Introductiion
Scientific name Oryza sativa L.
Local Name Dhan, Chamal
Hindi Name Dhan, Chawal
Rice is one among the oldest cultivated crop as evident from Vedic literatures and Archeological excavation. It is being cultivated in India and China since thousands of years. About 90 % of world’s area under rice is in Asia and about 90 % of world’s rice is produced and consumed in Asia. Globally rice is grown in more than 150m ha area. India and Chine together hold about half the world’s rice area and more than 60 % people are rice eaters. Rice is the main staple food and the first cultivated crop in Asia long before the era of which we have the historical evidences (Parthasarathi, 1960 and Ghosh et al., 1960). No one really knows exactly where first seeds of rice originated.
Cultivation of rice in Tropical Asia probably began about 10,000 years ago (De Datta, 1981). In India, oldest specimen of rice was found in Hasthinapur (UP) in a carbonized form during excavation (1000-750 BC). India may have had the earliest date of cultivation as wild rice is found in abundant. Domestication process first took place in China and later transmitted to South East Asia. It is also believed that wild rice first cultivated in Bangladesh, Assam, Orissa or its surrounding areas. It is also cultivated in most countries of west and North Africa (Egypt), east and central Africa. Its cultivation further extended to south and Central American countries (Latin America), Australia, USA and Southern European countries like Spain, Italy, and France.
Rice is one among the staple food crop in Sikkim as inferred from the epithet “Denzong”-meaning “Valley of Rice”. Its antiquity is Sikkim is difficult to trace out but some experts consider the entire NE Region including Sikkim and adjoining area of China shall be the probable home of rice. A large number of landraces are cultivated in Sikkim in addition to introduced since 1970s.
Evolution
There are 20 valid species in Oryza, but only Oryza sativa and Oryza glaberrima are cultivated. O. sativa is cultivated in Asia while O. glaberrima is in Africa. Oryza sativa probably evolved from a wild rice, Oryza perennis. Oryza rufipogon is Asian perennial types and Oryza nivara is an annual type. The Oryza glaberrima might be evolved from Oryza breviligulata or Oryza barthii some where in Sudan or West Africa.
Area and distribution
Rice is one of the most important cereal crops of Sikkim grown in all places having warm and humid climate with shallow water. It is cultivated over an area of about 14.15 thousand hectare. The production of rice was 22.69 thousand tones in 2005- 06 and 21.45 thousand tones in 2006-07. This yield could be increased by and effective implementation of special food grain production programme (SFPP) and special rice development programme (SRPP). The distribution of rice in Sikkim is given below:
District wise Area of Rice Cultivation in Sikkim:
District Area in 000’ hectares Production in 000’ tones Yield / hectares in kg
North 0.85 0.85 1062.50
East 5.50 8.50 1546.55
South 2.30 3.75 1630.43
West 5.50 8.35 1518.18
State 14.15 21.45 1515.90
Source: Annual progress report 2006-07, Food Security and Agriculture Development Department, Govt of Sikkim.
Use and Importance:
Rice is the staple food for more than 65 % population globally. It has great importance in Indian culture and since birth to death its existence always prevails. The rice is consumed after cooking as Bhat, Palau, Briyani and so many others ways. In India, rice occupies the highest area, around 42 m ha and recorded the highest production of 91.8 m t, (Economic survey of India, 2006). It provides not only staple food grain but also generate additional employment throughout the world. The by-products are used for preparing various industrial products especially in textile industries as it contains good amount of starch. The straw of rice is used for packing. It is a good source of fodder and may be used as litter. Rice bran is a source of edible oil. The bran is also used in manufacturing cardboard.
Nutritive value:
Starch constitutes the bulk (75-76%)of the rice grain. The protein content of the rice is lower than that of wheat but is of superior quality and utilize better by the body than wheat protein. The composition of rice kernel is given below:
Composition of rice grain:
Sl. No Nutrient Element Course Rice Raw Hand pounded Rice Raw Milled Rice
1 Moisture (%) 12.0 13.3 13.7
2 Protein (%) 7.5 7.5 6.8
3 Fat (%) 1.9 1 0.5
4 Ash (%) 1.2 0.9 0.6
5 Total Carbohydrates (%) 77.4 76.7 78.2
6 Fiber (%) 0.9 0.6 0.2
7 Calcium (mg/100g) 32.0 10 10
8 Phosphorus(mg/100g) 221.0 190 160
9 Iron (mg/100g) 1.6 3.3 3.1
10 Sodium (mg/100g) 9.0 - -
11 Potassium (mg/100g) 214.0 - -
12 Thiamin(mg/100g) 0.34 - -
13 Riboflavin (mg/100g) 0.05 - -
14 Niacin (mg/100g) 4.7 - -
Factors affecting nutritive value
The major factors that affect the nutritive value of rice are discussed below:
Milling
Milling is the process in which the husk and part of pericarp are. During milling process aleurone layer and embryo are also removed. The loss of nutrient is directly proportional to polishing. Hand pounding remove little amount of vitamin B1 while by machine milling the loss is 2/3 and by parboiling it is 1/3 of the total B1 content of rice. Regular consumption of completely polished rice will lead to thiamin deficiency/beriberi. Parboiled rice is more nutritive than raw milled rice because the nutrient loss while washing is less in parboiled rice. The cooked rice greatly swells and is dry and fluffy but not pasty. This quality depend on the age, parboiling, volume of water loosed during cooking, method of cooking i.e. water or steam cooking etc.
Storage Condition:
Heat, moisture, insect and mould cause hydrolytic and oxidative deterioration of the fat and reduction in the thiamin content. Moisture content in grain 9% or below does not allow fat rancidity. But at above 15%, the grains are liable for insect and mould attack which impairs the quality. However rice storage at 9% or below requires moisture proof container and stores because of higher atmospheric humidity. This increase cost of storage and become practically impossible. Therefore, for satisfactory storage of rice the moisture content must be at or below 12%.
Processing and Hulling
Hand pounding in village is still a very common practice. The rice obtained from hand pounding is found to be more nutritious compared to milled rice. There are two types of power mills i.e. huller type and sheller-cum-polisher type. The later type is more harmful from nutritious point of view as there is a greater loss of quality constituents when rice is processed by this type of huller.
Genetic Factors
The nutritional status of rice does not vary much from variety to variety but at the times the rice of different species and genus differ in their nutritional status.
Cultural Factors
Cultural factors especially fertilizer and water management affect grain filling and in turn affect the grading.
Genetic classification
Genus Oryza has about 23 species out of which only two are commercially cultivated. The rice grown in Asia is classified into three sub species namely, Indica, Japonica and Javanica. The variety javanica is cultivated only in Indonesia and is characterized by low tillering, broad and stiff leaves, stiff straw, long hairs on lemma and palea. They are long duration varieties. The variety indica is grown in tropics which are late in maturity, photosensitive having tall weak and thin culms with long, broad, profuse tillering, drooping, pale green leaves and large lax panicles. These plants are susceptible to lodging. They are mostly awnless, with thin and short hairs on lemma. Therefore, if there is rain at maturity the grain may germinate on the panicle.
The variety japonica is grown in temperate zones which are early in maturity, photosensitive having thin, short and sturdy culms. The leaves are bold, narrow, erect, somewhat thickened and dark green in colour. The leaves are photosynthetically very active even when the grains reach to maturity. These plants are very responsive to nitrogen fertilizer with no lodging tendency; therefore if there is rain at maturity the grain may germinate on the panicle.
Crop improvement work in Sikkim
The State Department of Agriculture has been introducing HYV of rice into Sikkim since 1976, a year after the state was annexed to India. During 1976-’77 about 60 varieties were introduced in the state along with a large collection of local varieties. Varieties like Pusa -33 , Ngoba, K-33-1, DR- 92, Chaunery, CB- 988, JS-52-102, JBS Mut- 508-270, RPA-5929,OR-1, OR-2, IET- 1444, Giza-14, JS-1620, CR-126-42-1, CR-126-53-5,CR-126-27-53,IET-2914,Kalinga-I and Kalinga-II were tested at Pakyong, Mangan, Gyalshing, Daramdin and Mazitar for their adaptation and yeld..
Initially PUSA 33 was recommended but it was drawn at later due to its susceptibility to blast. Then varieties like IET- 1444, Giza- 14, CR-126 were also recommended. GIZA-14 were recommended.
During 1980s, VLK 39 was recommended and it occupied the highest area. the varieties recommended by the ICAR at present are:
Scented rice : Geetanjali, Pusa Sugandha
Non aromatic : PD 10, VL Dhan 61, Satyaranjan, RCPL-1-87-8
In spite of tremendous efforts by the State Govt. in introducing HYV, the local cultivar Attey is still popular and occupy 40-50% of the rice acreage. The reasons shall be:
Wider adaptability across altitude,
Less sensitivity to photoperiod,
Moderate grain yield with good quality.
Assured yield in low and medium fertile soil, and
Good growing quality.
Other popular local varieties are Krishnabhog, Bhuiphool, Taprey, Dutkati, Champasarey, Godula Phudungey, Kanchi Attey, Nunia, Bhagery Thulasi, Chemtey, Taichung, etc.
The ICAR Research Complex for NEH Region, Sikkim Centre has initiated a location specific rice breeding programme for Sikkim in 2006-’07. The objective of the work was to improve the local rice Attey for
Semi-dwarf nature,
Reduce the duration to 10-15 days, and
Improve the yield.
The various rice development programmes undergoing in Sikkim under micromanagement which are given below:
Integrated Cereal Development Programme (ICDP)
It is a centrally sponsored scheme in which the following different programmes has been proposed to be taken up for coarse cereals
Distribution of Certified Seeds
Certified seeds of paddy, wheat and millet are distributed to the farmers at the rate of Rs 1800 per unit as per the guidelines of the Govt of India.
Encouraging Varietal Replacement
Under this component as per the guidelines of the Govt of India, farmers are given a subsidy of Rs 200 per quintal for adopting new varieties in place of old and traditional varieties for better production. This programme will be implemented in all the four districts of Sikkim during Kharif and Rabi season.
Full Pack Demonstration
Under this programme demonstration are conducted in paddy during season and in wheat during kharif season by using new and improved technology. The rate per hectare is Rs 2500 per hectare.
Adaptation
Rice has wide adaptability to environment and soil conditions. Geographically rice is grown up to 400 South and 50O North of the equator with varying temperature and duration of day length. The average yield per unit area is generally increases as the countries are situated further away from the equator due to higher photosynthetic efficiency. Accordingly, in Japan, Italy and Spain situated at 30O latitude, the yield varies from 4480 to 5136 kg per hectare while India, China and Egypt lying between 21° to 30° latitude, have an average yield of 1344 to 2464 kg per hectare. The countries nearer to the equator show an average yield of 560 to 1120 kg per hectare.
The higher yield in temperate latitude is not all due to the use of fertilizers alone or improved varieties but to a great extent climate is an important factor. The analysis of climatic factors appears to indicate that the greater yield is obtained in warm temperate region.
In India, rice is found to be grown at an altitude below sea level (Kuttanad area of Kerala), at or near sea level in most areas, at 2000 m in Kashmir, 600-1700m in Sikkim, and 2621 m in Jumla valley in Nepal. It is even grown 3000 m altitude in Himalayas (Grist, 1975).
Botanical description:
Rice belongs to Poaceae family which is annual grass. It is a self pollinated crop. It is a short day plant. Rice is a semi-aquatic plant and consists of arenchymatic tissues. The presence of arenchymatic cell on leaf, culm and roots diffuses oxygen from aerial parts downward to roots.
Root system:
The root system is fibrous, which consists of rootlets and root hairs. Soon after sowing rice seed gives out seminal roots from radical. These are of short lived. The real functional roots are secondary adventitious that are produced from the lower nodes of the culm.
a) Primary & Secondary Leaf b) Mesocotyl and Adventitious roots
Shoot system:
The rice stem known as culm is hollow, round, jointed and is made up of a series of nodes and internodes that are in alternate orders. The basal node on the main culm bears a leaf and bud, which may grow into a shoot or tiller. Primary tillers grow out of the main culm. The primary tillers give out secondary tillers and the secondary tillers branch into tertiary tillers. Tillering continues in rice up to vegetative phase. Some tillers die during the reproductive phase due to competition for water and nutrients. Panicles bearing tillers are known as fertile or productive tillers.
Leaf: Each nodes of the culm bears a flat leaf which is borne at an angle of every node. Each leaf consists following parts:
Leaf sheath: It originates from the node of culm and many a times encloses it and sometimes even the next upper node and a part of the leaf sheath of the upper leaf.
Leaf blade: It is the upper expanded part of leaf and begins at node, where it is jointed with leaf sheath. At the joint there is a thick collar.
Auricles: These are hairy appendages at the base of the leaf blade.
Ligules: It is a thin papery structure just above the auricles. Different parts of leaf are of importance in identifying the varieties.
Flag leaf: It is the uppermost leaf just bellow the panicle. It is generally shorter in length and remains erect at an angle. The number of leaves on the stem goes on reducing from main culm to primary tillers and from primary to secondary and then to tertiary tillers.
Note: The auricles and ligules is a distinguishing character of rice to differentiate from Echinocloa sp. (a most common weed of rice crop).
Panicle: The inflorescence of rice plant is borne on terminal shoot and is known as panicle. It is a determinate type and droops at maturity. Panicle bears the spikelets.
Spikelet: A spikelet is the floral unit and consists of two sterile lemmas called glumes, a lemma, a palea, anthers and styles.
Lemma: It is a 5 nerved hardened bract with a filiform extension known as awn. Rice varieties may or may not have an awn.
Palea: It is a three nerved bracts slightly narrower and endorsed within lemma.
Flower: It consists of 6 stamens with two –celled anthers and a pistle with one ovary and two stigmas. The pistil consist one ovule.
Grain: Rice grain is the ripened ovary with lemma and palea firmly adhered to it. The lemma and palea with other smaller components from the hull and are removed while shelling the paddy. The rice fruit is a caryopsis in which single seed is fused with the wall of the ovary (pericarp). The seed consists of endosperm and an embryo. The embryo is very small and is found on the ventral side of the caryopsis. It contains plumule (embryonic leaves) and radicle (root primordia). On submergence in water or on sowing the radicle grows as root and plumule grows as shoot.
The rice shows considerable variability in grain-size, shape, colour of hull and the kernel. The kernel size may vary from short bold or short slender to long bold or long slender. Rice is grouped into 5 classes on the basis of kernel length, breadth and length/ breadth ratio. The various group of rice can be differentiated as follows:
SL No Group Specific Feature
1. Long slender Length of kernel is excess of 6mm, length breadth ratio 3 and greater than 3
2. Short slender Length of kernel less than 6mm, length breadth ratio 3 and greater than 3
3. Medium slender Length of kernel is less than 6mm, length breadth ratio 2.5 to 3 or length less than 4.5mm and length breadth ratio between 2and 2.5.
4. Long bold Length is excess of 6mm, length breadth ratio lower than 2.5.
5. Short bold Length less than 6mm, length breadth ratio 2.5
The rice is normally white but red and purple rice are also grown in Sikkim. The red and purple rice is available only in local varieties. The red rice cultivar is Bacchi and Purple rice cultivar is Kalo dhan. The variations of colour are due to either anthocynin or non anthocynin content in rice. Variability is also considerable in other morphological character such as root system, plant height, tillering ability, leaf attributes such as photosynthetic ability, degree of sensitivity to day length and temperature.
Growth and development phase
Physiologically the life cycle of rice is divided into three phase which are discussed below:
Vegetative phase: It contains four stages i.e.
a) Seedling Stage
The seeds sprout into young seedlings having seminal and adventitious shoot and green leaves. These seedlings depend upon carbohydrate reserve of endosperm up to 15 days or until first two leaves have come out. The phase ends after fifth leaves have developed and during this period the seedlings exhaust almost entire endosperm.
b) Transplanting Stage
The stage covers the period from uprooting, transplanting of seedling till full recovery following transplanting. The secondary adventitious roots develop within four to ten days after transplanting and they start absorbing nutrients from the soil and sustain the growth. The root injury due to uprooting of seedlings can be reduced if they are uprooted carefully in presence of water. In case of direct seeded rice there is no recovery phase and the vegetative growth phase is correspondingly reduced by four to ten days.
c) Tillering Stage:
The period is of ten days after seedling establishment to maximum tillering stage which comes between 35 to 42 days after transplanting. Usually plants stop producing tillers after tertiary tillers have been produced. The tiller number decline after the plant has reached the maximum tillering stage.
d) Vegetative Lag Phase
This is the period between maximum tillering and panicle initiation in which some of the tillers die because of completion. This phase is absent in early maturing varieties but it occurs in long durations ones. Lag is a sort of rest period. The vegetative lag phase is also known as photoperiod sensitive phase. In a typical photosensitive variety, this period may extend even up to a month or two. This is the end of basic vegetative phase.
Reproductive Phase: : It consists of four stages.
Panicle Initiation Stage:
This is the beginning of the reproductive phase which succeeds the maximum tillering stage in long duration varieties but in early maturing varieties, it may precedes or even overlap the maximum tillering stage. This stage occurs approximately between 21 to 25 days before heading but flowering primordium can be recognized only a week after initiation stage has occurred.
Internodes Elongation and Booting Stage
After panicle initiation stage the internal auxin concentration in the plants accelerates the elongation of the internodes. This elongation takes place soon after panicle initiation stage. In early maturing varieties the elongation of upper internodes may begin much earlier than the panicle initiation stage. This shows the beginning of the booting stage when the developing panicle bulge in the leaf sheath.
Heading Stage
The emergence of panicle tip or heading takes place after booting stage is over. This comes about 15 days after the booting in all rice varieties.
Flowering Stage:
Flowering occurs about 20 to 25 days after booting. It continues successively until all the spikelets in the panicle bloom. This is followed by pollination and fertilization.
Ripening Phase:
The rice ripening is completed between 25 to 35 days after the crop has passed through the following stage
Milky Stage
Between 7 to 12 days after anthesis of water content of the grain turn milky inconsistency and the stage is said to be milky stage.
Dough Stage
The milky grain turns into soft dough stage and later turn into hard dough stage. The period required from milky to dough stage is about 2 to 3 weeks.
Maturity Stage
This is the stage at which the grains turn hard clear and free from greenish tint.