Grafting is a centuries old technique used to unite two different plants of same specie or of different species for desirable traits. In fruits grafting is very old technique but in vegetables it is comparatively new. The oldest record of grafting vegetable plants is in 500 AD in China, when farmers joined together multiple gourd plants to develop a greater root system to increase the size of gourd fruit that were used for rice storage during the winter season. Now a day, it is used in many countries which include Spain, Germany, Turkey, America, Canada and Mexico. Commercial production and demand for vegetable grafted plants continuous to increase in Asia and Europe. It is an environment friendly technique use to control soil borne diseases, to induce resistance or tolerance against abiotic and biotic stresses to increasing the yield of susceptible cultivars. It is currently used for different vegetable such as watermelon, melon, cucumber, pepper, tomato and eggplant. Many countries utilize vegetable grafting and get better yield from limited land.
By Bilal Akram and Dr. Muhammad Azher Nawaz (Horticulture, UOS)
Here is an overview of different factors that are directly supported by use of vegetable grafting technique and these factors are of great importance for Pakistan. Water is becoming an increasingly scarce resource in many parts of the world including Pakistan. The competition among industrial and agricultural use of water creates the need for improving irrigation practices. By use of grafted transplants we can minimize the need of water by selecting a drought tolerance rootstock. There are evidences of improving the drought tolerance of plants by use of vegetable grafting such as grafting of tomato on eggplant helps to survive transplants under drought stress conditions due to its strong roots system compared with tomato. Grafted transplants help plants survive under water logged conditions but also increase the chlorophyll content in the leaves. Grafting improve flooding tolerance of bitter gourd when grafted onto lufa. We can save a plenty of water by use of vegetable grafting technique.
Agricultural land is speedily converted in to barren land due to salt accumulation. Every year thousands of acre land became useless because of high rate of salts. As salinity is a big threat to agricultural and there is no effective system to reclaim these types of degraded lands and we have to live with them. Using salt tolerance and vigorous rootstock we can use salt effected lands for growing vegetables. Wild types of rootstocks for different vegetables are tolerant to salt to some extent.
Yield of vegetables (tons/hectare) in different countries.
(Source: Nawaz et al., 2017)
In Pakistan farmers are facing shortage of quality fertilizers and government also fails to facilitate them. Increase in the price of fertilizer is a big issue for farmer. Farmers are not applying the fertilizers according to recommendation due to their high prices. By use of vegetable grafting we can save more than 50% of the fertilizers without compromising yield. By using vigorous rootstocks the frequency of agrochemical application can be significantly reduced. In watermelons, the amount of chemical fertilizers can be reduced to about one-half to two-third compared with the standard recommendation for the non-grafted plants.
Nutrient uptake can also improve by grafting. Drought tolerance provided by either rootstock or scion improves nitrogen fixation in soybean. Grafting also improves the absorption and translocation of nitrogen, magnesium, phosphorous, and calcium and several other essential nutrients. Improved nutrient uptake in grafted transplants also increases photosynthesis under unsuitable climatic conditions such as weak sun light and low level of CO2.
Today’s most dangerous threat to agriculture sector is changing environmental conditions like very low and very high temperature. Growing seasons as well as growth habit of plants is badly affected due to sudden change in temperature. In grafting we use rootstock which is normally temperature hardy, may help to compete with rapidly changing temperature. To reduce resistance against low or high temperature grafting is used. Grafting not only makes plants resistant to survive under extreme temperature but also increases the yield. Figleaf gourd rootstock has been used commercially for water melon, cucumber and melons to increase tolerance to low soil temperature. Grafting helps plants to survive under low temperature due to presence of more Linolenic Acid. Pepper had a higher yield under high temperature when grafted onto sweet pepper rootstock.
Vegetable grafting is proved as a shield against heavy metals. Grafted plants survive effectively under heavy metal stress compared with non-grafted plants under same environmental conditions. Grafting minimize the negative effect of copper, cadmium, vanadium, and manganese toxicity.
Using vegetable grafting we can control diseases attack on crops by using resistant rootstock. The disease tolerance in grafting seedlings may be entirely due to tolerance of rootstock to the diseases. Soil borne fungal diseases can be effectively controlled by using vigorous rootstocks.
Grafting has a direct effect on yield of crop. By using selected, compatible and vigorous rootstock we can get maximum marketable yield. In oriental melons, increases of 25-50% yield have been reported by using grafted plants. There is also evidence of increased yield in tomato by 54%. In other vegetables such as cucumber, chili, eggplant and watermelon yield was increase by up to 8.80-57%, 9.20%, 27.70% and 22.7-43%, respectively by using grafted transplants.
Grafting is an effective approach to improve fruit quality under both optimum growth conditions and salinity. Grafted plants have higher marketable yield, fruit quality and sugar content of fruits depending on rootstocks. Total phenolic contents increased in grafted eggplants compared with non-grafted plants.
Why vegetable grafting in Pakistan?
Pakistan is not an economically strong state; our resources are decreasing with time. By using vegetable grafting technique minimize the impact of shortage of water, land and fertilizers and can also handle changing environmental conditions. Agriculture department, public universities, private universities and private sector have to work on vegetable grafting to make it useable for local farmers and to provide them with quality transplants to move towards precision agriculture.
There is a need of vegetable grafting in Pakistan to boost production of vegetable and to take it at the level of other countries to full fill the increasing demand of vegetables. By the use of grafted transplants the use of pesticides is minimized thus it promotes organic vegetable production.
Major limitations/ constraints in adopting vegetable grafting in Pakistan
There are several limitations in successful utilization of vegetable grafting technique in Pakistan that includes
- Lack of awareness among farmers
- Lack of interest of public sector
- Lack of funds for research and development
- Uncharacterized germplasm for rootstock and scion cultivars
- Unavailability of proper infrastructure (green house, germination and healing chambers)
- Enhanced utilization of seeds for the preparation of grafted transplants.
- Lack of trained labor/staff
- Expected high price of grafted transplants
Nawaz, M.A., F. Shireen, Y. Huang, B. Zhilong, W. Ahmed and B.A. Saleem, 2017. Perspectives of vegetable grafting in Pakistan: current status, challenges and opportunities. International Journal of Agriculture and Biology, 19: 1165‒1174