Effect of rootstock and foliar application of some treatments on certain growth traits of grapefruit scion cv. Dancan

Introduction

Citrus (Citrus sp.) belongs to the family Rutaceae, which is characterized by the presence of oil glands in most plant parts, giving them a distinctive aromatic scent. This family includes three genera, the most economically important of which is Citrus. Due to the diversity of species within this genus, it has been classified into five groups: mandarins, sweet oranges, hybrids, acidic group, and grapefruit (Ladanyia, 2008) [17] . Grapefruit (Citrus paradisi) is considered either a hybrid of pummelo (shaddock) or a result of a genetic mutation. Grapefruit cultivars are generally grouped into those with white pulp and those with colored pulp, and both groups include seeded and seedless varieties. The Dancan cultivar is a seeded white-pulp variety that has proven successful in Iraq under openfield cultivation. It is characterized by early fruiting, good fruit quality, and suitability for canning (AlKhafaji et al., 1990) [2] . Several rootstocks are used in Citrus propagation. Volkameriana rootstock is known for its resistance to quick decline, gummosis, and Citrus psorosis, and it is compatible with many Citrus species. Trees grafted on it produce high yields, excellent fruits, and show vigorous growth (Hussain, 2000; Nemeth, 2012) [13,18] . Rangpur is a hybrid between rough lemon and lime, and it has recently gained attention as a promising rootstock due to its desirable traits, which made it widely adopted in Citrus propagation. It has been extensively used in many countries, including Asian countries and Brazil, one of the world's largest Citrus producers (Allan et al., 2021) [9] . especially under unfavorable soil conditions such as drought or temperature fluctuations (Lovatt, 2013) [16] . The use of nanotechnology in fertilizer formulation has opened new perspectives in agricultural and biotechnological applications. Nano-fertilizers are innovative agricultural inputs that help reduce the environmental risks associated with conventional fertilizers, while enhancing plant growth and yield both quantitatively and qualitatively (Janmohammadi et al., 2016) [14] . Compared to traditional fertilizers, nano-fertilizers are more soluble, rapidly penetrate plant tissues, and are more efficiently metabolized. The use of nano-fertilizers, either in solution or solid form, has proven superior in enhancing the growth and productivity of various crops. They represent one of the important strategies for supplying plants with essential nutrients while simultaneously reducing the negative environmental impacts of high concentrations of conventional fertilizers, thus contributing effectively to minimizing pollution (Singh et al., 2017) [21] . Al-Awadi (2024) [3] demonstrated that the application of nano NPK fertilizer at concentrations of 1 and 2 g L⁻¹ to orange seedlings grafted on Rangpur rootstock resulted in a significant increase in most vegetative and chemical traits. Organic fertilization is considered one of the important approaches to supply plants with nutrients without causing harmful effects on the environment, whether applied through soil or foliar application (Nardi et al., 2016) [20] . Numerous researchers have confirmed the role of humic acid in promoting plant growth by enhancing photosynthesis, facilitating nutrient transport within the plant, improving nutrient absorption, and increasing plant dry matter. Furthermore, it plays a vital role in soil structure improvement, serving as a reserve source of nutrients, particularly nitrogen (Al-Zurfi, 2012) [5] . Similarly, Hethal (2014) reported that the application of humic acid at a concentration of 1.5 g L⁻¹ improved most vegetative growth parameters of Citrus seedlings grafted onto different rootstocks. Vitamins are also essential for plant metabolism as enzymatic cofactors, and they possess strong antioxidant activity. These include water-soluble compounds such as vitamins C and B, and fat-soluble compounds such as vitamins A, D, and E (Pogson and DellaPenna, 2006) [11] . Vitamin C, a vital amino sugar with the chemical structure CHO, plays multiple physiological roles in plants, including its participation in respiration, photosynthesis, stimulation of nucleic acid and protein synthesis, and other metabolic processes (Wheeler et al., 1998; Smirnoff, 2000) [22] .

Due to the limited number of studies on the application of these compounds and their influence on the growth of Duncan grapefruit scions grafted onto Volkameriana and Rangpur rootstocks, the present study was conducted.

The fresh weight of the shoot system (stem, leaves, and branches) was measured using a sensitive balance after carefully removing the seedlings from the soil, washing them thoroughly with running water to remove adhered particles, and separating the root system.

The shoot parts were cut into small pieces and placed in perforated bags for air-drying in an oven at 70 °C until a constant weight was obtained, after which they were weighed using a sensitive balance.

Fresh root weight was measured by extracting the plant from the soil, washing it thoroughly with running water, separating the shoot system, and weighing the root system with a sensitive balance.

This was determined in the same manner as dry shoot weight.

After oven-drying, the dry matter percentage of leaves was calculated according to the following equation (Al-Sahaf, 1989) [4] :

\text{Dry matter%} = \frac{\text{Dry weight of leaves}}{\text{Fresh weight of leaves}} \times 100

Results and Discussion

Fresh shoot weight (g): Table (1) shows a significant effect of foliar application on fresh shoot weight. The treatment with humic acid recorded the highest mean value (51.035 g), while the control treatment gave the lowest mean (37.47 g). The rootstock factor did not show significant differences for this trait. However, the interaction between rootstocks and foliar treatments was significant. The treatment A2T3 (Rangpur × humic acid) achieved the highest mean fresh shoot weight (62.34 g), whereas A2T0 (Rangpur × control) recorded the lowest mean (37.42 g). (2) shows that both Rangpur and Volkameriana rootstocks did not exhibit any significant effect on dry shoot weight. Similarly, foliar application treatments, including water (control), nano NPK, humic acid, vitamin C, and tryptophan, did not result in significant differences in this trait.

However, the interaction between rootstocks and foliar treatments was significant. The treatment A2T3 (Rangpur × humic acid) recorded the highest mean dry shoot weight (26.49 g), while A1T0 (Volkameriana × control) gave the lowest mean value (15.43 g). (3) indicates that foliar application treatments had a significant effect on fresh root weight. The treatment with humic acid recorded the highest mean value (52.82 g), whereas the control treatment gave the lowest mean (38.79 g).

In contrast, the rootstock factor did not show any significant effect on this trait. However, the interaction between rootstocks and foliar treatments was significant. The treatment A2T3 (Rangpur × humic acid) recorded the highest mean fresh root weight (64.48 g), while the treatment A2T0 (Rangpur × control) gave the lowest mean (32.13 g).

Table 3: Effect of two Citrus rootstocks, foliar application of some treatments, and their interaction on fresh root weight (g).

The Origins N Transactions T A Average

NPK nano T1

Table (4) shows that the two rootstocks, Rangpur and Volkameriana, did not have a significant effect on dry root weight. Similarly, foliar treatments with water, nano NPK, humic acid, vitamin C, and tryptophan did not produce significant differences for this trait.

However, the interaction between rootstocks and foliar treatments was significant. The treatment A2T3 (Rangpur × humic acid) recorded the highest mean dry root weight (25.47 g), while A2T4 (Rangpur × Vitamin C) gave the lowest mean (12.1 g).

Table 4:

Effect of two Citrus rootstocks, foliar application of some treatments, and their interaction on dry root weight (g)

The Origins N Transactions T A Average

NPK nano T1

Table (5) shows that the two rootstocks, Rangpur and Volkameriana, did not have a significant effect on leaf dry matter percentage. Similarly, foliar treatments with water, nano NPK, humic acid, vitamin C, and tryptophan did not produce significant differences for this trait.

However, the interaction between rootstocks and foliar treatments was significant. The treatment A1T4 (Volkameriana × Vitamin C) recorded the highest mean leaf dry matter percentage (34.04%), while A2T2 (Rangpur × Tryptophan) recorded the lowest mean (29.34%). The results presented in the previous tables indicate slight increases in the vegetative traits of Dancan grapefruit scions grafted onto the Rangpur rootstock compared to the Volkameriana rootstock; however, these increases were not statistically significant. Regarding the effect of foliar spraying with different treatments, nano-fertilizer showed superior performance. This significant increase in traits such as fresh weight of the vegetative shoot, dry weight of the vegetative shoot, and leaf potassium percentage can be attributed to the presence of growth hormones, particularly auxins, in organic fertilizers, which enhance cell division, as well as vitamins and amino acids that influence vegetative growth. Moreover, applying organic fertilizers to the soil improves its quantitative properties and increases carbon content, while also enhancing the availability of N, P, and K, thereby promoting their uptake by roots and leading to significant increases in vegetative and root growth indicators (Vajranabhiah & Krishnamoorthy, 1986) [15] . These findings are consistent with those reported by Abd El-Naby et al. (2017) [10] in their study on fig trees. The observed increase in fresh root weight (Table 3) following foliar application of humic acid is due to its content of essential mineral elements in suitable amounts, which are easily absorbed by the plant. This promotes activation of vital physiological processes and the synthesis of metabolites required for cell division and formation of new cells, leading to enhanced nutrient accumulation and transport to roots, thereby increasing root growth and fresh root weight. These results are in agreement with Huthal (2014) [8] and Abdel-Wahab & Al-Mushari (2017) [6] . The positive effect is also reflected in the increase in dry root weight (Table 4), which results indirectly from improved root growth due to enhanced vegetative growth, ultimately leading to a larger root system and an increase in the percentage of dry matter in roots. These findings are consistent with those of Baha et al. (2018) and Ghani et al. (2009).

References

1. Ibrahim AS, Ishraq SA, Raed NS, Rafiq AA, Fadhel SQ. Effect of seven Citrus rootstocks on growth and yield of Washington Navel orange. Syrian J Agric Res. 2014;1(1):59-69.
2. Khafaji MA, Aliwi S, Jameel AA. Evergreen Fruits. Baghdad, Iraq: National Library and Documentation Center, University of Baghdad; 1990. 388 p.
3. Al-Awadi RMN. Effect of conventional and nanofertilizer and cytokinins foliar application on some vegetative and chemical traits of local orange seedlings grafted on Rangpur rootstock [MSc thesis]. Al-Qasim: College of Agriculture, Al-Qasim Green University; 2024.
4. Al-Sahaf FHR. Applied Plant Nutrition. Baghdad, Iraq: Ministry of Higher Education and Scientific Research, University of Baghdad; 1989.
5. Al-Zurfi MTH. Effect of foliar application of two organic fertilizers (Izomen and Laq Humus) on the growth and propagation of Agave americana. Al-Kufa J Agric Sci. 2012:221-30.
6. Abdel-Wahab NI, Al-Mushari BYJ. Effect of foliar application of humic acid and cytokinins on some growth parameters of Washington Navel orange and local lemon. Diyala J Agric Sci. 2017;9(1):215-27.
7. Baha AA, Khadr IF, Mahmoud AS. Effect of nitrogen (urea) and humic acid on growth of almond seedlings (Prunus amygdalus Batsch). Tikrit J Agric Sci. 2009;9(1):534-94.
8. Diyala: College of Agriculture, University of Diyala; 2014.
9. Allan JD, Castillo MM, Capps KA. Stream Ecology: Structure and Function of Running Waters. Cham: Springer Nature; 2021.
10. Abd El-Naby SKM, Abd El-Moniem EAA, Eman AA, Abd-Allah ASE. Effect of source and date of organic manure application on growth, yield, fruit quality and mineral content of fig trees grown in sandy soil. Minufiya J Agric Res. 2017;33(3):515-40.
11. Della Penna D, Pogson BJ. Vitamin synthesis in plants: tocopherols and carotenoids. Annu Rev Plant Biol. 2006;57:711-38. https://doi.org/10.1146/annurev.arplant.56.032604.1443 01
12. Ghani F, Khan MR, Bostan N, Nabi G, Muhammad H, Ali A, et al. Effect of humic acid and seed size on germination of mango (Mangifera indica L.) seed. Pure Appl Biol. 2018;7(1):315-320.
13. Hussain FA, Ihreb SH. Effect of rootstock on successful grafting and saplings growth for some Citruses fruits in Iraq. Iraqi J Agric. 2000;5(3):124-140.
14. Janmohammadi M, Navid A, Segherloo AE, Sabaghnia N. Impact of nano-chelated micronutrients and biological fertilizers on growth performance and grain yield of maize under deficit irrigation condition. Biologija. 2016;62(2).
15. Krishnamoorthy RV, Vajranabhiah SN. [Title missing]. 1986. (Note: Citation incomplete-please provide full title and source.)
16. Lovatt CJ. Properly timing foliar-applied fertilizers increases efficacy: A review and update on timing foliar nutrient applications to Citrus and avocado. HortTechnology. 2013;23(5):536-41.
17. Ladanyia MS. Citrus Fruit: Biology, Technology and Evaluation. Burlington (MA): Academic Press/Elsevier; 2008.
18. Nemeth M. Citrus Rootstocks: their Characters and Reactions. UC Riverside Science Library [retired]; 2012.
19. Wu GA, Berol J, Ibanez V, Lopez-Garcia A, PerezRoman E, Borreda C, et al. Genomics of the origin and evolution of Citrus. Nature. 2018;554:311-6.
20. Nardi S, Pizzeghello D, Schiavon M, Ertani A. Plant biostimulants: physiological responses induced by protein hydrolysate-based products and humic substances in plant metabolism. Sci Agric. 2016;73(1):18-23.
21. Singh MD, Chirag G, Prakash PO, Mohan MH, Prakasha G, Vishwajith. Nano fertilizers is a new way to increase nutrients use efficiency in crop production. Int J Agric Sci. 2017;9(7):3831-3833.
22. Smirnoff N, Wheeler GL. Ascorbic acid in plants: biosynthesis and function. Crit Rev Plant Sci. 2000;19(4):267-290.
23. Chou GJ. A new method of measuring the leaf area of Citrus. Acta Hort Sci. 1966;5:7-20.