2. Introduction
■ Genetics: Biological science which deals with the principle of heredity and variation.
■ Biometric: Science that deals with the application of the statistical concept and
procedure to study the biological problems. Also known as biometry or biostatistics.
■ Biometric Genetics: Branch of biology that utilizes the various concept and procedure of
statistics to study the genetic principles.
■ Biometric techniques: Various statistical procedure employed in biometric genetics.
3. Introduction
■ Biometric Techniques : Useful to plant breeders in four different ways.
■ Also called the basic principles of biometrics genetics.
■ Aids to the assessment of the variability:
Simple Measurement of dispersion such as Range, Standard Deviation, Variance,
Standard Error, Coefficient of Variation, Meter glyph Analysis and D2 Statistics.
■ Aids to selection of elite genotypes.
Correlation analysis, path analysis and discriminant function.
■ Aids to the choice of the suitable parents and breeding procedure.
Diallel Cross, Partial Diallel Cross, line*tester cross, triallel cross, etc.
■ Aids to the assessment of varietal adaptation.
4. Aids To The Choice Of The Suitable
Parents As Evaluation Techniques.
■ For the evaluation of the varieties or strains, the suitable breeding procedure is necessary.
■ Leads to the suitable parent selection for the further generations
■ Consists of the following biometric techniques.
1. Diallel Cross Analysis
2. Partial Diallel Analysis
3. Line X Tester Analysis
4. Triallel and Quadriallel Analysis:
5. Biparental Cross Analysis:
5. Diallel Cross Analysis:
■ Refers to the mating of selected parents in all possible
combination and evaluation of a set of crosses
■ Two types, Full Diallel and Half Diallel Cross.
■ Full Diallel design: All the possible mating among the
selected parents is made in both the direction i.e. direct
and reciprocals.
■ Total number of single crosses in a full diallel is given
by P(P-1), where P is the number of parents used.
■ Used when reciprocal differences are significant and
parents do not have the male sterility or self-
incompatibility.
■ Permits estimation of the maternal effects
6. Diallel Cross Analysis:
■ Half Diallel : All the possible crosses among the selected
parents are made in one direction only.
■ Parents are used either as male or as female in the mating.
■ The number of single cross is equal to P(P-1)/2, where P
is the number of parents used.
■ Used when the reciprocal differences are not significant.
■ Can be used when the parents have male sterility and self-
incompatibility
7. Partial Diallel Analysis:
■ Developed by Kempthorne in 1957 and was further elaborated by
Kempthorne and Curnow in 1961.
■ Utilizes only a part of all possible crosses from a diallel.
■ Each Parent is crossed to some of the other parents, but not all.
■ Total no. of crosses is given by ns/2 where n and s are the number of
the parents and sample crosses respectively.
8. Partial Diallel Analysis:
■ The total number of sampled crosses is equal to ns/2.where, n is the number of parents and s
is the number of sampled crosses per parent array. The following three points are important
for sampling.
• The s should be a whole number. It cannot be in decimal fraction.
• The s should be either greater than or equal to n/2
• Both n and s can neither be odd nor even. If n is odd, s should be even and vice-versa.
■ For the purpose of sampling, first a constant K is worked out as follows
■ K=(n+1-s)/2 where, n and s =number of parents and sampled crosses, respectively
■ If n=10 and s=5, K will be = (10+1-5)/2=3
■ This means that in each array five crosses are to be made (s=5), and sampling is to being
after 3 arrays, i.e., the 4th array as depicted below in this partial diallel, only 25 crosses will
be conducted.
9.
10. Line X Tester Analysis:
■ Developed by Kempthorne in 1957.
■ Modified form of top cross scheme.
■ Top cross only one tester used, while in case of line x tester cross several testers used.
■ Line x tester analysis involves mf crosses, where m and f are number of male and female
parents.
■ Can evaluate large number of germplasm lines in terms Of GCA and SCA variances and
effects and D and H components. Results obtained from this technique have high level
of precision.
■ Simple as compared to diallel and partial diallel analysis.
11. Triallel Analysis:
■ Developed by Rawlings and Cokerham in 1962.
■ Triallel:analysis of a three-way cross.
■ Includes all possible three-way crosses among n parents.
■ Total number of three-way crosses is equal to n (n-1) (n-
2) 2 where n is the number of parents.
■ Involves three different parents.
■ Provides general and specific line effects and helps in
deciding the mating order of parents for developing
superior three-way hybrids.
12. Quadriallel Analysis:
■ Developed by Rawlings and Cokerham (1962)
■ Refers to the analysis of double cross hybrids which are
the first-generation progeny of a cross between unrelated
F1 hybrids.
■ Involves all possible double crosses among n parents.
■ Total no, of crosses is equal to n(n-1) (n-2) (n-3)/8 where n
is the number of parents.
■ Helps in deciding the mating order of parents for
development of superior double cross hybrids in cross
pollinated crops.
■ More crosses than diallel and triallel have to be made. i.e.,
630 among in 10 Parents.
13. Biparental Cross:
■ Developed by Comstock and Robinson (1948, 1952).
■ Plants are randomly selected in F2 or subsequent generation of a cross between two pure
lines having contrasting characters and the selected plants are crossed in a definite
fashion.
■ Has the following types:
North Carolina Design I
North Carolina Design II
North Carolina Design III
14. Biparental Cross:
North Carolina Design I:
■ Each male is mated to a different set of females.
■ Each set consists of f crosses, where f is the number of
female plants.
■ Variance between males provides an estimated of D and
that of females provides estimated of H & influenced
by the presence of maternal effects.
15. Biparental Cross:
North Carolina Design II:
■ Each male is mated to the same set of females.
■ Each set consists of mf crosses, where m and f denote
number of male and female plants.
■ Variances due to males and female provide an estimate
of D.
■ Variance due to male x female provides an estimate of
H.
■ Influence by the presence of maternal effects.
16. Biparental Cross:
North Carolina Design III:
■ Each male is mated to parents of original cross.
■ Each consists of 2m cross, where m is the number of
male plants in a Variance due to male provides estimate
of D.
■ Variance due to male x female provides an estimate of
H.
■ Not affected by the presence of maternal effects.
■ The main use of the Design III is for estimating the
average degree of dominance.
