Performance of low-cost healing chamber for healing and survival of brinjal grafts

Introduction

Eggplant is a versatile vegetable that can be cooked in various ways, such as frying, roasting, grilling, or baking. It's a staple in many traditional dishes and cuisines, offering numerous health benefits, including supporting digestive health, reducing inflammation and protecting against certain diseases. Rich in dietary fiber, vitamins and minerals, eggplant is a nutritious addition to a balanced diet. It's also packed with antioxidants like anthocyanin, chlorogenic acid and nasunin. Consumption of brinjal helps to mitigate the risk of chronic diseases like heart disease and certain cancers. The potassium and vitamin B6 in eggplant support healthy blood pressure, while its low calorie and high fiber content make it an excellent choice for weight management. In Ayurvedic medicine, eggplant is believed to have a cooling effect, stimulating digestion and appetite. Its bitter flavour is thought to ignite the digestive fire, helping to break down food. Topically, eggplant paste or poultice may be used to alleviate swelling, inflammation and joint pain. Due to its unique flavour and texture, eggplant is a popular ingredient, available in a range of sizes, colours and shapes, from purple to green, white and yellow. Brinjal is also known to have some medicinal properties and anticholestrol property due to presence of poly-unsaturated fatty acid (Linolenic and Lenoleic acid) present in flesh and seeds of fruit in higher amount to about 65%. Presence of magnesium and potassium salt in fruits are important in anti-cholestrol action. Brinjal is used in curing diabetic patient, asthma, liver complaints, cough due to allergy, colilithiasis leucorrhea, rheumatism, intestinal worms and cholera (Gopalkrishnan, 2007) [1] . Brinjal is popularly cultivated in rice-based cropping system during rabi season in entire Konkan region. However, the commercial cultivation of these vegetables poses limitations and one of them is incidence of bacterial wilt disease. Grafting is one possible way in which bacterial wilt resistant tolerant types can be used as rootstock and commercial varieties as scion. These solanaceous fruit vegetables mainly grafted by tongue, cleft and splice method of grafting and their success varies according to crops. Investigations conducted on tomato, brinjal, cucumber and watermelon revealed that grafting had a pronounced positive effect on yield, quality, tackling soil borne diseases, stress due to water and salinity, heavy chemicals etc. (Lee et al., 2010) [2] . Also introduction of new rootstocks with desirable traits compatible with locally selected scions can boost the status of grafting technology (Yassin and Hussen, 2015) [13] . Therefore, application of grafting in fruit vegetables has bright prospects in future. As a result of its benefits and value, demand for high-quality grafted seedlings by growers is increasing. The varieties have been recommended viz., Konkan Prabha (brinjal) as resistant to bacterial wilt having better field adaptation (Anonymous, 2020) [4] . However, the size, shape and fruit quality of these varieties is not much acceptable to the consumers in the production belts of these vegetables. As the choice of fruit colour, shape and size differs with the market demand. Hence, it is very essential to find out the technology which will provide solution to the problem so that the consumer preferred varieties can be commercially grown in agro-climatic conditions of Konkan region especially during rabi-summer season. Vegetable production with grafted plants was originated in Japan and Korea to avoid the serious crop loss caused by infection of soil-borne diseases aggravated by successive cropping. Grafting is now rapidly spreading and expanding over the world. Vegetable grafting has been safely adapted for the production of organic as well as environmentally friendly produce and minimizes use of undesirable agrochemical residues (Lee et al., 2010). In tomato and brinjal grafting is becoming a well-developed practice worldwide with many horticultural advantages. Specific to a particular agro-climatic region. Studies have shown that grafting can increase yields, promote robust root systems and enhance photosynthesis and disease resistance (Xu et al., 2005; Qi et al., 2006; Wu et al., 2006) [5] . Vegetable grafting offers numerous benefits over traditional methods, including reduced chemical pesticide use, improved resource efficiency and enhanced disease resistance. However, grafting requires specialized knowledge and skills, which can be a barrier for farmers. Limited access to formal training and reliance on traditional practices can hinder the adoption of grafting techniques. To use research is needed to standardize grafting methods and acclimatization processes. Successful grafting requires optimal temperature and humidity control as well as proper air circulation and ventilation. Challenges such as inadequate temperature control, low humidity and poor air circulation can impede graft healing, while bacterial and fungal infections can also pose risks. Additionally, lighting conditions, including intensity, duration and consistency, can impact graft healing and plant growth. In India, the production of solanaceous vegetables, especially brinjal and tomato is severely hampered by the bacterial wilt disease (Ramesh et al., 2014) [6] . There are numerous strains of the bacterial wilt pathogen and it can persist longer in the soil even in the absence of a host hence its management is a very difficult task. The bacterium is quickly transmitted and can enter uninfested areas through water, soil, contaminated plant material or mechanical means. In brinjal, bacterial wilt may result in yield losses of 30-100% (Ramesh), or 4-86% (Sabitha et al., 2000) [7] . In India, many commercial varieties and local cultivars of brinjal exhibit high susceptibility to the disease (Gopinath and Madalageri, 1986) [8] . A soil borne bacterium Ralstonia solanacearum is a causal organism for bacterial wilt. In all solanaceous vegetable the bacterium get entered into the plant through wounds in the roots caused during transplantation, infestation by nematodes and through natural wounds. After entering the plant, it quickly grows in the vascular system and fills the xylem components with bacterial cells, obstructing the flow of water. Plant infected with bacterium shows symptoms of yellowing, wilting and dieing rapidly (Huet, 2014) [9] . Number of methods with varying degrees of success, have been reported for managing the bacterial wilt disease, including resistant varieties, soil amendments, soil solarization, grafting on resistant root stocks, bio-fumigants, plant growth-promoting rhizobacteria, the use of SAR inducers and biocontrol agents etc (Phadake, 2012). Out of these the least expensive and most straight forward method of bacterial wilt management is breeding for host resistance (Huet, 2014) [9] . Source of bacterial wilt resistance has been reported in many improved varieties and landraces of brinjal (Rakha et. al., 2020) [11] . Bacterial wilt poses a barrier to the successful cultivation of the brinjal and tomato crop in regions with high temperatures and humidity levels especially under tropical coastal conditions. The complete failure of a crop may occasionally cause the vegetable grower to suffer significant financial losses. The farmers of konkan region are small and marginal. The grafting protocol which can be adopted by small and marginal farmers will help the growers prepare the grafts at lower level will be feasible for preparing required number of grafts on farm without requirement of sophisticated climatic control facilities standardization of such protocol will be also cost effective way for preparation of tomato and brinjal grafts for commercial utilization of bacterial wilt susceptible scion varieties in the region. Vegetable grafting originated as a method to boost resistance to biotic stresses, but it has since been explored for its potential to enhance tolerance to abiotic stresses like extreme temperatures, drought, salinity and flooding. By combining resistant rootstocks with desirable scions, grafting aims to mitigate both biotic and abiotic stresses, ultimately increasing crop yields. This technique reduces the need for chemical treatments, making it a valuable tool for organic farming. As an eco-friendly approach, grafting promotes sustainable production by controlling soil-borne diseases and minimizing reliance on agrochemicals, thereby supporting a more environmentally friendly method of vegetable cultivation. Resistant breeding remains the most effective and ecofriendly approach to managing Bacterial wilt. Alternatively, grafting onto resistant rootstocks offers a viable solution for controlling soil-borne pathogens in crops like tomatoes and eggplants. Eggplant rootstocks are often preferred over tomato rootstocks due to their enhanced resistance to Bacterial wilt and improved tolerance to flooding, making them a popular choice for grafting tomatoes globally (Wang et al., 2011). Grafting and cultivating grafted seedlings pose several challenges. Key issues include the labor-intensive grafting process, requiring specialized techniques and post-graft care for 7-10 days to facilitate healing. Skilled grafters can produce around 1200 seedlings daily, depending on the skill of person and method to be adopted. Post-graft handling also varies as per the situation. Environmental factors like high temperature, humidity and light can hinder healing if not managed properly. Excessive light can stress newly grafted plants, while insufficient light can impede growth. Poor sanitation and uneven plant aging can lead to disease onset and spread. Additionally, high costs associated with rootstock seeds and grafting equipment can be a significant drawback (Tirupathamma et al., 2019) [12] . Thus, unavailability of suitable acclimatization condition and improper management during acclimatization may drastically reduce the grafting success there by increasing the cost and poor establishment of these grafts in the field. The data presented in Table revealed variation in temperature as well as humidity inside the designed chamber for acclimatization of tomato grafts. It was recorded daily from the day of grafting up to 15 DAG at 7:30 am, 2:30 pm, and 6:00 pm. The temperature ranges morning hours (7.30 am) the temperature in grafting chamber was in the range of 12.5 °C to 16.5 °C during the 15 day period. The afternoon temperature (2:30 pm) was 21.1 to 31.7 °C whereas, evening temperature (6.00 pm) was in the range of 22.4 to 25.6 °C. The optimum temperature range for grafted tomato to healing is between 21 and 22 °C, with a maximum range of 28 to 29 °C which also helped to keep the appropriate humidity levels and provided the optimum growth condition required for healing of grafts.

Material and Methods Experimental Details

Sterilization of Potting Media

The key environmental factor for a successful graft union is humidity. It should be maintained in the range of 85-95%. In this study, relative humidity was measured daily at 7:30 am, 2:30 pm and 6:00 pm throughout the healing period, from the day of grafting up to 15 DAG. The relative humidity inside the healing chamber showed variation across different times of the day till 15-day period.

RH was recorded at 7:30 am, 2:30 pm, and 6:00 pm daily. The morning relative humidity (7:30 AM), ranged from 82.6-97.4% (peak 97.4% on Day 6). The afternoon RH inside the chamber was 79.1-88.8% and evening 51.9-93.4%. Average RH was 82.30-92.40% during 0-7 DAG and 73.47-77.67% during 8-15 DAG. The temperature and relative humidity inside the healing chamber showed variation across different times of the day over the 15-day period. The temperature peaked in the afternoon due to maximum outside solar radiation, heat entrapment inside polycarbonate sheet and MS pipe structure and low air circulation as chamber was covered with polythene to maintain humidity. This was a normal greenhouse effect. In Konkan region, rabi season nights was cool (12-16 °C). Due to radioactive cooling at night and no fogging operation in early morning, the lowest temperature is recorded at 7:30 am. Evening temperature (22.4-25.6 °C) was lower than afternoon because solar intensity decreases after 3 pm, fogging and misting was done, which causes evaporative cooling.

Per cent survival on 7 days and at 21 days of brinjal grafts in grafting chamber

Per cent survival on 7 days and at 21 days in brinjal grafts in grafting chamber

References

1. Gopalkrishna TR. Brinjal. In: Peter KV, editor. Vegetable crops: horticulture science series. 2007. p. 65.
2. Lee J, Kubota C, Tsao SJ, Zhi-Long B. Current status of vegetable grafting. Scientia Horticulturae. 2010;127(2):93-105.
3. Yassin H, Hussen S. Breeding for bacterial wilt resistance in eggplant (Solanum melongena L.): progress and prospects. Crop Prot. 2020;137:105270.
4. Anonymous. Final area and production estimates for horticultural crops. Gurgaon (Haryana): Horticultural Board; 2020.
5. Xu CQ, Li TL, Qi HY, Wang H. Effects of grafting on growth and development, yield, and quality of muskmelon. China Vegetables. 2005;6:12-14.
6. Ramesh R, Achari GA, Gaitonde S. Genetic diversity of Ralstonia solanacearum infecting solanaceous vegetables from India reveals the existence of unknown or newer sequevars of Phylotype I strains. Eur J Plant Pathol. 2014;140:543-562.
7. Sabitha JN, Boruah BM, Rachid HA. Yield potentiality of some brinjal cultivars in severely bacterial wilt infected condition. Veg Sci. 2000;27:76-77.
8. Gopinath G, Madalageri BB. Bacterial wilt (Pseudomonas solanacearum E.F. Smith) resistance in eggplant. Veg Sci. 1986;13:189-195.
9. Huet G. Breeding for resistances to Ralstonia solanacearum. Front Plant Sci. 2014;5:1-5.
10. Phadke GS. Rhizosphere and endophytic bacteria for the suppression of eggplant wilt caused by Ralstonia solanacearum. Crop Prot. 2012;37:35-41.
11. Rakha M, Namisy A, Chen JR, El-Mahrouk ME, Metwally E, Taha N, et al. Development of interspecific hybrids between a cultivated eggplant resistant to bacterial wilt (Ralstonia solanacearum) and eggplant wild relatives for the development of rootstocks. Plants. 2020;9:1405.
12. Tirupathamma TL, Ramana CV, Naidu LN, Sasikala K. Vegetable grafting: a multiple crop improvement methodology. Curr J Appl Sci Technol. 2019:1-10.
13. Yassin H, Hussen S. Reiview on role of grafting on yield and quality of selected fruit vegetables. Global Journal of Science Frontier Research. 2015;15(D1):1-5.