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Strategies for Increasing the Productivity of Rice in Medium-flooded Areas of Bangladesh

M. A. Salam
Plant Breeding Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

P. S. Biswas
Plant Breeding Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

M. Akhlasur Rahman
Plant Breeding Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

Abstract/ Executive Summary:

Flash-flood submergence, medium-deep stagnant, and shallow-flooded deepwater rice (within 100 cm flood depths) subecosystems are discussed in this paper. Major constraints to, varietal needs in, and strategies for varietal development in these subecosystems are discussed. BR11, BRRldhan 32, and BRRldhan 38 showed moderate tolerance for flash-flood submergence. Chechua and Arman Sardar had submergence tolerance similar to that of FR13A. Several advanced lines were developed with tall seedlings and tall plant height and were expected to be adaptable to the medium-deep stagnant subecosystem. Several deepwater rice (DWR) lines were identified that could tolerate submergence by slow stem elongation and maintain plant height to coincide with flood depths. These lines showed significantly higher yields than local DWR checks in farmers' fields.

Keywords: Flash-flood, Shallow-flooded, Deepwater rice, DWR, Rice

Location:

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Non-commodity: Rice

Objectives:

To described the progress made and future needs for varietal development in the shallow flood-prone environments and for increasing the productivity of rice in Medium-flooded areas of Bangladesh.

Methodology:

The characteristics of this environment are the sudden submergence of the rice crop for 10-15 d any time between transplanting and the maximum tillering stage because of heavy rainfall or the onrush of early monsoon floodwater (Miah 2000). However, the early tillering stage of the rice plant is the period most vulnerable to submergence. Recovery of growth after submergence is considered to be the most important adaptation mechanism (Miah 2000). FR13A is used as a submergence tolerant check. It can tolerate complete submergence of 10 days (Hille Ris Lambers and Gomosta 1986). The evaluation of modern varieties showed that BRl1, BRRI dhan32, and BRRI dhan38 had a moderate degree of tolerance at 10 d of complete submergence. Very few progenies have been made by using FR13A in breeding programs. It is important to note that advanced breeding materials were screened for submergence tolerance, but ignoring early generation progenies. As a result, tolerant materials are not properly identified. Recently, screening of local varieties showed that Chechua and Arman Sardar had submergence tolerance similar to that of FR13A (BRRI 2000). Constraints of the flash-flood subecosystem: Submergence may be more than 10 d, Poor crop establishment because of submergence at the tillering stage. Varietal needs for the flash-flood-prone subecosystem: Submergence tolerance of 10-15 d, Fast recovery after submergence. Breeding strategies for the flash-flood subecosystem: Combining ability of local varieties should be determined and efficient use made of the general combiners in breeding programs, unlike FR13A, a poor combiner. Early generation screening should be done under proper environmental conditions and attention should be given to recovery ability of the selected progenies. Water depth during crop growth ranges from 50 to 80 cm and water is stagnant for 2- 3 months in the MDS subecosystem. Traditional varieties have been grown in this environment with low yield. Several advanced lines were developed possessing sufficiently tall seedlings and tall stature that were moderately resistant to lodging and had potentially higher yields than the standard variety. The photoperiod sensitivity of the lines would lead to flowering coinciding with the reduced water depth in the field at the end of October to early November. Therefore, evaluation of these materials in farmers' fields in different MDS areas is in progress. Constraints of the medium-deep stagnant subecosystem are (1) poor crop establishment because of submergence at transplanting, (2) reduced tillering because of a prolonged period of waterlogging, and (3) proneness to submergence at any time of the vegetative growth phase. Varietal needs for the medium-deep stagnant subecosystem are (1) tallness of seedlings from 50 to 60 cm within 40-50 d after seeding, (2) photoperiod sensitivity for use of aged seedlings with required tallness, (3) tall stature (130-150 cm) with sturdy stem, and (4) good tillering habit in a waterlogging situation.

Source of Information: Rice research and development in the flood-prone ecosystem. Proceedings of the international workshop on flood-pron rice systems held in Gazipur, Bangladesh, 9-11 January 2001. Los Banos (Philippines): Internal Rice Research Institute.

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Achievement/Findings:

Breeding lines developed at IRRI showed a positive response to flood depths such that their leaf and stem elongation coincided with the flood depths to limit submergence and maintain the required plant height. This physiological adjustment in plant height of the genotypes is important to conserve the energy necessary for grain yield. These advanced lines had shorter stature and significantly higher yields than the local varieties. It is important to note that these advanced lines had yield potentials of >4.0 t ha^-1 in rainfed lowland rice conditions. Furthermore, these lines showed a maturity duration more or less similar to that of the local checks Digha and Chamara. Constraints of shallow-flooded DWR are extravagant vegetative growth and poor response to nitrogen application. Varietal needs for shallow-flooded DWR are slow elongating type, growth duration similar to that of local varieties, adjustment of plant height to coincide with flood depth, and responsiveness to nitrogen management. Breeding strategies for shallow-flooded DWR are a combining ability test for slow elongating genotypes and the use of general combiners in breeding programs, early generation progeny selection of slow elongating types at 100 cm flood depths, and the evaluation of slow elongating genotypes in shallow-flooded DWR areas of the Padma, Jamuna, Meghna, and Ganges floodplains.

Knowledge Management: Report/Proceedings