Abstract
Sustainability of transplanting systems for rice crop establishment in Sri Lanka is threatened due to climatic changes and heavy rains. Tolerance to anaerobic germination (AG) stress is a key trait that will ensure good crop establishment in direct seeded rice (DSR) farming systems. In this study Marker Assisted backcross breeding was carried out to transfer the quantitative trait loci - QTL AG1 (qAG-9-2), in to the local variety Bg 358 for the development of AG stress tolerant elite lines by AG1 donors IR64-AG1 and Ciherang-Sub1AG1. Marker assisted selection (MAS) was carried out through foreground and recombinant selection. Molecular marker optimization for RM24161, RM8300 and RM553 to the QTL AG1 was carried out using BC1F1 populations. DNA was extracted and PCR was performed using simple sequence repeat (SSR) markers and visualized on 2.5% agarose gel. Based on polymorphism exhibited, RM24161 was chosen as the foreground selection marker, RM553 and RM8300 chosen as proximal and distal markers for recombinant selection. It was suggestive through this study to choose flanking markers RM105 & RM219, closer to the qAG-9-2 locus for recombinant selection as the selected recombinant makers were ineffective and exhibited marker segregation distortion. RM24161 was found to be a tightly linked marker to the AG tolerant QTL AG1 (qAG-9-2) and was successfully used for selection of lines by MAS in generation of anaerobic germination tolerant elite lines.
Highlights
IntroductionDrought and salinity limit crop production worldwide
Abiotic stresses including flooding, drought and salinity limit crop production worldwide
The development of cultivars with enhanced tolerance to abiotic stresses has been advocated as a low-cost means to improve productivity in stressful environments (Ismail et al, 2009). Efforts to develop such varieties have typically relied entirely on phenotypic selection in target environments, but with the advances made in marker assisted selection (MAS) development of varieties for abiotic stress conditions have being made easier due to the numerous advantages associated with MAS, including rapid identification of quantitative trait loci (QTL) introgression, selection independent to environmental variation and accuracy
Summary
Drought and salinity limit crop production worldwide. Modern rice varieties are sensitive to flooding during germination and early growth, a problem commonly encountered in rain-fed areas, but few landraces including KhaoHlan On, Ma-Zhan (red), Khaiyan and Kalongchi are capable of germination under abiotic stress conditions, enabling research in to anaerobic stress tolerance mechanisms (Angaji et al.,2010). Sustainability of transplanting systems for rice crop establishment in both irrigated and rain-fed conditions in Sri Lanka is threatened due to increasing rainfall, flooding and labor scarcity for rice cultivation. Thereby adaption to mechanization by DSR farming systems and development of rice varieties tolerant to AG stress is a key trait that will ensure good crop establishment. The availability of anaerobic germination stress tolerant varieties will help increase mechanization in farming systems in Sri Lanka. The AG trait can be combined through gene pyramiding with the SUB1 QTL conferring resistance to submergence, to ensure additive tolerance to flooding during the vegetative stage of the rice crop development
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