Selection for Resistance to Aphanomyces euteiches in Red Clover

Abstract

Red clover (Trifolium pratense L.) is known to be a moderate host for Aphanomyces euteiches Drechs. Recently, an isolate of A. euteiches (Ae‐572) was observed to be highly virulent on red clover. This research was conducted to determine inheritance of, and select for, resistance to A. euteiches in red clover using an inoculated seedling assay. Resistant and susceptible red clover plants were intercrossed to study the inheritance of resistance. Frequency distributions of resistant and susceptible F1 plants indicated that resistance to A. euteiches is inherited as a quantitative trait. Three cycles of selection for resistance to A. euteiches in red clover resulted in significant improvement in resistance from the original selected population (Cycle 0 = 3.64 mean disease severity index (DSI); Cycle 3 = 2.43 mean DSI). Narrow‐sense heritability estimates were high enough ((h2n = 51% for Cycle 3) to assure that a recurrent selection program utilizing family selection could be used to improve red clover populations for resistance to A. euteiches.

Inheritance of Dollar Spot Resistance in Creeping Bentgrass

“…Krupinsky and Berdahl (1982) and Yin et al (1996) used similar methods to determine resistance vs. susceptibility. Chi square tests were used to evaluate goodness‐of‐fit of the observed segregation ratios to expected disomic segregation patterns (Table 2) Elgin and Ostazeski (1985) and Tofte et al (1991) have also utilized this method. Minimum number of effective factors (loci) was determined using the Castle‐Wright formula (Poehlman and Sleper, 1995, p. 71–75) modified for environmental variation.…”