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VARYING IMPACT OF BREEDING ACTIVITIES IN DIFFERENT ECOSYSTEMS AND IN DIFFERENT REGIONS

The number of varieties released is an indicator of the impact of breeding activities in different ecosystems and regions; another partial indicator is the increase in production and productivity over a period of time (Table 12). In Asia, the countries with most of the area (>50%) under rice in the irrigated ecosystem are: Pakistan (100%), Republic of Korea (99%), Japan (99%), China (92.7%), Sri Lanka (77%), Indonesia (72%), Democratic People’s Republic of Korea (66%), Philippines (61%) and Viet Nam (53%). Overall, 56 percent of the total rice area in Asia is under irrigated ecosystems.

TABLE 12
Area and productivity (by ecosystem) in different countries of Asia

Country

Total area

Irrigated

Rainfed lowland

Flood prone

Upland

Area (%)

Productivity (t/ha)

Area (%)

Productivity (t/ha)

Area (%)

Productivity (t/ha)

Area (%)

Productivity (t/ha)

Asia

131.91

56.1

4.9

26.0

2.3

8.7

1.5

9.2

1.1

Bangladesh

10.24

24.2

2.6

43.1

4.3

24.1

2.5

8.6

1.6

Bhutan

0.03

50.0

-

3.8

-

42.3

-

3.8

-

China

33.01

92.7

5.9

5.6

3.0

0.0

0.0

1.7

2.5

India

42.64

43.8

3.6

30.1

2.4

11.4

1.5

14.6

0.8

Indonesia

10.28

72.0

6.3

7.8

3.0

6.4

1.7

13.8

1.6

Japan

2.05

99.0

5.9

0.0

0.0

0.0

0.0

1.0

2.5

Korea (Rep.)

1.21

99.0

6.5

0.0

3.0

0.0

0.0

1.0

2.5

Korea (DPR)

0.68

66.7

9.1

20.0

4.6

0.0

0.0

13.3

3.8

Myanmar

4.57

18.0

4.2

52.8

3.0

14.3

1.5

14.9

1.0

Nepal

1.41

23.0

4.2

60.6

2.2

13.3

0.8

3.1

1.0

Pakistan

2.01

100.0

2.4

0.0

0.0

0.0

0.0

0.0

0.0

Philippines

3.42

61.0

3.4

32.0

2.0

2.0

1.3

5.0

1.0

Sri Lanka

0.79

77.1

3.7

14.9

2.5

1.1

1.0

6.9

1.0

Thailand

9.27

6.3

4.0

72.2

1.8

10.4

2.0

11.1

1.5

Viet Nam

6.30

53.0

4.3

23.4

2.0

16.3

1.5

7.3

1.0

Thailand, Nepal and Myanmar are the countries in Asia with greatest area in rainfed shallow lowlands. The shallow lowland ecosystem occupies 72, 62 and 52 percent of the total rice area in these countries. Major flood-prone areas occur in Bhutan (42%), Bangladesh (24%), Viet Nam (16%), Myanmar (14%) and Nepal (13%). The greatest upland areas are found in Myanmar (14.9%), India (14.6%), Indonesia (13.8%), Democratic People’s Republic of Korea (13.5%) and Thailand (11%).

The production potential and major constraints of the various ecosystems in West Africa are given in Table 13. The greatest rice area in West Africa is under humid or sub-humid uplands (40%), followed by rainfed lowlands (38%). Very little area (around 5% each) is under irrigated, mangrove swamp and deep-water ecosystems. Maximum actual productivity and potential productivity are achieved in irrigated ecosystems, followed by shallow lowland ecosystems.

TABLE 13
Production potential and major constraints to rice production across the major rice-producing ecosystems in West Africa

Rice ecosystem

Regional share
(% area)

Yield (t/ha)

Major constraints

Current

Potential

Humid/subhumid zone Upland

40

1

1.5-4.5

Drought, weeds, blast, N deficiency, acidity

Rainfed lowland

38

1.4

2.5-5.0

Weeds, water control, N deficiency, iron toxicity, blast

Irrigated

5

2.8

5.0-7.0

N deficiency, iron toxicity, blast, stem borer, rice yellow mottle virus, gall midge

Sahel (irrigated)

7

3.5

5.0-8.0

Poor water control, extreme temperature, salinity, N deficiency

Mangrove swamp

4

2

2.5-6.0

Sulphate acidity, salinity, crabs

Deep water/floating

6

1.2

1.5-3.0

No water control, low-yielding varieties, low fertilizer-use efficiency

The percentage share of modern semi-dwarf varieties in various ecosystems in Latin America and the Caribbean is given in Table 14. Modern varieties occupy 97.6 percent of the irrigated ecosystem and 71.7 percent of the rainfed lowland ecosystem, contributing 98.3 percent and 76.7 percent to production. In upland ecosystems, modern semi-dwarf varieties account for between 18 and 31 percent and contribute between 24 and 30 percent to total production. The impact of modern semi-dwarf varieties has been high in the irrigated ecosystem, whereas in the upland ecosystem it has been very low.

TABLE 14
Percentage share of modern semi-dwarf rice varieties in rice production and area in Latin America and the Caribbean, 1966-1995


Percentage in production

Percentage in area

1966

1981

1989

1995

1966

1981

1989

1995

Irrigated

0.0

79.3

88.1

98.3

0.0

76.4

84.7

97.6

Rainfed

0.0

53.3

69.3

76.7

0.0

50.3

61.8

71.7

Subtotal, wetlands

0.0

73.5

84.2

92.8

0.0

69.7

79.1

89.5

Mechanized upland

0.0

6.9

13.3

24.7

0.0

5.8

10.3

18.0

Traditional upland

0.0

30.0

30.0

30.0

0.0

26.0

28.2

31.2

Total

0.0

49.9

67.5

80.3

0.0

28.2

43.6

58.8

The coverage of high-yielding modern varieties in various ecosystems in Bangladesh is given in Table 15. Coverage under high-yielding varieties has steadily increased in all ecosystems. No high-yielding variety has been developed to date for deep water. Of the 10 Mha of rice area in Bangladesh, about half is covered by modern high-yielding varieties (HYVs). In boro (winter season), coverage by HYVs is about 90 percent; in transplanted aman (rainy season), coverage is around 50 percent; in aus (pre-rainy season), coverage is 21 percent; under deep-water ecosystems, coverage is practically zero.

TABLE 15
Rice area covered by high-yielding modern varieties in Bangladesh

Year

Area (Mha)

Aus

Transplanted Aman

Deep water Aman

Boro

Total

1975/76

3.42

3.37

1.83

1.15

9.77

1980/81

3.11

4.46

1.57

1.16

10.30

1985/86

3.10

4.66

1.35

1.57

10.60

1990/91

2.11

4.84

0.94

2.55

10.44

1991/92

1.92

4.86

0.83

2.63

10.24

1992/93

1.73

4.94

0.91

2.60

10.18

Table 16 presents data on the coverage of HYVs in the various ecosystems in Latin America and the Caribbean. The impact of breeding activities varies greatly between ecosystems; the greatest progress has been made in irrigated ecosystems, followed by shallow lowlands, rainfed uplands and, finally, deep-water ecologies. Some of the major factors responsible for this varying impact are:

TABLE 16

Modern semi-dwarf varieties (MSV) in production and area implicit yield, Latin America and the Caribbean (LAC), 1966-1995

Varieties

Production (‘000 tonnes)

Area (ha)

Yield (t/ha)

1966

1981

1989

1995

1966

1981

1989

1995

1966

1981

1989

1995

Anaerobic:

Irrigated

4 328

7 710

11 022

12 518

1 252

1 952

2 475

2 519

3.5

3.9

4.5

5.0

MSV

0

6 110

9 708

12 310

0

1 491

2 097

2 459





Rainfed

2 026

2 178

2 840

4 273

674

678

816

1 144

3.0

3.2

3.5

3.7

MSV

0

1 162

1 968

3 277

0

341

505

820





Subtotal

6 354

9 888

13 862

16 792

1 926

2 630

3 291

3 663

3.3

3.8

4.2

4.6

Subtotal MSV

0

7 272

11 676

15 587

0

1 832

2 602

3 279





Aerobic (Upland):

Mechanized

2 809

5 070

3 684

2 920

2 812

4 786

3 146

2 123

1.0

1.1

1.2

1.4

MSV

0

350

489

722

0

279

325

381





Manual

990

788

877

959

1 100

847

904

940

0.9

0.9

1.0

1.0

MSV

0

236

263

288

0

220

255

293





Subtotal

3 799

5 858

4 561

3 879

3 912

5 633

4 050

3 063

1.0

1.0

1.1

1.3

Subtotal MSV

0

586

752

1 009

0

499

580

674





Total LAC

10 153

15 746

18 423

20 670

5 838

8 263

7 341

6 726

1.7

1.9

2.5

3.1

Total LAC MSV

0

7 858

12 428

16 596

0

2 331

3 182

3 953






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