Combining Cytoplasmic Male Sterility and Xenia Increases Grain Yield of Maize Hybrids

ABSTRACT Male sterility is documented in many plant species. When a plant is male‐sterile, an open pollination by a genetically diverse pollinator is possible. This study investigates the combined effects of nonrestored cytoplasmic male sterility (CMS) and xenia (cross‐pollination) on the grain yield of seven European flint × dent single‐cross maize ( Zea mays L.) hybrids. Open pollinated field experiments were conducted in six environments in Switzerland in 1998 and 1999; the design was a split‐plot. The effect of CMS on grain yield was statistically significant ( P < 0.05). Three CMS hybrids in nonrestored T‐cytoplasm, pollinated by their male‐fertile isogenic counterparts, had a higher grain yield (+7.4%) than their male‐fertile isogenic counterparts. The higher grain yield was due to a greater number of kernels per square meter (KN). The average increase in grain yield due to xenia was 2.6%. The effects of pollinator hybrids on grain yield, kernel weight (KW), and KN were statistically significant ( P < 0.001), whereas the pollinator × environment and pollinator × CMS hybrid interactions were not significant. Thus, the general pollinator ability (GPA) of the pollinator hybrids differed significantly and consistently. Averaged across the six environments, the three CMS hybrids, pollinated by five nonisogenic hybrids, outyielded their male‐fertile, isogenically pollinated counterparts by 2.1, 9.3, and 15.8%, respectively. The best combination of a CMS hybrid and a nonisogenic pollinator hybrid increased grain yield by 21.4% compared with the male‐fertile isogenic counterpart of the CMS hybrid. Therefore, the plus‐hybrid system (CMS hybrids grown in mixtures with male‐fertile nonisogenic pollinator hybrids) combines the grain yield advantages brought about by CMS and xenia.