English abstract
Genotypic variation in nitrate concentrations of different lettuce genotypes belonging to four types (Butterhead, Cos/Romaine, Crisphead, and Stem lettuce) and its relationship to nitrate reductase genes (Nia) for low nitrate concentrations of leaves was investigated. The results showed that the Romaine genotype 'Lobjoit's Green' exhibited the lowest leaf nitrate concentration (4877.7 mg/kg dry weight). The highest nitrate levels were recorded in the Butterhead genotypes 'Augusta and Kennedy'. Nitrate concentrations in the roots were significantly higher in the Romaine genotype ' Little Gem' and the Butterhead genotypes 'Augusta and Merveille Des Quatre Saisons' than the other lettuce genotypes. Total N concentrations were higher in the Butterhead and Crisphead genotypes than in the Romaine and Stem lettuce genotypes. A significant positive association (r = 0.80, p > 0.01) was observed between leaf NO- concentrations and total N concentrations. Moreover, gene-specific primer pairs for amplification of nitrate reductase revealed the presence of the gene (Nia) in Butterhead type (Ambassador, Bath, Merveille des QuatreSaisons), Cos/ Romaine type (Romain de Benicardo genotype), Crisphead type (Colona genotype), and Stem lettuce type (Chinese stem genotype). These genotypes showed lower leaf nitrate concentrations than the other Butterhead genotypes "Augusta and Kennedy" and Crisphead genotype "Salddin" which did not amplify with the Nia gene. Based on these results, it is concluded that the gene-specific primer pairs for amplification of nitrate reductase gene (Nia) might be useful in screening lettuce breeding material for low leaf nitrate content.
