Dept. of Agronomy, University of Georgia, Athens, Ga., 30602, USA
1Present address: Dept. of Plant Genetics, Texas Tech. University, Lubbock.
*Part of the dissertation submitted by the senior author to the Department of Agronomy, University of Georgia.
Seeds of the long-time maize (Zea mays L.) inbred, CI 21 (Athens), were prepared with the genotype of CI 21 (A) and the cytoplasms of inbreds GA 199, GT 112, and CI 21 (A) separately in backcross programmes. Similarly, two cytoplasms of inbreds GA 199 and CI 21 were prepared with the genome of the GA 199 inbred. Thus, each lot of seed had either the CI 21 (A) or the GA 199 genotype with a different cytoplasm.
The cytoplasms were classified for reaction to Helminthosporium turcicum Pass, based on a 1 to 5 visual rating scale. Results with CI 21 (A) genome indicated a highly significant difference between GA 199 and GT 112 cytoplasms. The GA 199 cytoplasm offered more tolerance than the GT 112 cytoplasm.
A highly significant difference was also obtained between cytoplasms CI 21 and GA 199 with the GA 199 nucleus. The CI 21 cytoplasm was much more resistant than the GA 199 cytoplasm.
These differences demonstrate cytoplasmic influences. Therefore, it might be beneficial to screen inbred cytoplasms for resistance to northern leaf blight of maize so that cytoplasmic diversification can be practised in a breeding programme. Today, nuclear gene pools for disease resistance are in existence. Perhaps similar cytoplasmic pools should be established.
