Jari Sugano

Molecular characterization of closteroviruses infecting Cordyline fruticosa L. in Hawaii

In Hawaii, common green ti plants (Cordyline fruticosa L.) have been shown to harbor Cordyline virus 1 (CoV-1) which, along with Little cherry virus 1 (LChV-1), and Grapevine leafroll-associated virus 7 (GLRaV-7), form a distinct clade within the family Closteroviridae. Preliminary work has indicated that, aside from CoV-1, three additional closteroviruses may infect common green ti plants in Hawaii. In this study, pyrosequencing was used to characterize the genomes of closteroviruses infecting a single common green ti plant. The sequence data confirmed the presence of CoV-1 as well as three additional closteroviruses. Although all four viruses had the same general genome organization, the sequence divergence between the RNA-dependent RNA polymerase, heat shock protein 70 homolog, and coat protein ranged from 22 to 61%, indicating these represent four distinct closterovirus species. The names CoV-2, CoV-3, and CoV-4 are proposed for the three new viruses. Phylogenetic analyses placed CoV-2, CoV-3, and CoV-4 in the same clade as CoV-1, LChV-1, and GLRaV-7.

Differentiation and Distribution of Cordyline Viruses 1-4 in Hawaiian ti Plants (Cordyline fruticosa L.)

Common green ti plants (Cordyline fruticosa L.) in Hawaii can be infected by four recently characterized closteroviruses that are tentative members of the proposed genus Velarivirus. In this study, a reverse-transcription polymerase chain reaction (RT-PCR) assay developed to detect and distinguish Cordyline virus 1 (CoV-1), CoV-2, CoV-3, and CoV-4 was used to determine: (i) the distribution of these viruses in Hawaii; and (ii) if they are involved in the etiology of ti ringspot disease. One hundred and thirty-seven common green ti plants with and without ti ringspot symptoms were sampled from 43 sites on five of the Hawaiian Islands and underwent the RT-PCR assay. Eleven ornamental ti varieties were also sampled and assayed. Based on this survey, it appears none of the CoVs are involved in the etiology of ti ringspot. The observation of a non-uniform geographic distribution of the CoVs in common green ti, combined with the presence of CoVs in seed-derived ornamental varieties, suggests active vector transmission. Eight herbarium specimens collected between 1903 and 2003 from plants on the island of Oahu also underwent the RT-PCR assay. Amplifiable RNA was isolated from accessions collected in 1985 or later, however only the 2003 accession was found to harbor CoVs.

Use of Organic Fertilizers to Enhance Soil Fertility, Plant Growth, and Yield in a Tropical Environment

Soils rarely have sufficient nutrient for crops to reach their potential yield. Applying organic fertilizers without prior knowledge of their properties may cause yield decline under low application or pollute the environment with excessive application. Under‐ standing the nutrient variability and release pattern of organic fertilizers is crucial to supply plants with sufficient nutrients to achieve optimum productivity, while also rebuilding soil fertility and ensuring protection of environmental and natural resour‐ ces. This chapter presents the authors’ experiences with different organic amend‐ ments under Hawaiis tropical conditions, rather than an intensive literature review. For meat and bone meal by‐products (tankage), batch‐to‐batch variability, nutrient content/ release pattern and quality, and plant growth response to the liquid fertilizer pro‐ duced from tankage were evaluated. For animal livestock, dairy manure (DM) and chicken manure (CM) quality, changes in soil properties, and crop biomass produc‐ tion and root distributions were evaluated. For seaweed, an established bio‐security protocol, nutrient, especially potassium (K) variability, and plant growth and yield response were evaluated in different tropical soils.