Improvement of performance of introduced varieties over generations is called:
Acclimatization describes gradual adaptive improvement in performance of introduced variety over successive generations grown in new environment. Initially introduced genotype may flower late, show asynchronous maturity or susceptibility to local leaf rust races. Continuous natural and farmer selection favours individuals with favorable alleles for photoperiod insensitivity, thermal tolerance, efficient nutrient uptake and pathogen defense mediated by polygenic QTL. Epigenetic modifications such as DNA methylation changes altering gene expression without sequence change also contribute. Over time mean yield, harvest index and stability increase as allele frequencies shift toward local optimum. Unlike heterosis which is immediate, acclimatization involves progressive narrowing of genotype x environment interaction variance, exemplified by Mexican wheat adapting to Indo-Gangetic plains after several cycles of selection for earliness. This understanding supports competitive exam preparation for NEET, GATE and CSIR NET concepts linking genotype with phenotype through molecular pathways involving transcription factors, hormones and metabolic enzymes that regulate development, adaptation and reproductive biology in applied breeding programs.
Ref: Allard RW Principles Plant Breeding Acclimatization chapter; e-courses Breeding Fruit Crops Acclimatization; FAO Adaptation.