End-of-day far-red lighting combined with blue-rich light environment to mitigate intumescence injury of two interspecific tomato rootstocks

Effects of end-of-day far-red (EOD-FR, 700-800 nm) light and high blue photon flux ratio during the photoperiod on intumescence injury were examined for 'Beaufort' and `Maxifort' tomato rootstock seedlings (Solanum lycopersicum x Solanum habrochaites) grown with 13 mu mol m(-2) d(-1) daily light integral (199 mu mol m(-2) s(-1) photosynthetic photon flux, 18 h photoperiod). The EOD-FR light treatment (1.1 mmol m(-2) d(-1) provided by 6.0 mu mol m(-2) s(-1) FR photon flux for 3 min at EOD) significantly reduced intumescence injury. For example, by the EOD-FR light treatment, the incidences of leaf abscission were reduced from 88 to 8% for 'Beaufort' and from 79 to 25% for 'Maxiforr. However, EOD-FR light caused undesirable stem extension (41% greater than that without EOD-FR light). By combining relatively high B (blue, 400500 nm) to R (red, 600-700 nm) photon flux ratio (50%B-50%R) during the photoperiod with EOD-FR light, intumescence injury was further decreased without causing undesirable stem extension. For example, the incidences of leaf abscission were reduced from 88 to 0% for 'Beaufort' and from 79 to 0% for `Maxifort, compared to those under 10%B-90%R without EOD-FR light. Also, the percentages of leaves that exhibited intumescences were reduced from 68 to 30% for 'Beaufort' and from 55 to 19% for 'Maxifore. Our study demonstrated that blue-rich light quality combined with a small dose of EOD-FR lighting could be applied to mitigate the problematic intumescence injury of tomato seedlings grown under LEDs.