Abstract
Rice (Oryza sativa) is a salt-sensitive species and improvement of salt resistance is a major goal for plant breeders. Some species of Oryza genus may constitute an interesting source of genes involved in stress resistance for cultivated rice improvement. The African rice Oryza glaberrima is poorly described for its response to salt stress. Twenty-five accessions of O. glaberrima were exposed during 2 weeks to 0 or 60 mM NaCl in nutrient solution. Morphological and physiological parameters were recorded and used to perform principal component analysis allowing us to consider three contrasting groups (salt-resistant, medium, and salt-sensitive). Most of the tested lines appeared more salt-sensitive than the moderately salt-resistant cultivar I Kong Pao from O. sativa. Salt-sensitivity index was higher for roots than for shoots and O. glaberrima was poorly efficient for regulation of Na+ translocation from the root to the shoot. Some accessions such as TOG5307 however were able to maintain a high net photosynthesis under salt conditions and exhibited a high level of tolerance to accumulated Na+ ions and a high capacity for osmotic adjustment. It is concluded that these salt-tolerant accessions constitute a promising material for rice improvement through inter-specific crosses with O. sativa. Key words: African rice, NaCl, Oryza glaberrima, salinity, salt stress.
Highlights
Rice is an important staple food for more than half of the human population
Mean sensitivity remained low for TOG5307 and TOG5775, suggesting that these accessions displayed a similar level of tolerance comparatively to I Kong Pao (IKP)
The mean shoot WC decreased in response to salinity (78.4%), no significant difference was recorded among the considered accessions
Summary
Rice is an important staple food for more than half of the human population. It provides 50% of the calories consumed in several areas of Asia and Africa (Khush, 2005). In numerous African countries, rice production is still not sufficient and the estimated rice import in Africa accounts for several millions of tones each year which represent more than one-fourth of its requirements (Nhamo et al, 2014). There is an urgent need to increase rice production, especially considering that the world‟s population is predicted to reach around 10 billion people by 2050 (Hoang et al, 2016). Numerous environmental constraints are limiting rice production. Drought and soil salinity are probably the most prevalent abiotic stresses hampering
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