Abstract
Marker assisted backcross breeding was used to transfer Saltol, a major QTL for seedling stage salinity tolerance from the donor FL478 to Pusa Basmati 1509 (PB 1509), a high yielding and early maturing Basmati rice variety. Foreground selection was carried out using three markers namely, AP3206f, RM3412b and RM10793, linked to Saltol. In addition, 105 genome-wide SSR markers polymorphic between FL478 and PB 1509 were used in background selection. Among the BC3F4 near isogenic lines (NILs) developed, recurrent parent genome recovery ranged from 96.67 to 98.57%. Multi-season evaluation identified some of the NILs showing significantly higher yield with grain and cooking quality comparable to PB 1509. All the NILs exhibited tolerance to salinity with significantly higher relative water content, membrane stability index and proline content as compared to PB 1509. The root and shoot concentration of Na+, K+ and Na+/K+ in NILs was at par with FL478 under stress conditions. The gene OsHKT1;5 located in the Saltol region showed higher expression levels under stress indicating its role in conferring salinity tolerance. Salt tolerant NILs of PB 1509 will be useful in stabilizing production in salt affected areas.
Highlights
Rice is highly sensitive to salinity stress at seedling and reproductive stages
NaCl (EC of 13.9 dS/m), the seedlings of Pusa Basmati 1509 (PB 1509) were highly sensitive with a score of 9, while FL478 was highly tolerant with a score of 1 (Supplementary Fig. S1)
The F 1s generated from the cross PB 1509/FL478 were tested for hybridity with Saltol linked markers viz. AP3206f, RM3412 and RM10793
Summary
Rice is highly sensitive to salinity stress at seedling and reproductive stages. The symptoms of salt injury in rice are stunted growth, rolling of leaves, white tips, drying of older leaves and grain sterility. Development of varieties with seedling stage salinity tolerance can sustain the production of the crop in salt affected areas by promoting the good initial establishment of plants, leading to healthy vegetative growth that can increase crop yield[7]. Pusa Basmati 1509 (PB 1509) developed by the ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi, India, is an early maturing Basmati rice variety with seed to seed maturity of 120 days, semi-dwarf plant stature with high yields and excellent grain and cooking quality t raits[24]. This variety is sensitive to salinity at seedling as well as the reproductive stages. We report introgression of Saltol QTL from donor parent (DP) FL478 into the recurrent parent (RP) PB 1509 using Marker assisted backcross breeding (MABB) approach
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