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 .

Biological agents and their metabolites to control <i>Meloidogyne</i> spp. when growing vegetables (review)

Aim. Analysis of modern studies on the effectiveness of fungi and antagonist   bacteria   against   Meloidogyne   root‐knot   nematodes   on vegetable crops.

Materials and Methods. Studies of Russian and foreign scientists on the use of biological agents and their metabolites to control Meloidogyne spp. when growing vegetables have been carefully analysed.

Results.   The   harmfulness   of   gall   nematodes   on   vegetable   crops   is described.  Studies  on  the  most  pathogenic  species  of  Meloidogyne, including those common in Russia, are summarised. Information is given regarding  features  of  the  relationship  between  the  host  plant  and phytoparasites are highlighted. An analysis of the range of chemical and biological nematicides is presented. The problem of the lack of effective environmentally friendly products able to control root‐knot nematodes on vegetables, including  the  prospect of using  biological agents, has  been identified.   The   features   of   ongoing   research   on   the   study   of   the nematicidal activity of biological agents and their metabolites to control various   stages   of   development   of   Meloidogyne   species   have   been collected, analysed, systematised and described. The prospect of studying the mechanisms of action of microorganisms against root‐knot nematodes is substantiated in order to create new effective biological nematicides that allow the growth of high‐quality and healthy vegetable products.

Conclusion. Gall nematodes (Meloidogyne spp.) remain a current pest of soil‐grown  vegetables.  Scientists  are  actively  working  on  the  study  of nematophagous fungi and antagonist bacteria to create environmentally friendly  biological  nematicides.  With  proper  use,  biological  agents  and their metabolites can help protect plants from phytoparasites at the level of chemical nematicides and have an additional beneficial effect on the growth and development of vegetable crops.