Mass Selection in Crop Plants

MASS SELECTION IN FIELD CROPS : 

MASS SELECTION IN FIELD CROPS

INTRODUCTION : 

INTRODUCTION It is a method of crop improvement in which individual plants are selected on the basis of phenotype from a mixed population, their seeds are bulked and used to grow the next generation.

MASS SELECTION : 

MASS SELECTION Plants are selected on the basis of phenotype. It is applicable to both self pollinated & cross pollinated crops. More commonly used in the improvement of C.P. Crops than S.P. Crops. Oldest breeding method based on phenotype selection.

MAIN FEATURES : 

MAIN FEATURES Genetic constitution Adaptation Variation Selection Quality Resistance

GENETIC BASIS OF MASS SELECTION : 

GENETIC BASIS OF MASS SELECTION Used in both self & cross pollinated species. In a self pollinated crops, a mass selection variety is a mixture of several pure lines. Thus it constitutes a homozygous but heterogeneous population. In cross pollinated crops, a mass selected variety is a mixture of several homozygotes & heterozygous. Thus such variety is a heterozygous but heterogeneous population.

Slide 6: 

TYPES OF MASS SELECTION POSITIVE MASS SELECTION NEGATIVE MASS SELECTION

POSITIVE MASS SELECTION : 

POSITIVE MASS SELECTION When desirable plants are selected from a mixed population & their seeds are mixed together to grow further generation. Continued for several years. Old varieties or land races are used as the base material.

NEGATIVE MASS SELECTION : 

NEGATIVE MASS SELECTION When only undesirable off type of plants are removed from field & rest are allowed to grow further. Used for varietal purification in seed production & certification programmes. Helps in maintaining genetic purity in the varieties especially in self pollinated species.

SUCCESS FACTORS OF MASS SELECTION : 

SUCCESS FACTORS OF MASS SELECTION Variability in the base population. Mode of inheritance of character to be improved. Heritability of the character.

APPLICATIONS OF MASS SELECTION : 

APPLICATIONS OF MASS SELECTION Improvement of local varieties. Purification of existing pureline varieties.

Slide 11: 

FIRST YEAR SECOND YEAR THIRD TO FIFTH YEAR SIXTH YEAR (i)Select 200-2000 plants from a variable population. (ii)Seeds from selected plants are composited. (i)Composited seed is planted in a preliminary yield trial along with standard checks. (ii)Phenotype of the selected population is critically evaluated. (i)Promising selections are evaluated In coordinated yield trials at several Locations. (ii)If outstanding, released as a new Variety. Seed multiplication for distribution. Mass selection in S.P. Crops as used to develop new variety.

Slide 12: 

FIRST YEAR SECOND YEAR THIRD YEAR FOURTH-SIXTH YEAR SEVENTH YEAR (i)Select 200-2000 plants of similar but superior phenotype. (ii)Harvest seeds separately from each selected plant. (i)Grow individual plant progenies. (ii)Reject inferior progenies. (iii)Bulk the seeds from remaining progenies. (i)Preliminary yield trial from the bulked seed; Standard checks are included. (ii)If superior, the new line is included in multi- Location yield trial. (i)Multilocation coordinated yield trials. (ii)If superior, released as a new variety. Seed multiplication for distribution. Mass selection in self pollinated crops coupled with progeny test.

MERITS OF MASS SELECTION IN S.P. CROPS : 

MERITS OF MASS SELECTION IN S.P. CROPS The varieties developed through mass selection are likely to be more widely adapted than purelines. Reduces the time & cost needed for developing the new variety. Retains genetic variability in the new variety. Less demanding method. Provide protection against diseases.

DEMERITS OF MASS SELECTION IN S.P. CROPS : 

DEMERITS OF MASS SELECTION IN S.P. CROPS Varieties developed by mass selection is less uniform than pureline varieties. It can’t generate variability. Difficult to identify the varieties. Not commonly used in the improvement of self pollinated crops. Absence of progeny test.

MASS SELECTION IN Cross Pollinated CROPS : 

MASS SELECTION IN Cross Pollinated CROPS In mass selection, a no. of plants are selected on the basis of their phenotype, and the open pollinated seed from them is bulked together to raise the next generation. Thus mass selection is based on the maternal parent only. There is no control on the pollen parent. No progeny test is conducted.

Slide 16: 

Original population Selection cycle may be Repeated one or more times FIRST YEAR SECOND YEAR (i)Plants are selected on the basis of phenotype. (ii)Open pollinated seed from the selected plants harvested and bulked. (i)Bulk seed from the selected plants Grown. (ii)Mass selection may be repeated. Yield trials Mass selection as applied to cross pollinated crop species.

MERITS OF MASS SELECTION IN Cross Pollinated CROPS : 

MERITS OF MASS SELECTION IN Cross Pollinated CROPS Simple breeding method. Selection cycle is very short. Have high heritability. Effective in improving yields of cross pollinated crops.

DEMERITS OF MASS SELECTION IN Cross Pollinated CROPS : 

DEMERITS OF MASS SELECTION IN Cross Pollinated CROPS No control on the pollination. Inbreeding depression. Phenotypic performance is greatly influnced by environmental factors such as soil heterogenety.

MODIFICATIONS OF MASS SELECTION : 

MODIFICATIONS OF MASS SELECTION Rejection of inferior pollen plants. Use of composite pollen. Stratification of field.

COMPARISION BETWEEN MASS SELECTION & PURELINE SELECTION : 

COMPARISION BETWEEN MASS SELECTION & PURELINE SELECTION