The cotton charcoal rot causal agent, Macrophomina phaseolina, biological and chemical control

Abstract

The fungus Macrophomina phaseolina causes charcoal rot disease (CRD) in cotton, whose symptoms develop in the late stages of growth and result in wilting and death. Despite significant research efforts to reduce disease incidences, effective control strategies against M. phaseolina are an ongoing scientific effort. Today’s CRD control tends toward green options to reduce the chemicals’ environmental footprint and health risks. Here, different Trichoderma species were examined separately and in combination with Azoxystrobin (AS) in semi-field open-enclosure pots and a commercial field throughout a full season. In the pot experiment, the T. asperellum (P1) excelled and led to improvement in growth (13%–14%, day 69) and crops (the number of capsules by 36% and their weight by 78%, day 173). The chemical treatment alone at a low dose had no significant impact. Still, adding AS improved the effect of T. longibrachiatum (T7507) and impaired P1 efficiency. Real-time PCR monitoring of the pathogen DNA in the plants’ roots at the harvest (day 176), revealed the efficiency of the combined treatments: T. longibrachiatum (T7407 and T7507) + AS. In a commercial field, seed dressing with a mixture of Trichoderma species (mix of P1, T7407, and Trichoderma sp. O.Y. 7107 isolate) and irrigation of their secreted metabolites during seeding resulted in the highest yields compared with the control. Applying only AS irrigation at a low dose (2,000 cc/ha), with the sowing, was the second best in promoting crops. The molecular M. phaseolina detection showed that the AS at a high dose (4,000 cc/ha) and the biological mix treatments were the most effective. Reducing the AS chemical treatment dosages by half impaired its effectiveness. Irrigation timing, also studied here, is proven vital. Early water opening during the late spring suppresses the disease outburst and damages. The results demonstrated the benefits of CRD bio-shielding and encouraged to explore the potential of a combined bio-chemo pest control approach. Such interphase can be environmentally friendly (reducing chemical substances), stabilize the biological treatment in changing environmental conditions, achieve high efficiency even in severe CRD cases, and reduce the development of fungicide resistance.

Integrated Management of the Cotton Charcoal Rot Disease Using Biological Agents and Chemical Pesticides

“…The current study intended to establish an integrated control method to protect cotton plants against charcoal rot pathogen using selected Trichoderma fungal strains, which demonstrated success in lab and seedlings tests [30] and entire season trials [9], and a previously successfully tested systemic chemical fungicide, Azoxystrobin [9]. Our prior research confirmed the tolerance of the Trichoderma species to Azoxystrobin, even at relatively high compound concentrations [33].…”

“…The pathogen typically enters the roots by exploiting cracks in the phelloderm, resulting from dense soils' expansion and cracking in hot, dry weather [4]. Preceding the irrigation timing can result in better growth, yield, and health than late spring watering [9]. The fungal uses cell-wall-degrading enzymes to penetrate and kill the host plant cells [10].…”

“…This research line focuses on combining the benefit of microorganisms with low dosages (or low toxicity) of chemical fungicides to protect cotton plants from CRD over the growing season [9]. Integrating biological agents with chemical pesticides presents several potential benefits [32].…”

“…In a previous study, we applied an integrated pest management approach, combining a Trichoderma-based biological treatment with Azoxystrobin irrigation to minimize cotton CRD in a semi-field (open-enclosure) full-season potted experiment [9]. The eco-friendly treatments with T. asperellum (P1) and T. longibrachiatum (T7507) alone protected cotton plants' growth and enhanced health indexes throughout the season.…”

“…In the commercial field, the biological and chemical pesticides were tested separately [9]. The highest yields came from treating seeds with a Trichoderma species blend (P1, T7407, Trichoderma sp.…”