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

Ahydroponic experiment was conducted between April and May in 2018 by using anaerated Deep Water Culture (DWC) technique in a controlled growth chamber ofErciyes University, Agricultural Faculty in Kayseri, Turkey. To evaluatecontribution of roots for growth and physiology a commercial watermelon [Citrullus lanatus (Thunb.) Matsum. andNakai] cultivar (Crimson Tide F1) was grafted onto two differentbottle 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 weregrown in 8 L pots filled continuously aerated nutrient solution, in RandomizedBlock Design with 4 replications for 6 weeks. Results indicated that shoot androot fresh (FW) and dry (DW) weights, main stem length, total leaf area, leafchlorophyll index (SPAD), photosynthetic activity of leaves of watermelon weresignificantly (P<0.001) affected by rooting type, genotype and genotype x rootingtype interaction. Irrespective of rooting type, the grafted genotypes usuallyshowed significantly higher performance in growth and physiological developmentthan ungrafted control plants. Among graft combinations, the highest growthperformance was shown by C.Tide/Argenterio while the lowest was shown byC.Tide/39-01. In terms of rooting type, watermelon plants usually showed abetter performance in growth and physiological development when they were usedas rooted seedlings compared to unrooted ones. Grafting watermelon ontounrooted seedlings caused a significant reduction in shoot FW by 21.6%, inshoot DW by 12.8%, in root FW by 29.5%, in root DW by 33.7%, in stem length by11.5%, 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 incontribution to growth and development of plants, particularly at the beginningof growth stage. Therefore, our study suggested that grafting with unrootedseedlings is not a useful application strategy for watermelon plants grownunder hydroponic conditions, even when they are grafted onto vigorousrootstocks.