A rapid and economical method for hybrid purity testing of tomato (Lycopersicon esculentum L.) F1 hybrids using ultrathin‐layer isoelectric focusing of alcohol dehydrogenase variants from seeds

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Abstract
In the cultivated tomato (Lycopersicon esculentum L.), two electrophoretic variants of the enzyme alcohol dehydrogenase (ADH) encoded by the alleles Adh-1+ and Adh-11 are found. A rapid and economic method for testing the hybrid purity of tomato F 1 seeds, based on the expected presence of Adh-1 alleles, was developed. The method is based on the analysis of the ADH variants by ultrathin-layer isoelectric focusing, pH range 3–10, of crude extracts from imbibed seeds followed by enzyme activity staining. The isoelectric points (pIS) of the ADH variants were estimated to be 5.5 and 5.7 for Adh-1+ and Adh-11; respectively. Using the procedure described and a newly developed sample applicator strip, it is Possible for one person to routinely analyze 1152 seeds per day using only a single electrophoresis unit. An investigation of a large number of inbred lines, both experimental and commercial hybrids, together with open-pollinated varieties, showed the potential of the method. Among F1 hybrids, a higher frequency of the Adh-11 allele was found than among open pollinated varieties, suggesting that F1 hybrid breeding has resulted in a higher frequency of Adh-11 alleles by selection of linked genes.