Inheritance characteristics of brown patch resistance in tall fescue
Brown patch disease, caused by Rhizoctonia solani Kühn, is one of the most devastating fungal pathogens that occur on tall fescue [Lolium arundinaceum (Schreb.) Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort]. The development of genetic resistance to brown patch would provide the most effective long term control to this disease; however, the genetic mechanism of brown patch resistance in tall fescue is not known. For this study, a diallel cross involving six parents was conducted to investigate the genetic inheritance characteristics of brown patch resistance in tall fescue. Parents and their progeny were evaluated for brown patch resistance in a field experiment conducted over two years in which the field experiment was inoculated with a single isolate of R. solani. Both general combining ability (GCA) and specific combining ability (SCA) effects were significant; however, the GCA accounted for a greater proportion of the sum of squares. Moderate narrow-sense heritability estimates [0.62 (2007) and 0.57 (2008)] were calculated from mid-parent-progeny regression analysis. Estimates of the minimum number of effective genes ranged from 1.0 to 3.2 depending on the parents used in the crosses. The presence of a major gene for resistance was not detected in the study. These results support the idea that brown patch resistance is quantitatively inherited.