- •Relationships between crop reflectance in the visible and the near infrared wavelengths are closely correlated with the amount of photosynthetically active tissue in the crop. Reflectance measurements were used to quantify genotypic differences in light interception, dry matter (DM) conversion efficiency and senescence pattern within the genus Miscanthus. The aim was to verify this method as a selection tool in plant breeding programmes.
- •Spectral reflectance of nine genotypes was measured weekly throughout their second and third growing seasons in a field experiment conducted in Denmark. Leaf greenness was assessed by visual scoring.
- •Significant differences between genotypes in the calculated fraction of PAR intercepted in green tissue (f ipar ) occurred mainly early and late in the growing season. The f ipar values correlated well with visual estimates of leaf greenness. Within genotypes accumulated intercepted PAR ranged from 632 to 737 MJ m −2 in the third year, while the DM : radiation quotient, ɛ, ranged from 1.06 to 2.53 g MJ −1 .
- •Yield variation between genotypes was mainly caused by differences in ɛ. Measuring spectral reflectance was less time consuming than visual leaf scoring. The significant physiological variation within the genus Miscanthus gives good prospects for future breeding.