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Title: The genetics of salinity tolerance in Tilapia species
Author: Buya, J. K.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1997
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Path coefficients were applied to estimate the amount of variation each physiological factor determines in the serum water content (SEWCON) or time-to-succumb (TS). Each estimate was used to reconstitute its own mean. In all cases, the re-constructed variables exhibited a higher value of VG/VP than in the original. This infers the expression of genetic variability masked by the composite action of many gene differences on the trait (Mather and Harrison 1949). VG/VP was related to neither the correlation or regression between groups. Correlation estimates differed from their intra-class correlations (rI). ANOVA values of VG/VP were similar to those of rI, which estimates the amount of genetic variability in the trait (Falconer 1981). VG/VP estimates from repeatability are not about how "repeatable" measures are (Falconer 1981), but rather the degree to which individuals differ from each other, the individuality (I). Both being standardized values (Bentsen 1994), the individuality readily translates into the heredity (h), the degree to which an individual's phenotype is determined by additive genetic factors. This idea was developed by Wright (1911) to define the heritability (h2); where hPPx ½hOP = ½h2 and hPP, the covariance between additive genetic and phenotypic values (COV (Ai, Pj)) which is also the covariance between parents and their respective family genotypic values (CO (giP, gjF)) (Mather and Harrison 1949). This is the additive degree of divergence (d), between parents (Bentsen 1994). When this quantity is estimated from half-siblings it has a magnitude of ¼h. The offspring-parent path (hOP), is the correlation of parent additive and offspring phenotypic values, (COV(AiP, PjO)). Its value is ½h. A domestication selection programme for tilapia species is proposed, where several lines of known genetic differences are generated to aid improvement programs through reciprocal recurrent selection (RRS).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available