Flow cytometric analysis of nuclear DNA content,mitotic chromosome number and protein separation by SDS-PAGE in three accessions of African locust bean (<Emphasis Type="Italic">Parkia biglobosa</Emphasis> Benth.)

Nuclear DNA of three accessions of Parkia biglobosa collected from three locations in northern Cross River State was investigated using a Patec PA II flow cytometer equipped with an argon ion laser (488 nm), and pictures of mitotic chromosomes were taken using a digital micro-camera (Canon) placed on the eye piece of a binocular microscope at 100X oil immersion. Metaphase chromosome counts of 2n = 22 for accessions A and C and 2n = 24 for accession B, were obtained and through flow cytometry, the three accessions were confirmed to be diploids. The nuclear DNA content and genome size for the accessions were 1.5085, 1.489, and 1.5266 pg (737.7054, 728.121, and 746.5074 Mbp) for accessions A, B, and C, respectively. In another experiment, leaf samples from greenhouse-germinated seeds were analyzed for variation in the banding pattern of the protein by SDS-PAGE in the three accessions. Protein was resolved into three banding groups according to their electrophoretic mobility: slow, medium, and fast, clustering between 100–200, 40–70, and 10–25 kDa, respectively. There was 76% similarity in the banding pattern between the accessions.     

Evaluation of yeasts for biological control of Fusarium dry rot of potatoes

Thiabendazole-resistant strainsof Fusarium sambucinum andF. solani var.coeruleum threaten to negate chemical control options for post harvest treatment of Fusarium dry rot. Biological control of dry rot of storage tubers is feasible using bacterial antagonists (25). The impact of yeasts on dry rot has not been investigated. Initial biological control tests employed strains of twenty species of yeasts from the ARS Culture Collection (NRRL). Strain selection was based on strain isolation from plant matter or from environments that would indicate a high likelihood of strain survival in soil. The control potential of these and 29 additional strains isolated from soil adhering to recently harvested tubers was evaluated using a whole Russet Burbank tuber bioassay. At 2xl0⁶ cells/ml, only two unidentified strains andCryptococcus laurentii strain NRRL Y-2536 reduced disease (P=0.05, P=0.10, respectively) while bacterial strainPseudomonas fluorescens 2-79 (NRRL B-15132) was more effective (P=0.01). Conversely,Debaryomyces robertsiae increased disease (P=0.05). No yeast strains significantly controlled disease in a subsequent trial. One of six additional strains ofC. laurentii (P=0.10), none of five strains ofPichia farinosa and neither unidentified strain controlled disease at 5 x 10⁷ cells/ml whereasP. fluorescens again reduced disease (P=0.01). After 6 h, four yeast strains decreased and three increased conidial germination ofF. sambucinum R-6380 though there were no differences after 18 h. Five yeast strains, including two strains ofC. laurentii (NRRL Y-2536, NRRL Y-7139) were marginally effective in controlling disease incited byF. solani var.coeruleum S-1257. Though additional testing may identify yeast strains with considerable promise as biological control agents active against Fusarium dry rot, evidence to date indicates bacterial agents have a greater potential for commercial development.     

Evaluating persistence and its predictors in a West African carnivore community

Carnivore extinctions frequently have cascading impacts through an ecosystem, so effective management of ecological communities requires an understanding of carnivore vulnerability. This has been hindered by the elusive nature of many carnivores, as well as a disproportionate focus on large-bodied species and particular geographic regions. We use multiple survey methods and a hierarchical multi-species occupancy model accounting for imperfect detection to assess extinction risk across the entire carnivore community in Ghana’s Mole National Park, a poorly studied West African savanna ecosystem. Only 9 of 16 historically occurring carnivore species were detected in a camera-trap survey covering 253 stations deployed for 5469 trap days between October 2006 and January 2009, and our occupancy model indicated low overall likelihoods of false absence despite low per-survey probabilities of detection. Concurrent sign, call-in, and village surveys, as well as long-term law enforcement patrol records, provided more equivocal evidence of carnivore occurrence but supported the conclusion that many carnivores have declined and are likely functionally or fully extirpated from the park, including the top predator, lion (Panthera leo). Contrary to expectation, variation in carnivore persistence was not explained by ecological or life-history traits such as body size, home range size or fecundity, thus raising questions about the predictability of carnivore community disassembly. Our results imply an urgent need for new initiatives to better protect and restore West Africa’s embattled carnivore populations, and they highlight a broader need for more empirical study of the response of entire carnivore communities to anthropogenic impact.     

Influence of processing cassava peels on the hydrogen cyanide concentration, nutritive value and performance of growing rabbits

Forty-eight rabbits used to investigate the response of growing rabbits to diets containing differently processed cassava peel meals were divided into four groups balanced for sex and weight. These groups were then assigned at random to the experimental treatments. Four diets were formulated such that the diets contained 200 g/kg of the experimental feedstuffs, sun-dried cassava peel meal (S), ensiled cassava peel meal (E) and retted cassava peel meal (R), and the control did not contain any cassava peels. Hydrogen cyanide (HCN) concentration in the processed cassava peel meal was lower relative to the unprocessed meal. It was, however, lowest in R and highest in E. With the exception of S, fibre fractions were lower in the processed meal compared to the unprocessed meal. The E depressed (p < 0.05) feed and digestible nutrient intakes, weight gain, nutrient digestibility, digestible protein (DP), digestible energy (DE) and DP/DE ratio but increased protein intake to gain and feed to gain ratios compared to other diets. Intake of HCN decreased (p < 0.05) successively in this order: R, S and E. The results indicate that retting and sun-drying are more effective in cassava peel detoxification than ensiling, and dietary HCN concentration and intake of 56 and 4 mg/kg BW, respectively, were not toxic under the conditions of the experiment.