Comparative Salinity Response of African and Asian Rice.

In the California rice growing industry, irrigation-water holding requirements may result in yield losses due to salinity. Unfortunately, very little salt tolerance has been measured among the cultivars currently planted in California. At present, only two rice species are cultivated worldwide: Oryza sativa, or Asian rice, and Oryza glaberrima, or African rice. O. glaberrima is hardier than its Asian counterpart and may have characteristic which confer salt tolerance. The focus of this investigation was to determine if African rice species possess greater salt tolerance than Asian rice species. Salinity response was measured at two salinity levels, 4.5 dS/m (low), and 12.0 dS/m (high). Based on the grain yield of the two African rice cultivars tested (CG14 and TO6466), our results indicate that African rice does not exhibit greater salt tolerance than Asian varieties. Yield loss in African rice ranged from 85-90% at the low salinity levels to 100% at the high salinity levels. Yield loss in Asian rice varieties tested (M202, IR29, FL478, and Pokkali) ranged from 11%-55% at the low salinity tested and 33%-88% at the high salinity level. Further, the loss of yields exhibited by some African rice cultivars, especially at the high salinity level, may be related to higher Na+ uptake. Both CG14 and TO644 displayed the highest Na+ uptake levels among all the cultivars (2423 and 1924 mmol per Kg dry weight). We discuss our finding in terms of ion relations and ion selectivity.