This document discusses crop ideotypes, which are biological models for ideal crop varieties suited to a particular environment. It provides examples of ideotypes for several crops, including rice, wheat, cotton, millets, and barley. The rice ideotype model includes traits like moderate tillering, heavy panicles, tall stature, erect leaves, and a high harvest index. The wheat ideotype is proposed to have a short strong stem, erect leaves, few small leaves, a large ear, andawns to contribute to photosynthesis. The cotton ideotype model incorporates traits such as short stature, compact growth, determinate flowering, short duration, and pest and disease resistances.

1. CROP IDIOTYPES
TAILORING A MAXIMALLY SUITABLE
CULTIVAR

2. WHAT IS A CROP IDIOTYPE
• The term ideotype was given by Donald (1968). He gave the
ideotype for wheat
• Thereafter different scientists gave different ideotypes for
different crops
• Ideotype is a ‘biological model expected to perform or behave
in a particular manner in a defined environment’
• An ideotype may be developed according to the suitability of
the need, e.g. ideotype for disease resistance
• However in general for increasing the yield the ideotype
consists of optimizing the physiological growth parameters

3. Rice ideotype (Jennings, 1964)
• Moderate tillering capacity (270–300 panicles m-2),
• Heavy (5 g panicle) and drooping panicles at maturity,
• Plant height of at least 100 cm (from soil surface to unbent plant tip)
and panicle height of 60 cm (from soil surface to the top of panicles
with panicles in natural position) at maturity,
• Attributes of the top three leaves:
a. Flag-leaf length of 50 cm and 55 cm for the 2nd and 3rd leaves.
b. All three leaves are above panicle height.
c. Should remain erect until maturity.
d. Leaf angles of the flag, 2nd, and 3rd leaves are around 58, 108,
and 208°, respectively.
e. Narrow and V-shape leaves (2 cm leaf width when flattened).
f. Thick leaves (specific leaf weight of top three leaves = 55 g m-2).
g. Leaf area index (LAI) of top three leaves is about 6.0.
• Harvest index of about 0.55.

4. Wheat Ideotype (Donald 1968)
• A short strong stem. It imparts lodging resistance and reduces
the losses due to lodging.
• Erect leaves. Such leaves provide better arrangement for
proper light distribution resulting in high photosynthesis or
CO2 fixation.
• Few small leaves. Leaves are the important sites of
photosynthesis, respiration, and transpiration. Few and small
reduce water loss due to transpiration.
• Larger ear. It will produce more grains per ear.
• A presence of owns. Awns contribute towards photosynthesis.
• Presence of awns. Awns contribute towards photosynthesis.
• A single culm.

5. Cotton Ideotype (Singh and
Narayana 1993)
• Short stature (90-120 cm) ,
• Compact and sympodial plant habit making pyramidal shape,
• Determinate the fruiting habit with unimodal distribution of
bolling,
• Short duration (150-165 days),
• Responsive to high fertilizer dose,
• High degree of inter plant competitive ability,
• High degree of resistance to insect pests and diseases, and
• High physiological efficiency

6. Millets (Swaminathan 1972)
• Superior population performance,
• High productivity per day,
• High photosynthetic ability,
• Low photo respiration,
• Photo and thermo sensitivity,
• High response to nutrients,
• High productivity per unit of water,
• Multiple resistances to insect and diseases,
• Better protein quantity and quality
• Crop canopies that can retain and fix a maximum of CO2, and
• Suitability to mechanization.

7. Barley Ideotype (Rasmusson
1987)
• Larger thermal time from anthesis to physiological maturity
• Smaller thermal time before anthesis
• Smaller photoperiod and larger vernalization sensitivity
• Larger SLA and maximum LAI
• Larger Amaxor RUE
• Higher water use efficiency
• Larger grain number
• Larger HI