The inheritance of pericarp tenderness in sweet corn

In a study of the inheritance of pericarp tenderness in sweet corn, data were obtained from a cross between a very tender, open-pollinated variety and a tough pericarp Crosby inbred line. The two parents used in the cross showed a consistent difference of approximately 100 units as measured with a puncture tester, while the F1 cross between the tender and tough parents was approximately intermediate in puncture test value and also in its coefficient of variability. In studies of the F2 Carried on in 1935 and 1936 with populations of 79 and 136, respectively, segregation occurred with a coefficient of variability greater than that of the F1 and the H parent. In 1937, from a population of 430 F2 plants in comparison with 390 of the tender pericarp and 299 of the tough pericarp parent, the F2 slightly exceeded the range of the tender pericarp parent in tenderness and of the tough pericarp parent in toughness. In a study of F3 progeny rows and in first year selfed lines from backcrosses to-the tender parent, lines were obtained with as low a coefficient of variations as the inbred, tough pericarp parent. The recovery of relatively pure lines having an average puncture test value in the classes intermediate between the parents suggests that several factor pairs condition pericarp tenderness. There was only, one line in F3 out of 34 with as low a mean as that of the H parent. Sixteen of 42 first year selfed lines from the first backcross gave as low means as obtained from the rows of the tender pericarp parent. In backcrosses to the tough pericarp parent, selection for tenderness during two segregating generations has maintained the same range in distribution of puncture test values as that obtained when the F1 was backcrossed to the tough parent. These results indicate that the genes for pericarp tenderness from the tender parent have been successfully carried in a heterozygous condition. In backcrosses to the tender pericarp parent, selection for tenderness has apparently been effective in an almost complete recovery of the genotype of the tender parent in the second backcrossed generation. In a study made to determine the daily changes in puncture test values from the period 18 to 22 days after pollination, a daily increase of approximately 30 units was obtained in one cross and 20 units in a later maturing hybrid. Puncture test values from ears pollinated when the silks had been emerged for 1, 3 and 5 days showed an increase of over 20 units in puncture test for each interval of two days after the silks had emerged. These results indicate that the pericarp in sweet corn continues to develop without fertilization for a period of at least five days.