Effect of far-red radiation on flowering of saccharum spp. hybrids

Abstract

Many tropical sugarcane clones (Saccharum spp. hybrids) are unavailable for hybridization because of poor flowering. Methods are required to improve the flowering of such clones. This study was conducted to determine whether far-red radiation (> 700 nm) at end-of-day would improve flowering. Three treatments in a photoperiod facility (PPF) were compared to an external control (EC) under natural photoperiod. A basic treatment known as modified Florida (MF) was used in all PPF treatments and served as the internal control. This was altered to provide a far-red (FR) treatment, by addition of either 5 or 10 min of far-red radiation at end-of-day, and a day interrupt (DI) treatment, by imposition of 2 hr of darkness in mid afternoon. Percent flowering as harvested panicles was 21.0, 24.2, 24.6, and 9.5 for FR, DI, MF, and EC, respectively. Total flowering was 23.4, 28.9, 27.0, and 10.7, respectively. The PPF treatments did not differ significantly for either measure. All were highly significantly greater than EC. The far-red treatments did not differ for harvested panicles. Treatments differed significantly for time of flowering. The flowering sequence was EC, MF, FR, and then DI. There were significant differences among clones in all treatments for emergence day, initiation day, elapsed days, and pollen test. Correlations among these measures were varied, with some being significant. Far red at end-of-day neither stimulated nor inhibited flowering in the PPF treatments. The FR and DI treatments delayed emergence of flowering.