Success in tissue culture of all plant species depends on the removal of exogenous and endogenous contaminating microorganisms. Rhododendron wardii is a parent of many of the best yellow hybrids and it has been identified as a Least Concern spp. An efficient protocol was developed for sterilization of seeds of R. wardii for in vitro cultivation for mass propagation and conservation. Three sterilizing agents, namely, HgCl2 (w/v), NaOCl (v/v) + Tween20 and H2O2 (v/v) at varying their concentration and time of exposure were tested. Treatment with 25% H2O2 for 20 min was the most effective with no contaminated cultures, where the germination percentage was 92.6% (ex vitro germination percentage was 58.61%) and produced 100% healthy plants. Even though the exposure to 15% NaOCl + Tween 20 for 20 min produced 100% contamination-free cultures, the percentage seed germination was 51%. Seeds could be sterilized with 5% NaOCl, for 20 min and 15% for 10 min for maximum germination (64%), but contamination rate was 1:2. Sterilization with HgCl2 did not produce any satisfactory result (maximum germination percentage = 18%).

Rock melon is a high value greenhouse crop. Reduction of economical crop yield in high temperature stress due to global warming is an emerging issue with Rock melon. Therefore, this study was conducted for evaluate the growth, physiology and yield of different Rock melon cultivars grown under high temperature stress. Four cultivars of rock melon (Lady-gold, Lady-green, Himalai-99 and Glamour) were evaluated for their physiological behaviors under two temperature (42±3°C and 47 ±3°C) regimes. In four cultivars of rock melon, leaf area, specific leaf area, relative growth rate, chlorophyll content, photosynthesis rate, stomatal conductance, intercellular carbon dioxide concentration, transpiration rate, malondialdehyde content and fruit yield of Rock melon were significantly differ in each temperature regime. Temperature significantly affects the fruit position in main branch. When temperature increases, Rock melon fruits shifts in to upper branches. While Lady-green and Glamour shown similar attributes in extreme temperature, most susceptible cultivar was the Lady-gold and most tolerant cultivar was the Himalai-99.This study identified the issues of extreme temperature related to the economical yield of rock melon cultivars which can be use in future crop modification and breeding.

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