, Rodrigo A.



Available for download on Wednesday, July 05, 2028