Effect of ploidy level on expression of lycopene biosynthesis genes and accumulation of phytohormones during watermelon (Citrullus lanatus) fruit development and ripening oleh Jun-ling DOU, Ping-li YUAN, Sheng-jie ZHAO, Nan HE, Hong-ju ZHU, Lei GAO, Wan-li JI, Xu-qiang LU, Wen-ge LIU