Transcriptome-based analysis of candidate gene markers associated with resistance mechanism to Phytophthora melonis that causes root and crown rot in pumpkin.

Root and crown rot incited by an oomycete, Phytophthora melonis , causes significant yield losses in commercial pumpkin (Cucurbita pepo ) production worldwide. Currently, resistant cultivars and knowledge of molecular mechanism of C. pepo against P. melonis are scarce. Here, we analysed the quantitative gene expression changes of 10 candidate gene markers (bHLH87, ERF014, HSF, MYB, PR-1, WRKY21, CPI, POD, PSK, SGT ) in pumpkin roots and leaves at three time points (h post-inoculation, hpi) following inoculation with P. melonis in two resistant (Ghelyani and Tanbal), and two susceptible (Marmari and Khoreshti) varieties of pumpkin. Gene expression using quantitative real time PCR along a time course revealed the strongest transcriptomic response at 48 and 72hpi in resistant genotypes, 1.1-2.7-fold in roots and leaves, respectively, with a high significant correlation (r =0.857**-0.974**). We also found that CPI , PSK, SGT1 and POD act as a dual regulator that similarly modulate immunity not only against P. melonis , but also against other diseases such as early blight (Alternaria cucumerina) , powdery mildew (Podosphaera xanthii ), downy mildews (Pseudoperonospora cubensis ), and pathogenic plant nematodes (Meloidogyne javanica ). Furthermore, significantly higher activities of the ROS scavenging defence enzymes, catalase (1.6-fold increase) and peroxidase (6-fold increase) were observed in the roots of resistant cultivars at different hpi compared with non-inoculated controls. In addition, the biomass growth parameters including leaf and root length, stem and root diameter, root fresh weight and volume were significantly different among studied genotypes. Cumulatively, the transcriptome data provide novel insights into the response of pumpkins for improving pumpkin breeding to P. melonis .

Identification of novel associations of candidate genes with resistance to Rhizoctonia solani AG-3PT in Solanum tuberosum stem canker.

To develop an understanding mechanism to define responding of potatoes to R. solani, we analyzed the expression of ten novel candidate gene-markers using reverse-transcription-quantitative PCR (RT-qPCR) in resistant 'Savalan' and partially resistant 'Agria' in contrast to susceptible 'Sagita', and partially susceptible 'Pashandi'. In addition, oxidant-enzymatic-activity of catalase and superoxide-dismutase, as well as biomass-growth-parameters; shoot and root length, fresh and dry weight, and root volume were considered as complementary factors to the involving mechanism accordingly. Gene-markers up-regulated maximum up to 3.5-fold with the highest correlation, r = 0.939** following R. solani-inoculation, predominantly in resistant genotypes. Surprisingly, WRKY8-gene, basically resistant to late-blight-Phytophtora infestans was also up-regulated to 2.3-fold in resistant 'Savalan' followed by 'Agria'. Similar results with 3.1-fold were obtained on Osmotin-gene resistant to early-blight-Alternaria alternata. Enzymatic-activity of catalase with 1.6-fold and superoxide-dismutase, 6.8-fold also showed the highest level of activity in resistant genotypes, and had a high significant correlation, r = 773** and r = 0.881** with expression levels of related gene-markers respectively. Similarly, there were significant differences in biomass-growth-parameters, but with reductions in partially susceptible 'Sagita' and susceptible 'Pashandi'. Conclusively, S. tuberosum-R. solani interaction revealed that certain gene-markers can cover resistance to more than one disease simultaneously.