Previous PageTable Of ContentsNext Page

Drought resistance of NERICA (New Rice for Africa) compared with Oryza sativa L. and millet evaluated by stomatal conductance and soil water content

Michihiko Fujii, Chika Andoh and Seiji Ishihara

Faculty of Education, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan Email eimfuji@ipc.shizuoka.ac.jp

Abstract

In Africa, as population increase is severe, increase of crop production is a major problem. Recently to solve the problem, NERICA (New Rice for Africa) was developed in West Africa by the cross between African rice (Oryza glaberrima Steud.) and Asian rice (Oryza sativa L.). In this study, eight rice cultivars including two parents of NERICA, six NERICA lines and two millet species (common millet and Italian millet) were grown in field under drought condition, and physiological measurements were made. Stomatal conductance was measured by porometer, and soil water contents at individual depths were measured by TDR (Time domain reflectometry) method as water uptake characteristics. Some NERICA lines showed high dry weight and yield under drought condition among the rice cultivars and lines tested, though there were line differences in NERICA. Including all rice cultivars and lines tested, dry weight at harvest under drought condition was correlated with stomata conductance (r= 0.638**), and cultivars and lines that maintained high growth showed high stomata conductance. In Asian rice (O. sativa L.), dry weight at harvest was closely correlated with soil water content at harvest (r= -0.953*), and cultivars and lines that maintained high growth showed high water uptake. On the other hand, correlation between dry weight and soil water content was not significant in NERICA lines (r=0.106). It became clear that there are some lines in NERICA that show high growth with low uptake of water and they seem to be appropriate for long periods of cultivation in drought condition.

Media summary

Some NERICA lines showed high growth with low uptake of water and seemed to be appropriate for long periods of cultivation in drought condition.

Key Words

Drought resistance, Dry weight, NERICA, Rice, Soil water content, Stomatal conductance.

Introduction

The world food problem is serious. Especially in Africa, population increase is severe, so increase of crop production is becoming a major problem. Recently in order to solve the problem, NERICA (New Rice for Africa) was developed in West Africa by the cross between African rice (Oryza glaberrima Steud.) and Asian rice (Oryza sativa L.) (WARDA 1999; Ishii 2003; Futakuchi et al. 2003). Lilley and Fukai (1994), Kobata et al. (1996) and Fujii and Horie (2001) showed that high dry matter production performance by drought resistant cultivars of rice (O. sativa L.) is caused by superior ability to gather soil water. But physiological characteristics of NERICA are not fully investigated yet. The objective of this study is to clarify the physiological characteristics of NERICA compared with cultivars of O. sativa and millets under drought condition, both from aboveground and underground. Eight rice cultivars including two parents of NERICA, six NERICA lines and two millets (common millet and Italian millet) were grown in field under drought condition, and both aboveground and underground physiological measurements of stomatal conductance and soil water contents at individual depth were made to investigate water uptake characteristics. Stomatal conductance was measured by porometer, and soil water contents at individual depths were measured by TDR (Time domain reflectometry) method. These physiological characteristics of NERICA were investigated in relation to dry matter production.

Methods

Plant materials

NERICA was developed in West Africa by the cross between African rice (O. glaberrima Steud.) and Asian rice (O. sativa L.). In this study six NERICA lines and their two parent cultivars as follows were used. NERICA 1: WAB450-11-1-P26-2-HB, NERICA 2: WAB450-24-3-4-P18-3-1, NERICA 3: WAB450-24-3-P3-1-HB, NERICA 4: WAB450-I-B-P-23-HB, NERICA 5: WAB450-I-B-P-6-1-1, NERICA 6: WAB450-11-1-P31-1-HB, O. sativa parent: WAB56-104, O. glaberrima parent: CG 14. Two millet species (common millet: Panicum miliaceum L.; Italian millet: Steria italica (L.) P.Beauv.) and rice cultivars of O. sativa L. Koshihikari, Kanniho, Asamurasaki (japonica, lowland, Japan), Dular (indica, lowland-upland, India), IRAT 13 (japonica, upland, Cote d’Ivoire), Kinandang Patong (japonica, upland, Philippines) were also used. Plants were seeded in paper pots on May 22, 2003 and seedlings were planted at upland field in the vinyl house of Shizuoka University (3.2 x 14m) on June 20 with planting distance of 15 x 30cm. Sides of vinyl house were kept open to ventilate. Irrigation was applied for the establishment on June 20, 26, 30, July 2 and 18, and after that no irrigation was applied to create drought condition. Plots were fertilized by compound fertilizer 8-8-8 at the rate of 60kg/ha as nitrogen for the basal application and 40kg/ha as nitrogen for the supplement application. Only for Koshihikari, a compost plot was included where 25t/ha of compost was applied.

Measurements of Stomatal conductance

Stomatal conductance was measured at the center of abaxial side of topmost three leaves by dynamic diffusion porometer (AP4, Delta-T Devices Ltd., Cambridge, UK) on sunny days from ten to twelve o’clock. Measurements in all plots were made on August 21, 25, 29, September 3, 8 and 16. On September 2 and 9, measurements of diurnal change were made for several plots.

Measurements of Soil water contents

Soil water contents at individual depths were measured by TRIME-T3 tube access probe system (IMKO micromodultechnik, Ettlingen, Germany) by TDR (Time domain reflectometry) method to investigate water uptake characteristics. Measurements were made at intervals of ten cm depth on July 24, August 11, 20, September 4, 16 and 18. Data presented are average of 20cm depth increments from surface to 60cm depth.

Measurements of Dry weight

Plants were sampled to measure top dry weight on June 25, July 22, 23, September 24 and at harvest of each cultivar and line from October 6 to November 13 depending on the heading date. After dividing into leaf, dead leaf, stem and ear, dry weight was measured after desiccating in the drying oven at 80 for 48 hours.

Results

For stomatal conductance averaged from August 21 to September 16, Dular, sativa parent of NERICA and common millet showed high values of about 200mm/s, and Japanese lowland rice cultivars showed low values of about 100mm/s (Figure 1). NERICA lines showed intermediate values of 100-150mm/s.

Figure 1. Average stomatal conductance from August 21 to September 16. Bars show standard errors

For soil water content at 0-20cm depth on September 18, the last date of water content measurement, Dular, sativa parent of NERICA and IRAT 13 showed low values of about 10%, and Kanniho and common millet showed high values of about 18% (Figure 2). Other Japanese lowland rice cultivars and NERICA lines showed intermediate values of 10-15%. For soil water content at 40-60cm depth on the same day, Dular, sativa parent of NERICA and IRAT 13 showed low values of about 25%. This means that these cultivars absorbed water also from deep layers (Figure 3). On the other hand, Japanese lowland rice cultivars, NERICA lines and common millet showed high values of about 30%, and it means that they did not absorb much water from deep layers.

Figure 2. Soil water content at 0-20cm depth on September 18. Bars show standard errors

Figure 3. Soil water content at 40-60cm depth on September 18. Data are not shown for Koshihikari, Asamurasaki and Kinandang Patong due to measurement error. Bars show standard errors

At top dry weight of individual organs at harvest, common millet and Italian millet showed higher top dry weight and yield than rice (Figure 4). NERICA 3 showed highest top dry weight in rice, and Dular, NERICA 3 and sativa parent of NERICA showed higher yield than other rice cultivars and lines. Some lines in NERICA showed high values but some showed low values and there were large line differences among NERICA. There was significant correlation (r=0.638**) between average stomatal conductance and top dry weight at harvest for all plots, and plots with large stomatal conductance showed high dry weight (Figure 5).

Figure 4. Top dry weight of individual organs at harvest. Bars show standard errors

In the relationship between soil water content on September 18 and top dry weight at harvest, there was significant correlation (r=-0.953*) in Asian rice (O. sativa L.), and it seems that Asian rice cultivars with high dry weight absorb much water and so soil water content decrease (Figure 6). This agrees with the results of Lilley and Fukai (1994) and Kobata et al. (1996). On the other hand, in NERICA lines the correlation was not significant (r=0.106), and it seems that in NERICA lines there is a large variability in water use efficiency, and that there are some lines in NERICA that show large dry weight with small absorption of water.

Figure 5. Relationship between average stomatal conductance from August 21 to September 16 and top dry weight at harvest. **: significant at 1%

Figure 6. Relationship between soil water content on September 18 and top dry weight at harvest. In Koshihikari, Asamurasaki, Kinandang Patong and Italian millet, data are not shown due to measurement error. *: significant at 5%

Drought resistant cultivars in Asian rice (O. sativa L.) showed high growth by absorption of much soil water. Millet, with C4 photosynthesis, showed high growth with small amount of water. In NERICA, some lines showed higher growth than other rice cultivars and lines with small amount of water uptake, though there were line differences. And those NERICA lines seem to be appropriate for long periods of cultivation in drought condition.

Conclusion

Including all rice cultivars and lines tested, dry weight at harvest under drought condition was related with stomatal conductance, and cultivars and lines which maintained high growth showed high stomatal conductance. In Asian rice (O. sativa L.), dry weight at harvest was closely related with soil water content at harvest, and cultivars which maintained high growth showed high water absorption. On the other hand, correlation between dry weight and soil water content was not significant in NERICA lines. It became clear that there are some lines in NERICA that show high growth with small absorption of water and they seem to be appropriate for long periods of cultivation in drought condition.

Acknowledgement

We thank Professor Horie and Associate Professor Shiraiwa, Kyoto University, for kindly giving an opportunity to use seeds of NERICA in this study. This study was supported in part by the Grants-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan (No. 14560010).

References

Fujii M and Horie T (2001). Relative contributions of tolerance and avoidance to drought resistance in dry-matter production of different rice cultivars and different fertilization levels. Jpn J. Crop Sci. 70 (1), 59-70. (In Japanese with English abstract.).

Futakuchi K, Tobita S, Diatta S and Audebert A (2003). WARDA’s work on the New Rice for Africa (NERICA) –Interspecific Oryza sativa L. x O. glaberrima Steud. Progenies. Jpn. J. Crop Sci. 72 (extra 1), 324-325.

Ishii R (2003). Can rice save Africa? Jpn. J. Trop. Agr. 47 (extra 1), 35-48. (In Japanese.).

Kobata T, Okuno T and Yamamoto T (1996). Contributions of capacity for soil water extraction and water use efficiency to maintenance of dry matter production in rice subjected to drought. Jpn. J.Crop Sci. 65 (4), 652-662.

Lilley JM and Fukai S (1994). Effect of timing and severity of water deficit on four diverse rice cultivars. III. Phenological development, crop growth and grain yield. Field Crops Research 37, 225-234.

WARDA (1999). New Rice for Africa--- with a little help from our friends. WARDA Annual Report 1999, 9-15.

Previous PageTop Of PageNext Page