Theoretical aspects and practical implications of cross-pollination on seed regeneration of field crop genetic resources

Consequences of seed regeneration such as changes in allele frequency and the determination of the number of generations required for an allele to be lost under environmental conditions which differ from those existing where the population evolved, are well described by population genetics. The biological characteristics of self-pollinated crops make the task of handling germplasm collections relatively easy: their seed lots can easily be renewed by harvesting the seeds produced by plants grown without specific care. Competition among genotypes, differential seed viability, cold and photoperiodic requirements, resistance to environmental factors can all result in an increased or decreased fitness of each genotype. Population size often has to be reduced during seed regeneration due to limitations in personnel and availability in resources. Indian maize growers from North America probably saved few spikes to obtain seeds to be sown in their small fields and sometimes new populations have been produced from a single spike.