Abstract
Sabitri is a rice variety grown in a large part of the rainfed areas of Nepal. It was originally developed for irrigated condition; hence, this variety suffers high yield decline under drought. Two QTLs, qDTY3.2 and qDTY12.1, with large effects on grain yield under drought were identified in the Sabitri background in separate QTL mapping studies. The present study reports the development of Sabitri near isogenic lines (NILs) with combinations of these two QTLs and their characterization under drought. To do so, marker-assisted backcross breeding (MABB) was combined with phenotypic selection to develop high-yielding drought-tolerant NILs with Sabitri grain type. Apart from this, drought-tolerant variants for grain type with high yield under non-stress were identified among the developed NILs. Early days to flowering of up to 13 days and reduction in plant height of up to 13 cm as compared to Sabitri were observed in the developed NILs. Some of these NILs showed higher yield compared to Sabitri and relatively higher tolerance to drought, indicating the capture of positive alleles and interactions during the course of selection. The developed NILs possessed high yield potential which make them suitable materials for the testing of water-saving technologies in irrigated areas. Based on their performance, these NILs can be deployed in rainfed areas in Nepal and other countries of South Asia to increase yield stability.
Highlights
Sabitri is a rice variety grown in a large part of the rainfed areas of Nepal
This study reports the introgression of qDTY3.2 and qDTY12.1 into Sabitri to develop drought-tolerant near isogenic lines (NILs) with high yield and preferred grain quality using marker-assisted backcross breeding (MABB)
Marker-assisted selection was conducted at the start, once the QTLs were fixed, marker-assisted selection coupled with phenotypic evaluation were performed
Summary
Sabitri is a rice variety grown in a large part of the rainfed areas of Nepal. It was originally developed for irrigated condition; this variety suffers high yield decline under drought. For rice cultivation to be sustained, an increased use of watersaving technologies in irrigated areas is vital (Kumar and Ladha 2011) These scenarios highlight the need for the development of high-yielding, good quality rice varieties with drought tolerance in order to maintain yield stability under varying environmental conditions and cultivation practices. A large proportion of rainfed areas in Nepal are still planted with drought-susceptible varieties which are developed for irrigated ecosystems An example of such variety is Sabitri which is popular in Nepal because of its high yield and grain quality. It is grown in a large area across rainfed rice ecosystems despite its high declines in yield in cases of drought. The establishment of grain yield as a selection criterion (Venuprasad et al 2007, 2008; Kumar et al 2009, 2013, 2014; Dixit et al 2014a), the identification of large-effect quantitative trait loci (QTLs) (Bernier et al 2007; Venuprasad et al 2009; Vikram et al 2011; Ghimire et al 2012; Swamy et al 2013; Palanog et al 2014; Sandhu et al 2014; Dixit et al 2014b, c), and understanding the molecular
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