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ISSN : 1225-8504(Print)
ISSN : 2287-8165(Online)

Journal of the Korean Society of International Agriculture Vol.32 No.1 pp.1-6
DOI : https://doi.org/10.12719/KSIA.2020.32.1.1

Growth and quality of Ethiopian peppers grafted on Korean peppers

Yoon-Seon Do^*

, Samuel Tilahun Assefa^**, Do-ham Pae^*†

^*KOPIA Ethiopia Center, Ethiopian Institute of Agricultural Research, P.O. Box 2003, Ethiopia
^**Ethiopian Institute Agriculture Research

KOPIA, Rural Development Administration

^†Corresponding author (Phone) +251116677107 (E-mail) paedoham@gmail.com

Received November 30, 2018 Review February 20, 2020 Accepted February 28, 2020

Abstract

Vegetable grafting is a century-old technique used in Asia in order to enhance plant production, including reduction in disease susceptibility and increase in plant vigor. Nevertheless, in Africa (Ethiopia), vegetable grafting is rarely existent. Vegetables are among the major agricultural crops in Ethiopia, and pepper is one of the most important vegetable crops cultivated in the country. However, both biotic and abiotic factors limit pepper productivity, keeping it very low. Hence, this study investigates grafting methods and the impact of grafting on growth and quality of two Ethiopian pepper varieties (Mareko Fana and Melka Zala) grafted on two commercial Korean rootstocks varieties. Both Ethiopian varieties showed 100% grafting union success with the Korean varieties when wedge grafting method was used, while the splice grafting method resulted in lesser success. Furthermore, grafting the Mareko Fana variety on PR3 resulted in statistically significant higher yield compared to the control, while the yield of the Melka Zala was reduced when grafted on PR3. On the other hand, fruit diameter and fruit length of the Ethiopian pepper was not significantly affected by the rootstocks. Finally, grafting was found to increase the TSS content of the Mareko Fana variety. This study documented the standardization of grafting methods and grafting effects on growth and quality traits of pepper under greenhouse conditions. The results of this study will be indispensable for the beginning of the grafting technology in Ethiopia.

Key Words : Vegetable grafting , pepper , wedge grafting , yield , TSS

한국 고추 품종(대목)에 접목된 에티오피아 고추 품종(접수)의 생육 및 품질

도 윤선^*

, 사무엘 틸라훈 아세파^**, 배 도함^*†

^*KOPIA에티오피아센터
^**에티오피아농업연구소

초록

키워드 :

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Rural Development Administration

INTRODUCTION

According to Johnson et al. (2011), ‘vegetable grafting is a century-old technique utilized in Asia to improve plant production, reduce disease susceptibility, and increase plant vigor’. The popularity of this method has showed many advantages, including plant protection against soilborne diseases and nematodes (Louws et al., 2010), abiotic stresses such as salinity and different temperature range (Colla et al., 2010), drought and flooding (Schwarz et al., 2010), and high concentrations of heavy metal in soil (Savvas et al., 2010). In a study carried out by Khah in 2005 on grafted eggplants compared to non-grafted ones, several positive outcomes were identified including increased plant height, leaves size and, in general, a more productive yield. In peppers, tomatoes and eggplants, grafting can also have effects on the quality of the fruits, from their shape, skin color, texture of flesh, to soluble solids concentration, firm-ness and postharvest life (Nkansah et al., 2013, Cheng et al., 2012). As a consequence, the demand on the markets in Asia, Europe and USA of grafted vegetables – as well as its production – is constantly expanding (Johnson et al., 2011).

In Ethiopia and in many other African countries, vegetable grafting is not a common cultivation method, and it is rarely used. Agriculture is the mainstay of Ethiopian economy wherein crop production comprises about 60% of the sector's output. Fruits and vegetables are among the major agricultural crops in Ethiopia. Pepper is one of the most important vegetable crops cultivated in the country. Although pepper is one of the major ingredients in the local dishes and exported in the form of oleoresin as coloring agents for processing industries, its national productivity is unfortunately low compared to the world average production. The pepper world average productivity is 1,035 kg/ha compared to the national pepper average productivity which is only 528 kg/ha (FAOSTAT, 2016). The low productivity is due to the limited improved varieties with important traits such as disease resistance, and low availability of quality seed of varieties released to the farmers. Soil-borne disease is the most widespread problem that is devastating pepper farms every year during the main rainy season. In other parts of the world such as in Asia, vegetable grafting is being used in improving the yield and quality and controlling different soil-borne diseases such as Phytophtora in pepper plants. Grafting has been widely adopted in the Korean peninsula for winter greenhouse production, and resistance to diseases - including Phytophthora root, crown rot, Phytophthora blight and bacterial wilt - has been achieved through grafting of pepper onto other solanaceous plants (Kwon et al., 2006;Jang et al., 2012). Moreover, production of fruits per plant is higher on grafted plants with respect to non-grafted ones (Gisbert et al., 2010), with increases of harvest by 81% (Colla et al., 2006). Similarly, adaptations of this graft technology in Ethiopia will have a significant impact in the vegetable sector specifically for pepper production. In this study, standardization of grafting methods and effects of grafting on growth and quality traits of pepper will be analyzed under greenhouse condition.

MATERIALS AND METHODS

Plant Materials

Two Ethiopian pepper varieties, ‘Mareko Fana (MF)’ (Holeta Agricultural Research Center of EIAR (HARC)) and ‘Melka Zala (MZ)’ (HARC) were used as scions. Two commercial rootstocks resistant to Phytophtora blight, ‘PR illgeoyangdeouk (PR2)’ (Dongwon nongsan seed Co., Ltd.)’ and ‘PR maeilldda (PR3)’ (K-won seed Co., Ltd.) were used as rootstocks. Non-grafted pepper plants from each variety were used as control.

Grafting Methods

Two methods namely wedge grafting and splice grafting were compared in this study. The methods were compared based on their graft union success rates. Briefly, the experiment was conducted as follows: (1) Rootstock used for wedge grafting ranged from 0.22-0.24 cm in diameter and was straight grained, (2) Scion, 15-20 cm long, had the same diameter of rootstock, straight, and long enough to have at least three buds, and (3) Splice grafting was used to join a scion onto the stem of a rootstock or onto an intact root piece. It is used on plants with a stem Diameter of $\frac{1}{2}$ - cm or less. In splice grafting, both the stock and scion must be of the same diameter (Bilderback et al., 2012).

Growing Grafted Pepper Transplants

The seeds of rootstock were sown on 12^th April 2017 in the seed bed. It is 5 days earlier than sowing of the seeds of scion in order to obtain seedlings of similar diameter with rootstocks. The seeds of rootstock and scion were sown into the 50-cell plug trays (W 280 × L 540 × H 45 mm, Bumnong Co., Ltd.). The seedlings were then watered daily.

When the seedlings developed seven or eight true leaves at 65 days after sowing of scion seeds, scions were grafted on rootstocks. The epicotyl of scion and rootstock were cut 1 cm below the first true leaf using a blade (Surgical blade stainless steel No.11, Feather Safety Razor Co., Ltd.). After placing the scion on the rootstock, the grafted position was fixed with a grafting clip by wedge and splice grafting methods. Then, following the method used by Lee et al. (2010), plants were healed and acclimatized in the tunnel covered with double-layered plastic film and shade cloth in the greenhouse for one week. With the aim of boosting the healing process and protect grafted plants from wilting by excessive transpiration, during the first three/four days the tunnel was closed and on the following days the opening and closing of the tunnel was managed based on weather and plants conditions (Jang et al., 2013). After this period, grafted transplants were grown inside the greenhouse.

Greenhouse experiment

The experiment was carried out in a factorial Randomized Complete Block Design. Each treatment were repeated three times, with 12 plants in each replicate. Two rootstock varieties, two scion varieties, and the un-grafted scion varieties as control were used in the experiment. The grafted and non-grafted pepper seedlings were transplanted with 60 cm spacing between rows and 30 cm between plants in 1 m × 1.2 m plot. Manure and chemical fertilizers were applied in the experimental plot. Two rows of drip irrigation tubing were placed on each plot. The seedlings were transplanted at 30 days (19^th July 2017) after grafting (20^th June 2017). The intercultural operations, such as weeding, irrigation, and plant protection measures were taken when necessary.

Data collections

Growth and quality traits of grafted pepper plants were measured and collected. Grafting methods were compared using functional graft union percentage that is the ratio between total number of plants with functional grafted union and total number of grafted plants. Fruits were harvested at two weeks intervals and morphological and quality traits like fruit number, weight, diameter, length, and TSS were measured at each harvesting time. The total soluble solids from pepper fruits were determined by using hand-held refractometer (Model RHB-32ATC, brix range 0-32 % at 10~30°C, Shen Zhen Yieryi Technology Co., Ltd.).

Statistical Analysis

All data were subjected to analysis of variance (ANOVA) using SAS version 9.1 (SAS Institute Inc., Cary, NC, USA) software. Duncan’s multiple range test was performed at p = 0.05 on each of the significant variables measured. Statistical computations were carried out using the Sigma Plot version 14 (Systat Software Inc., San Jose, CA, USA) and GraphPad Prism version 5 (GraphPad Software, Inc., San Diego, CA, USA).

RESULTS

Graft union success rates

The two grafting methods were compared based on their graft union success rates. Generally, wedge grafting showed higher graft success compared to splice grafting. In wedge grafting, the success rates of grafting PR2 and PR3 rootstock with MF and MZ were 100 %. On the other hand, in splice grafting, the success rates of grafting between (PR2 and MF) and (PR2 and MZ) were 52.63 % and 47.37 %, respectively. Similarly, splice grafting between (PR3 and MF) and (PR3 and MZ) resulted in success rate of 60 % and 46.66 %, respectively. According to the results of the grafting success rates, further studies were carried out on the morphological and quality response of wedge grafted pepper plants to grafting. Due to the shortage of seedlings, splice grafted plants were not used in the experiment.

Fruit TSS (°Brix)

The analysis of variance showed statistically significant difference for TSS content among the treatments. The highest TSS was found from both grafted and un-grafted MZ pepper variety while the least brix value was observed from non-grafted MF pepper variety (Table 1). The TSS content of MZ pepper variety was found to be higher than MF in both grafted and non-grafted plants.

The yield of grafting pepper

The yields were estimated based on the total fruit weight. In this study, the yields of two scion varieties grafted on two different rootstocks were investigated during harvest period. Statistically, significant difference was observed among the grafted pepper plants. For instance, grafting MF on PR3 resulted in significant increase in yield, 28,810 kg/ha (compared to non-grafted control plant 14,655 kg/ha, 96.6% increased) while grafting MZ on the same rootstock showed decrease in the yield, 9,794 kg/ha (compared to non-grafted control 14,952 kh/ha, 34.5% decreased). However, the PR2 rootstock resulted in no significant effects on yield of both MZ and MF when compared to fruit yield obtained from non- grafted control plants (Table 1). In contrast, the total yield from PR2×MF and PR2×MZ were decreased 13,552 kg/ ha, and 12,698 kg/ha, respectively, non-grafted MZ and MF gave 14,952 kg/ha and 14,655 kg/ha. As a result, the reasonable grafting combination is grafting MF on PR3 for yield. Thus, an increase in yield can consequently lead to higher profits, as also found out by Turhan et al. (2011) on grafted tomato plants.

Fruit number, weight, diameter and length

The number of fruits on, PR3×MZ and PR2×MZ plants were significantly affected by grafting in comparison to nongrafted MZ (Fig. 3). However, no significant difference was observed among PR3×MF, PR2×MF and non-grafted MF variety (Fig. 3). Similarly, the fruit diameters in each scion varieties were not significantly affected through grafting but the fruit diameter from non-grafted MF variety was significantly higher than non-grafted MZ variety. In contrast, varieties and grafting did not have significant effect on pepper fruit length (Table 1).

DISCUSSION

Effects of grafted plants bring out uniform rootstock and scions, increase the total number of fruits per truss, fruit yield per plant, and reduce diseases (Ibrahim et al., 2001). The results of this study confirmed that wedge grafting has a higher graft success compared to splice grafting, as claimed by Pauline et al. (2017). Also, it was found out that grafted plants with ‘PR maeilldda (PR3)’ had higher fruit number compared to non-grafted plants (Fig. 3). This indicates that grafting pepper on suitable rootstocks have positive effects on the number of fruits and yield. It was reported that total fruit yield was higher in grafted than in non-grafted plants (Colla et al., 2006) and ‘grafted plants improved plant growth and yield without any harmful effects on fruit quality’ (Ozlem et al., 2007). Furthermore, the results agree with those reported for tomato plants by Turhan et al. (2011): grafting has a positive effect on harvest by improving fruit number, weight and index, and higher productivity also means higher profits. The method of grafted pepper plants in greenhouse can be considered as a potential system to improve total yield with no significant in taste of the peppers compared to non-grafted plants (Colla et al., 2008). Additionally, this study shows that total soluble solids (TSS), diameter and length of fruit between grafted and non-grafted peppers of MZ variety were not affected by grafting (Table 1), as also found out by Cushman and Huan (2008). Similar results were also highlighted in a study carried out by Colla et al. (2008), where no significant difference was detected in nutritional qualities of grafted peppers such as fruit dry matter, total soluble solids contents, and titratable acidity with respect to non-grafted plants. The results of this study will provide information for the start of grafting technology in Ethiopia.

Future plan

This study was tested in greenhouses during Ethiopia’s rainy season from June to December. This is the main season when pepper is grown in most part of the country. However, most of the plants are being damaged by soilborne disease during this period and use of grafting technique on resistant pepper such as PR rootstock should be conducted in an open field condition.

적 요

채소 접목은 토양병 저항성 증대, 불량 환경에 대한 내성 향상, 양수분 이용효율 증진 등을 목적으로 아시아에서 오랜 세기 동안 사용되어온 기술이지만 아프리카 특히 에티오피아 에서는 접목 기술의 적용이 전무한 상황이다. 채소 작목은 에 티오피아에서 농업의 중요한 부분을 차지하는 산업 중의 하나 이다. 그 중 고추는 가장 중요한 채소작물 중의 하나이다. 그 러나 고추 생산량은 다양한 생물적, 비생물적 환경요인으로 인 해 매우 낮은 수준이다. 따라서, 이 연구에서는 에티오피아의 고추 접수 2품종과 한국의 대목용 고추 2 품종을 이용하여 접 목 방법 및 효과를 조사하였다. 에티오피아 품종(접수), 한국 상업용 품종(대목) 접목에서 할접 방법을 이용하였을 때 접목 활착률이 100 %로 높았지만 합접 방법은 접목 활착률이 매우 낮았다. Mareko Fana 에티오피아의 접수 품종과 PR3 한국의 대목 품종간의 접목 재배 시 고추 생산량이 무접목보다 유의 하게 많았지만 Melka Zala(접수) 품종과 PR3 (대목) 품종간의 접목 재배 시 무접목보다 고추 생산량은 낮았다. 에티오피아 고 추 품종을 대상으로 한국의 대목 품종과 접목 처리 시 과폭, 과 장은 대목에 의해 영향을 받지 않았다. Mareko Fana 접수 품 종을 한국 고추 대목 2품종과 접목 재배 시 TSS 함량이 증 가되는 효과가 있었다. 에티오피아에서 한국 고추 대목 2품종 과 에티오피아 고추 접수 2품종을 이용하여 2가지 접목 방법 으로 접목하여 비닐 하우스 내에서 고추의 생장 및 품질 특성 에 대한 평가를 실시하였다. 이 연구의 결과는 에티오피아의 고추 접목 재배기술의 시초가 될 것이다.

ACKNOWLEDGMENTS

This work was supported by the project: “Introduction of the high productivity variety in solanaceae crop and development of customized cultivation technology”. We are grateful to the financial support of the South Korean Government through the Korea Program on International Agriculture (KOPIA) of Rural Development Administration (RDA) Republic of Korea. We thank EIAR for the institutional and technical support towards the successful implementation of this work. The assistance provided by Giordano, C. from AICS for comments was greatly appreciated.

Figure

Fig. 1.

Common grafting methods, (A) Wedge grafting. (B) Splice grafting.

Fig. 2.

Grafting success rate by 2 grafting methods (splice grafting and wedge grafting).

Fig. 3.

Effects of different scions on fruit number of wedge grafted pepper.

Table

Table 1.

ANOVA analysis of effects of wedge grafting on TSS, yield, fruit diameter and length of scion varieties ‘Mareko fana (MF)’ and ‘Melka zala (MZ)’ grafted unto ‘PR maeilldda (PR3)’ and ‘PR illgeoyangdeouk (PR2)’ rootstocks.

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