Identification of two new drought specific candidate genes in sugarcane (Saccharum spp.)

Effective identification and understanding of genes contribute to improve plant drought resistance. A study was conducted to identify drought responsive candidate genes in sugarcane. Two genes viz., SOD (Superoxide dismutase) and IGS (Indole 3- glycerol phosphate synthase) were used as gene specific markers. Specific primers were designed based on the sequences in Genbank databases. Mapping population developed by crossing a drought tolerant parent (Co 740) and a drought susceptible parent (Co 775) were phenotyped using physiological and sugar yield contributing parameters and were characterized into groups of varying levels of resistance and susceptibility. Parental polymorphism for SOD and IGS specific primers was established using genomic DNA from field grown drought tolerant and susceptible parents, as the presence in Co 740 (resistant) and absence in Co 775 (susceptible) respectively. Resistant and susceptible parents and six each resistant and susceptible progeny were subjected to drought imposition and RNA were isolated and RT - PCR analysis performed using these gene specific primers. A specific band of 618 bp was identified in drought tolerant parent and progeny, absent in drought susceptible parent and progeny genotyped using SOD gene. A specific band of 340 bp was identified in drought tolerant parent and progeny while it was absent in drought susceptible parent and progeny genotyped using IGS gene. These two fragments of interests were cloned in PTz57R/T vector and sequenced. SOD618 sequence was BLAST searched that showed 98 % homology with the drought inducible protein in Saccharum hybrid and IGS340 showed 80 % homology with the hypothetical protein expressed in rice genome. These new genes hold promise improving drought resistance of sugarcane through their use as candidate genes in marker assisted selection and in genetic transformation.