120
T. Das and A. K. Das
22 agrobiodiversity hotspots in India the northeastern India forms 4 agrobiodiversity
hotspots.
Since the agrobiodiversity in South-East Asia is mainly maintained by rural communities in traditional farming systems- homegardens, shifting cultivation and rice
fields, the majority of the agrobiodiversity analysis in the tropics have been focused
on important traditional farming systems—Homegardens (Fernandes and Nair 1986),
shifting cultivation (Ramakrishnan 1992) and Rice ecosystems (Dennis 1987). In the
present discussion however homegardens and rice fields were considered as the components of agrobiodiversity analysis. Agrobiodiversity maintenance by rural people
is not done with a view to conservation but because it is related to their very survival.
3 Agrobiodiversity Management in the Traditional Rice
Fields
Paddy rice (Oryza sativa L.) is the main crop in the northeastern states. Household
food and nutritional security of northeastern states of India predominantly depends
on rice. The northeastern region is considered to be one of the hot pockets of rice
genetic resources in the world and a potential rice-growing region with extremely
diverse rice growing conditions as compared to other parts of the country. Being the
secondary centre of origin of rice, the northeastern region is rich in diverse germplasm
that shows the distinctness amongst the germplasm which have been collected so
far. The widely diverse agro-climatic conditions along with other physiographic
conditions have led to immense variability among rice cultivars in the northeastern
region (Ngachan et al. 2011). Germplasm survey and collection made so far by the
National Bureau of Plant Genetic Resources (NBPGR) from major rice ecologies
indicated that about 2000 local landraces are available and it forms about 60% of all
rice sown on a small scale by the marginal farmers. The causes of exhibiting wide
diversity in rice landraces in the northeastern region may be attributed to the heavy
natural selection pressures of diseases and pests, introductions over time and space
from adjoining countries, introgression from the wild and weedy relatives, tribal
preferences and environmental stresses. Due to a wide range of climatic, edaphic
and physiographic conditions the requirement of varieties is diverse. The ecological
conditions are ranging from deepwater to high-altitude situation (Hore 2005). Thus,
it can be classified into six major classes (Borthakur 1992). These are (i) Autumn
Rice (Ahu); (ii) Kharif or Winter Rice (Sali); (iii) Spring or Summer Rice (Boro);
(iv) Shallow water (1–2 m) Rice (Asra); (v) Deep-water (2–5 m) Rice (Baon) and (vi)
Hill Rice. Such traditional farming systems are important in situ conservation sites of
crop diversity. Farmers in such traditional agricultural systems have been known to
retain “folk-varieties” (Brush 1995) also known as “landraces” which can be defined
as “geographically or ecologically distinctive population (of plants and animals)
which are conspicuously diverse in their genetic composition” (Brown 1978). Thus
such traditional agricultural systems serve to maintain the landraces (Bellon et al.
T. Das and A. K. Das
22 agrobiodiversity hotspots in India the northeastern India forms 4 agrobiodiversity
hotspots.
Since the agrobiodiversity in South-East Asia is mainly maintained by rural communities in traditional farming systems- homegardens, shifting cultivation and rice
fields, the majority of the agrobiodiversity analysis in the tropics have been focused
on important traditional farming systems—Homegardens (Fernandes and Nair 1986),
shifting cultivation (Ramakrishnan 1992) and Rice ecosystems (Dennis 1987). In the
present discussion however homegardens and rice fields were considered as the components of agrobiodiversity analysis. Agrobiodiversity maintenance by rural people
is not done with a view to conservation but because it is related to their very survival.
3 Agrobiodiversity Management in the Traditional Rice
Fields
Paddy rice (Oryza sativa L.) is the main crop in the northeastern states. Household
food and nutritional security of northeastern states of India predominantly depends
on rice. The northeastern region is considered to be one of the hot pockets of rice
genetic resources in the world and a potential rice-growing region with extremely
diverse rice growing conditions as compared to other parts of the country. Being the
secondary centre of origin of rice, the northeastern region is rich in diverse germplasm
that shows the distinctness amongst the germplasm which have been collected so
far. The widely diverse agro-climatic conditions along with other physiographic
conditions have led to immense variability among rice cultivars in the northeastern
region (Ngachan et al. 2011). Germplasm survey and collection made so far by the
National Bureau of Plant Genetic Resources (NBPGR) from major rice ecologies
indicated that about 2000 local landraces are available and it forms about 60% of all
rice sown on a small scale by the marginal farmers. The causes of exhibiting wide
diversity in rice landraces in the northeastern region may be attributed to the heavy
natural selection pressures of diseases and pests, introductions over time and space
from adjoining countries, introgression from the wild and weedy relatives, tribal
preferences and environmental stresses. Due to a wide range of climatic, edaphic
and physiographic conditions the requirement of varieties is diverse. The ecological
conditions are ranging from deepwater to high-altitude situation (Hore 2005). Thus,
it can be classified into six major classes (Borthakur 1992). These are (i) Autumn
Rice (Ahu); (ii) Kharif or Winter Rice (Sali); (iii) Spring or Summer Rice (Boro);
(iv) Shallow water (1–2 m) Rice (Asra); (v) Deep-water (2–5 m) Rice (Baon) and (vi)
Hill Rice. Such traditional farming systems are important in situ conservation sites of
crop diversity. Farmers in such traditional agricultural systems have been known to
retain “folk-varieties” (Brush 1995) also known as “landraces” which can be defined
as “geographically or ecologically distinctive population (of plants and animals)
which are conspicuously diverse in their genetic composition” (Brown 1978). Thus
such traditional agricultural systems serve to maintain the landraces (Bellon et al.