Abstract
BACKGROUND: Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.) are generally considered among the crop species most sensitive to salt stress. A handful of lines are known to be tolerant, and a small number of these have been used extensively as donors in breeding programs. However, these donors use many of the same genes and physiological mechanisms to confer tolerance. Little information is available on the diversity of mechanisms used by these species to cope with salt stress, and there is a strong need to identify varieties displaying additional physiological and/or genetic mechanisms to confer higher tolerance. RESULTS: Here we present data on 103 accessions from O. sativa and 12 accessions from O. glaberrima, many of which are identified as salt tolerant for the first time, showing moderate to high tolerance of high salinity. The correlation of salinity-induced senescence (as judged by the Standard Evaluation System for Rice, or SES, score) with whole-plant and leaf blade Na+ concentrations was high across nearly all accessions, and was almost identical in both O. sativa and O. glaberrima. The association of leaf Na+ concentrations with cultivar-groups was very weak, but association with the OsHKT1;5 allele was generally strong. Seven major and three minor alleles of OsHKT1;5 were identified, and their comparisons with the leaf Na+ concentration showed that the Aromatic allele conferred the highest exclusion and the Japonica allele the least. A number of exceptions to this association with the Oryza HKT1;5 allele were identified; these probably indicate the existence of additional highly effective exclusion mechanisms. In addition, two landraces were identified, one from Thailand and the other from Senegal, that show high tissue tolerance. CONCLUSIONS: Significant variation in salinity tolerance exists within both cultivated Oryza species, and this is the first report of significant tolerance in O. glaberrima. The majority of accessions display a strong quantitative relationship between tolerance and leaf blade Na+ concentration, and thus the major tolerance mechanisms found in these species are those contributing to limiting sodium uptake and accumulation in active leaves. However, there appears to be genetic variation for several mechanisms that affect leaf Na+ concentration, and rare cases of accessions displaying different mechanisms also occur. These mechanisms show great promise for improving salt tolerance in rice over that available from current donors.
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Claims 15
Claim · model-written summary
Many of the 103 O. sativa accessions were newly identified as salt tolerant, with moderate to high tolerance of high salinity.
- Taxon
- O. sativa
Oryza sativae1 - Material
- accessionse1
- Outcome
- tolerance of high salinitye1
- Qualifier
- moderate to highe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“103 accessions from O. sativa and 12 accessions from O. glaberrima, many of which are identified as salt tolerant for the first time, showing moderate to high tolerance of high salinity”
Claim · model-written summary
O. glaberrima shows significant salt tolerance, reported for the first time.
- Taxon
- O. glaberrima
Oryza glaberrimae2 - Outcome
- significant tolerancee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“this is the first report of significant tolerance in O. glaberrima”
Claim · model-written summary
Leaf blade Na+ concentration correlates highly with the SES senescence score across nearly all accessions of both species.
- Taxon
- O. sativa and O. glaberrimaOryza sativaOryza glaberrimae3
- Organ / stage
- leaf bladee3
- Outcome
- whole-plant and leaf blade Na+ concentrationse3
- Direction
- highe3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“The correlation of salinity-induced senescence (as judged by the Standard Evaluation System for Rice, or SES, score) with whole-plant and leaf blade Na+ concentrations was high across nearly all accessions, and was almost identical in both O. sativa and O. glaberrima”
Claim · model-written summary
Leaf Na+ concentration is only very weakly associated with cultivar-groups.
- Taxon
- Oryza sativaOryza sativae0
- Material
- cultivar-groupse4
- Organ / stage
- leafe4
- Outcome
- leaf Na+ concentrationse4
- Direction
- very weake4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e4“The association of leaf Na+ concentrations with cultivar-groups was very weak, but association with the OsHKT1;5 allele was generally strong”
Claim · model-written summary
Leaf Na+ concentration is generally strongly associated with the OsHKT1;5 allele.
- Taxon
- Oryza sativaOryza sativae0
- Gene
- OsHKT1;5e4
- Outcome
- leaf Na+ concentrationse4
- Direction
- stronge4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e4“The association of leaf Na+ concentrations with cultivar-groups was very weak, but association with the OsHKT1;5 allele was generally strong”
Claim · model-written summary
Seven major and three minor alleles of OsHKT1;5 were identified.
- Taxon
- Oryza sativaOryza sativae0
- Gene
- OsHKT1;5e5
- Outcome
- allelese5
- Value
- Seven major and three minore5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e5“Seven major and three minor alleles of OsHKT1;5 were identified”
Claim · model-written summary
The Aromatic OsHKT1;5 allele gives the highest Na+ exclusion.
- Taxon
- Oryza sativaOryza sativae0
- Material
- Aromatic allelee6
- Outcome
- exclusione6
- Direction
- higheste6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e6“the Aromatic allele conferred the highest exclusion and the Japonica allele the least”
Claim · model-written summary
The Japonica OsHKT1;5 allele gives the least Na+ exclusion.
- Taxon
- Oryza sativaOryza sativae0
- Material
- Japonica allelee6
- Outcome
- exclusione6
- Direction
- leaste6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e6“the Aromatic allele conferred the highest exclusion and the Japonica allele the least”
Claim · model-written summary
A number of accessions do not follow the association with the OsHKT1;5 allele.
- Taxon
- Oryza sativaOryza sativae0
- Outcome
- exceptions to this associatione7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e7“A number of exceptions to this association with the Oryza HKT1;5 allele were identified”
Claim · model-written summary
The exceptions probably reflect additional highly effective Na+ exclusion mechanisms.
- Taxon
- Oryza sativaOryza sativae0
- Outcome
- exclusione1
- Qualifier
- additional highly effective exclusion mechanismse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e1“these probably indicate the existence of additional highly effective exclusion mechanisms”
Claim · model-written summary
Two landraces, one from Thailand and one from Senegal, show high tissue tolerance.
- Taxon
- Cultivated rice speciesOryza sativae0
- Material
- landracese1
- Outcome
- high tissue tolerancee1
- Qualifier
- the other from Senegale1
- Setting
- Thailande1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e1“two landraces were identified, one from Thailand and the other from Senegal, that show high tissue tolerance”
Claim · model-written summary
Significant variation in salinity tolerance exists within both cultivated Oryza species.
Verbatim
e1“Significant variation in salinity tolerance exists within both cultivated Oryza species”
Claim · model-written summary
Genetic variation appears to exist for several mechanisms that affect leaf Na+ concentration.
- Taxon
- Oryza sativaOryza sativae0
- Outcome
- genetic variation for several mechanismse1
- Qualifier
- that affect leaf Na+ concentratione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e1“there appears to be genetic variation for several mechanisms that affect leaf Na+ concentration”
Claim · model-written summary
The major tolerance mechanisms in these species limit sodium uptake and accumulation in active leaves.
- Taxon
- Oryza sativaOryza sativae0
- Outcome
- major tolerance mechanismse1
- Qualifier
- limiting sodium uptake and accumulation in active leavese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivated rice species (Oryza sativa L. and O. glaberrima Steud.)”
e1“the major tolerance mechanisms found in these species are those contributing to limiting sodium uptake and accumulation in active leaves”
Claim · model-written summary
The identified mechanisms show great promise for improving rice salt tolerance over current donors.
- Taxon
- riceOryza sativae1
- Outcome
- salt tolerancee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“These mechanisms show great promise for improving salt tolerance in rice over that available from current donors”