Innovative F₁ hybrid method enables testing of large number of line to line crossings for combining ability

Hybrid vigor has been demonstrated in the early 20^th century after hybrid corn was invented. Procedures to breed hybrid cultivar are more complex than breeding open-pollinated cultivars or pure lines. Hybrid cultivars are most often based on the crossing of two true breeding lines that should genetically complement each other. This complementarity of genotypes of genetically different parental lines in the F₁ hybrid often results in a considerable improvement of e.g. growth characteristics, yield or adaptation to environmental stresses as compared to the individual parental lines and non-hybrid cultivars. Numerous methods have been proposed, the most common is based on development of large numbers of inbred lines originated form heterozygous parents by either self pollination or doubled haploid induction. Inbred lines are then tested for hybrid vigor often in two steps, by which first “general combining ability” and then “specific combining ability” is tested to identify a pair that expresses optimal characteristics. This standard procedure allows only a very limited number of line to line crosses since it is laborious and long lasting. Here we are proposing a new method that allows much higher number of line to line crosses as previously known. Our invention relates to innovative method of testing combining ability of inbred lines, which is based on genotyping of each genetically diverse inbred line followed by allowing the plants of the donor lines to intercross to obtain F₁ hybrid progeny. In the next season progeny is phenotyped on individual basis. For superior individuals parental lines are revealed by paternity testing, which due to homozygosity of lines and previous genotyping allows identifying both parental lines. By this method a much larger number of line to line testing can be achieved thus overcoming major bottleneck in breeding hybrid cultivars. Details of the protocol and its utilization will be discussed.