Abstract

A doubled-haploid barley population derived from a cross between the Tunisian cultivar ‘Roho’ and the local line ‘90’ was used to assess the genotype x environment interaction, heritability estimates and correlations between disease parameters of net blotch resistance at adult growth stage in three environments. Net blotch reaction was evaluated using the mass disease index, the area under the disease progress curve and the apparent infection rate. The DH lines showed different levels of quantitative resistance to Pyrenophora teres under low, moderate and high epidemic conditions. Large variation of the mass disease index, the area under the disease progress curve and the apparent infection rate was obtained under high-pressure conditions that facilitate identifying tolerant lines. Significant genotypic differences were noted, however preponderant genotype x environment interactions were the major sources of variation. Broad sense heritability values were large for all parameters using data from single environment and low for the mass disease index, the area under disease progress curve and the apparent infection rate using estimates from different growing conditions. In a single environment, resistance related parameters were found to be genetically associated. Excepting mass disease index, lack of associations between area under the disease progress curve and apparent infection rate measured on the three field conditions were obtained. The results obtained suggest that loci for mass disease index may be pleiotropic or linked and loci for areas under the disease progress curve and apparent infection rate may be independent. Multi-location screening for quantitative resistance to P. teres should be considered in a breeding program.

Key words: Heritability, genotype x environment interactions, genetic correlation, disease parameter, Hordeum vulgare, Pyrenophora teres.