Root colonization by Piriformospora indica promotes growth, induces earliness in flowering, enhances yield and citrulline content in watermelon (Citrullus lanatus<i> </i>(Thunb.) Matsum. & Nakai)

Piriformospora indica is a unique and versatile fungal root endophyte that colonizes a wide range of plant species, and promotes growth, early flowering and yield in addition to enhanced tolerance to abiotic and biotic stresses. The performance of P. indica colonization in water melon was evaluated in two improved, seeded watermelon varieties viz., Sugarbaby, and Durgapur Lal and two seedless F1 hybrids viz., Swarna and Shonima. The seedlings of the varieties colonized with P. indica increased root and shoot growth biomass compared to the control. Early initiation of female flowers was also observed due to the fungal colonization. Indole acetic acid (IAA) and Gibberellic acid (GA) contents of watermelon seedlings were enhanced in P. indica-colonized plants compared to non inoculated control plants. The endophytic association in watermelon also increased the fruit yield in terms of the number and size of fruits, the number of seeds per fruit in seeded varieties, and citrulline, lycopene, and beta-carotene contents. Interestingly, the severity of bud necrosis was significantly reduced in P. indica-colonized plants compared to the uninoculated control. This is the first report on P. indica root colonization in watermelon which positively influences growth, yield and quality of seedless F1 hybrids and seeded varieties of watermelon. This study also indicated the potential of P. indica to overcome the limitations of seedless watermelons in growth and yield compared to the seeded varieties. Therefore, there is tremendous scope for improving watermelon through P. indica-colonization including the seedless F1 hybrids.