Dear Omikunle Oluwaseun,

First of all: what crop and what traits (e.g. dry matter, harvest weight, genotype, etc) are you investigating?

Simple correlation is a relationship or link between two sets of data from e.g. (phenotypic) traits, expressed by the coefficient of determination r2 (r squared); it gives the proportion of the variance (fluctuation) of one variable that is predictable from the other variable. r is the correlation coefficient, where:

1 is a perfect positive correlation

0 is no correlation (the values don't seem linked at all)

-1 is a perfect negative correlation

0 < r 2 < 1, representing the percentage of the data that is the closest to the line of best fit. 

Correlations between genotypic effects for different traits are called genotypic or genetic correlations (rG).

Genotypic effects for the same traits are expressed differently in different environments, and there is a genotype x environment interaction.

Higher genotypic variation in the plant population causes wider differences in association between the presence of a genotype and the resulting physical trait; the genotype - phenotype correlation.

According to quantitative genetic theory, genetic and environmental causes of correlation combine together to produce the phenotypic correlation (Falconer, 1996).

To be able to calculate these  correlations, you first have to obtain the components of variance for these traits. Also broad-sense heritability (H2, h squared) representing the flow of traits from one generation (parents) to the next (progeny) can be calculated, which is useful in breeding trials.

More info:

Clewer, A. G. and D. H. Scarisbrick (2001). Practical Statistics and Experimental Design for Plant and Crop Science, John Wiley & Sons.

Falconer, D. S. and T. F. C. Mackay (1996). Introduction to quantitative genetics. Harlow, Essex, England, Longman.

http://thalamus.wustl.edu/cheverudlab/publications/1988/Cheverud_Evolution_42.pdf

Holland, J. B. (2006). "Estimating genotypic correlations and their standard errors using multivariate restricted maximum likelihood estimation with SAS Proc MIXED." Crop Science 46(2): 642-654

Cooper, M. and I. H. DeLacy (1994). "Relationships among analytical methods used to study genotypic variation and genotype-by-environment interaction in plant breeding multi-environment experiments." Theoretical and Applied Genetics 88(5): 561-572.

Waitt, D. E. and D. A. Levin (1998). "Genetic and phenotypic correlations in plants: a botanical test of Cheverud's conjecture." Heredity 80(3): 310-319.

Dear Sir,

 Gd question... Wouter Leonard Ballizany is absolutely right...but i think u r not asking this..whnevr u seen analyzed data for correlation in any research paper...u would found almost similar value of both genotypic  and phenotypic correlation, there is no much difference. when dealing with quantitative,polygenic trait, expression of traits affected by environment in such cases phenotype deviate from genotype....and in most of the cases genotypic corr. is higher.........environment, gene expression, and stable association among traits, on the basis of that a predictable breeding prog. could be designed for trait improvement.....................

hello dear

i think

1- SAS analysis correlation is simple correlation between two group of data for example dry weight and photosynthesis but genotype correlation is relation between two genotype trait.the two concept of correlation is not different in calculation method   but hare seprat mean.

2- it is simple for calculate each correlation you must mate data from that.for example if you want to calculate genotype correlation you should use genotype data.

i hope answer your question.

best regard