The term ideotype was introduced by Colin Malcolm Donald (1968) He defined it as a biological model, which is expected to perform or behave in a predictable manner within a defined environment. In ideotype breeding, goals are specified for each trait, resulting in a description of a model plant for the traits of interest (Rasmusson, 1987).

1. Topic:
Ideotype concept in Rice
PRESENTED BY :
M.V. Sai Krishna Rohit
Ph.D (Ag.) I Year I
Sem.
Deptt. Of Genetics and
Plant Breeding
COLLEGE OF AGRICULTURE
INDIRA GANDHI KRISHI VISWAVIDHYALAYA, RAIPUR

2. Contents to be discussed
◦ What is an ideotype ?
◦ Historical aspects
◦ Types of Ideotypes
◦ Differences between Ideotype and Traditional plant breeding
◦ Steps to develop an ideotype
◦ Steps in Ideotype breeding
◦ Progress in Rice
◦ 1st generation NPT ‘s
◦ 2nd generation NPT ‘s
◦ Super Rice
◦ Lessons to the breeders when ideotype approach used in other crops
◦ Advantages of ideotype breeding
◦ Disadvantages of Ideotype breeding
◦ Case study

3. What is an ideotype ?
• The term ideotype was introduced by Colin Malcolm Donald
(1968)
• He defined it as a biological model, which is expected to
perform or behave in a predictable manner within a defined
environment
• In ideotype breeding, goals are specified for each trait, resulting
in a description of a model plant for the traits of interest
(Rasmusson, 1987).
C. M. Donald

4. Historical aspects
In 1914, Beaven had introduced the concept of coeffcient of efficiency
of grain production; in 1962, this was redesignated as harvest index (HI)
by Donald.
In 1962, Donald also argued for selection of specific characters like leaf
angle, etc. that influence photosynthetic capability of plants and drew
attention to the effects of interplant competition during selection
(carried out at low plant densities) in segregating generations. These
thoughts culminated in the introduction of ideotype concept by Donald
in 1968.
In 1976, Donald and Hamblin introduced the concepts of isolation,
competition and crop (or communal) ideotypes.

5. Types of
Ideotypes
Isolation
ideotype
Competition
ideotype
Crop
ideotype

6. Isolation
ideotype
It is the model plant type that
performs best when the plants
are space-planted.
In case of cereals, isolation
distance is free-tillering, leafy,
spreading plant that can explore
the environment as possible.
It is unlikely to perform well at
crop densities.

7. Competition
ideotype
This ideotype perform well in
genetically heterogeneous populations,
such as the segregation populations
from crosses.
In case of cereals, competition
ideotype is tall, leafy, free-tillering
plant that is able to shade its less
aggressive neighbors and, thereby gain
a large share of radiation, nutrients and
water.
In case of annual seed crops, such an
ideotype will include the following
features: annual habit, tallness, leafy
canopy, tillering or branching, seed
size, speed of germination and root
characters.

8. Crop ideotype
◦ 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 can 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.

9. Characters of Crop ideotype
It should be a weak competitor, i.e., individual plants of a crop ideotype will compete each other to a
minimum degree when grown as a crop. Therefore, such an ideotype may be expected to (1) perform
relatively poorly in isolation, and (2) to be a poor competitor with other genotypes
As a result, a successful crop ideotype achieves a high biological yield in a dense stand
virtue of having the morphology of a weak competitor, which also imparts on it a high
Harvest index.
◦ Such an ideotype will be the most effcient in utilizing its environmental resources. As a result, it will
make a minimum demand on the resources for producing each unit of dry matter.
◦ Each unit of dry matter will include such a number of flowers/ florets or other sinks that is able to accept
all the photosynthate either from its own green surface or from other parts of the plant.
◦ Ideotype is a moving goal. As it changes with alterations in the environment and in the wake of
information accumulated in various studies.
◦ The design of crop ideotypes is likely to involve concurrent modification Of the environment. This
would enable evaluation of the newly designed plant types in new environments, including components
like population density, planting arrangement and nutrient level. Because crop ideotype is sensitive to
cultural practices.

10. ◦ Features 1-5 concern biological yield (= net photosynthesis). The economic yield
is only a part
◦ of the biological yield. The ideotype, therefore, must include such morphological
and physiological characteristics that result in a high harvest index; this is a
critical aspect of plant design.
◦ A crop ideotype must be grown, as far as possible, in a weed-free situation in
view of it being a weak competitor.
◦ 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.

11. ◦ Donald (1968) had proposed several other ideotypes that include traits
concerned with specific features. For example, market ideotype includes
traits like seed colour, seed size, cooking and baking quality, etc. since
these traits determine market acceptability of the produce.
◦ Similarly, a Climatic ideotype includes traits important in climatic
adaptation, e.g., early maturity, thermoperiod-insensitivity, heat and cold
tolerance, drought tolerance, photoperiod-insensitivity, etc. Some other
ideotypes are edaphic ideotype (traits: salinity tolerance, mineral
toxicity/deficiency tolerance, etc.),
◦ Stress ideotype (traits: resistance to the concerned abiotic and biotic
stresses)
◦ Disease/pest ideotype (traits: resistance to the concerned diseases and
insect pests), etc.

12. Traditional Breeding Ideotype Breeding
The breeder usually has an idea, howsoever vague, of
the type of plant he wishes to develop, but he does
not describe it formally.
The breeder must define the ideotype to be developed
based trait analysis and other considerations
Selection uses yield per se as a criterion. Yield is not used as a basis of selection; selection is
based traits constituting the ideotype
Selection for individual traits (other than yield) is also
done for defect correction, but the goal for the traits
is not defined beforehand.
The breeding goal for each trait is defined beforehand
while defining the ideotype
It is usually based on the improved gene pool (of
primary gene pool) of a crop.
It will usually necessitate introgression of desirable
genes from unimproved gene pool (of primary gene
pool)

13. It does not encourage systematic thinking and
accumulation of information on how yield is
achieved in a crop
Its basic philosophy is to understand how yield is
achieved. The information generated from various
studies leads to the develop of models that are
further tested and refined
It does not deliberately generate genetic diversity that
may or may not be useful in the future
It generates genetic diversity deliberately to test various
models and to achieve the defined ideotypes. Some of
this variation also be useful in traditional breeding
Progress is relatively rapid, but may reach a plateau
after a period
Progress is rather slow due to its very nature, but it may
to break the plateau reached in traditional breeding
It constitutes the main activity and is likely to remain so It may be considered to augment traditional breeding
efforts not to replace it

14. Steps to develop an Ideotype
◦ Definition of Target area and environment
◦ Quality considerations 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 potential in the target environment. Often information will not be
sufficient for a proper assessment. Therefore, adequate information may have to be
developed from appropriate studies
◦ Simulation models have been used as aids to trait analysis, e.g., to assess the yield of
varying a character in a defined environment. Such models are on several assumptions;
therefore, they must be used with sufficient caution. This procedure, however, can not be
of practical value at present.
◦ The choice of characters to be included in a will also depend on certain considerations

15. Steps in ideotype breeding
Ideotype breeding may be viewed as consisting of the following four
steps:
◦ Development of a model plant type, i.e., ideotype
◦ Creation of adequate genetic diversity for the concerned traits,
◦ Selection of plants/lines with the desired phenotype,
◦ Evaluation of the phenotype in several genetic and agricultural
backgrounds.

16. ◦ The concept of plant type in Rice was first introduced by Matsushima
in 1957, and later by Jennings (1964).
◦ The Rice ideal or model plant type given by Jennings consists of
(1) Semi dwarf stature
(2) High tillering capacity
(3) Short, erect, thick and highly angled leaves (Jennings, 1964;
Beachell and Jennings, 1965).
Jennings (1964) also included morphological traits in his model. Now
emphasis is also given to physiological traits in the development of rice
ideotypes.
Ideotype in Rice

17. ◦ In 1969, Chandler proposed the ideotype of 'dwarf rice' as follows.
l. Shorter culm length (100 cm or less).
2. Greater culm diameter
3. Lower relative internode elongation
4. Short erect leaves of medium width.
5. High tillering capacity
6. More panicles/m2
7. High (55% or more) harvest index.

18. ◦ The proposed modifications to the plant architecture included a reduction in tiller number, an increase in the
number of grains per panicle and increased stem stiffness

19. Progress in Rice
◦ In the 1960s, scientists quickly realized that most tall traditional rice varieties lodged
easily when nitrogen fertilizer was applied, which was the major limitation to grain yield
(Khush et al., 2001).
◦ The sd-1 gene was first identified in the Chinese variety Dee-geo-woo-gen (DGWG),
and was crossed in the early 1960s with Peta (tall) to develop the semidwarf cultivar IR8
◦ Reducing plant height is accomplished through incorporation of recessive gene sd1 for
short stature.
◦ First semi-dwarf or short statured variety IR8 developed at International Rice Research
Institute (IRRI) also had a combination of other desirable traits such as profuse tillering,
dark green and erect leaves for good canopy architecture and sturdy stems for lodging
resistance.
◦ It is responsive to nitrogenous fertilizer and can produce higher biomass of about 20 tons
per hectare. It has HI of 0.45. Its yield potential is 8–9 tons per hectare (Chandler, 1969).
◦ even though IR8 had a major drawback regarding its poor grain quality, it still became
the symbol of the green revolution in rice.

20. Janoria (1985) has suggested an alternative ideotype of rice that has been developed to
maximize utilization of the available horizontal space (the arable earth surface) and the
resources from the vertical space. The characteristic features of the novel ideotype include
◦ Taller stature;
◦ Fewer, tough, non-lodging and all effective culms;
◦ Upright growth habit;
◦ Fewer, well spaced, thick, large but stiff leaves able to maintain erect position;
◦ Heavy panicles with limited intra plant variation for panicle yield,
◦ High light transmission ratio and a deep, extensive root system.
Janoria emphasized that the semi tall plant type would require closer spacing.

21. ◦Ideotype
model given by
Janoria (1985)

22. ◦ To increase the yield potential of semi-dwarf rices, further IRRI
scientists proposed a new plant type (NPT; IRRI 1989) with
following characteristics:
◦ Plant height of 90 to 100 cm
◦ Reduced tillering ( 3-4 when direct seeded and 9–10 for
transplanted conditions)
◦ No unproductive tillers
◦ 200–250 grains per panicle
◦ Dark green and erect leaves
◦ Vigorous and deep root system
◦ Growth duration of 110–130 days
◦ Multiple disease and insect resistance
◦ Higher harvest index
◦ Thick and sturdy stem (Peng et al., 1994)

23. ◦ Through simulation models Dingkuhn et al., 1991 predicted that a 25% increase
in yield potential was possible by modification of the following traits of the
current plant type:
(1)Enhanced leaf growth combined with reduced tillering during early vegetative
growth;
(2) Reduced leaf growth and greater foliar N concentration
(3) A steeper slope of the N concentration gradient in the leaf canopy
(4) Increased carbohydrate storage capacity in stems,
(5) A greater reproductive sink capacity and an extended grain-filling period.

24. 1st Generation NPT ‘s (New plant types)
◦ Breeding work began in 1989 when about 2000 entries from the IRRI germplasm bank
were grown during the dry and wet seasons to identify donors for the desired traits
(Khush, 1995).
◦ Donors for low-tillering , large panicles, thick stems, vigorous root system and short
stature were identified in the ‘‘bulu’’ or javanica germplasm mainly from Indonesia.
This germplasm is now referred to as tropical japonica.
◦ Many bulu varieties were crossed with a semi-dwarf japonica breeding line Sheng
Nung

25. Contd.,
◦ More than 2000 crosses were made, and over 1,00,000 pedigree lines were
evaluated. Breeding lines with desirable ideotype traits were selected, and more
than 500 so-called NPT-TJ lines were produced.
◦ They were grown in a replicated observational trial for the first time in late 1993.
◦ It was observed that reduced tillering contributed to lower biomass. Some of
these lines showed good performance in temperate areas where japonica grain
quality is preferred. Three of these lines were released as varieties in Yunnan
province of China as Diancho 1, 2 and 3 (Khush, 1995).

26. ◦ In 1995, development of second-generation NPT lines began by crossing first-
generation tropical japonica NPT lines with elite indica parents.
◦ To improve the acceptability of these NPT-TJ lines for tropical conditions and to
improve their yield potential, they were crossed with elite indica lines and
varieties with disease and insect resistance and good grain quality. Four NPT-IJ
lines have been released as varieties in the Philippines and Indonesia. Numerous
NPT-IJ lines were distributed to all the breeding programmes throughout the
world through INGER nurseries(International Network for Genetic Evaluation
of Rice).
2nd Generation NPT ‘s (New plant types)

27. Contd.,
◦ Many have been used in hybridization programmes and have contributed to
widening of gene pools. For example, IR 66154-521-2-2 a NPT-TJ line has been
used widely in hybridization programmes in China and Vietnam.
◦ One second-generation NPT line, IR77186-122-2-2-3, was released under the
name of NSIC Rc158 in the Philippines in 2007.

28. In order to achieve a 10% increase in the yield potential of irrigated lowland rice in
the dry season of the tropics with second generation NPT lines, Peng and Khush,
(2003) summarized the following traits:
1. 330 panicles per m2,
2. 150 spikelets per panicle,
3. 80% grain filling,
4. 25 mg grain weight (oven-dry),
5. 22 t ha-1 aboveground total biomass (at 14% moisture content),
6. 50% harvest index.

29. Super Rice
China’s rice breeding activities for increasing yield potential using an ideotype approach
were not organized at the national level until 1996. Stimulated by IRRI’s NPT breeding
program, China established a nationwide mega project on the development of ‘‘super’’ rice
in 1996 (Cheng et al., 1998, 2007), with the following objectives:
1. To develop ‘‘super’’ rice varieties with a maximum yield of 9– 10.5 t ha-1 by 2000, 12 t
ha-1 by 2005, and 13.5 t ha-1 by 2015 measured from a large planting area of at least 6.7
ha-1.
2. To develop ‘‘super’’ rice varieties with yield potential of 12 t ha-1 by 2000, 13.5t ha-1
by 2005, and 15 t ha-1 by 2015. These yields will be achieved in experimental and
demonstration plots.
3. To raise the national average rice yield to 6.9 t ha-1 by 2010 and to 7.5 t ha-1 by 2030 by
developing ‘‘super’’ rice varieties.

30. ◦ Chinese Scientists under the leadership of Professor Yuan Long Peng initiated super hybrid rice
breeding programme for improving the level of heterosis. Like the NPT breeding programme,
they proposed the following ideotype (Yuan, 2001).
1. Moderate tillering capacity (270–300 panicles m2)
2. Heavy (5 g/panicle) and drooping panicles at maturity
3. Plant height slightly taller (about 100 cm)
4. Top three leaves with following characteristics:
◦ Flag leaf length about 50 and 55 cm for the second and third leaves.
◦ All three leaves should be above panicle height
◦ Should remain erect until maturity.
◦ Leaf angles of flag, 2nd and 3rd leaves should be 58, 108 and 208°, respectively.
◦ Should be narrow and V shaped (2 cm leaf width when flattened)
◦ Should be thick and dark green
◦ Leaf area index (LAI) of top three leaves should be about 6.0.
5. Harvest Index of 0.55

31. Improvement in Super hybrid rice over
NPT
The improvement in plant type design of ‘‘super’’ hybrid rice over
IRRI’s original NPT design was
◦ The great emphasis on the top three leaves. Length, angle, shape,
thickness, and area of the top three leaves were quantitatively defined
in detail in the ‘‘super’’ hybrid rice design.
◦ Other improvement is the inter sub-specific heterosis.

32. ◦ Yang et al. (2006) compared grain yield and yield attributes among three high-yielding
groups of rice viz. indica inbred, indica/indica F1 hybrid, and NPT lines to identify
the morpho-physiological traits responsible for the yield difference among the three
groups grown in the dry (DS) and wet seasons (WS) of 2003 and 2004.
◦ On average, hybrids produced 11 to 14% more grain than indica inbreds and NPTs in the
dry season.
◦ In the wet season, the difference in grain yield was relatively small among the three
groups.
◦ They concluded that high grain yield of hybrids in the dry season was the result of a high
number of spikelets per square meter due to a large number of spikelets per panicle
and high harvest index rather than biomass production.
◦ The NPTs did not show a yield advantage over the indica inbreds and had significantly
lower yield than the hybrids, mainly because of fewer spikelets per panicle and per
square meter.
◦ It was suggested that increased harvest index and spikelet production efficiency with
more spikelets per panicle should be emphasized for improving the grain yield of NPTs.

33. Lessons to the breeders when Ideotype approach used in other
crops:
◦ The genetic background of an inferior donor parent for desirable
traits may have a negative effect on the performance of progenies
(Marshall, 1991).
◦ The targeted morphological traits should be related to the
physiological processes that determine the ultimate performance of
the plant.
◦ Extremes in plant type traits should be avoided (Belford and Sedgley,
1991). For example, the initial design of IRRI’s NPT aimed at 200–
250 grains per panicle, which resulted in poor grain filling. We have
modified this to 150 spikelets per panicle.

34. Contd.,
◦ Interrelationships among the traits and compensation among plant
parts should be considered (Marshall, 1991).
◦ The ideotype breeding approach is not an alternative but a
supplement to empirical breeding approaches because selection for
yield is still needed in ideotype breeding.

35. Advantages of Ideotype Breeding
◦ In the past, yield has been enhanced by selecting for individual traits associated
with yield, reduced plant height in wheat and reduced plant height coupled with
erect leaf in rice are well known cases.
◦ Grain yield is the direct or indirect product of individual plant traits. Substantial
diversity is therefore, generated for such traits that are considered to contribute to
yield.
◦ The primary gene pool of a crop may be divided into improved and unimproved
gene pool. The unimproved gene pool is occasional used for the transfer of
specific traits. In ideotype breeding, genes for specific traits would be intro-
gressed from the unimproved into the improved gene pool in order to generate the
desired level of variability for the trait.

36. Contd.,
◦ It encourages development and evaluation of hypotheses regarding how yield is
achieved. These objectives are tested and revised based on the results. This is
expected to lead to a more effective breeding strategy.
◦ Even when conventional breeding efforts include specific
morphological/physiological traits in their selection criteria, the breeder does not,
ordinarily, specify the goals to be achieved. In such a situation, exploitation of a
trait over time is likely to be haphazard, i.e., in opposing directions, and
inefficient. Therefore, it is important that the goals for specific traits are
established with a view to maximize their effects on yield.

37. Disadvantages of Ideotype Breeding
◦ It has not been possible to identify individual traits that enhance yield universally
or in a relatively limited genetic and environmental situations.
◦ Use of physiological and biochemical traits in the ideotype concept is
cumbersome, costly and time taking, while their usefulness is not well
established.
◦ Progress in individual trait breeding would largely depend on the amount of
information available on how yield is achieved.
◦ New methodologies, including techniques and instruments need to be developed
so that breeders can include a larger number of traits, including root traits, in their
selection programmes.

38. Contd.,
◦ Transfer of traits from unimproved gene pool would often be necessary.
This would involve considerable breeding effort. Ultimately, a germplasm
bank for ideotype traits could be established to promote ideotype breeding
effort.
◦ Ideotype breeding should be considered as a method to augment
conventional breeding; it can not be regarded either as an equal or as a
substitute of the latter
◦ Development of a single plant type, i.e., the ideotype, may narrow the
genetic diversity within the crop leading to increased genetic vulnerability.
One approach would be to produce several elite but diverse
populations/lines, each containing the desired traits, in different genetic and
cytoplasmic backgrounds (Mock and Pearce, 1975).

39. Case
study

40. GIST of the case
◦ Submergence tolerance and jasmine-like cooking quality are desirable for rice varieties grown in
rainfed and irrigated lowland ecosystems in the Mekong region of Southeast Asia.
◦ Hybridization between varieties IR57514 and Kao Dawk Mali 105 (KDML105) was initiated with the
goal of producing an ideotype that combines submergence tolerance and jasmine-like cooking quality
by SSD.
◦ 2 categories of ideotypes were isolated from the RIL ‘s produced from the segregating populations
where
Ideotype 1 (ID 1) carrying the Sub1IR, badh2KD, WxKD and SSIIaKD alleles - 66 RILs
Ideotype 2 (ID 2) carrying the Sub1IR, badh2KD, WxKD and SSIIaIR alleles and consisting of 31 RILs.
◦ All the ID1 lines exhibited submergence tolerance and jasmine-like cooking quality and displayed a
low amylose content, a fragrance and a high alkali spreading value
◦ ID2s showed the same characteristics as ID1, except for a low alkali spreading value, which was
inherited from IR57514.
◦ In this study, they identified the superior genotype of Hom Cholasit, an elite line derived from the ID2
group, with desirable traits of submergence tolerance, a low amylose content, fragrance, lodging
resistance (short plant height), a non photoperiod sensitivity and a high yield (7.2 t/ha in the farmer’s
field)

41. Thank You