Transgressive segregation and maternal genetic effects of non–target site fluazifop-P-butyl tolerance in Zoysia spp.

Zoysia germplasm exhibit different levels of sensitivity to fluazifop-P-butyl, but the genetic factors responsible for such differences are unknown. Segregation patterns of the fluazifop-P-butyl tolerance trait were studied under greenhouse conditions. In total, 244 F-1 lines were generated from multiple crosses between the tolerant line 5337-2 (non-target site tolerance) and three more-sensitive lines (123, 252, and 5330-23). Progeny segregation showed that fluazifop-P-butyl tolerance within zoysiagrass (Zoysia spp.) is expressed as a quantitative trait with a wide range of intermediate phenotypes between parental phenotypes. Transgressive segregation was extensive and largely favored susceptibility in most families, but was especially evident for 5337-2 x 123 and 5337-2 x 5330-23. The segregation patterns for biomass reduction and percent injury were different within reciprocal crosses and among three different family crosses. Reciprocal effects were observed in growth reduction for 5337-2 x 5330-23, in percent injury at 3 wk after the treatment (WAT), and for 5337-2 x 252 at 6 WAT. This indicated that fluazifop-P-butyl tolerance was not completely controlled by nuclear genetic factors in 5337-2 and maternal/cytoplasmic inheritance was also partially responsible. These results suggested that fluazifop-P-butyl tolerance may be attributed to multiple genetic mechanisms, which could present a challenge for future breeding efforts because of the difficulty of fixing multiple traits within a breeding population.