Marker-assisted introgression of Pup1, a major QTL associated with tolerance to low soil phosphorus into the elite rice variety MTU1010

Abstract

MTU1010 is an elite variety, grown widely because of its short duration and high productivity, but is highly susceptible to low soil P, limiting the spread of the variety in uplands. We attempted to improve the tolerance of MTU1010 to low soil P by introgressinga recently cloned and characterized major QTL associated with tolerance- Pup1 through marker-assisted backcross breeding (MABB). A drought tolerant variety, Vandana possessing Pup1 was used as the donor. A co-dominant marker specific for Pup1, named K20-1-1, developed by us was used for foreground selection along with a dominant functional marker-K46-1, while SSR markers RM28011 and RM28157 flanking the QTL on either side at ~1.5Mb was used for recombinant selection. In addition, at each backcross generation, a set of 65 SSR markers polymorphic between the parents were used for background selection to identify backcross plants possessing maximum recovery of MTU 1010 genome and backcrossing was done till BC2 generation. At BC2F1, a plant possessing Pup1 along with 93% recovery of MTU 1010 genome was identified and selfed to generate BC2F2s. A total of 18 homozygous BC2F2 plants were identified and screened in a plot having low soil phosphorus (< 2 ppm) for their tolerance. All the plants showed high degree of tolerance and three of these also possessed plant type and grain type equivalent to that of MTU1010. These are being advanced for further evaluation of their tolerance, agro morphological traits and yield.