Mapping QTLs for the tissue culture performance of rice mature embryo using indica-japonica recombinant inbred lines

Abstract The tissue culture performance is the determinant factor of genetic transformation in indica rice (Oryza sativa L.). Quantitative trait loci (QTLs) associated with the tissue culture performance of mature embryo were detected by 202 genetic markers and 190 recombinant inbred lines (RILs) derived from the cross between two rice varieties, 93-11 (indica) as female parent and Nipponbare (japonica) as male parent. A composite interval mapping (CIM) was used to identify the QTLs for the tissue culture performance. The tissue culture performance of rice mature embryo were evaluated by six parameters, embryogenic calli induction rate (ECR), callus subculture capability (CSC), plantlet regeneration rate (RR), average number of regenerated shoots per callus (NRS), green plantlet regeneration rate (GRR) and average number of regenerated green shoots per callus (NRGS). Nipponbare has better tissue culture response than 93-11 because all indicators were higher in Nipponbare except CSC. Four QTLs for ECR, five QTLs for CSC, three QTLs for RR, two QTLs for NRS, four QTLs for GRR and three QTLs for NRGS were detected. These putative QTLs associated with tissue culture performance were distributed on eight rice chromosomes. These results demonstrated the possibilities of improving the tissue culture performance of indica rice by marker assisted selection (MAS) with those desirable alleles of japonica rice. Keywords: mature embryo; quantitative trait loci (QTLs); rice; recombinant inbred lines (RILs); tissue culture performance. Abbreviations: CAPS-cleaved amplified polymorphic sequence; CIM-composite interval mapping; CSC-callus subculture capability; DH-doubled haploid; ECR-embryogenic calli induction rate; GRR-green plantlet regeneration rate; LOD-logarithm of odds; MAS-marker assisted selection; NRGS-average number of regenerated green shoots per callus; NRS-average number of regenerated shoots per callus; QTLs-quantitative trait loci; RILs-recombinant inbred lines; RR-plantlet regeneration rate; SSRsimple sequence repeats; STS-sequence-tagged site

Effects of different Wx alleles on amylopectin molecular structure and enzymatic hydrolysis properties of rice starch

Allelic variation at the Wx locus plays a vital role in regulating apparent amylose content (AAC) as well as other important starch properties in rice grain. However, the extent of Wx allelic variation affecting amylopectin fine structure and enzymatic hydrolysis properties of rice starch remains unknown. In this paper, a series of rice single-segment substitution lines with five different Wx alleles (wx, Wxt, Wxg1, Wxg2 and Wxg3) were used for comparative studies. The results showed that the five Wx alleles exhibited a wide variation in amylopectin molecular structure, hydrolysis and in vitro digestion properties of rice starch. Amylopectin chain length distribution as evaluated by fluorophore-assisted capillary electrophoresis was significantly different for the five Wx alleles, which might result in different functional properties. The hydrolysis degree of the five Wx genotype starches by α-amylase or amyloglucocidase was in the order wx > Wxt > Wxg1 > Wxg3 > Wxg2. The rapidly digestible starch (RDS) content of the tested rice starches followed the order wx = Wxg3 > Wxt = Wxg1 > Wxg2. The extent decrease of slowly digestible starch (SDS) content was wx = Wxt > Wxg1 > Wxg2 > Wxg3, while the trend in resistant starch (RS) content was Wxg2 > Wxg3 > Wxg1 > Wxt > wx. Correlation analysis indicated that AAC was significantly positively correlated with RS but significantly negatively correlated with SDS and hydrolysis. The RDS showed a significant positive correlation with amylopectin short chains (DP 6–12) but no significant correlations with other structural properties. The present results could provide important information for the application of rice starches with different Wx genotypes