Features of Crop Ideotype
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 is required for irrigated cultivation or rainfed cultivation. Ideal plant 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 bean. The important features of Ideotype for some crops are briefly described below:
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 reduce water loss due to transpiration.
4. Larger ear. It will produce more grains per ear.
5. A presence of owns. Awns contribute towards photosynthesis.
6. Presence of awns. Awns contribute towards photosynthesis.
7. A single culm.
Thus, Donald included only morphological traits in the Ideotype. However, all the traits ere based on physiological consideration. Finally (1968) doubted the utility of single clum in wheat Ideotype. Considered tillering as important features of wheat flag type a wheat plant with moderately short but broad flag leaf, long flag leaf sheath, short ear extrusion with long ear, and moderately high tillering capacity should give yield per plant (Hsu and Watson, 1917). Asana proposed wheat Ideotype for rainfed cultivation. Recent workers included both morphological and physiological characters in wheat Ideotype.
The concept of plant type was introduced in rice breeding by Jennings in 1964, through the term Ideotype was coined by Donald in 1968. He suggested that the rice an ideal or model plant type consists of 1) Semi dwarf stature. 2) High tillering capacity, and 3) Short, erect, thick and highly angled leaves (Jennings, 1964, Beachell and Jennings, 1965). Jennings also included morphological traits in his model. Now emphasis is also given to physiological traits in the development of rice Ideotype.
In 1975, Mock and Pearce proposed ideal plant type of maize. In Maize , higher yields were obtained from the plants consisting of 1) Low tillers, 2) Large cobs, and 3) Angled leaves for good light interception. Planting of such type at closer spacings resulted in higher yields.
Rasmusson (1987) reviewed the work on Ideotype breeding and also suggested ideal plant type of six rowed barley. He proposed that in barley, higher yield can be obtained from a combination of 1) Short stature, 2) Long awns, 3) High harvest index, and 4) High biomass. Kernel weight and kernel number were found rewarding in increasing yield.
In cotton, genotypes with zero branch, short stature, compact plant, small leaves and fewer sympodia were considered to enhance yield levels. Singh et al. (1974) proposed and ideal plant type of uplant cotton growing belt. The proposed Ideotype includes
1) Short stature (90-120 cm) ,
2) Compact and sympodial plant habit making pyramidal shape,
3) Determinate the fruiting habit with unimodal distribution of bolling,
4) Short duration (150-165 days),
5) Responsive to high fertilizer dose,
6) High degree of inter plant competitive ability,
7) High degree of resistance to insect pests and diseases, and
8) High physiological efficiency, Singh and Narayana (1993) proposed an Ideotype of above two species for rainfed conditions. The main features of proposed Ideotype include, earliness ( 150-165 days), fewer small and thick leaves, compact and short stature , interminate habit, spares hairness, medium to big boll size, synchronous bolling , high response to nutrients, and resistance to insect and diseases.
Sorghum and Pearl millet:
Improvement in plant type has been achieved in Sorghum and Pearl millet through the use of dwarfing genes. In these crop dwarf F1 hybrids have been developed which have made combine harvesting possible.
Genetic improvements have been achieved thorough modification of plant type in several crop species. New Ideotype have been proposed for majority of crop plants. Swaminathan (1972) has listed several desirable attributes of crop Ideotype with special reference to multiple cropping in the tropics and sub tropics. These features include:
1) Superior population performance,
2) High productivity per day,
3) High photosynthetic ability,
4) Low photo respiration,
5) Photo and thermo sensitivity,
6) High response to nutrients,
7) High productivity per unit of water,
8) Multiple resistances to insect and diseases,
9) Better protein quantity and quality
10) Crop canopies that can retain and fix a maximum of CO2, and
11) Suitability to mechanization.