Submergence Tolerance in Irrigated and Rainfed Lowland Rice Varieties: Agro-Morphological Basis for Rice Genetic Improvement in Southern Benin

Objective: The study was carried out, on the rice perimeter of Southern Benin, to evaluate the response of irrigated and lowland rice varieties to the complete and partial submergence using agro-morphological traits. Method: Thus, 15 rice varieties were submerged in the field during 60 days according to split plot experimental design with two factors and three replications. Agro-morphological parameters such as plant height, number of tillers, the distance of internodes and the number of internodes were measured respectively at 13 days and 45 days. After harvest, some traits such as length, width and thickness of grains, panicle length, number of primary and secondary branches, the average number of empty grains and full grains per panicle and 1000-grain weight were recorded. Results: Very highly significant ( P ≤ 0.0001) differences were identified between agro morphological parameters according to the type of submergence while the factor type of immersion has significant influence on the number of internodes at 45 days after transplanting (P ≤ 0.01). The submergence was not significant effect on tillering and length of internodes. Conclusion: The plant height, the weight of thousand grains and the average number of empty grains per panicle constitute key aspects and have been essential for evaluating tolerance to submergence in Benin.

• Rice
• Submergence
• Tolerance
• Benin

1. Introduction

90% of the rice-growing areas are submerged during cultivation of rice in Asia, compared with 40 percent in Latin America and Africa in the West [1] . Indeed, rice is grown in different ecologies from uplands to swampy areas [2] . However, when it is exposed to more than 25 cm of water or full immersion, the rice is severely damaged resulting in losses [3] . With the climate trend observed over the last thirty years [4] , there will be an excessive rainfall, thus causing an increase in the negative effect of the floods on food production; a situation that could get worse for rice production. In addition, it is important to remember that climate variations affect rice production, and will continue to do so through irregular precipitation, more dry periods during the wet season, droughts and floods that penalize rice yields [5] . The yield of rice in terms of submergence is very low for most of the time below 1.5 t/ha because producers continue to grow their traditional low-yield and susceptible to abiotic and biotic constraints; this is due to non-availability of rice varieties tolerant to flooding or submergence [6] .

It’s important to know that the years 2009 and 2010 were exceptional in rainy and raw years in the region, West African [7] . In the Oueme Valley rice six Commons were severely affected. It’s the Cove towns, Zangnanado, of Ouinhi, of Bonou, of Adjohoun, of Dangbo [8] . Zagnanado and Ouinhi towns located at the entrance of the delta have been particularly affected more than the other four (04) towns. These communities have experienced overall 59 km of degraded slopes, 10,995 washed tons of crops of maize and Cowpea in stock, 8860 heads of cattle all missing species, 148 fish holes submerged in the period from July to October [8] these statistics show the extent of the problem of flooding and as a result the flooding of crops in South - Benin. In addition, water supply is sufficient during the rainy season in such a way that without artificial irrigation; agricultural production can take place throughout the year. Due to the strong population growth and the reduction of arable land, exploitation of the underground is so very important for the future of this region [9] . The additional production required to meet this demand will have to come largely from the gutter, although they represent only a small fraction (5%) of the arable land in Africa from the West [10] . However, these rice ecologies are facing flooding, crops irrigated with water (rice to submergence) control, and/or to the flood, for crops without water (flooded rice or rice to submergence is not controlled) control. Lowlands’s soils are subject to intense leaching, vertical or longitudinal, which is often initially under the surface horizon, of sands or clays white, totally leached horizons. This internal flow may also carry fine particulates, enriching in sands; the upstream areas or lateral of the lowlands. The homoscedasticity blocks the evolution of organic matter, which accumulates on the surface, in a more or less decomposed form. There are then soils organic, very acidic, with very low capacity of cationic Exchange. In mineral soils, organic matter rates are highly variable and can reach 8% to 10%. However, far to be a sign of fertility, this accumulation of organic matter, high C/n, is actually a sign of the more or less complete blocking of biological life. The mineral wealth of the soils of lowland is often very low. Flooding creates in effect of anaerobic conditions, resulting in reduction reactions [11] . As a result, plants grown in frequently flooded areas are often reduced biological production [12] . This therefore translates into a decline in performance [13] and the death of submerged rice plants. The main constraint for plants, during the flood, is the lack of oxygen [14] . This decreases root respiration, inhibits the growth of the underground and aerial part and results in the senescence of the latter [15] .

Although over three quarters of West Africa are located in semi-arid and arid climates, several areas are flooded during the winter period and are temporarily inaccessible and abandoned. These areas have a clayey or silty structure does not allow a quick interflow during heavy precipitation. The choice of species to grow on these soils is of considerable importance for the cultivation of rice in order to contribute to food security and sustainability of local resources of small producers of rice in West Africa.

The current study was conducted in the town of Cove (adjacent municipality of Zagnanando) specifically to Koussin-lele. Indeed, every year, an overflow of the river Zou observed on rice Koussin-lele perimeter; that creates a situation of total submergence or partial submergence of rice plants at any stage of their development.

2. Study Area

The area of study for this research is located in the district Cove of Benin between 2˚58' east longitude and 7˚25' north latitude It covers an area of 525 km² and is remote to Cotonou Agreement of 150 km about by Bohicon. The soil types encountered in the study area are dominated by soils hydromorphic whose texture is clay-silty.

Figure 1 presents the heights of rainfall recorded in study area during the course of the year 2015 with a precision of the number of days of rain. This figure confirms that the period of July to October (period of implementation) is a

period during which the maximum heights of rains have been recorded. It is important to note that the month of August usually marks the beginning of the period of flood during which the flood is observed on the Rice perimeter of Koussin-lele. Figure 1 show the heights of rainfall.

3. Implementation of Study

The test has been put in lowland perimeter of Koussin-lele. This test has need 15 varieties submitted in condition of submergence in a device of split-plot composed of three large plots. Has this effect, after a nursery in 17 days, the young seedlings were transplanted in lines by reason of a single plant per hill following the plan of randomization. For the experimentation, each variety has been installed on a plot of 1 m² according to a clearance of 25 cm between seedlings and lines per plot. The plants of rice have stayed in the water during 60 days. The level of the water has been increased and adjusted for each type of treatment to a maximum height amounting to up to 100 cm.

As regards fertilization, a manuring of funds to reason to 200 kg/ha NPK and 100 kg/ha of urea which 50 kg/ha and 50 kg/ha to filling of the grain has been performed. Finally, for the management of weeds, manual weeding was performed three times before the stage of maturity of the grain more particularly in the block have not suffered flooding. An adjustment of the fluctuation of the blade of water in the racks is performed every three days by a contribution or withdrawal of water according to the case and the need in the various types of flooding (T0, T1 and T2).

4. Methods

In total, 15 varieties from two species of cultivated rice (O. glaberrima and O. sativa) as well as the varieties of intra and interspecific (NERICA-L and the ARICA, etc.) have formed the working collection. Table 1 demonstrates Genetic characteristics of plant material.

The experimental design used is a split plot. Three large plots were carried out each with three repetitions of 15 varieties and therefore 45 under plots by large parcel. The first large parcel is subjected to a treatment witness T0 without submergence, the second is subjected to a treatment T1 (partial submergence) and the third large parcel to the T2 (total submergence) treatment. Indeed, all three types of treatment are not in a large parcel. Thus, each large parcel in this case represents a type of treatment T0, T1 or T2. Two factors have been so studied during the test. It's the type factor of submergence and the variety factor. 15 varieties were tested in different heights or blade of water (without submergence, partial submergence, and total submergence). Figure 2 shows the randomization plan adopted during the test.

Growth parameters measured include: the height, number of tillers, number of internodes, and length of internodes. These measures were made on 4 plants per plot of 1 m². About measured performance metrics, its length, width and

Table 1

Genetic characteristics of plant material

References

1. Bailey-Serres, J. and Voesenek, L.A.C.J. (2008) Flooding Stress: Acclimations and Genetic Diversity, Annual Review of Plant Biol-ogy.

2. Bailey-Serres, J., Fukao, T., Ronald, P., Ismail, A., Heuer, S. and Mackill, D. (2010) Submergence Tolerant Rice: SUB1’s Journey from Landraceto Modern Cultivar, Published with Open Access at Springerlink.com. 141.

3. Balasubramanian, V., Sié, M., Hijmans, R.J. and Otsuka, K. (2007) Increasing Rice Production in Sub-Saharan Africa: Challenges and Opportunities. Advances in Agronomy, 55-133. https://doi.org/10.1016/S0065-2113(06)94002-4

4. Catling, D. (1992) Rice in Deep Water. International Rice Research Institute, Manila, 542 p. https://doi.org/10.1007/978-1-349-12309-4

5. Colmer, T.D. (2003) Long-Distance Transport of Gases in Plants: A Perspective on Internal Aeration and Radial Oxygen Loss from Roots. Plant, Cell & Environment, 17-36. https://doi.org/10.1046/j.1365-3040.2003.00846.x

6. Colmer, T.D. and Voesenek, L.A.C.J. (2009) Flooding Tolerance: Suites of Plant Traits in Variable Environments. Functional Plant Biology, 665-681. https://doi.org/10.1071/FP09144

7. Emes, M.J., Wilkins, C.P., Smith, P.A., Kupkanchanakul, K., Hawker, K. and Charlton, W.A. (1988) Starch Utilization by Deepwater Rice during Submergence. Proceedings of the 1987 International Deepwater Rice Workshop, International Rice Research Institute, Manila, 319-326.

8. World Bank and United Nations (2011) Needs Assessment Report Post Disaster. 84 p.

9. Futakuchi, K., Jones, M.P. and Ishii, R. (2001) Physiological and Morphological Mechanisms of Submergence Resistance in African Rice (Oryza glaberrima Steud.). Japanese Society for Tropical Agriculture, 8-14.

10. Ghesquiere, A., Sequier, J., Second, G. and Lorieux, M. (1997) First Steps towards a Rational Use of African Rice, Oryza glaberrima, in Rice Breeding through Acontig Line Concept. Ibid. 31-39.

11. Haefele, S.M., Ismail, A.M., Johnson, D.E., Vera Cruz, C. and Samson, B. (2010) Crop and Natural Resource Management for Climate-Ready Rice in Unfavorable Environments: Coping with Adverse Conditions and Creating Opportunities. Presentation at the CURE Workshop on Climate Change, Siem Reap, Cambodia, 4 May 2010.

12. Ismail, A.M. and Mackill, D.J. (2013) Response to Flooding: Submergence Tolerance in Rice. In: Jackson, M., Ford-Lloyd, B. and Parry, M., Eds., Plant Genetic Resources and Climate Change, 251-269.

13. Jackson, M.B., Kimiharu, I. and Osamu, I. (2009) Evolution and Mechanisms of Plant Tolerance to Flooding Stress. Annals of Botany, 103, 137-142. https://doi.org/10.1093/aob/mcn242

14. Mallik, S., Kundu, C., Banerji, C., Nayak, D.K, Chatterji, S.D. and Nanda, P.K. (1995) Rice Germplasm Evaluation and Improvement for Stagnant Flooding. In: Ingram, K.T., Ed., Rainfed Lowland Rice: Agricultural Research for High Risk Environments, International Rice Research Institute, Manila, 97-109.

15. Mackill, D.J., Coffman, W.R. and Garrity, D.P. (1996) Rainfed Lowland Rice Improvement. International Rice Research Institute, Manila, Philippines, 242 p.

16. Palada, M. and Vergara, B.S. (1971) Environmental Effect on the Resistance of Rice Seed-lings to Complete Submergence. Crop Science, 12, 209-212. https://doi.org/10.2135/cropsci1972.0011183X001200020018x

17. Setter, T.L., Ingram, K.T. and Tuong, T.P. (1995) Environmental Characterization Requirements for Strategic Research in Rice Grown under Adverse Conditions of Drought, Flooding or Salinity. In: Ingram, K.T., Ed., Rainfed Lowland Rice-Agricultural Research for High Risk Environments, International Rice Research Institute, Manila.

18. Sossou-agbo, A.L. (2013) Socio-Economic Impacts of Floods of 2010 in the Delta of the Ouéme in Benin, 26th Symposium of the International Association of Climatology. Pacte Laboratory-Territories, UJF-Grenoble. sossoulazare@yahoo.f

19. Voesenek, L.A.C.J, Colmer, T.D., Pierik, R., Millenaa, F.F. and Peeters, A.J.M. (2006) How Plants Cope with Complete Submergence. New Phytologist, 170, 213-226. https://doi.org/10.1111/j.1469-8137.2006.01692.x

20. Colmer, T.D., Cox, M.C.H. and Voesenek, L.A.C.J. (2006) Root Aeration in Rice (Oryza sativa): Evaluation of Oxygen, Carbon Dioxide, and Ethylene as Possible Regulators of Root Acclimatizations. New Phytologist, 170, 767-778. https://doi.org/10.1111/j.1469-8137.2006.01725.x

21. Catling, D. (1992) Rice in Deep Water. Macmillan Press, London.https://doi.org/10.1007/978-1-349-12309-4

22. Armstrong, W. and Drew, M.C. (2002) Root Growth and Metabolism under Oxygen Deficiency. In: Waisel, Y., et al., Plant Roots: The Hidden Half, 3rd Edition, New York, Basel, 729-761.

23. Cho, H.T. and Kende, H. (1997) Expansins in Deepwater Rice Internodes. Plant Physiology, 113, 1137-1143. https://doi.org/10.1104/pp.113.4.1137