Occurrence of Rice Yellow Mottle Virus resistance breaking isolates in Lowland Catchment Zones of Uganda
Loading...
Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
African Crop Science Journal
Abstract
Rice (Oryza spp; 2n=24.) production in Uganda and Africa in general, is seriously threatened by the
Rice yellow mottle virus disease (RYMVD), a disease caused by Rice yellow mottle virus (RYMV)
within the genus Sobemovirus; family Sobemoviridae. This study investigated the existence and
distribution of resistance-breaking RYMV pathotype in the three major lowland rice catchment areas
in Uganda. Four known rice accessions resistant to Rice yellow mottle virus (RYMV) namely;
Gigante, Tog5672, Tog5674 and Tog5681, carrying resistant allele’s rymv1-2, rymv1-4 & RYMV3,
rymv1-5 and rymv1-3, respectively, were tested for their response to different RYMV isolates. The
isolates were collected from three major lowland rice catchment areas of Doho, Kibimba, and Olweny
in Uganda. Out of 100 leaf samples collected from the field and assayed for RYMV and confirmed to be
positive using RT-PCR, 83 isolates induced symptoms on IR64- the RYMV susceptible line. Seventyseven (92.8%) isolates were able to overcome resistance in at least one of the four differential rice accessions, as confirmed by the presence of RYMV symptoms; while 6 (7.2%) isolates were
asymptomatic. Variation in time (days) for symptom development post-inoculation (dpi) and AUDPC
were observed. Symptoms appeared within 5-7 days on IR64; while it took on average 11, 18, 36, and
18 days to appear on Gigante, Tog5672, Tog5674 and Tog5681, respectively. The highest AUDPC was
observed on IR64 (254.7); while the lowest was observed on Tog5681 (74.1). Two major patho-groups
were observed; those that broke down resistance in Gigante only (25.3%) and Gigante & Tog5672
(33.7%). Five isolates from Doho (Budaka & Bugiri districts) and Kibimba (Butaleja district) catchment
areas broke down RYMV resistance in three accessions i.e. (Tog5681, Gigante & Tog5672) and (Tog5674, Gigante & Tog5672), respectively. Resistance breaking isolates were confirmed in all the three sampled catchment zones, however, Doho and Kibimba had some unique isolates that broke down resistance in accessions carrying resistance allele rymv 1-3 and rymv1-5 in addition to rymv1-2. Results from this study showed that RYMV isolates in Uganda can break down resistance conferred by the rymv1-2 resistance gene allele. However, accessions Tog5681 and Tog5674 seem to hold stable RYMV resistance and, thus are recommended for RYMV breeding.
Description
Keywords
Accession, Breakdown, Catchment, Oryza sativa, Resistance
Citation
Ramathani, I., Mukasa, S. B., Alicai, T., Nanyiti, S., & Lamo, J. (2021). Occurrence of rice yellow mottle virus resistance breaking isolates in lowland catchment zones of Uganda. African Crop Science Journal, 29(3), 383-400. DOI: DOI: 10.4314/acsj.v29i3.5