DNA and biochemical analysis of a potential opaque2 maize population

Abstract

Maize has low nutritional value because it is poor in essential amino acids lysine and tryptophan, but different mutations have been identified that increase their content. Two high lysine/tryptophan populations from Maize Research Institute genebank (IP1 and IP2) were identified in a previous research. In both populations, analysis with umc1066 opaque2 specific marker detected a recessive (o2), a dominant (O2) and an unknown allele (UA). However, IP2 lacked homozygous recessive o2o2 genotypes. The aim of the present research was to determine by DNA and biochemical analysis if UA allele was a recessive allele and/or if high tryptophan content was due to the o2 or some other mutation. Tree more opaque accessions with different mutations - IP3o5, IP4o14 and IP5floury (no data on type of mutation) were used in biochemical analysis for comparison with IP1 and IP2. Kernels were divided into two samples - with hard and with soft kernels. The UA allele sequencing revealed that it was a dominant allele with four GCCAGA repeats. SSR analysis showed presence of o2 in IP1 in both hard and soft kernels. Decrease in 22 kDa, 19 kDa and 27 kDa zeins in soft kernels was observed only in IP1 and IP2. Tryptophan content was high in soft kernels of IP1 (0.081) and IP2 (0.085), and in both hard and soft kernels of IP3o5 (0.083 and 0.085, respectively). It can be concluded that IP1 is an o2 mutant and that IP2 carries a high tryptophan mutation other than o2, o5, o14 or floury.