TEOSINTE CYTOPLASMIC GENOMES .2. PERFORMANCE OF MAIZE HYBRIDS WITH TEOSINTE CYTOPLASMS

Alien cytoplasm substitution effects on quantitative agronomic charact ers in maize breeding germplasm have been studied many times, but few cytoplasmic effects have been found. This research was conducted to ev aluate the importance of nuclear sources of variation often confounded with cytoplasmic effects, and to study effects of substituting teosin te cytoplasms into Zea mays ssp. mays hybrids. Cytolines were develope d by transferring 11 cytoplasms to maize inbreds A619 and W23 by at le ast six generations of backcrossing, Reciprocal testcrosses were made between cytolines and three testers as well as between A619 and W23 an d the same testers. Nuclear effects on reciprocal cross differences an d effects of incomplete recovery of cytoline nuclear genotypes were la rge enough to cause bias in estimates of cytoplasmic effects, had appr opriate comparisons not been available to account for these sources of variation, The 11 teosinte cytoplasms reduced grain yield by an avera ge of 0.20 Mg ha(-1) or 2.2%. Cytoplasmic effects averaged across all cytoplasms and hybrids were not significantly different from zero for any other trait. One of 11 cytoplasms studied had stable effects on hy brid performance. Four additional cytoplasms had appreciable effects t hat varied widely with the nuclear genotype. Direct substitution of an y of these cytoplasms into maize hybrids would not likely be of great benefit because desirable effects were generally small and difficult t o predict in different nuclear-cytoplasmic combinations.