Evaluations and correlated responses for resistance to chloramben herbicide in cucumber

The US cucumber germplasm collection (753 accessions) and US adapted processing cucumber inbreds and hybrids were surveyed for response to 6.7 ae/ha of chloramben. Nine plant introductions were classified as tolerant of chloramben, based on percentage and rate of field emergence and seedling vigour. All adapted strains evaluated were susceptible to chloramben injury. The chloramben-tolerant accessions (C₀) were subjected to 2 cycles of recurrent half-sib family selection that resulted in 11 C₂ families. These families, a susceptible adapted line (WI2870), and the resistant PI436609 were evaluated in the field (6.7 kg ae/ha) and laboratory (0.0, 0.01 and 0.0001 smallcap~M) for response to chloramben challenge. Significant differences between families were observed for percentage emergence and phytotoxicity ratings. Correlations between emergence and phytotoxicity ratings at 2 dates were low (r$