Plant Stress Resilience Lab

Background
The Food and Agriculture Organization has reported approximately 40 % of food loss due to damage from plant pests and diseases, including fungal infections. Continuous application of agrichemicals for controlling fungal infection cause the occurrence of fungicide resistance. Colletotrichum spp., major causal agents for strawberry anthracnose, have gained concern for fungicide resistance issues.
Methods
We developed novel antifungal strategies in the present study by integrating multibranched flower-like ZnO (fZnO) and agrochemicals (trifloxystrobin). fZnO compounds were synthesised using an eco-friendly and efficient hydrothermal method. Charged polymers with steric structures, such as hydrophilic polyacrylic acid (PAA) and polyethyleneimine (PEI), were grafted onto fZnO surfaces to improve the suspension ability of the compounds. We used the grafted fZnO compounds in combination with the fungicide trifloxystrobin to evaluate the in vitro and in vivo activities.
Significant findings
Grafted fZnO (80 ppm) and trifloxystrobin (100 ppm) effectively inhibited the growth of fungicide-resistant Colletotrichum spp. and limited strawberry anthracnose on leaves. PEI-grafted fZnO shows promise as an eco-friendly additive in sustainable agriculture due to its photocatalytic activity and ability to withstand environmental factors.

Successive cultivation of fungi on artificial media has been reported to cause the sectorization, which leads to degeneration of developmental phenotype, and virulence. Fusarium oxysporum f. sp. niveum (Fon), the causal agent of watermelon Fusarium wilt, forms degenerated sectors after successive cultivation. In the present research, we demonstrated that subculture with aged mycelia increased the incidence of degenerations. To further investigate the differences between the Fon wild type (sporodochial type, ST) and variants (MT: mycelial type and PT: pionnotal type), developmental phenotypes and pathogenicity to watermelon were examined. Results in variants (PT2, PT3, PT11, and MT6) were different from ST with mycelia growth, conidia production and chlamydospore formation. Virulence of degenerated variants on susceptible watermelon Grand Baby (GB) cultivar was determined after inoculation with Fon variants and Fon ST. In root dipping methods, Fon variants showed no significant differences in disease progress compared with ST. Fon variants showed a significant decrease in disease progression compared with ST through infested soil inoculation. The contrasting results of two inoculation methods suggest that the degenerative changes due to repeated successive cultivation may lead to the loss of pathogen virulence-related factors of the early stage of Fon infection process. Therefore, cell wall-degrading enzymes (CWDEs; cellulase, pectinase, and xylanase) activities of different variants were analyzed. All Fon degenerated variants demonstrated significant decreases of CWDEs activities compared with ST. Additionally, transcript levels of 9 virulence-related genes (fmk1, fgb1, pacC, xlnR, pl1, rho1, gas1, wc1, and fow1) were assessed in normal state. The degenerated variants demonstrated a significantly low level of tested virulence-related gene transcripts except for fmk1, xlnR, and fow1. In summary, the degeneration of Fon is triggered with successive subculture through aged mycelia. The degeneration showed significant impacts on virulence to watermelon, which was correlated with the reduction of CWDEs activities and declining expression of a set of virulence-related genes.