Inheritance of host plant effect on latent period of wheat leaf rust in single-seed descent F8 lines

Latent period (LP) and infection type (IT) were determined in single-seed descent F8 wheat lines from the crosses Westphal 12A (PR = partially resistant) × BH1146 (PR), Akabozu (PR) × BH1146 (PR), and BH1146 (PR) × Little Club (susceptible), inoculated with the Flamingo isolate of the wheat leaf rust pathogen. Each parental line showed a significantly longer LP than the highly susceptible standard Morocco indicating that each parent carried at least one LP-prolonging gene. Significant transgression was found for shorter LP in each cross, indicating that BH1146 differed from Westphal 12A, Akabozu, and Little Club at least partly in genes affecting LP. Significant transgression for longer LP was observed only in the cross Akabozu × BH1146 in one F8 line. In each cross, significantly more lines were found that showed a shorter LP than the most susceptible parent, than lines that showed a longer LP than the most resistant parent, indicating non-additive gene effects on LP. BH1146 was estimated to carry at least five genes which are involved in prolonging the LP. LP and IT were negatively correlated. Correlation coefficients were low and lines were present showing similar ITs but different LPs which suggested that collapse of host plant cells could not be the only reason for growth retardation of colonies of the wheat leaf rust pathogen. This revised version was published online in July 2006 with corrections to the Cover Date.