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What is ideotype?
Ideotype is biological model which is expected to perform or behave in predictable manner within a defined environment .
More Specially, crop ideotype is a plant model which is expected to yield greater quantity of grains fibre , oil or other useful products when developed as a cultivar.
This concept proposed by Donald in 1968.
Plant Ideotype
According to Donald, an ideotype is a biological model expected to perform in a specific environment. A crop ideotype is a plant model designed to yield more or higher-quality products when developed as a cultivar.
Features of Crop Ideotype
Crop ideotypes consist of several morphological and physiological traits aimed at enhancing yield, either in irrigated or rainfed conditions. Ideal plant types have been discussed in various crops like wheat, rice, maize, barley, cotton, and beans. Key features for some crops include:
Wheat
The term "ideotype" was coined by Donald in 1968 while working on wheat. He proposed the following main features:
- Short, strong stem: Provides lodging resistance and reduces losses due to lodging.
- Erect leaves: Improves light distribution for higher photosynthesis.
- Few small leaves: Reduces water loss due to transpiration.
- Larger ear: Produces more grains per ear.
- Presence of awns: Contributes to photosynthesis.
- Single culm: Initially included by Donald but later reconsidered due to the importance of tillering.
Donald included only morphological traits in the wheat ideotype, but later works also incorporated physiological traits.
Rice
The concept of plant type was introduced in rice breeding by Jennings in 1964. The ideal rice plant type includes:
- Semi-dwarf stature
- High tillering capacity
- Short, erect, thick, and highly angled leaves
Initially focused on morphological traits, the development of rice ideotype now also emphasizes physiological traits.
Maize
In 1975, Mock and Pearce proposed an ideal plant type for maize, focusing on:
- Low tillers
- Large cobs
- Angled leaves for optimal light interception
Planting these at closer spacings resulted in higher yields.
Barley
Rasmusson (1987) suggested that in six-rowed barley, higher yields could be achieved with:
- Short stature
- Long awns
- High harvest index
- High biomass
Kernel weight and number also contributed to increased yield.
Cotton
For cotton, ideal plant types include:
- Short stature (90-120 cm)
- Compact and sympodial plant habit with a pyramidal shape
- Determinate fruiting habit with unimodal bolling distribution
- Short duration (150-165 days)
- Responsive to high fertilizer doses
- High inter-plant competitive ability
- Resistance to insect pests and diseases
- High physiological efficiency
These traits enhance yield, especially in rainfed conditions.
Sorghum and Pearl Millet
Improvements in plant types for sorghum and pearl millet have been achieved using dwarfing genes, leading to dwarf F1 hybrids suitable for mechanized harvesting.
General Crop Ideotype Features
Swaminathan (1972) listed desirable attributes for crop ideotypes, especially for multiple cropping in the tropics and subtropics:
- Superior population performance
- High productivity per day
- High photosynthetic ability
- Low photorespiration
- Photo and thermo sensitivity
- High response to nutrients
- High productivity per unit of water
- Multiple resistances to insects and diseases
- Better protein quantity and quality
- Crop canopies that maximize CO2 fixation
- Suitability to mechanization