Student/presenter: Swarupa Nanda Mandal, Ph.D. candidate, Crop Science
Format: Oral presentation
Title: Genomic interactions governing novel salinity tolerance mechanisms in chromosome segment substitution lines of Oryza sativa x Oryza rufipogon
Swarupa Nanda Mandal, Oluwatobi C.M. Bello, Jacobo Sanchez, Ai Kitazumi, Coenraad R Van-Beek, Isaiah C.M. Pabuayon, and Benildo G. de los Reyes
Department of Plant and Soil Science, Texas Tech University, Lubbock, TX-79415, USA
The Asian cultivated rices (Oryza sativa ssp. japonica, indica) were the outcomes of independent domestication events from Oryza rufipogon about 10,000 years ago. As progenitor, the O. rufipogon gene pool represents a rich reservoir of genetic novelties and cryptic functions that have been left behind in the wild. To explore the potential of this genetic system for the creation of genetic/epigenetic novelties for stress adaptive traits, we examined a set of 48 Chromosome Segment Substitution Lines (CSSL) harboring 97.6% of O. rufipogon genome in the background of japonica cultivar Curinga. Comprehensive physiomorphometric evaluation of the CSSL population showed that introgression of certain O. rufipogon genomic segments created transgressive (non-parental) phenotypes under salinity stress. Two introgression lines (CR-1, CR17) out-performed both their donor (O. rufupogon) and recurrent (O. sativa) parents in terms of survival under extreme salinity (EC = 12) at the vegetative stage. Among the many traits examined, cellular membrane stability and retention of K+ appeared to explain much of phenotypic variances. Interval mapping aided by a genotyping-by-sequencing approach delineated a 3.9-Mb region of O. rufipogon chromosome-4 as the culprit behind the transgressive nature of CR-1 and CR-17. Detailed analysis of such region, which encodes a total of 331 protein-coding gene loci, revealed that 162 genes within the interval were O. rufipogon-specific, while 156 other genes were novel alleles of evolutionarily conserved gene loci. Integration of physiomorphometric profiles with gene function enrichment within the introgressed genomic segment revealed that rewired networks for photosynthesis and respiration are crucial for transgressive salinity tolerance. This study supports a breeding paradigm based on interspecies genomic interaction and cryptic genetic/epigenetic effects hidden in wild progenitors to create adaptive phenotypic novelties. Analyses of transcriptome and methylome along with their networks will illuminate the regulatory mechanisms rewired by introgression from O. rufipogon.