Study On Early Screening Method In Breeding Second Cycle Inbred Lines Of Sweet Corn

The selection of parent inbred line is one of the keys for the using of hybrid heterosis in sweet corn in the course of hybrid breeding. The general method of breeding is to select by the means of agronomic character in early generations and by combining ability in late generations. But selecting of agronomic character and combining ability can not fit well, sometimes even contrary, thus lack of predicting efficient ways for heterosis. In this paper we design the early screening method for second cycle inbred lines of sweet corn to enhance the combining ability and agronomic trait at the same time, in order to promote the selection efficiency of early generation group. In this experiment, four parent inbred lines from two advantageous sweet corn species, Sutian No.8 (35x33)and JingtianNo.3(403×452),are used to make four new hybrid combinations, at the same time these four lines are used to test, for the sake of getting four ordinary sweet test cross varieties, 403/35//33,403/33//35,452/35//33,452/33//35, and four super sweet cross varieties, 403/35//452 403/33//452 452/35//403,452/33//403, through the back cross by 35, 33and 403 respectively, we get five backcross descendants, which then be tested with relevant testing inbred lines, so as to getting the five screening backcross varieties, (452/35//452)/33, (403/33//33)35, (403/35//403)/452, (403/33//403)/452; we make a comparison analysis of agronomic character for test and back cross, and probe the using of early screening method with which to select combination, with the regular breeding method, we get F₄ selective lines, and pursue the match test with the test inbred lines, the results were as follows:1) Early screening method for selective breeding in the second cycle inbred lines of sweet corn is better for realizing the entity selecting of combining ability and agronomic character, the degree of combinations coincidence is 75%, the degree of single ear selecting lines can achieve 52.3-60%, so as to promoting the efficiency of group early generation selecting and selective breeding probability of second cycle inbred lines.2) According to the early screening for test cross which have been selected in the course of selecting breed, we get the better common sweet test cross varieties No 3and No4, and make a match test for 11 selecting lines of second cycle inbred lines with relevant test inbred lines 35, 33, the result we came out is basically confirming to the early generation screen result, but the slight difference in ears' height. We get 3-5and 4-6 lines with the obviously higher productivity and better second cycle...