Question

what is mass selection and pure line selection

Answer 1

Mass selection and pureline selection are two methods of selection of superior recombinants in plant breeding:
In mass selection, a large number of plants with similar phenotype are selected and their seeds are mixed together to constitute the new variety. The plants are selected on the basis of their appearance or phenotype. Therefore, selection is done for easily observable characters such as plant height, ear type, grain colour, grain size, disease resistance etc.
In pureline selection, a large number of plants are selected from a self-pollinated crop and are harvested individually; individual plant progenies from them are evaluated and the best progeny is released as a pureline variety.