Breeding or Achievement of Rice (Paddy)

                                                             Breeding or Achievement of Rice (Paddy)

 

Rice is one of the principal food crops being cultivated throughout the world. It has been grown in humid tropics and subtropics for its nutritive grains, Rice grain is rich in starch with a low content of protein (7%). It is the staple food of nearly half of the world's human population. There are two species of cultivated rice Oryza sativa and Oryza glaberrima. Of these two, O.sativa is an Asian species whereas O.glaberrima is an African species. The genus Oryza be longs to the family Poaceae (Graminiaceae). Most of the rice varieties are diploid with chromosome number 24, but haploids (n=12), tetraploids (4n=48) and triploids (3n-36) have also been bred in recent years.

In rice, crop improvement is aimed for improving grain qual ity, yield, disease resistance and pest resistance and for early maturation. The following methods have been employed in the breeding for improvement of rice varieties:

1. Pure-line selection

2. Hybridization

3. Mutation

4. Genetic engineering

1. Pure-line Selection:

In pure-line selection, seeds of a better individual are selected for several times till a superior variety is formed. Early workers performed pure-line selection to improve rice varieties from a mixed population of individuals. The improved rice variety ASDI was se lected from a single individual of Kar Samba - Red crop.

Some other rice varieties improved via pure-line selection are given below:

1. CO4 (Anaikomban)
2. CO10 (Kar)
3. CO5 (Chinnasamba)
4. CO17 (Vadasamba)
5. CO6 (Sadaisamba)
6. CO9 (Karsamba)
7. CO19 (Sirumani)

2. Hybridization:

The crossing of two genetically different parent plants to produce a new variety is called hybridization. Eminent plant breeders like Parnell, Ramiah, Parthasarathy, Hector and Graham took much efforts for the improvement of rice varieties through hybridization. GEB 24, CO 25, T 141 and Latisail are rice varieties released in India before 1950s.

 Indica-Japonica Hybridization Project:

This was an International Rice Hybridization project to cross Oryza sativa var. Indica and Oryza sativa var. Japonica. This project was conducted by the Central Rice Research Indica variety had enough hardiness and wide adaptability to grow in wide areas of India, but had poor fertilizer effectiveness and productivity. On the other hand. Japonica variety had high fertilizer effectiveness. high productivity and resistance to lodging and grain shattering. By the way of crossing, the genes of Japonica rice were incorporated into Indica rice, but no one improved variety was released as the result of the research. The ICAR then sponsored to CRRI to continue the project to achieve the goal of the project. The F1 and F2 individuals of Indica X Japonica cross exhibited 10-100% sterility. The fertile seeds were collected and subjected to pure-line selection to get improved varieties. Thus many ADT series of improved varieties were released in India. Of these, the most important one is ADT 27. ADT 27 was obtained by crossing Norin 8 (a Japonica rice) with GEB24 (an Indica rice), which are the races of O.sativa. GEB 24 was tall and matured in 160-170 days, whereas Norin 8 was dwarf and matured in 100 days. The hybrid ADT 27 was semi-dwarf and matured in 105 days. It responded well to high manuring and gave 5.2 tonnes/ha. The grain size is medium and cooking quality is well and good.

IRRI Projects:

The International Rice Research Institute (IRRI) was established at Los Banos in the campus of the University of Philip pines in 1962. Researchers underwent studies to detect the rea sons for low rice yield in tropical and sub-tropical countries. The tall varieties produced only 1.5-1.7 tonnes/ha. They found out the following as the major causes for low rice yield in tropics:

• Tall and weak straw
• Poor utilization of solar energy
• Cloudy weather
• Poor cultural management
• Excess of water during early stages
• Lack of adequate water supply during grain development.

As early as 1950s. a spontaneous dwarf mutant rice called Dee geo-woo-gen evolved in Taiwan. That mutant was characterized by-

• Dwarf plant habit (60 cms height)
• Stiff, erect leaves to absorb maximum light
• Insensitivity to light
• Lack of seed dormancy
• Good growth in all seasons.

Scientists at Taichung District Agricultural Improvement Station (Taiwan), crossed Dee-geo-woo-gen with another Indica variety called Thai Yuan-Chung to create the first improved dwarf variety Taichung Native I (TNI). The TN I was susceptible to diseases and pests and hence it remained unexploited for cultivation.

At the first attempt, the IRRI collected about 10,000 varieties of rice from different countries and established a World Germplasm Bank of rice. Similar Germplasm banks were also established at CRRI (Cuttack) and Plant Introduction Division (USDA). In the second attempt, the IRRI performed massive hybridization works with different dwarf and tall varieties of rice to produce improved hybrids. The IRRI has released IR series of rice varieties.

Peta is a tall variety of rice growing in Philippines. It was crossed with Dee-geo-woo-gen by H.M. Beachell working at the IRRI. As a result of his research, the IRRI released the famous variety IR8 in November 1966. Later, IRRI has released IR 5, IR 20, IR 22, IR 24, IR 36, IR 50, IR 56, etc. for cultivation. These improved varieties give 5-8 tonnes/ha.

 

All India Co-ordinated Rice Improvement Project (AICRIP):

The AICRIP was conducted at State Agricultural Colleges and their substations in various districts in 1965.That project was financed by the ICAR, New Delhi. It was started to produce disease and pest resistant dwarf varieties of rice for farmer's benefits. Many improved rice varieties have been released in India through the AICRIP. Examples -

Pvr I is derived from a cross between Mtu I being grown in Andhra Pradesh and SR 26 being cultivated in Orissa. It is best to grow in alkaline areas of Tamilnadu under pH 8.7. It gives 3-3.5 tonnes/ha and the grains are finer than SR 26.

CO 31 is the product of hybridization between GEB 24 ( strain of Oryza sativa) and Oryza perennis. Being a drought resistant variety, it gives medium fine grains with white colour and good cooking quality in 145 days.

CO 41 is derived from a cross between CU 2410 and IR22. It is a medium tall variety with fine grains. Maturity duration is 100-105 days and the yield is 5 tonnes/ha.

TKM 9 is a derivative of TKM7 X IR 8 cross. It is a semi dwarf variety with bold grains. Maturity duration is 100-105 days and the yield is 5 tonnes/ha.

 

1. Ponni (TG 65 X ME 80)
2. Kannagi (IR 8 X TKM6)
3. Bhavani (Peta X Bpi 76)
4. CO 37 (TN1 X CO 29)
5. ADT 31 (IR8 X CUE 340)
6. ADT 36 (Triveni X IR 20)
7. IET 1444 (TN 1 X CO 29)
8. PYI (Ponni X IR 8)
9. PY 2 (Kannagi X Cul. 12032)
10. C044 (ASD5 X IR 20)
11. Ponmani (Pankaj X Jaganath)
12. C043 (Dasal X IR 20)
13. Paiyur 1 (IR 1721-14 X IR 1330-33-2)
14. Jaya (TN1 XT 141)
15. Cauvery (TN1 X TKM 6)
16. Bala (TN1 X N 22)
17. Vijaya (T 90 X IR 8)
18. Ratna (TKM 6 X IR 8)

3. Mutation:

Mutations at gene level bring out some favourable variations leading to evolution of improved varieties. Basmathi (India) and Dee-geo-woo-gen (Taiwan) are examples of rice varieties arose through spontaneous mutation. Artificial mutation is also induced to breed improved varieties. In rice, mutation breeding is aimed for more tillering, resistance to lodging, high yield, altered grain colour, high response to manures and earliness in maturity. White Ponni is a mutant of Ponni. It is obtained by irradiating the grains of Ponni by y-rays. It is taller than Ponni with lodging habit. The grains are more slender than those in Ponni. The husk is straw coloured in white Ponni instead of brown in Ponni.. P500-28 is yet other mutant produced by y-ray irradiation of T-1145 variety. It is released by Bose Research Institute, Kolkutta. It is a high yielding variety giving 7 tonnes/ha.

4. Genetic Engineering:

Genetic manipulation of plants in such a way as to have a likely trait in the plants by introducing specific genes is known as genetic engineering. Many important genes have been transferred to rice plant to create new improved varieties. For instance, gene coding for viral coat protein of Rice stripe virus and viral sat of Rice tungro virus are transferred to rice plants to enable them to resist the virus attacks. Genes for ß-carotene synthesis are transferred to rice to create golden rice producing vitamin A.

                                                        Achievements through Hybridization

Hybridization plays an important role in the improvement of cereals, pulses, vegetables and fruit crops. India has produced thou sands of improved varieties through intervarietal hybridization Interspecific hybridization and intergeneric hybridization also do some beneficial roles in breeding for disease resistance, drought resistance and pest tolerance. The improved varieties show many desirable qualities expected by the farmers.

The improved varieties show the following unique features 

1. They give 10-45% more yield than unimproved varieties. 

2. They have good adaptability to wide range of local, edaphic and climatic conditions.

3. They are early maturing varieties.

4. They are resistant to diseases, pests, drought, flood, water logging, salinity and alkalinity.

5. They have yield response to higher doses of manures

6. They have good adaptability to cultural practices. 

7. They are good in taste and nutritive value.

The works of hybrid improvement have been performed in Ag ricultural Universities and Agricultural Research Institutes in India. The varieties thus evolved are released in India after the approval by the Central Variety Release Committee (CVRC) of the ICAR, New Delhi. The following are common improved variet ies of crops evolved via hybridization in India for cultivation:

Rice:

• NLR 9676 (Bulk 9 x Millikinnings)

• CO 41 (CU 2410 x IR 22)

• TKM 9 (TKM 7 x IR 8)

• IR 20 (IR 262 x TKM 6)

• Ponni (TG 65 x ME 80)

• Kannagi (IR 8 x TKM 6) 

• Bhavani (Peta x BPI 76)

• CO 37 (TN 1 x CO 29) 

• ADT 31 (IR 8 x CUI 340)

• ADT 36 (Triveni x IR 20) 

• IET 1444 (TN 1 x CO 29)

• PY 1 (Ponni x IR 8)

• PY 2 (Kannagi x CUI 12032)

• IR 50 (IR 2153-14 x IR 28 x IR

• Ponmani (Pankaj x Jaganath) 

• CO 44 (ASD5 x IR 20)

• MDU 2 (CO 25 X IR 8)

• TPS 1 (IR 8x Kattisamba)

• PKM 1 (CO 25 x ADT 31)

• ADT 27 (Norin 8 x GEB 24)