Effects of shade regimes and planting geometry on growth, yield and quality of natural sweetener plant stevia (Stevia rebaudiana Bertoni) in north western Himalaya

During 2008 and 2009, field experiments were conducted at the research farm of CSIRInstitute of Himalayan Bioresource Technology, Palampur, India to assess the effect of shade levels (no shade, 25% shade, 50% shade, 75% shade) and plant geometry levels {30 × 15 cm (north-south, N-S), 45 × 10 cm (N-S), 30 × 15 cm (east-west, E-W) and 45 × 10 cm (E-W)}. Plants development was fastest in controls and slowest in stevia plants growing at minimum light (75% shade). These plants showed delayed bud formation and flowering. Significantly higher dry leaf yield was recorded when the crop was grown under 25% shading as compared to 50 and 75 % shade. Total steviol glycosides content decreased with increasing shade levels. All shade levels resulted in the same leaf to stem ratio, which was significantly higher than obtained under ambient light. Plant geometry significantly affected number of leaves and leaf dry weight plant–1. During both the years, dry leaf weight was highest in wider row spacing (45 × 10 cm) as Accepted Manuscript Downloaded by [N B of Plant Genetic Resources ] at 04:21 08 June 2012 compared to narrow row spacing (30 × 15 cm). Stevia spaced at 30 × 15 cm in E-W direction recorded significantly highest total steviol glycosides at 2 months after transplanting (MAT)