Maize Genotypes Show Striking Differences for Induction and Regeneration of Haploid Wheat Embryos in the Wheat × Maize System

A number of maize (Zea maysL.) genotypes were tested for their influence on induction and regeneration of haploid wheat (Triticum aestivumL.) embryos to improve further the efficiency of the wheat × maize system of haploid production. Fifteen maize genotypes were crossed to five diverse wheat F1hybrids in a line × tester fashion in three replications. Two efficiency parameters, caryopses formation frequency (CFF—number of caryopses/100 pollinated florets) and embryo formation frequency (EFF—number of embryo‐carrying caryopses/100 pollinated florets), were estimated. Analysis of variance revealed that lines (wheat genotypes), testers (maize genotypes), and their interaction showed significant effects on both efficiency parameters, but the effect of maize genotypes was greater than that of wheat genotypes. The EFF of individual maize genotypes ranged from 1.1 to 23.4% and the EFF of individual wheat genotypes ranged from 8.4 to 10.2%. Maize genotypes also showed significant differences for general combining ability estimates. In addition to EFF, maize genotypes had a striking effect on haploid embryo regeneration as analyzed using one of the wheat genotypes. The values ranged from 0.0 to 87.8%. For maize genotypes producing the highest EFFs, the regeneration frequency was not necessarily higher. Hence, we suggest a new index, haploid formation efficiency (HFE—number of haploid plants formed /100 pollinated florets), be used for identification of efficient pollinators. The HFE ranged from 0.0 to 9.9%. In this study, a pop corn cultivar, Pearl Pop Corn, was identified as the best pollinator with an average EFF of 15.1% across five wheat genotypes and an HFE of 9.9% with the one wheat genotype tested.