Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
Based on temperature requirements, chrysanthemum cultivars are classified into 3 groups:
A. Thermo zero cultivars: They flower at any temperature 10-27ºC; consistency is at 16 ºC.
B. Thermo positive cultivars: They require a minimum of 16ºC for bud initiation and at 27ºC
there will be rapid initiation.
C. Thermo negative cultivars: Bud initiation occurs at low or high temperature between 10ºC
and 27ºC but continuous high temperature delay bud development.
Propagation
1. Terminal cutting: This is commercial method. In this method, 5-7 cm length cutting are made
by shearing basal leaves and cutting half of the open leaves. Cuttings are dipped in 2500 ppm IBA
or eradex/keradex. Cuttings are put in the plug trays or sand bed in semi shed condition and
watered immediately and thereafter regularly. Use of mist chamber for rooting of cutting result in
higher percentage of rooting. Terminal cuttings are taken in June and transplanted after rooting at
the end of July.
2. Suckers: After flowering, the stem is cut back just above the ground to induce the formation of
suckers. Suckers are separated from the mother plant carefully. Plant in the sand bed or can be
directly transplanted in field.
Disadvantages: a. Transmission of parental diseases
b. Lack of uniformity
c. Poor flower quality
d. Less number of plants produced
3. Micropropagation: Multiply at a fast rate by culturing shoot spex in vitro from somatic callus,
peduncle leaves and other floral parts. Here 2-3 cm long terminal cutting with at least one node
are taken, washed and further trimmed after sterlizing in 70% ethanol followed 4% sodium
hypochloride, place them on nutrient agar substrate in test tubes kept in 23.2 0 C for 16 hr/day
under 4000 lux. Rooted mini cuttings are potted in peat and kept at 20-25 0 C for 10-15 days before
planting out.
Cultivars: The choice of cultivars varies with purpose of the plant to be grown. This varies with the
uses as given below:
Pot mum: Dwarf and compactness, profuse branching, uniform spreading of branching,
simultaneous blooming habit, attractive color and good colour retention, quality and health of
leaves.
Cut flower purpose: Attractive colour, long erect stem, uniform bloom opening, tough florets, long
vase life and healthy leaves.
Garland type: Yellow or white colour of blooms, diameter of bloom about 5 cm. Fluffy blooms,
disc absent or invisible, good quality recovery from pressure, high yielding (15 tons/ha or 150
g/plant). Good colour retention. Long blooming season. Profuse branching and sweet scented
blooms.
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