1. Early prediction of rice tolerance to salinity
based on intake of essential elements
S. Bado(1), R. Padilla-Alvarez(2,3), A.M.A Ghanim(1), S. Nielen(1), M.A. Migliori(2),
M. Jaksic(4), Y. Diawara (2), M. Laimer(5)
(1) Plant Breeding and Genetics Laboratory, International Atomic Energy agency (IAEA), Vienna, Austria
(2) Nuclear Science and Instrumentation Laboratory, International Atomic Energy agency (IAEA), Vienna, Austria
(3) Centro de Aplicaciones Tecnologicas y Desarrollo Nucelar (CEADEN), Havana, Cuba
(4) Institut Ruđer Bošković, Zagreb, Croatia
(5)Plant Biotechnology Unit, Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
Introduction
Salinity is a major stress threatening crop productivity in many parts of the world, especially in arid, semi-arid and costal regions.
Salt stress reduces growth and crop yields. Salt tolerant plants are able to maintain growth and complete their life cycle with reasonable (>50%) yields (Munns et al., 2012).
Rice (Oryza sativa L.) is a major crop and a staple food for over half of the world’s population. Most rice cultivars are susceptible to salt and breeding for salt tolerance is a major objective. Genetic variation may be exploited by plant breeding to develop salt tolerant cultivars.
Mutation breeding has been successful in producing salt tolerant cultivars. While screening for salt tolerances remains a major bottle neck in breeding (Do et al., 2009).
The present study was conducted to investigate essential elements in control and salt stressed rice seedlings, with the aim of developing a quick and simple screen of selecting putative salt tolerant individuals in plant populations, e.g. cultivars, breeding lines, segregating generations and mutant populations.
Results and discussion
In total, 12 elements were analysed (Na, Mg, P, S, Cl, K, Ca, Mn, Fe, Cu, Zn and Br) in shoots from control and treated samples.
PCA space discriminated two groups in response to treatment applied: treated samples appear clustered in the lower right whereas control appear in the upper left area (Figure 2). That shows that the treated samples have a decrease in the intake of nutrients Mg, P, S, K, Ca, Mn, Fe, Cu and Zn as compared to the non-treated samples. Subsequently PCA differentiated the tolerant genotypes to susceptible genotypes with moderate genotypes occupying the middle position in the accumulation of essential nutrients.
The canonical discriminant analysis of the control shoots allowed the three salt tolerance categories (tolerant, moderate tolerant and susceptible) to be separated (Figure 3). That indicates that the element discrimination is phenomena consecutive which is more demanded under salt stress condition.
Materials and methods
Sixty rice genotypes with known tolerance to salt were grown in hydroponic culture for one month at 0 dS/m (control) and 10 dS/m (NaCl) (Figure 1). The nutrient elements uptake were assessed by analysis of element content in shoot using X-ray Fluorescence (XRF) and Particle Induced X-ray-Emission (PIXE).
The tendency in the variations of concentrations of the twelve elements in the different genotypes was explored by Principal Components Analysis and Canonical Discrimination Analysis (Figure 2 & 3).
Statistical analysis was carried out using the SPSS 11.5 statistical application software for Windows.
Fig. 2. Ordination of the samples according their scores in the PC-space. Each point represents the results for individual genotype samples, which is in turn labelled according to the tolerance to salt (S – susceptible, M- Moderate, T- tolerant genotypes) and to the group C- Control, S – Salt treated.
Fig.1. Effects of salt stress on rice genotypes differing in salt tolerance after 2 weeks exposure 0 and 10 dS/m at salt after treatment.
Fig. 3. Clustering of rice genotypes with known salt tolerance into the three salt tolerant categories (Tolerant, moderate and susceptible) base on conical discrimination analysis shoot element content of control samples after 2 weeks. Group centre for each cluster is indicated by a solid symbol.
Conclusions
Shoot elements contents in non-stressed conditions can be used as an indicator for pre-field salt tolerance screening. This approach offers an effective method for predicting salt tolerance and to support efficient plant mutation breeding.
References
Munns et al., Wheat grain yield on saline soils is improved by an ancestral Na+ transporter gene. Nat. Biotech. 30(4):
Do, K.T Socio-economic impacts of mutant rice varieties in southern Vietnam. p In: Q. Y. Shu, (eds.), Induced plant mutations in the genomics era. FAO, Rome.
Acknowledgements
We thank Mr Guenter Berthold for technical support. The Food and Agriculture Organization of United Nations and the International Atomic Energy Agency, through their Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture, supported this work.
22nd International Conference on Ion Beam Analysis, June , Opatija, Croatia