Browsing by Author "Nyangoko, Baraka"

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Climate change impacts outweigh conservation efforts in coral reefs that are highly exposed to thermal stresses in Zanzibar, Tanzania
(Elsevier, 2023-05-01) Chauka, Leonard; Nyangoko, Baraka
With a greater range of management practices and so many threats to coral reefs, assessing coral reef resilience using social-ecological approaches is an important way towards understanding the climatic and non-climatic impacts, and proper conservation efforts in coral reefs. In this study, six reefs (Changuu, Chapwani, Chumbe, Kizimkazi, Mnemba East and Mnemba West) were selected as case study sites to explore resilience potential of coral reefs in Zanzibar in relation to contrasting conservation strategies. Data were collected through household surveys, key informant interviews and biological survey (line-intercept transect and direct observations). Results showed that, Chumbe reefs was perceived to be highly protected followed by Kizimkazi reefs, while Changuu and Chapwani were considered to be less protected. Fishing pressure, climate change, inadequate management and pollution were regarded as the most critical drivers of coral reefs degradation. Coral bleaching was identified to be a main cause of coral reef damage by communities in Chumbe and Mnemba East, whereas inadequate management, pollution and uncontrolled tourisms were identified as the major driver by those in Changuu and Chapwani. Overall, reefs from Kizimkazi was found to have the highest resilience potential as it is under community-based conservation compared to other reefs. We conclude that coral reef resilience is context-specific and influenced by multiple factors, and although conservation efforts have a positive impact on coral reef health, climate change effects outweigh conservation efforts in reefs that are highly exposed to thermal stresses, such as the Chumbe and Mnemba East reefs. We recommend further promotion of viable alternative livelihood activities to reef reliant communities and collaborative management for the improvement of corals' resilience and conservation in the study area.
Elevated viral small RNA profiling in cassava cultivars suppress the occurrence of Cassava brown streak disease (CBSD)
(Elsevier, 2024-03) Ngazi, Veneranda; Nyangoko, Baraka; Mukasa, Settumba; Ndunguru, Joseph; Tairo, Fred
Cassava brown streak disease (CBSD), caused by cassava brown streak virus (CBSV) and; Ugandan cassava brown streak virus (UCBSV) causes the most destructive cassava disease in Tanzania. Thus, breeders urgently need CBSD-resistant cultivars to combat the impact of this disease, safeguard cassava production, improve the yields and secure food supply for communities reliant on this staple crop. In this study, we used four cassava cultivars; Albert, KBH 2002/135, KBH 2006/026 and Kiroba to explore how viral small interfering RNA (vsiRNAs), an antiviral silencing mechanism, confers CBSD resistance. Cassava plants were inoculated by grafting method using the single infection of CBSV, UCBSV and mixed infection of these viruses (co-infection). Total RNA was extracted from leaves of each cultivar followed by deep sequencing. The result showed that high level of vsiRNAs was produced in inoculated plants, with the most prominent class being 21 and 22 nucleotides. Kiroba produced the highest level of vsiRNA in both CBSV and UCBSV, whereas KBH 2006/026 produced high level of vsiRNA only with UCBSV infections. In contrast to UCBSV, inoculation with CBSV stimulated severe symptoms but relatively low levels of vsiRNA. Co-infection treatment showed a more complex interaction between the host and virus, with variations in the severity and amount of vsiRNA produced. We conclude that resistance to CBSD varies depending on the type of cultivar and virus species, and the occurrence of CBSD is suppressed in plants with elevated vsiRNA. Therefore, a good understanding on the resistance status of parental materials for breeding is recommended to breeders as a basis for improving cassava production.