Timelines in conventional crop improvement: pre-breeding and breeding procedures

This article is aimed at highlighting the timelines and breeding procedures of clonally propagated, self-fertilizing and cross-fertilizing crops in conventional crop improvement. Plant breeding is aimed at developing crop cultivars with improved genetic constitution to serve diverse human needs. Cultivar development follows well-defined activities, including plant breeding research or ‘prebreeding’, followed by the actual breeding per se . These discrete activities are the components that determine the pace at which cultivars are released to growers. The two activities, in turn, depend upon factors, such as breeding goals, genetics and agronomy of the crop, breeder’s vision, availability of testing facilities and national cultivar-registration requirements. Given these factors, there are established steps and procedures found in any conventional breeding program. These include parental choice, making crosses among chosen parents, selections from recombined parents followed by extensive field testing at targeted sites, followed by maintenance and multiplication of candidate cultivars for seed production and distribution. The present review outlined the approximate timelines at 7, 9, or 17 minimum breeding generations before the release of an improved cultivar of vegetatively reproducing, self-fertilizing or cross-fertilizing crop, respectively through conventional breeding. The traditional breeding procedures can be complemented with other approaches, such as marker-assisted selection and doubled haploidy breeding to accelerate and shorten the timeline to release of new crop cultivars.