Browsing by Author "Mwakosya, Joseph Andongwile"

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    The effects of illegal anthropogenic activities on the vegetation community structure in the western Rungwe mountain forest reserve, Tanzania
    (University of Dar es Salaam, 2015) Mwakosya, Joseph Andongwile
    It was assessed the effects of illegal anthropogenic activities on the vegetation community structure in western Rungwe Mountain Forest Reserve. Nested sampling technique was used to collect data in the field. A total of 99 plant species distributed among 47 families were identified where the dominant families were Rubiaceae, Poaceae, Euphorbiaceae, Asteraceae and Leguminosae. The moderately disturbed site had significantly higher species richness, diversity and evenness than the least and highly disturbed sites and hence concurs with the intermediate disturbance hypothesis. TWINSPAN, two vegetation communities were identified based on anthropogenic disturbance. Community A included samples from least to moderately disturbed area and B was from the highly disturbed area. The difference in density of trees among disturbance levels was obvious that a total of 567 stems/ha was recorded in the least disturbed, 810 stems /ha in the moderate disturbed site and 83 stems/ha in the highly disturbed sites. The diameter size class distribution pattern displayed an inverted J shape which indicates an active regeneration. The least disturbed site had many individuals with DBH ranging from 19 to 57 cm, moderately disturbed sites from 10-47 cm and highly disturbed site had 11-14 cm. It can be concluded from this study that charcoal cutting, firewood cutting, clearance for cultivation, pole cutting and burning were anthropogenic activities that have significant effects on forest structure and plant species composition.
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    Molecular identification and characterization of cassava mosaic begomoviruses (cmbs) in non-crop plants from Unguja and Pemba
    (University of Dar es salaam, 2021-10) Mwakosya, Joseph Andongwile
    Cassava mosaic begomoviruses (CMBs) cause cassava losses up to 100%. Recently, it has been reported that some of CMBs infecting cassava plants are from non-crop plants. This study identified and characterized CMBs in non-crop plants collected from Unguja and Pemba Islands. A total of 108 symptomatic and asymptomatic non-crop leaf samples were collected. The results of this study confirms the occurrence of four African Cassava Mosaic Virus (ACMV) and seven East African Cassava Mosaic Virus (EACMV) isolates in non-crop plants by using PCR, nanopore MinION sequencing, Sanger sequencing and phylogenetic analysis. Plant DNA barcode genes (rbcL and matK) were used in the identification of non-crop plants harboring CMBs. Through, basic local alignment search tool (BLAST) and phylogenetic analysis Datura stramonium, Solanum incanum, Senna occidentalis, Wild Solanum melongena, Ricinus communis and Sida acuta were identified as non- crop plants that harbour CMBs. Assessment of infectivity of CMBs isolated from Solanum incanum and Sida acuta was done on a model TMS60444 and Chereko susceptible cassava varieties by particle bombardment using rolling cycle amplification products. Mild curling leaves and yellowing mosaic symptoms were observed in seven out of sixteen inoculated plants with ACMV and eight out of sixteen inoculated with EACMV. All symptomatic experimental cassava plants inoculated with both ACMV and EACMV tested positive in PCR using CMBs specific primers. For the first time, the present study documented Solanum incanum as an alternative host of ACMV and Sida acuta as an alternative host of EACMV. Therefore, management efforts to control cassava mosaic disease (CMD) caused by ACMV and EACMV should consider these non-crop plants for sustainable control of these viruses which affect cassava worldwide.