Early foliar decline is a recurring problem of Pima cotton (Gossypium barbadense L.) in the San Joaquin Valley of California, where it has been implicated in yield and fiber-quality losses. The primary objectives of our investigation were to determine the heritability of tolerance and susceptibility to early foliar decline and to identify earlier maturing, early foliar decline-tolerant germplasm. Three populations, created by crossing putatively tolerant and susceptible parents, were evaluated for early foliar decline, agronomic traits, and fiber quality in the F2, F3, and F4 generations over three successive years at Tulare and Buttonwillow, CA. Early foliar decline heritability estimates between F2 individual plants and F3 progeny rows were low (h2 = 0.14 to 0.19) and appeared to preclude efficient selection for tolerance in the F2 generation. Higher F3:F4 heritability estimates (h2 = 0.37 to 0.46) suggested that selection may be feasible in unreplicated early generation (F3) progeny rows. However, the highest heritability estimates occurred among replicated F4 progeny rows (h2 = 0.84 to 0.89), indicating that the greatest selection efficiency could be expected in advanced generation tests planted at multiple locations. Early foliar decline was negatively correlated with final plant heights of F3 and F4 progeny at both Tulare and Buttonwillow, and with nodes above bloom (r = -0.47 to -0.61) of F4 progeny at Tulare. The above negative correlations suggest that early foliar decline severity is positively related to early plant maturity and increased determinacy, and may indicate difficulty in simultaneous selection for tolerance to early foliar decline and early plant maturity.
