Genetic analysis of net blotch resistance in a two-row × six-row cross of barley, using doubled-haploid lines

The effect of spike type on net blotch resistance is not fully understood in barley (Hordeum vulgare L.). A doubled-haploid barley population derived from a cross between a susceptible two-row (Roho) and a resistant six-row (line 90) genotypes was used to study the genetics of net blotch resistance and to determine the effect of spike type on net blotch resistance at the adult plant growth stage across three environments. Net blotch rating was evaluated using a mass disease index, area under the disease progress curve and the apparent infection rate. Partial resistance to Pyrenophora teres was observed in many DH lines and in the parental line 90 in the three environments. This result indicated that selecting for partial resistance is feasible under severe net blotch conditions where differential responses among DH lines were noted as in Mograne in 2003–2004. The normality test and/or the means comparison method suggested that additive × additive epistasis effects influenced the expression of all disease parameters in the three environments. Both the coefficient of skewness and the number of transgressive lines indicate the presence of a complementary gene interaction for most disease parameters. Results showed that two-row lines were particularly associated with net blotch resistance in Mograne 2002–2003 and in Tunis greenhouse 2004. A strategy for improving the level of quantitative resistance to P. teres in later generations is recommended. Key words: Hordeum vulgare, doubled-haploid population, quantitative resistance, Pyrenophora teres, net blotch, genetic analysis