Micropropagation or tissue culture is an integral component of applied biotechnology, and is routinely used in different laboratories worldwide. Plant tissue has contributed immensely in large-scale production of resistant and pest free plantlets, germplasm exchange and conservation. A common feature of in vitro-regenerated plants is the potential of genetic variation generated during tissue culture called somaclonal variation, which can be passed onto progeny. Objective: This paper reviews the factors responsible for this phenomenon, its occurrence in some crops, with emphasis on banana and plantain and its application in the genetic improvement of Musa.

The precision of using full polynomial response surface designs on models with missing coefficients (reduced models) is studied using efficiency measures. The loss in D-and G-efficiency of constructed first-order exact designs is minimized for the model with missing interaction coefficient. However, higher losses in D-and G-efficiency are recorded when constructed second-order exact designs are used on the model with missing interaction coefficient with few exceptions showing preferences for using the designs on the reduced model. Lower condition numbers are observed for the designs under the first-order reduced models thus indicating that the N-point exact designs are closer to being orthogonal for the reduced model than for the full model. Perfect orthoganality is achieved at design sizes 4 and 8. In fact, N-point exact designs of multiples of N=4 show perfect orthoganality when defined either for the full or reduced first-order models. In comparison to a design with perfect orthoganality, the second-order designs are far from being orthogonal.

Missing observations in an experimental design may lead to ambiguity in decision making thereby bringing an experiment to disrepute. Robustness, therefore, enables a process, not to break down in the presence of missing observations. This work constructed a modified central composite design (MCCD) from a four-variable central composite design (CCD) augmented with four center points using the leverage of a hat-matrix. The robustness of the CCD and MCCD were assessed when a design point is missing at the factorial, axial, and center points of the experiment, for a non-standard model, using the loss criterion, D-optimality, D-efficiency, and relative D-efficiency. When the designs are complete the MCCD shows higher D-efficiency and D-optimality for the non-standard model when compared to the CCD. In the absence of an observation from any of the designs, the CCD is found to be a more robust and efficient design compared to the MCCD as it has overall lower loss values at all the factors levels.

Organic materials are alternatives to chemicals for safe and healthy fish production. This study aimed at comparing the buffer efficiency of pawpaw leaves and stem with calcium carbonate on acidic borehole water at different dosages for aquaculture. Forty-eight, 25-litres shaded plastic tanks of three replicates per treatment were used. The tanks were 20 litres filled with experimental water (pH 4.7). There were sixteen treatment (T) levels (T0 to T16). T1 to T15 were classified into three groups of three dosage levels (G) (2.4g [G1], 6g [G2] and 12g [G3]) per pawpaw leaves and stem [dried leaves (DL), fresh leaves (FL), dried stem (DS) and fresh stem (FS)] and calcium carbonate (CA). pH and temperature were monitored once daily while dissolved oxygen, alkalinity and calcium were measured weekly for thirty-one (31) days using standard method. Data were analyzed for analysis of variance, Duncan Multiple Range and descriptive statistics. At the end of the study period, the minimum (4.7) and maximum (7.30) pH were recorded in T0 and T11 respectively. Water pH progressively increased from Day 1 to Day 31 in all the treatment levels. The order of buffer efficiency of pawpaw leaves and stem at the end of the experiment in all the treatment groups was FS<DS<FL<DL. pH values ranged between 6.41 ±0.01 (T4) and 7.03 ±0.02 (T11) on Day 28 and were within the acceptable range of 6.5-9.0. This study therefore suggests the use of DL, FL, DS and FS for fish production. It is free of cost and safe for fish production and human consumption.

Organic materials are alternatives to chemicals for safe and healthy fish production. This study aimed at comparing the buffer efficiency of pawpaw leaves and stem with calcium carbonate on acidic borehole water at different dosages for aquaculture. Forty-eight, 25-litres shaded plastic tanks of three replicates per treatment were used. The tanks were 20 litres filled with experimental water (pH 4.7). There were sixteen treatment (T) levels (T0 to T16). T1 to T15 were classified into three groups of three dosage levels (G) (2.4g [G1], 6g [G2] and 12g [G3]) per pawpaw leaves and stem [dried leaves (DL), fresh leaves (FL), dried stem (DS) and fresh stem (FS)] and calcium carbonate (CA). pH and temperature were monitored once daily while dissolved oxygen, alkalinity and calcium were measured weekly for thirty-one (31) days using standard method. Data were analyzed for analysis of variance, Duncan Multiple Range and descriptive statistics. At the end of the study period, the minimum (4.7) and maximum (7.30) pH were recorded in T0 and T11 respectively. Water pH progressively increased from Day 1 to Day 31 in all the treatment levels. The order of buffer efficiency of pawpaw leaves and stem at the end of the experiment in all the treatment groups was FS