**Interactive E**ff**ects of Grafting Techniques and Scion-Rootstocks Combinations on Vegetative Growth, Yield and Quality of Cucumber (***Cucumis sativus* **L.)**

**Rana Shahzad Noor 1,2, Zhi Wang 1, Muhammad Umair 2, Muhammad Yaseen 3, Muhammad Ameen 4, Shoaib-Ur Rehman 5, Muzammil Usman Khan 5, Muhammad Imran 6, Waqar Ahmed <sup>7</sup> and Yong Sun 1,\***


Received: 13 April 2019; Accepted: 31 May 2019; Published: 5 June 2019

**Abstract:** The density of herbaceous crops creates a suitable environment to produce pathogens in the soil that intensify the attack of pathogens traditionally controlled by disinfectant, which are mostly prohibited and unlisted because of their toxicity. Grafting is an alternative technique to enhance abiotic stress tolerance and reduce root diseases due to soil-borne pathogens, thus enhancing crop production. This research study was conducted during the crop season of 2017 and 2018 in order to investigate the interactive effect of different grafting techniques of hybrid scion onto local rootstocks on plants survival, plant phenological growth, fruit yield and fruit quality under a controlled environment. The hybrid cucumber was also planted self-rooted. The cucumber (*Cucumis sativus* L.) cv. Kalaam F1, Syngenta was grafted onto four local cucurbitaceous rootstocks; ridge gourd (*Lu*ff*a operculate* Cogn.), bitter gourd (*Momordica charantia* L.), pumpkin (*Cucurbita pepo* L.), bottle gourd (*Lagenaria siceraria* (Molina) Standl.) using splice grafting, tongue approach, single cotyledon and hole insertion grafting techniques and self-rooted hybrid cucumber under greenhouse conditions. The experimental results indicated that all local cucurbitaceous rootstocks showed a high compatibility with hybrid cucumber scion in the splice grafting method compared to other grafting and non-grafted methods. *Lagenaria siceraria* rootstocks were found highly compatible with cucumber cv Kalaam scion which gave significantly maximum plant survival rates (95%) due to high sap contents, high SPAD value, better vegetative growth and maximum fruit yield when compared with other rootstocks by employing the splice grafting method followed by tongue approach, single cotyledon and hole insertion grafting while the fruit quality of all rootstocks was observed to be similar. The non-grafted cucumber cv. Kalaam F1 showed significant results of plant vegetative growth, fruit development and fruit quality and encountered grafting methods while the lowest result were associated with the hole insertion grafting method in all scion/rootstock combinations. The grafted plants have no significant effect on cucumber fruit dry matter and fruit quality while the

fruit mineral compositions (N, P, K, Ca and Mg) were higher among grafted and non-grafted plant fruits. The results indicate that grafting hybrid cucumber onto four local cucurbitaceous rootstocks influenced growth, yield and fruit quality. Grafting can be alternative and control measure for soil-borne disease and to enhance cucumber production.

**Keywords:** cucumber; grafting techniques; rootstock-scion; soil-borne disease; resistant; tolerant crop growth; fruit yield; fruit quality

#### **1. Introduction**

Grafting entails a deliberate combination of parts of different plants of the same species by which vascular continuity is established [1]. The crown of the plant (Scion) adheres to the root part of the plant (rootstock) resulting in composite plant growth and development of a single plant (graft) [2]. The callus related to parenchyma cells develops from the plant tissue of the rootstock and scion around the joint portion to develop vascular connection [3]. Grafting is a horticultural technique applied in the sustainable agricultural practice for the protection of cucurbitaceous crops from soil-borne pathogens, nematodes, soil pH and salinity. This problem has been globally important since 2005 when the application of methyl bromide was prohibited [4]. The rapid multiplication of soil-borne pathogens and nematodes is due to the intensive use of soil and absence of crop rotation. This affects vegetable growth particularly under greenhouse conditions [5]. It is a big challenge to reduce the impact of soil pathogens for a sustainable agriculture production system [6] and monoculture is more susceptible than a diversified agricultural system [7]. The rootstocks resistant for nematodes are not available; nematodes cause 11 % annual average yield loss [8].

Grafting has become a technique with a high potential to improve the efficiency of modern and intelligent vegetable cultivation, and indicates adoptability and resistance under different stress situations [9]. The grafting of plants is carried out to develop tolerance against temperature variation, salt stress and heavy metal contents in the soil. The grafting scion on appropriate local rootstocks can medicate these issues [10–12]. The structural and biological development of graft between scion and rootstock has been studied and three basic phases have been observed, namely: combining scion and rootstock, callus creation around the joint and establishing continuity at joint through vascular re-differentiation [1,3,13,14]. These discussed events determine the success of the scion-rootstock combination, considering the role of plant growth hormones (auxin) in the grafting technique [15]. The graft may grow through the wound healing mechanism and formation of conductive vessels [16]. Therefore, the formation of vascular connection represents the last and most critical stage in wound healing because after healing, the transportation of water and solute start from the rootstock to the scion and the graft union develops a strength [13,17]. The time required for the completion of grafting stages is a little unpredictable [17] because an appropriate method for the assessment of development in grafting does not exist [18]. However, the development can be predicted by destructive and non-destructive methods, including the visual determination of graft [19], thermal camera image [19], cutting graft vertically at union to observe vascular system [20], electrical resistance measurement from scion to rootstock [19] asses tensile strength at scion-rootstock union [21,22], disruptive evaluation of hydraulic connection [23] and the nuclear magnetic resonance (NMR) method to show water flux inside vessels [23].

Cucurbitaceous crops are mostly grown during the warm season (greenhouse conditions, 21 ◦C to 32 ◦C). The temperature below 16 ◦C is not suitable for the germination of cucumber seeds [24]. Cucumber is grown during the warm season when vegetables produce good crops when grown under protection [24]. The above discussed problems severely influence the area and production under greenhouse conditions [25]. The grafting of scion on local rootstocks is the most effective solution to this problem. Cucumber (*Cucumis sativus* L.) grafted on different cucurbitaceous crop rootstocks are

Cucurbita maxima Duchesne, *C. moschata*, *C. ficifilia*, *Lagenaria* spp., *Lu*ff*a* spp. [26–28]. The selective method of grafting considerably depends upon crop type, grower decision and experience, as well as facilities availability [29]. Splice grafting [30,31], tongue grafting [32], single cotyledon [4,33] and hole insertion grafting [19,34]. Several studies indicated that the grafting technique showed productive findings such as increase growth, yield and tolerance against stress conditions [35–37]. These plant characteristics majorly linked with genotype of rootstock particularly plant growth and yield effected by rootstock [37,38]. The grafting of cucumber crop on different rootstock reduces precocity but the total yield significantly increased as compared with non-grafted plants [39].

The grafting had some undesirable effects such as deterioration in taste, changes in the fruit color, bigger fruit size. The grafting also resulted the increment in fructose content and sweetness of cucumber which indicates the significance of rootstock [40]. The collar size of grafted plants varies depending upon rootstock. Frequently, the diameter of the collar of the grafted plants is higher [39]. The concerning, uncertainties regarding scion-rootstock and environmental instructions. The best selection for rootstock based on production area, rootstock species and scion cultivars used under different conditions [41]. The combination of rootstock and scion must be carefully selected according to the specific calamitic and soil condition [42]. The adequate rootstock-scion combination could help to regulate the soil borne diseases, increase yield and improve fruit quality.

This motivates us to carry out a more detailed study of these significant parameters such as yield, earliness, taste and some fruit sensory characteristics of grafted cucumber plants on different cucurbit rootstocks. This study was carried out to investigate the effect of grafting a hybrid cucumber scion onto four local cucurbitaceous rootstocks by four different grafting technique under greenhouse conditions on plants survival, plant phenological growth, fruit yield and fruit quality in order to establish the most tolerant scion-rootstock combination and favorable method for cucumber grafting. The hybrid scion cucumber cv Kalaam F1 and four rootstocks, namely ridge gourd (*Lu*ff*a operculata*), bitter gourd (*Momordica charantia*), pumpkin (*Cucurbita pepo*), bottle gourd (*Lagenaria siceraria*) were used as scion-rootstock combinations in order to check the compatibility of tongue grafting, splice grafting, single cotyledon grafting and hole insertion grafting.
