In the improvement of most crops, gene recombination is the mechanism most commonly used to create new variability which in turn leads to new genotypes. Environmental effects on a plant are not transmitted to the plant's progeny. Simplistically - the characters or traits that develop or are expressed by a plant develop as a result of the action of genes on the chromosomes AND the interaction of the plant with it's environment during development. Genes direct the plant's development in combination with the environment, determines the traits of the plant that is measured or observed.
Examples are flower color and dwarfing genes.
Examples are yield and quality traits. The distribution of the gametes is influenced by their linkage relations. As the number of independently assorting genes increases, the minimum population that would allow for recovery of ideal genotypes increases exponentially.