Contribution of roots to growth and physiology of watermelon grafted onto rooted and unrooted seedlings of various bottle gourd rootstocks

Abstract

A hydroponic experiment was conducted between April and May in 2018 by using an aerated Deep Water Culture (DWC) technique in a controlled growth chamber of Erciyes University, Agricultural Faculty in Kayseri, Turkey. To evaluate contribution of roots for growth and physiology a commercial watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] cultivar (Crimson Tide F1) was grafted onto two different bottle gourd (Lageneria siceraria) genotypes (39-01 and 47-02) and one commercial rootstock genotype (Argenterio) by using two propagation techniques (unrooted or rooted seedlings). Plants were grown in 8 L pots filled continuously aerated nutrient solution, in Randomized Block Design with 4 replications for 6 weeks. Results indicated that shoot and root fresh (FW) and dry (DW) weights, main stem length, total leaf area, leaf chlorophyll index (SPAD), photosynthetic activity of leaves of watermelon were significantly (P<0.001) affected by rooting type, genotype and genotype x rooting type interaction. Irrespective of rooting type, the grafted genotypes usually showed significantly higher performance in growth and physiological development than ungrafted control plants. Among graft combinations, the highest growth performance was shown by C.Tide/Argenterio while the lowest was shown by C.Tide/39-01. In terms of rooting type, watermelon plants usually showed a better performance in growth and physiological development when they were used as rooted seedlings compared to unrooted ones. Grafting watermelon onto unrooted seedlings caused a significant reduction in shoot FW by 21.6%, in shoot DW by 12.8%, in root FW by 29.5%, in root DW by 33.7%, in stem length by 11.5%, in total leaf area by 26.3%, in SPAD by 11.2% and in photosynthesis by 18.2%. All these clearly indicate that roots are playing very essential role in contribution to growth and development of plants, particularly at the beginning of growth stage. Therefore, our study suggested that grafting with unrooted seedlings is not a useful application strategy for watermelon plants grown under hydroponic conditions, even when they are grafted onto vigorous rootstocks.