Plant Breeding Practices in Rice (Oryza sativa 2n=2x=24)

Plant Breeding Practices in Rice (Oryza sativa 2n=2x=24)

It is world’s most important crop after wheat and maize. It is a warm season crop grown extensively Korea, South eastern Asia account for 90 % of world rice production. In India, rice cultivated on large scale in Andhra Pradesh, Karnataka, Tamilnadu, Maharashtra, Assam, Oryza, Bengal, Bihar, U.P, M.P, Punjab and Haryana. The high yielding rice and wheat cultivars led to the birth of Green revolution.

Origin:

Oryza sativa originated from India and China. The greatest diversity is observed in Assam and Meghalaya area and southwest china. The several authors considered annual type was likely to be the progenitor. Cultivated spp2, and wild up -16.

Types:

1) India Type:

It is tropical type rice. It is extensively grown in India, Srilankha, Thailand, Malaysia and adjacent countries. These are tall plants, weak stem, photoperiod sensitivity, easy shattering, and broad droopy leaves and having grain dormancy.

2) Japonica Type:

These are temperate type extensively grown Yangtze river valley of china, Korea, and Japan, these are tolerant low temperature, have more leaves, few tillers, relatively resistant to shattering. The grains are short, broad low in amylase content. Rice becomes sticky on cooking.

3) Javanica Type:

These are intermediate type. These are cultivated in Indonesia, Phillippines , Taiwan and Japan. These are tall, thick stemmed, low to tillering and resistant to shattering. These varieties have broad stiff leaves, long awns and large bold grains.

Botany and Floral Biology:

Annual plant growing 60 to 150 cm, stem erect and cylindrical, soild nodes and hollow internodes, buds in axil of basal leaves give rise tillers, leaves are alternate and linear with parallel venation. Inflorescence is terminal panicle. Each spiklet is complete flower consist of outer two glumes boat shaped pelia and flattered lemma. Lemma and pela from husk and enclose a grain after fertilization.

Lemma and pelia enclose six stamens with slender filament and pistil. During early stage spiklets are white with green anthers and closed style. On maturity spiklets turn green and anther become yellow and style separate out from each other.

Flowering:

Rice is predominantly self pollinated crop but natural cross pollination take place up to 3% depending upon varieties, season and environmental conditions.

A blooming starts from tip of the panicle and proceeds downward and continues for 7 to 10 days. Most of the flower blooms with in 2 to 4 days from emergence of panicle. Flowers open during morning hours between 9 to 11 hours depending upon temperature (30 to 35 0C) and relative humidity ( 70 to 80 %).

The flowers remain open for 30 to 70 minutes and close after fertilization. Anthers dehisce and shed pollens just before the flower opens. Anthers and pollination take place simultaneously with the opening of flower.

Breeding Objectives:

1) High grain yield,
2) Non shattering habit,
3) Dwarf growth habit    
4) Wider adaptability
5) Synchronous tillering habit
6) Resistance to pest stem borer, midge, gallfly, etc.
7) Resistance to diseases
8) Early maturity
9) Resistance to high doses of fertilizers.
10) Grain quality, shape, and size, scent cooking and milling quality.

Emasculation:

It is done in the afternoon on preveious day or early in the morning on the day of pollination. The ear just emerged is selected and all spiklets already opened are clipped the spiklets which are likely to be opened are selected and six anthers from each spiklet is removed with needle and fine pointed forceps. The emasculated ear after examination with lens covered with perforated butter paper bag and labelled.

In mass emasculation method hot water having temperature 42 to 45 0C is carried in thermos flask in the field. The panicle of the proper stage is selected and inserted in the water for 2 to 3 minutes. The flask is unopened spiklets are clipped off.

Pollination:

It is done on next day morning. Matured anthers are collected from protected male parent in petri dish and dusted on the stigma of emasculated flower with brush and forceps and covered with butter paper bag to protect natural cross pollination.

Breeding Methods:

1) Introduction:

The seeds of released varieties in other countries are imported tested, evaluatd along with native varieties and if found superior , released for commercial cultivation. The variety Taichung native -1 (T-N-1 ) is the cross between
Dee-geo-woo-gene and Tsai Taichung is imported in 1960 for seed multiplication and distribution. Another variety IR-8, a tall and heavy tillering disease resistant developed from cross between Indica variety of Indonesia and dee-geo-gene imported in 1966.

2) Selection:

From land races out standing lines are selected and evaluated along with existing varieties and superior types are multiplied and released for commercial cultivation. The varieties developed by selection are Terna, Tuljapur-1, Ambika, Ambemohor pussa -33, etc.     

3) Pedigree Method:

It is the most common method of rice breeding. Crosses made to combine genes for desirable characteristics from two or more parents. Seeds of such crosses sown in pedigree nursery. Selections are made in F3 and onwards generations and superior progenies are carried forward and tested with existing check variety and if found superior released for commercial cultivation.

Bulk selection method is not followed in rice but single seed decent known as rapid generation advance is in use in IARI. Two to three generation in green house can be grown in a year.

4) Breeding for Disease and Pest Resistance:

 
Basmati Rice:

Basmati rice is a good source of foreign exchange earning for us. Traditional basmati rice varieties are tall prone to logging later and poor in yield. The incorporation of Basmati quality in high yielding semi dwarf backgrounds has been quite challenging ne. it is likely due to and complicated inheritance of quality components. Basmati quality is characterized by pleasant aroma, linear kernel elongation on cooking and soft texture.

Basmati Varieties:

Basmati – 370, Pusa 150, Pusa-523, Kasturi , DRR-Hyderabd, Pusa basmati.

Hybrid Rice:

CGMS lines are used in production of hybrid seed china is the only country in the world where farmers use hybrid rice technology on commercial scale. To produce hybrid seed male and female parents are planted alternatively in specific row rations. The most common rations are 1:6 to 1:8 the technology includes.

1. Planting across the wind direction to increase pollen dispersal on female plants.
2. Clipping of flag leaves of male sterile and restores lines at booting to facilitate pollen circulation.
3. Applying 20-30 ppm GA3 to male sterile and Restore lines at heading to promote emergence of panicle from sheath.
4. Supplying pollination by rope pulling during flowering. Chinese now getting hybrid seed yield more than 1000 kg/ha. The seed rate used is only 25% of the conventional varieties and the country has sufficient manpower for hybrid seed production so the hybrid rice is popular in china. The countries where manpower is expensive and higher seedling rate is necessary. This production technique is not economically acceptable. Generally the hybrids must yield 25% higher than the commercial varieties to become technology commercially reliable. E.g. Karats Hy.1-(Saihydri).

National Programme/ Institutes:

1. All India co-ordinate Rice Improvement Project (AICRIP) Established in 1965. with headquarter. Hyderabad in the farm Project Directorate- Multidisciplinary team approach having countrywide testing with Agriculture Universities and ICAR stations.

2. Central Rice Research Institution Cattak (CRRI) Established 1946 controlled by ICAR, basic and applied research in different fields of Rice.

International Institutes:

Institutes Rice Research Institute (IRRI) – Established 1960, – Govt of philliplines at manila.

Coordinating Centres:

A.R.S Vadgan maval, Dist Pune
A.R.S Karjat Dist Thane
A.R.S Isatburi. Dist Nasik