TABLE 5.

Phenotypic correlation between grain protein content and eight spectral reflectance indices derived at the heading stage of a spring wheat population planted in three environments (2014–2016) in the United States Pacific Northwest.

GPC	NDVIa	NWIb	WIc	SRd	GNDVIe	PRIf	NCPIg	ARIh
2014	0.35***	0.35***	0.35***	0.38***	0.34***	0.19***	−0.38***	−0.12*
2015	0.19***	0.21***	0.21***	0.22***	0.28***	0.11*	−0.19***	0.27***
2016	−0.20***	−0.16***	−0.16***	−0.17***	−0.20***	0.02	0.08	0.12*

^aNDVI, normalized difference vegetation index. ^bNWI, normalized water index. ^cWI, water index. ^dSR, simple ratio. ^eGNDVI, green normalized difference vegetation index. ^fPRI, photochemical reflectance index. ^gNCPI, normalized chlorophyll pigment ratio index. ^hARI, anthocyanin reflectance index. ***significant at P < 0.0001; *significant at P < 0.05.