Heat Unit Accumulation and Phenological Development of Sweet Cherry (Prunus avium L.) Cultivars in the Sub-Himalayan Conditions of India
摘要
The present study aimed to assess energy summation indices and heat use efficiency in different sweet cherry (Prunus avium L.) cultivars under the temperate climatic conditions of Jammu and Kashmir during 2023–2024. The specific objective was to quantify variations in energy summation indices, namely growing degree days (GDD), photothermal units (PTU), and heliothermal units (HTU), at critical phenological stages of sweet cherry cultivars. Analysis of variance revealed significant differences among cultivars with respect to the duration of various phenophases. The cultivar ‘Karina’ accumulated the maximum thermal units to attain most phenophases, recording 111.33 days to maturity with GDD of 1070.95 °C days, PTU of 14,422.82 °C days, and HTU of 6970.42 °C days, except during inflorescence emergence and flowering, for which the cultivar ‘Regina’ registered the highest thermal accumulation. In contrast, the cultivar ‘Burlat’ required the minimum time and thermal units to reach phenological stages, with 86.00 days, GDD of 708.25 °C days, PTU of 9206.02 °C days, and HTU of 4129.45 °C days. Heat use efficiency, photothermal use efficiency, and heliothermal use efficiency were highest in ‘Burlat’ and lowest in ‘Regina’. Yield per tree and estimated yield per hectare were maximum in ‘Lapins’ (7.20 kg tree⁻1 and 15,998.4 kg ha⁻1, respectively) and minimum in ‘Karina’ (5.50 kg tree⁻1 and 12,221.0 kg ha⁻1, respectively). Overall, ‘Karina’ was classified as a late-maturing cultivar due to its higher accumulation of GDD, PTU, and HTU for most phenophases; on the other hand, ‘Burlat’ was classified as an early-maturing cultivar due to its accumulation of the lowest values for these indices. ‘Burlat’ appears to be a highly promising cultivar that can be used for breeding purposes for developing early-maturing varieties.