Phenological, biochemical and physiological response to salt stress of rice (Oryza sativa L.) japonica putative salt-tolerant Introgressed Lines in hydroponic culture Michele Pesenti1, Viviana Cavallaro1, Alessandro Abruzzese1, Giorgio Lucchini1, Silvia Morgutti1, Noemi Negrini1, Gian Attilio Sacchi1 1
Dipartimento di Scienze Agrarie e Ambientali – Produzione, Territorio, Agroenergia, Università degli Studi di Milano, Milano, Italia
The global climate warming process is determining the intrusion of saline wedge into coastal fresh-water streams, and the soil salt concentration of many European areas where rice (mainly of temperate cultivars of the ssp. japonica) is grown is constantly increasing. Soil salinization in European coastal areas is also a side-effect of the procedures adopted to contrast the apple snail (Pomacea insularum), a pest that, by slowly spreading in Europe, represents to date a serious threat to rice cultivation. Among cereals, rice is the most sensitive to salt and great effort is being made to identify salt-tolerant germplasm. In the framework of the EU Horizon 2020 Neurice project, investigations on a large number of genetic, physiological and biochemical traits aimed at identifying molecular tools useful for the selection and/or the constitution of high-yield salttolerant japonica (more largely grown in Europe) rice germplasm have been carried out. Among these tools, introduction of salt-tolerance QTLs into rice germplasm is widely applied. One of these QTLs is SalTol, firstly identified in the indica salt-tolerant rice genotypes Pokkali and Nona Bokra. From Pokkali, SalTol was introgressed into the IR29 line yielding FL478, and further transferred into the IR64 line, generating IR64-SalTol. In this context, the different response to salt conditions (salt susceptible/salt tolerant) of a few selected SalTolIntrogressed Lines (ILs; O11, VN25 and VN28) of japonica rice, obtained from crosses of IR64SalTol with either of two salt-susceptible recurrent parents widely grown in Italy, Onice or Vialone Nano, was tested. To better standardize the salt response, plantlets were grown under hydroponic conditions for 21 d in the absence or in the presence of 80 mM NaCl, and characterized in respect to several phenotypic/biochemical/physiological parameters. In the considered germplasm were determined: the phenological response to salt; a few parameters indicative of organ growth and health as affected by the presence of salt. Data are discussed in relation to salt tolerance/susceptibility of the different ILs; the results suggest the feasibility of this approach, in particular in relation to what observed in the O11 IL from Onice x IR64SalTol. Funding: Work supported from the European Union, grant n. 678168, Horizon 2020 Project Neurice, New Commercial European Rice (prof. G.A. Sacchi).
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