Inhibition of the lemon brown rot causal agent Phytophthora citrophthora by low‐toxicity compounds

Abstract

BACKGROUND Phytophthora spp., soil‐borne oomycetes, cause brown rot (BR) on postharvest lemons. The management of this disease is based on cultural practices and chemical control using inorganic salts of limited efficacy. In the search for new alternatives, the aim of this work was to evaluate the effect of low‐toxicity compounds to inhibit the growth of P. citrophthora and to control BR disease on lemons. Sodium bicarbonate, potassium sorbate, polyhexamethylene guanidine, Ascophyllum nodosum extract and a formulation containing phosphite salts plus A. nodosum (P+An) were evaluated. RESULTS All tested products inhibited mycelial growth, sporangia formation and zoospore germination of P. citrophthora in vitro. In postharvest applications on artificially inoculated lemons, only P+An exhibited a BR curative effect, with incidence reduction of around 60%. When this formulation was applied in field treatments, BR incidence was reduced by 40% on lemons harvested and inoculated up to 30 days post application. CONCLUSION Our results demonstrate the in vitro direct anti‐oomycete effect of low‐toxicity compounds and the in vivo efficacy of P+An formulation to control BR, encouraging the incorporation of the latter in the management of citrus BR. © 2020 Society of Chemical Industry

Cell wall modification and lignin biosynthesis involved in disease resistance against Diaporthe citri in harvested pummelo fruit elicited by carvacrol

“…Postharvest fungal diseases of pummelo fruit include: blue mold (caused by Penicillium italicum), green mold (Penicillium digitatum), Phomopsis stem-end rot (Diaporthe citri), Diplodia stem-end rot (Lasiodiplodia theobromae), anthracnose (Colletotrichum gloeosporioides), sour rot (Geotrichum citri-aurantii), black rot (Alternaria alternate) and brown rot (Phytophthora citrophthora). [3][4][5][6][7][8][9] Among these fungal diseases, Phomopsis stem-end rot causes a serious postharvest decay of Chinese local pummelo and is accompanied by peel browning (PB) and tissue softening, thereby reducing its storability and commodity value.…”