Influence of Different Photoperiod and Temperature Regimes on Growth and Bulb Quality of Garlic (Allium sativum L.) Cultivars

Growth and bulb development in garlic is affected considerably by variations in photoperiod and temperature thereby influencing its morphology, physiology, and nutritive quality. Varied combinations of photoperiods and temperatures may influence the bulb development and quality, and can determine the suitability of a cultivar for a particular region. Experiments were conducted to study the impact of different photoperiod and temperature combinations on the growth, morpho-physiology, and nutritive quality of garlic bulb. Three garlic cultivars viz; G103, G024, and G2011-5 were exposed to different combinations of photoperiod (8 h/16 h, 10 h/14 h, 12 h/12 h, 14 h/10 h, 16 h/8 h (light/dark)) and temperature (20 degrees C/15 degrees C, 25 degrees C/18 degrees C, and 30 degrees C/20 degrees C). Results revealed that longer photoperiod (14 h or 16 h) and higher temperature (25 degrees C or 30 degrees C) treatments significantly improved the garlic bulbing imparting maximum bulb diameter, height, bulbing index, and the shortest growth period. Whereas, 12-h photoperiod had maximum bulb weight. In addition, total soluble solid (TSS), content of soluble protein, soluble sugar, total sugar, glucose, sucrose, fructose, starch, total phenols, and total flavonoids increased significantly because of 14-h photoperiod and 30 degrees C temperature condition, however exhibited decline with 8 h photoperiod and lowest temperature (20 degrees C). These alterations were related to bulb characteristics and bulbing index. Maximum plant standing height and pseudostem diameter of the garlic plant were observed at 20 degrees C. Additionally, plants under the combination of 14 h-30 degrees C had maximum fresh weight, bulb diameter, shortest growth period, maximum physiological and nutritive quality traits of the bulb, while as 12 h-30 degrees C combinations resulted in maximum bulb weight and 16 h-30 degrees C had maximum bulb height. Among cultivars cv. G103 showed best response to tested photoperiod and temperature combinations in terms of morpho-physiological and biochemical attributes studied, except for bulbing index which was maximum in cv. G024. Present study concludes the influence of photoperiod and temperature combinations on garlic growth and bulbing characteristics through the modulations induced in soluble protein, sugars, and phenolic compounds.