Understanding the plant-pathogen interactions is of utmost importance to design strategies for minimizing the economic deficits caused by pathogens in crops. With an aim to identify genes underlying resistance to downy mildew, a major disease responsible for productivity loss in pearl millet, transcriptome analysis was performed in downy mildew resistant and susceptible genotypes upon infection and control on 454 Roche NGS platform. A total of ~685 Mb data was obtained with 1 575 290 raw reads. The raw reads were pre-processed into high-quality (HQ) reads making to ~82% with an average of 427 bases. The assembly was optimized using four assemblers viz. Newbler, MIRA, CLC and Trinity, out of which MIRA with a total of 14.10 Mb and 90118 transcripts proved to be the best for assembling reads. Differential expression analysis depicted 1396 and 936 and 1000 and 1591 transcripts up and down regulated in resistant inoculated/resistant control and susceptible inoculated/susceptible control respectively with a common of 3644 transcripts. The pathways for secondary metabolism, specifically the phenylpropanoid pathway was up-regulated in resistant genotype. Transcripts up-regulated as a part of defense response included classes of R genes, PR proteins, HR induced proteins and plant hormonal signaling transduction proteins. The transcripts for skp1 protein, purothionin, V type proton ATPase were found to have the highest expression in resistant genotype. Ten transcripts, selected on the basis of their involvement in defense mechanism were validated with qRT-PCR and showed positive co-relation with transcriptome data. Transcriptome analysis evoked potentials of hypersensitive response and systemic acquired resistance as possible mechanism operating in defense mechanism in pearl millet against downy mildew infection.

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There is a lack of information on the molecular characterization of Ocimum species and hence, efforts have been made under the present study to characterize 17 Ocimum genotypes belonging to 5 different species (O. basilicum, O. americanum, O. sanctum, O. gratissimum and O. Polystachyon) through random amplified polymorphic DNA (RAPD) and inter simple sequence repeats (ISSR) markers. PCR amplification using 20 RAPD primers generated a total of 506 loci, of which 490 (96.47 %) loci were found polymorphic. The PIC value for RAPD ranged from 0.907 (OPF 14) to 0.954 (OPC 11) with an average of 0.937. The ISSR primers generated a total of 238 loci, of them 234 (98.17 %) loci were polymorphic. The PIC value ranged from 0.892 (UBC 808) to 0.943 (ISSR A12) with an average of 0.923. The average Jaccard’s similarity coefficient based on RAPD and ISSR analysis was 0.58 and 0.52, respectively. Clustering pattern of dendrogram generated using the pooled RAPD and ISSR data showed all Ocimum genotypes in their respective species groups at a cutoff value of 0.49 and 0.42, respectively. Many unique species-specific alleles were amplified by RAPD and ISSR markers. In both marker systems, a maximum number of unique alleles were observed in O. sanctum. The results of the present investigation provided valid guidelines for collection, conservation and characterization of Ocimum genetic resources.

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In the present study, 20 sandalwood (Santalum album L.) genotypes were characterized using RAPD, ISSR and SSR markers. Twenty-five RAPD and twenty-one ISSR primers that generated clear and reproducible banding patterns amplified 225 and 208 bands, respectively, among 20 sandalwood genotypes. Out of 225, 181 (83.13 %) RAPD bands were polymorphic while out of 208, 156 (75.77 %) ISSR bands were polymorphic. The average polymorphism information content (PIC) for RAPD and ISSR was 0.84 and 0.86, respectively. A good correlation (0.96) was observed between the matrices produced by RAPD and ISSR primers. Though, there was high similarity among genotypes (0.79 for RAPD and 0.70 for ISSR), the observed genetic diversity was found good enough for the characterization of sandalwood genotypes. Cross-species transferability SSR markers developed in S. austrocaledonicum and S. insulare were found to be monomorphic. The results of the present investigation would provide valid guidelines for collection, conservation and characterization of sandalwood genetic resources.