PROPAGATION TECHNIQUES IN SMALL CARDAMOM

 

S.J.Ankegowda and Biju C.N.
Indian Institute of Spices Research,
Cardamom Research Centre,
Appangala,
 Heravanadu Post,
Madikeri 571 201, Karnataka.

 

Small cardamom (Elettaria cardamomum Maton), the exquisite member of spice family, Zingiberaceae originated in the evergreen expanse of Western Ghats. The spice endowed with its alluring qualities is appropriately acknowledged as “Queen of Spices”. Several varieties with superior quality traits for high yield, resistant to pests and diseases have been evolved through selection and hybridization process and being widely accepted among the farming community across the cardamom growing regions. Effective transfer of these desirable traits to the next generation without any dilution of the genetic fidelity and also to produce ample quantity of quality planting materials to cater needs of the farmers, appropriate methods of propagation need to be adopted. Cardamom is generally propagated by seeds and suckers (vegetative/clonal propagation). However, being a cross pollinated crop, considerable variation is observed in the seedling progenies and the seedlings may not possess all the qualities of the mother plant. Hence, vegetative propagation is normally adopted for mass multiplication of elite clones and also to maintain the genetic purity.

Seed propagation

Different steps involved in raising nurseries using seed material are given below:

Primary nursery

Selection of nursery site:

 

Gentle sloppy area, preferably adjacent to a perennial water source is suitable for raising the nurseries. Initially, the selected area is prepared by removing all existing vegetation, stumps, roots, stones etc. In the cleared area, beds are prepared with one meter width, 20 cm height and desirable length, generally six meters. Jungle top soil is spread to a thickness of two to three cm on the beds.

Selection of seeds:

Seeds should be collected from vigorously growing high yielding plants with well formed compact panicles and well ripened capsules. The plants should be free from the infestation of pests and diseases. Number of flowering branches produced on the panicles, percentage of fruit set and number of seeds per capsule are given due consideration while selecting the mother plants for collection of seed material. Apart from these desirable attributes, the mother clump should also have more number of tillers (shoots) per plant. On an average, one kg fruits contain 900-1000 capsules and 10-15 seeds per capsule. On an average, one kg of seed capsules is required to produce 3000-5000 seedlings and half kg seed capsules are sufficient to produce seedlings for an area of one acre. Seeds are collected from fully ripened capsules, preferably from second or third round of harvest during September. The seeds are either washed in water and sown immediately or mixed with wood ash and dried for two to nine days before sowing. Immediate sowing of seeds produces good results and is also the widely accepted method. After harvesting, the extracted seeds are immersed in water to separate immature and degenerated seeds. The seeds are then thoroughly washed with water to remove mucilaginous coating covering the seeds. After draining out water, the seeds are mixed with wood ash and dried under shade.

The seeds which are sown immediately after harvest germinate early and uniformly. The seedlings will be ready for transplanting 10 months after sowing. The ideal sowing season is reported to be November - January for Kerala and Tamil Nadu and September for Karnataka.

Pre-sowing treatments of seeds:

Cardamom seeds posses a hard seed coat, which delays its germination. Studies have been undertaken to evaluate the effect of pre-sowing treatments to enhance germination percentage (Table 1).

Table 1.	Effect of acid treatment on seed germination of cardamom
Treatment	Mode	Duration	Germination percentage (increase or decrease over control)
Con. Nitric acid	Soaking	five minutes	nine per cent increase
Conc. Hydrochloric acid	Soaking	five minutes	Increased germination
25 per cent Nitric acid	Soaking	10 minutes	55 per cent increase (fresh seeds) 25 per cent increase (six to eight months old seeds)
25 per cent Acetic acid 25 per cent Hydrochloric acid 25 per cent Nitric acid	Soaking	10 minutes	90 per cent germination
Acetone	Soaking	10 minutes	Increased germination

 

Soaking cardamom seeds in dilute or concentrated acids for 5-10 minutes increases the germination percentage to a considerable extent. In addition, soaking seeds in solutions of gibberelic acid (GA₃) and ethrel enhances germination significantly.

Apart from other factors, ambient temperature plays a vital role in germination process. Prevalence of low temperature in the cardamom growing areas reduces germination as well as delays the process of germination. In general, cardamom seeds fail to germinate at temperatures lower than 15^oC and greater than 35^oC. The ambient temperature prevailing during the months of September to October favours germination of the seeds.

Sowing

Fig. 1 - Primary nursery in raised beds under protective overhead shade net

On the beds, the seeds are sown in lines usually not more than one cm deep. Rows are spread at 10 cm apart and seeds are sown one to two cm apart within a row. Deep sowing should be avoided for better and quicker germination. Seed rate of 30 to 50 grams may be adopted for 6x1 meters size bed. After sowing, the beds are covered with a thin layer of sand and then with mulch materials such as dried leaves/grass or paddy straw. Supporting twigs are laid across the bed to avoid contact of mulch materials with the soil. The beds are irrigated at regular intervals to maintain adequate moisture. Germination commences in about 20-25 days after sowing, which may continue for a month or two. The mulch materials are removed soon after the commencement of germination. The young seedlings are protected from exposure to direct sunlight and rain by providing overhead pandals (Fig. 1).

Mulching of beds

Mulching seedbeds with appropriate materials influence germination of the seeds. Paddy straw and dry leaves are considered as ideal mulch materials. Besides these materials, mulching with coconut coir dust, paddy straw or goose berry leaves is also reported to enhance the germination.

 Secondary nursery

Generally two methods viz., bed and poly bag are adopted to raise seedlings in secondary nurseries.

 Bed nursery:

The beds are prepared as described in primary nursery. A layer of cattle manure is spread over the bed and thoroughly mixed with soil. Seedlings of four to five leaf stages from the primary nursery beds are transplanted in the secondary nursery at a distance of 20 to 25cm. In Karnataka, where seeds are sown during August-September, transplanting is normally undertaken during November-January. While, in Kerala and Tamil Nadu, seedlings from primary beds are transplanted to secondary nursery beds at a spacing of 20 x 20 cm during June-July. It is observed that, rate of seedling mortality is higher when transplanted at second leaf stage. Nevertheless, the mortality can be minimized to a greater extent by transplanting at four-five leaf stage.

On an average, 120 gram nitrogen, 20 gram phosphorus and 300 gram potash, 50 gram magnesium and 75gram calcium are removed from a bed planted with seedlings. To promote uniform growth, 250 gram mixture made of nine parts of NPK 17:17:17 and eight parts of zinc sulphate dissolved in 10 liters of water may be sprayed once in 15-20 days, starting one month after transplanting. It is observed that application of 45 gram N, 30 gram P₂O₅ and 60 gram K₂O per bed of 2.5 x 1 meters size in three equal splits at an interval of 45 days results in better growth and higher number of tillers. First dose of fertilizer may be applied 30 days after transplanting in the secondary nursery. Earthing up operation should be carried out after each fertilizer application and hand weeding should be undertaken once in every 20-25 days.

It is recommended to shift the nursery site once in two to three years to prevent buildup of pests and diseases and also to reduce the damage caused by these agents.  However, in those areas where such practice is not possible due to non-availability of alternate sites, the proposed nursery area may be left fallow for a year after deep digging/ploughing. This practice would help in exposing soil-borne pests and survival structures of pathogens to sun, thus killing them and brings down the inoculum levels to a considerable extent. By meticulously adopting the recommended packages, the seedlings would be ready for transplanting in main field, 10 months after sowing.

 Poly bag nursery

 

Fig. 2 - Secondary nursery raised polybag under rainout shelter

Polythene bags of 20x20 cm size and 100 gauge thickness with three to four holes at the bottom are used to raise seedling in poly bag nurseries. The bags are filled with jungle top soil, cowdung and sand in the ratio 3:1:1. The bags are arranged in rows of convenient length and breadth for easy management. Seedlings at four to five leaf stages are transplanted into each bag (one seedling per bag) (Fig. 2). Providing adequate space between the bags facilitates better production of tillers. The advantages of raising seedlings in poly bags are:

·         Seedlings of uniform growth and tillers are produced.

·         Duration of the nursery can be reduced to five to six months as against 10 to 12 months in the secondary nursery. in

·         Better establishment and growth of seedlings in the main field.

Cardamom plants from secondary nursery or poly bags can be transplanted to the main field during last week of May after the receipt of pre-monsoon showers or during the first week of June after commencement of the south west monsoon.

Vegetative propagation

Suckers from elite clones with desirable features like high production potential and resistant to pests as well as diseases are used for establishing plantations. Plants raised from suckers starts bearing earlier than plants produced from seeds. The planting material should not be collected from areas endemic to diseases, especially the viral diseases.  

Rapid clonal propagation

High yielding varieties/selections are generally multiplied in isolated clonal nurseries       (Fig. 3). Disease free high yielding plants are selected and sub cloned for subsequent multiplication. High yielding plants free from pest and diseases, with desirable characters like bold capsules with green colour are to be selected from plantations and part of the clump has to be uprooted for clonal multiplication leaving the mother clump in its original place to induce subsequent sucker production for further use.

 

Fig. 3 - Clonal nursery

 

For rapid multiplication the following agro-techniques need to be followed:

·         The planting unit should consist of one grown up sucker (rhizome) and a young growing shoot.

·         Trenches with 45 cm width and depth and convenient length have to be opened and filled with jungle soil, compost and topsoil.

·         The rhizomes (planting unit) are planted at a spacing of 1.8 x 0.6 meters in trenches, thus accommodating 9259 plants per hectare of clonal nursery area.

·         Overhead protection by erecting pandals, regular irrigation (once in a week during November to May) and application of fertilizers @ 48:48:96 grams. NPK per plant in two splits need to be practiced.       

·         On an average 32 - 42 suckers will be produced after 12 months of planting one planting unit. Taking the barely minimum of 50 per cent of this suckers/clump, 16-21 planting units (one grown up sucker along with a growing young shoot i.e. sucker) from one mother-planting unit after 12 months are produced.

·         Drenching the trenches with cowdung slurry with two kg of nutrients mixture (19:19:19 NPK) mixed in 200 liters of water, further hastens production of suckers and enhances the growth.

·         In an area of one hectare clonal nursery, 1,48,144 to 1,94,439 planting units can be produced after 12 months of establishment.

Major pests and diseases in nursery and management

Major diseases observed in the nursery are leaf spots, damping off/seedling rots and leaf rots.

 

Primary nursery leaf spots

 Primary nursery leaf spot caused by, Phyllosticta elettariae is a destructive disease in nurseries. The disease makes its appearance during the months of February- April with the receipt of pre-monsoon showers. The disease initially manifests as small dull white round to oval spots, which later turn necrotic and leave a hole (shot hole) in the center of necrotic area. The spots may be surrounded by water soaked area. The disease is more severe in open nurseries exposed to direct sunlight. However, the seedlings develop tolerance as they attain maturity.

The disease can be contained by undertaking the following management measures:

·         Sowing of the seeds may be undertaken during August – September, to ensure sufficient growth of seedlings, so that they develop tolerance to the disease.

·         Provide adequate shade by providing overhead pandals with coir material/ mat/agro- shade nets/thatched coconut fronds.

·         Prophylactic spraying with fungicides such as mancozeb (0.2 per cent) may be given on the leaves. First spray is to be given during March-April, depending on the receipt of summer showers and subsequent sprays at fortnightly intervals. Two to three rounds of spraying may be given.

·         Clipping and destructing   severely affected leaves after spraying is to be done to arrest further spread to the remaining healthy leaves.

·         Avoid raising nursery continuously in the same site.

Secondary nursery leaf spot

In secondary nurseries, another type of leaf spot incited by Cercospora zingiberi is of common occurrence. The disease is characterized with the formation of yellowish to reddish brown coloured rectangular patches on the lamina, which run parallel to the veins. In the advanced stages, the lesions assumes muddy red colour.

Prophylactic spraying with mancozeb (0.2 per cent) on the foliage effectively prevents the establishment and subsequent spread of the disease.

Nursery leaf rot

Normally seedlings of three to four months old are more vulnerable to the disease. The disease, which is of limited occurrence in the nurseries, is caused by Fusarium sp. and Alternaria sp. The symptoms include, formation of water soaked lesions on the leaves, which later becomes necrotic patches leading to decay of affected areas. Usually the damage is more pronounced on the leaf tips and distal portions of the foliage. Under favourable conditions, rotting extends to petiole and leaf sheaths also.

Avoiding excessive watering in the nurseries prevents initiation and further proliferation of the disease. When the disease is noticed in the nurseries, spray the seedlings with carbendazim (0.2 per cent) twice at 15 days interval after destroying the affected plant parts.

Damping off or seedling rot

 The disease appears usually in the nurseries during rainy season and favoured by the availability of excess soil moisture due to inadequate drainage facilities. The disease is caused by soil-borne fungi such as Pythium vexans and Rhizoctonia solani. Fusarium oxysporum also causes similar seedling rot, resulting in the wilting and withering of entire seedlings. In the initial stages of disease development, the leaves turn pale and with yellowish tips. Gradually, the symptoms spread over the entire leaf lamina, extending to leaf sheath and results in wilting of seedlings. The collar portion decays and the entire seedlings collapse.  In mature seedlings, rotting extends from the collar region to the rhizomes, resulting in decay and ultimate death of the plant.  

·                     In primary nurseries, practice thin sowing to avoid overcrowding of the seedlings.

·                     Prevent water stagnation by providing adequate drainage facilities.

·                     Remove affected seedlings and maintain proper phyotsanitary measures in the nursery.

·                     When infection is noticed, drench the nursery beds with copper oxychloride (0.2 per      cent).

·                     Pre-sowing treatment of seeds with antagonistic biocontrol agents such as Trichoderma or Pseudomonas protect the seedlings in the early stages of growth. Application of Trichoderma at 100 grams per square meter of the bed also helps in reducing the disease spread.

Damping off

The disease is a major problem in the secondary nurseries. Seedlings which have attained maturity (six to eight months old) are more susceptible to the disease. The disease is caused by soil-borne fungi, Pythium vexans and Rhizoctonia solani. Another soil-dwelling pathogen, Fusarium sp. incites root rot in the secondary nurseries. The disease attains severity during the monsoon season, when the soil moisture level is excess due to inadequate drainage. The diseases initiates on the leaves as pale yellow discolouration and withering of seedlings. Rotting or decay starts at the collar region and it also spreads to the rhizome as well as roots. In severe cases, the collar region breaks off and the seedlings collapse.  

·                     Uproot and destroy all the affected seedlings in the nursery.

·                     Avoid use of excess water for irrigation.

·                     Remove mulch materials a soon as the disease is noticed from the nursery beds and rack the soil gently.

·                     Drench the nursery beds with copper oxychloride (0.2 per cent) at the rate three to five liters per square meter. Two to three rounds of drenching should be resorted at 15 days interval. 

Pest Management in nurseries

 In nursery stage seedlings are affected by cut worm, shoot borer, root grub, leaf thrips and root knot nematode. Root grubs and root not nematode pose more problem in two season nurseries. To manage whole pest complex the following measures are to be followed at various stages of nursery.

Cultural Practices

·         Raise nurseries away from main plantations to reduce possibilities of infestation and reinfestation from the nearby infested plantations.

·         Provide sufficient organic fertilizers to encourage better vegetative growth.

·         Shift nurseries repeatedly to overcome soil- borne pest problems like root knot nematodes and root grubs.

·         Catch and destroy the beetles of root grubs using insect nets especially in 2 season nurseries.

·         Collect the cut worms hiding in the mulch in the affected area and destroy.

Chemical control

 

Insecticides like quinalphos (0.05 per cent), fenthion (0.075 per cent) or dimethoate (0.05 per cent) may be used to tackle the pest problem. The sprays may be undertaken at monthly intervals starting from rapid tillering stage. In the old nursery sites, exposed sandy loam areas and two season nurseries root knot nematode assumes severe proportion. Apply one round of carbofuran or phorate at 30-40 g/m² in one season nursery at rapidly tillering stage and apply two rounds of granular insecticides to two season nurseries at three monthly intervals. Application of granular insecticides at three monthly intervals is highly essential to protect the underground and sub-aerial parts in clonal nurseries.