WEST LAFAYETTE, INDIANA

Indiana Crop Improvement Association and Purdue University

AMES, IOWA

Iowa State University

 Utility of Tpi3 and Tpi4 variants in quality control of hybrid popcorn seed production --P. K. Bretting and J. F. Wendel Popcorn grown commercially in the U. S. is relatively depauperate in isozymatic variation as compared to dent corn, and is also isozymatically somewhat distinct from the latter (Stuber and Goodman, USDA/ARS Agric. Res. Results ARR-S-16, 1983). Isozymatic monitoring of quality in hybrid popcorn seed production therefore might require slight modifications of the methodology (Smith and Weissinger, MNL 58:103-105, 1984; Stuber et al., NCARS Techn. Bull. 286, 1988) commonly employed with dent corn.

Electrophoretic analysis of maize TPI (triosephosphate isomerase) isozymes (Wendel et al., J. Hered. 80:218-228, 1989) suggested that "their usefulness as genetic markers is somewhat hindered by relatively low levels of polymorphism, particularly in domestic germplasm" (op. cit., p. 227). Nevertheless, a preliminary survey of popcorn inbred lines and hybrids revealed allelic variation at Tpi3 and Tpi4 that is useful for quality control.

For example, P608--a widely grown Purdue public hybrid--is the single cross between SG1533 and HP72-11, two lines fixed for different alleles (2 and 4) at Tpi3 (Table 1). Plants in a seed lot of P608 with genotypes other than Tpi3 -2/4 would thus be offtypes. Genotypes at other isozymatic loci would help classify the offtypes as selfs, outcrosses, or contaminants. Allelic variation at Tpi4 may be similarly employed. Preliminary studies suggest that allelic variants at Tpi3 and Tpi4 also may be valuable for quality control of hybrid sweet corn production.

Table 1. Tpi genotypesa of selected U. S. popcorn inbred lines.
 
Inbred line  Tpi1  Tpi2  Tpi3 Tpi4 Tpi5
HP62-02 4/4 4/4 4/4 4/4 8/8
HP72-11 4/4 4/4 4/4 4/4 8/8
HP301 4/4 4/4 2/2 4/4 8/8
IDS53 4/4 4/4 2/2 4/4 8/8
SG1533 4/4 4/4 2/2 4/4 8/8
4722Ht 4/4 4/4 4/4 4/4 8/8
Proprietary 1 4/4 4/4 4/4 1/1 8/8

aAllelic and locus designations follow Wendel et al. and Stuber et al. (op. cit.)

We thank R. B. Ashman, A. Galbreth, and J. Sandage for their comments, and C. Shaner for technical assistance.


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