Generación de nuevas líneas de arroz mejoradas mediante la introgresión de caracteres de interés agronómico

Abstract

El objetivo principal de esta Tesis es producir estrategias para la productividad, perdurabilidad y calidad mediante el desarrollo de nuevas variedades comerciales de arroz mediterráneo (O. sativa) e introducir alelos de tolerancia a la salinidad y resistencia a herbicidas mediante speed breeding, para proteger el sector del arroz contra el cambio climático, la invasión de malas hierbas y penetración del caracol manzana (P. maculata).

En cuanto a los objetivos específicos, son los siguientes:

1. Cruzar líneas de arroz tolerantes a salinidad y resistente a herbicida por hibridación forzada siguiendo un esquema de retro-cruzamiento. 2. Poner a punto una técnica de rescate de embriones (embryo rescue) para optimizar el speed breeding (mejora acelerada de variedades) en el programa de retrocruces. 3. Establecer una selección in vitro de los embriones que presenten tolerancia al herbicida Cicloxidim. 4. Selección por PCR de los descendientes que presenten marcador SSR Saltol. 5. Selección por CAPS de los descendientes que presenten el alelo mutante de resistencia a Cicloxidim. 6. Aplicación de selección de mayor retorno al parental recurrente mediante marcadores KASPar. 7. Evaluación de las líneas Saltol en ensayos de campo en el Delta del Ebro.

Rice (Oryza sativa) is a crop with a major economic interest and the projection of global world growth make the increase of the food production an imminent need. Framed in the gramineous family (Poaceae), this crop is a diploid species with 24 chromosomes, and it is the most important basic harvesting plant in the world, as it satisfies the caloric needs of half of the world’s population. The Oryza genus includes 24 species, but just two of them are cultivated: Oryza sativa and Oryza glaberrima. Firstly, O. sativa is characterized by its length, approximately about 0.4 to 2 meters and its semiaquatic nature. O. sativa cultivars are classified in five subspecies, corresponding to indica, aus, aromatic, temperate japonica and tropical japonica. The aus are minor groups commonly considered subspecies or ecotypes indica (from the Himalayan region), the temperate japonica (from China, Korea, Japan and Europe), tropical japonica (from Malaysia, Indonesia and Philippines) and aromatic (from Pakistan, India and some other countries). Secondly, O. Glaberrima is cultivated in a minority way in west Africa. The japonica subspecies is the most cultivate in Europe due to its adaptation to temperate climates and its use as an ingredient of local typical dishes worldwide known as the Italian risotto or the Spanish paella. The global rice production in 2019 reached the 500.6 millions of tons, a value 0.8% lower than the historical maximum of 2018, with 506.3 millions of tons, due to climatic factors. In Europe, the production of rice only reaches the 0.6% of the global production, with Italy and Spain as the main producers. This Thesis is part of the NEURICE project (New commercial European RICE), a HORIZON 2020 project funded by the European Union. We used two varieties japonicas sensitive temperate salinity provided by Càmara Arrossera of the Montsià a long grain PL12 and one medium grain PM37, were crossed with two Indica donors carrying Saltol: FL478, a salinity-tolerant RIL obtained from the Pokkali x IR29 cross and IR64- Saltol, a salt-tolerant NIL obtained from the cross FL478 x IR64 . The crosses between PL12 and FL478 were called LP, and the crosses between PM37 and IR64- Saltol were called MS. This thesis has managed to evaluate, for the first time, tolerance to salinity in the new Saltol LP and MS lines from the crosses between the parents and to obtain the new Saltol lines. Therefore, the thesis is divided into three research areas or experiments: 1) The introgression of a QTL Saltol to obtain new lines of rice tolerant to salinity verified through two years of field trials where interesting morphological analogies were found with respect to the number of shoots / plants, number

of panicles / plants, length of the plant and panicle fertility percentage to mitigate the adverse impact of salinity and avoid the loss of apple snail production in the Ebro delta. 2) in vitro optimization for six different varieties of Mediterranean template japonica and a tropical indica by the addition of an adjustable concentration design such as 2.50 µM, 3.00 µM, 3.25 µM and 3.50 µM (concentration at the limit of lethality) of the herbicide Cycloxidim to select resistant individuals, 3) the crossing of a herbicide- resistant tropical indica line with six commercial Mediterranean elite lines by forced hybridization following a backcrossing scheme, using an optimized embryo rescue technique to accelerate the process and CAPS selection of the descendants presenting the mutant OsACC2 allele of resistance to the herbicide Cicloxidim.