Ideotype concept on cereal crops

1. Submitted By :
DHANENDRA DHANUKA

2.  An Ideotype may be described as a conceptual model plant, which has all such
characteristics that are considered ideal for the given environment. In other words, such a
model plant is optimally equipped for the maximum yield under the defined environment. In
1976, Donald and Hamblin proposed the concepts of isolation, competition and crop or
communal ideotypes, with special reference to cereals .
 Crop ideotype refers to model plants or ideal plant type for a specific environment. In
broad sense an ideotype is a biological model which is expected to perform or behave
in a predictable manner within a defined environment. More specifically, crop ideotype is
a plant model which is expected to yield greater quantity of grains, fibre, oil or other useful
product when developed as a cultivar. The term ideotype was first proposed by Donald in
1968 working on wheat.

3.  It is the model plant type that performs best when the plants are space-planted. In
case of cereals, isolation ideotype is lax, free-tillering, Leafy, spreading plant that is
able to explore the environment as fully as possible. It is unlikely to perform well at
crop densities.
2. COMPETITION IDEOTYPE
 This Ideotype perform well in genetically heterogeneous populations, such as the
segregating generation from crosses. In case of Cereals, competition ideotype is tall , free-
tillering plant that is able to shade its less aggressive neighbours and thereby gain a larger
share of radiation, nutrients and water . In case of annual seed crops, such an ideotype will
include the following features: annual habit, leafy canopy, tillering or branching, seed size ,
speed of germination and root characters.

4. 3. Ideotype concepts
 The crop ideotype performs best at commercial crop densities because it is a poor competitor. It
performs well when it is surrounded by plants of the same form. But it performs less well when it is
surrounded by plants of other forms, and also in isolation. In case of cereals , a crop ideotype or
communal ideotype is erect, sparsely-tillered plant, with small erect leaves and is able to survive in the
highly competitive situation of being surrounded by plants of the same form. The concept of ‘ week
competitor’ is the central theme of this ideotype

5.  The first step consists of definition of the target area and the target environment. Donald
(1968) suggested that the basic ideotype should be first developed for the optimum,
nonlimiting environment. Subsequently, the effect of any curtailment of resources, e.g.,
decreased nutrient or water supply, can be examined in terms of progressive modification of
the basic ideotype.
 Quality consideration would determine the size , shape, etc. of the economic parts .
 Current agronomic practices would determine the limits to plant stature, branching and other
agronomic features.
 The above considerations should allow one to draw a list of the desired traits in the model
plant type. It should now be assessed as to what changes in particular traits would improve
yield potential in the target environment. Therefore, adequate information may have to be
developed .
 The choice of characters to be included in an ideotype will also depend on certain other
considerations.
DEVELOPMENT OF
IDEOTYPES

6. Features of crop ideotypes
The crop ideotype consists of several morphological and physiological traits which
contribute for enhanced yield or higher yield than currently prevalent crop cultivars. The
morphological and physiological features of crop ideotype differ from crop to crop and
sometimes within the crop also depending upon whether the ideotype is required for irrigated
cultivation or rainfed cultivation. Ideal plant types or model plants have been discussed in
several crops like wheat, rice, maize, barley, cotton and beans.
 It should be a week competitor.
 Such an ideotype will be the most efficient in utilizing its environmental resources. As a result, it will make
a minimum demand on the resources fro producing each unit of dry matter.
 Each unit of the dry matter produced will include such a number of flowers/florets or other sinks that is
able to accept all photosynthate either from its own green surface or from other parts of the plant .
 Ideotype is a moving goal. It changes with alteration in the environment and in the wake of information
accumulated from various studies.
 A crop ideotype implies a plant form, which may be overlooked in the process of visual selection during
the segregating generations. Therefore, a conscious and planned selection has to be done for the features
of crop ideotypes.

7. The term ideotype was coined by Donald in 1968 working on wheat. He proposed
ideotype of wheat with following main features:
1. A short strong stem. It imparts lodging resistance and reduces the losses due to lodging.
2. Erect leaves. Such leaves provide better arrangement for proper light distribution
resulting in high photosynthesis or CO2 fixation.
3. Few small leaves. Leaves are the important sites of photosynthesis, respiration and transpiration. Few
and small leaves reduce water loss due to transpiration.
4. Larger ear. It will produce more grains per ear.
5. An erect ear. It will get light from all sides resulting in proper grain development.
6. Presence of awns. Awns contribute towards photosynthesis.
7. A single culm.
 WHEAT

8.  MAIZE
IN 1975, Mock and Pearce proposed ideal plant type of maize.
1. Stiff-vertically-oriented leaves above the ear.
2. Maximum photosynthetic efficiency.
3. Efficient translocation of photysynthate into grain.
4. Short interval between pollen shed and silk emergence.
5. Small tassel size.
6. Photoperiod insensitivity
7. Cold tolerance
8. Long Grain -filling period

9.  BARLEY
Rasmusson (1987) reviewed the work on ideotype breeding and also suggested ideal plant type of six
rowed barley.
1. Short stature
2. Long awns
3. High harvest index
4. High biomass.
Kernel weight and kernel number were found rewarding in increasing yield.