A Comparison of Topcross versus Line \u3ci\u3ePer Se\u3c/i\u3e Performance for Evaluating S\u3csub\u3e1\u3c/sub\u3e Lines of Corn

The present study was designed to determine the relative value of different types of line evaluation; S1 lines were grown as lines per se, and in test cross combination with a related and an unrelated synthetic variety, each providing a broad genetic base. A group of 196 So plants from Krug synthetics, KII(A) and KIII were selfed and the S1 lines topcrossed with two synthetic varieties, synthetic BIII syn-3. Both tester parents provided a relatively broad gene base and therefore provide evaluation for general combining ability which is dependent mainly on additive genetic effects. The S1 lines were grown as lines per se in replicated trails also. The line per se trails and topcrosses with the unrelated tester were grown in 1958 and 1959. The topcross trails with the related tester were grown in 1961 and 1962. Data were obtained on plant height, ear height, lodging, dropped ears, moisture in the grain at harvest and grain yield. Advisor: John H. Lonnquist