Control of Bean Rust using Antibiotics Produced by Bacillus and Streptomyces species - Translocation and Persistence in Snap Beans

Antibiotic culture filtrates produced by Bacillus (CA5) and Streptomyces spp. were tested for translocation and persistence when applied on snap beans inoculated with rust ( Uromyces appendiculatus ) in greenhouse pot experiments. The antibiotics were applied on the first trifoliate leaves and translocation was assessed as the number of rust pustules on non-treated leaflets or trifoliates while persistence was assessed as the number of rust pustules on rust infected plants at different times after antibiotic treatment. The treatments were replicated three times, each replicate consisting of a pot containing three plants. Antibiotics from both Bacillus and Streptomyces were found to have up to 100% trans-lamina and leaflet-to-leaflet translocation but no significant trifoliate-totrifoliate translocation. The antibiotic culture filtrates also retained significant rust control for up to 10 days after application on the bean plant. However, no significant rust control was found on the plants after 16 days of treatment. The study indicated that the antibiotics produced by antagonistic Bacillus and Streptomyces species possess systemic activity that can persist within the plant for over one week. These metabolites are potential bean rust control products that could be incorporated in integrated disease management program

Phenology of <i>Avicennia marina</i> (Forsk.) Vierh. in a disjunctly-zoned mangrove stand in Kenya

Avicennia marina in Gazi Bay, Kenya, displays a disjunct zonation pattern across the intertidal zone with a seaward and a landward A. marina fringe. Earlier studies revealed significant differences in its vegetation structure, physiognomy, root system and leaf morphology, which can be attributed to salinity and tidal inundation differences that characterise the forest zones. The main objective of this study was to investigate the phenology of A. marina in the disjunctly zoned stands by direct shoot observation. Vegetative and reproductive phenology of A. marina was studied from January 2005 to December 2006. Four natural and one reforested sites were used for the study in the landward and the seaward intertidal zone. Randomly selected shoots (54 per site) were carefully tagged for direct shoot observation and sampling done every fortnight for leaf emergence and fall, and bud, flower and fruit production. Vegetative and reproductive attributes of the species were clearly seasonal in both zones with distinct patterns. However, shifts in peaks in leaf fall and emergence were observed in 2006. Unimodal and bimodal leaf fall patterns were respectively observed at the landward and seaward sites. Monthly leaf emergence and fall was significantly different (p0.05) between sites. Mean leaf longevity was 11 months with a significant difference (pA. marina across the intertidal zone are discussed

Vegetative and reproductive phenological traits of Rhizophora mucronata Lamk. and Sonneratia alba Sm.

info:eu-repo/semantics/publishe

Vegetative and reproductive phenological traits of Rhizophora mucronata Lamk. and Sonneratia alba Sm.

Mangrove phenology is important in understanding the past, present and future response of mangrove species to impacts of climate change. Our study is the first long term direct observation of the phenology of Rhizophora mucronata and Sonneratia alba in Kenya. Objective of the study was to determine, interpret and document the timing of the various phenoevents and phenophases, and to establish relationships between phenology and the climatic variables. Phenological traits were investigated in six monospecific mangrove stands in Gazi Bay, south of Mombasa, for 2 years. Leaf emergence, leaf fall, flower bud, flower and fruit initiation data were recorded every fortnight in 54 shoots of 9 trees at each site. Continuous leaf emergence and loss characterized by multimodal peaks was observed for the two species. Leaf emergence and leaf fall peaked in the wet months and was reduced in the dry months. There was a relationship between the leaf emergence and drop with the reproductive phenology in the two species. Mean leaf longevity for R. mucronata and S. alba was 12.8. ±. 1.2 and 4.9. ±. 0.5 months respectively. The reproductive cycle took approximately 16-20 months in R. mucronata and 4-5 months in S. alba. Bud initiation in R. mucronata was seasonal and occurred in October and September. Buds were observed for 8-11 months developing slowly on the shoots. Shifts were observed in the timing of flower initiation, and the flowering period lasted in total for 4-5 months. The time period from flower appearance to the developmental start of immature propagules lasted about 1 month at reforested sites and up to 5 months in stands of natural vegetation. In R. mucronata initiation of immature propagules was not seasonal and varied among the sites. Fruiting in S. alba was short and seasonal without overlap, and shifts were observed in the timing of flowering, flowering and fruiting peaks. Abscission of reproductive parts started in July and in June, respectively, in the years 2005 and 2006. Fruiting was observed starting in August in both years, and fruiting peak was reached in October in 2005 and one month earlier in 2006. In R. mucronata vegetative and reproductive phenophases significantly correlated with climatic variables, whereas in S. alba only leaf emergence and leaf fall correlated with temperature. The flowering plasticity in the reproductive phenology of the two species indicates possible sensitivity to certain climatic and environmental triggers. Our results also indicate that R. mucronata trees have a distinctly higher investment in the reproductive cycle than S. alba. © 2013 Elsevier GmbH.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Litter Fall Dynamics of Restored Mangroves (Rhizophora mucronata Lamk. and Sonneratia alba Sm.) in Kenya

Mangrove forests are active carbon sinks and important for nutrient cycling in coastal ecosystems. Restoration of degraded mangrove habitats enhances return of ecosystem goods and services, including carbon sequestration. Our objective was to assess the restoration of primary productivity of reforested mangrove stands in comparison with natural reference stands in Gazi Bay, Kenya. Litter fall data were collected in nine Rhizophora mucronata and Sonneratia alba monospecific stands by use of litter traps over 2 years. Litter was emptied monthly, dried, sorted, and weighed. The reforested and natural stands showed seasonality patterns only in the production of reproductive material. Leaves constituted the highest percentage to total litter fall. Litter productivity rates for the R. mucronata stands were not significantly different and ranged from 6.61-10.15 to 8.36-11.02 t ha-1 yr-1 for the restored and natural stands, respectively. The productivity of 5 years R. mucronata stands reached 5.22 t ha-1 yr-1 and was significantly different from other stands. Litter productivity rates for S. alba stands was 7.77-7.85 for the restored stands and 10.15 t ha-1 yr-1 for the natural stand but differences were not significant. Our results indicate that plantations of at least 11 years have attained litter productivity rates comparable to the natural forests. This suggests that productivity of replanted mangroves is likely to reach complete recovery by this age under the prevailing environmental conditions.SCOPUS: ar.jFLWINinfo:eu-repo/semantics/publishe