Grafting Techniques for Controlling Fusarium Wilt of Bitter Gourd
This study on grafting techniques aimed to develop non-chemical methods which are effective against all the three seedling diseases. Using clean seeds and cultural substrate, bitter gourd seedling from seed, instead of shoot, as scion is used for cleft-grafting (1:1 cleft grafting method) (Fig. 2) or cleft-inarching (Fig. 2) on loofah to produce graft seedlings. These are grown in a moist chamber (Fig. 6) at 20oC. The growing of grafted seedlings in the field for several years has resulted in the gradual disappearance of Fusarium wilt. The bitter gourd yield also improved, and has now reached 82-127 t/ha, as compared to the average yield of 16 t/ha for nongrafted bitter gourd in Taiwan.
Grafting Methods of Bitter Gourd to Loofah Rootstock
Cleft Grafting (Fig. 2) and 1:1 Cleft Grafting (Fig. 2)
- Rootstock preparation
- Loofah seedlings are sown in seedling trays filled with 1:1 (vol/vol) mixture of peat and perlite for 3 weeks in the greenhouse. When the first true leaf appeared between the cotyledons, the seedlings are suitable for grafting. By using a single-edged razor blade, the true leaf and growing point of rootstocks are removed and a slit of 1-1.5 cm is made from the intermediate zone of cotyledons down to the hypocotyl tissue.
- Scion preparation
- Bitter gourd plants are grown in the greenhouse for more than one month. The healthy shoots (top node of secondary vine) are selected as scion. By using a single-edged razor blade, a wedge (V shape) about 1-1.5 cm is made at the cut-end of the scions. Seedling, instead of shoot, of bitter gourd is used as scion for the 1:1 cleft grafting method.
- Final grafting step
- The wedge of the scion is driven into the hypocotyl slit of the rootstock and clipped with a specially devised grafting clip to hold the scion and rootstock tightly.
- Post-graft care
- The grafts should be wrapped with a moist plastic bag or some other devise to maintain high moisture condition (Fig. 6) and to heal the grafting union for 7-10 days. Then, the grafts must be transplanted into the fields no later than one month after grafting.
Cleft Inarching Grafting (Fig. 2)
- Rootstock preparation
- Loofah seedlings are grown in the greenhouse for 3-4 weeks and are cut just 10 cm above the cotyledons of the rootstocks. The cut end of the rootstock stem is made into a wedge (V shape) about 1-1.5 cm by using a single-edged razor blade.
- Scion preparation
- Bitter gourd plants are grown in the greenhouse for 1-2 months. A 30-degree angle cleft (bottom to top direction) about 1-1.5 cm is made with the use of a single-edged razor blade on the stem of the scion, approximately 2 cm below the third node from the top.
- Final grafting step
- Put the wedge of the scion into the stem cut of the rootstock with the use of a grafting clip.
- Post-graft care
- Place the grafts in the greenhouse for 10-14 days to heal the grafting union, and then cut the scion stem approximately 2 cm below the grafting union. The grafts can be transplanted into the fields no later than one month after grafting.
Index of Images
Figure 1 Fusarium Wilt of Bitter Gourd Caused by Fusarium Oxyxporum F. SP. Momordicae in the Field
Figure 2 Diagram of Grafting Methods. (a) Cleft Grafting;
Figure 3 Symptoms of Seedling Blight of Cleft Grafted Bitter Gourd (a) Showing Early Lesion on Loofah Cotyledons; and (B) Severe Blight within a Few Days
Figure 4 (a) Sunscald of Cleft Grafted Bitter Gourd
Figure 5 Damping off of Cleft Grafted Bitter Gourd Showing (a) Water Soaking and Rot Lesion on the Grafting Union; and (B) Basal Stem Rot Symptoms.
Figure 6 High Moisture Incubation Conditions Are Highly Recommended for Post-Graft Care (a) in the Field and (B) in the Greenhouse.
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