Agricultural Botany

Heritability Ø   The ratio of genotypic variance to the phenotypic or total variance is called as heritability. Ø   It is generally expressed in percentage. Ø   It is the good index of the transmission of characters from parents to their off spring. Ø   The estimates of heritability helps the plant breeder in selection of elite genotypes from diverse genetic populations. Types of Heritability Ø   Depending upon the components of variance used as numerator in the calculation, heritability is of two types, viz; broad sense and narrow sense. Broad Sense Heritability Ø   It is the ratio of genotypic variance to the phenotypic variance. Ø   It is calculated from total genetic variance which consists of additive, dominance and epistatic variances. Main Features Ø   It can be estimated from both parental as well as segregating populations. Ø   It is estimated from total genetic variance. Ø   It is useful in selecton of elite types from homozygo...

QTL Mapping QTL mapping is  a statistical analysis to identify which molecular markers lead to a quantitative change of a particular trait . Principle of QTL Mapping Ø The objective behind QTL mapping is to find the association between genotypic and phenotypic data. The molecular markers are used to divide the mapping population into distinct genotypic classes depending on genotypes at the marker locus, and correlative statistics are used to see if individuals of one genotype vary substantially from those of the other genotype in terms of the characteristic under investigation. Ø A substantial variation in phenotypic averages between the two / more groups based on the marker system and population type suggests that the marker locus used to split the mapping population is related to a QTL regulating the trait. Ø Recombination is responsible for a large P-value reported for discrepancies between the marker and the QTL. The closer a marker is to a QTL, the less likely it ...