P-261 - Tissue-specific localization of East African cassava mosaic virus (EACMV) in cassava plants

Cassava is an important staple crop cultivated mainly in tropical regions of Africa, Asia, and Latin America, with Nigeria leading global production. It grows well with low input and thrives even on poor soils. This resilience makes it increasingly valuable, especially for small farmers who depend on its roots as a staple food. However, its production is significantly restricted by Cassava Mosaic Disease (CMD), predominantly caused by geminiviruses such as the EACMV. Resistance to CMD primarily relies on a dominant genetic locus called CMD2 which is linked to specific amino acid changes in the DNA Polymerase delta subunit 1 (POLD1) protein. With the aim of elucidating whether the host DNA polymerase contributes to EACMV replication and/or movement, we used the in situ hybridization chain reaction (HCR) technique to localize EACMV and MePOLD1 mRNA. We have found that EACMV is predominantly present in the vasculature of mature and young leaves of a susceptible cassava cv. However, EACMV was occasionally detected in the nuclei of mesophyll cells of mature leaves. HCR was also used to identify cells expressing MePOLD1 in the presence and absence of EACMV. We will discuss our findings and their significance to understanding CMD2-mediated resistance in this economically important crop.