Phytopatogenic fungi cause severe economic losses worldwide. Rhizoctonia solani Kühn is a pathogenic fungi affecting several crops, controlled mainly by agrochemicals. Biological control has arisen as another option for managing this pathogen. In this study, we evaluated the biocontroller potential of five orchid mycorrhizal fungi (OMF) isolated from terrestrial Chilean orchids on R. solani. We compared the biocontroller effect of these OMFs with that of Trichoderma harzianum Rifai in an in vitro dual culture experiment. We found that R. solani can be controlled in vitro by OMF isolated from native orchids. The OMF isolated from Chloraea virescens and C. lamellata showed the best biocontroller results, which were similar, or even higher, than with T. harzianum. Thus, OMFs could become a relevant alternative for the integral control of R. solani, contributing to the reduction in the use of agrochemicals in crops.
Degradation of ecosystems is one of the main causes of the global decline in biodiversity. Many species are threatened with extinction and urgent actions are needed. Chloraea disoides is a critically endangered terrestrial orchid endemic to Chile. Our main goal was to evaluate the effect of three culture media in the asymbiotic germination of this species, aiming at its propagation in the long term. We tested the effect of Malmgren modified terrestrial orchid medium (MM), modified Murashige & Skoog medium (MS1/2), and agar-water (AW). After one week of incubation, seeds in all three media reached pre-germination stage. After four weeks, germination was achieved in MM and MS1/2. Protocorm stage was reached after 6 weeks only in MM. After 13-14 weeks, embryos reached the rhizoid stage in MM and MS1/2 and did not further develop until the end of the experiment (week 16). Overall, asymbiotic germination was statistically higher in MM and MS1/2 compared to AW, but very low nevertheless, compared to other Chilean Chloraea species, being lower than 8%. The laboratory propagation of C. disoides could be a key strategy to avoid its extinction in the short term but further studies are needed to fully understand its low germination capacity.
In vineyards, Botryosphaeria dieback (BD) occurs in young and old plants. In the field, the prevalence and severity of the disease increase proportionally with the age of the vineyards. Among the pathogens that cause (BD), Diplodia seriata is the most prevalent species in Chile and other countries with a Mediterranean climate. To date, no information is available on the sus-ceptibility of adult wood to infection by this pathogen since most of the pathogenicity tests have been carried out on 1- or 2-year-old shoots or detached canes. Therefore, a pathogenicity test was carried out on plants under field conditions, with inoculations in plants, on one-year-old shoots, and 2- and 10-year-old wood in grapevine cv. Cabernet Sauvignon. A pathogenicity test was carried out with two isolates of D. seriata selected in an assay in detached canes that were 2-year-old. The results on plants showed that D. seriata was significantly more aggressive on 10-year-old than on one- or two-year-old tissue. These results were compared with the lesions ob-tained from two-year-old canes. The results of this work are consistent with the damage ob-served in the field, highlight the importance of identifying each pathogenic species that causes (BD) and contribute to the knowledge of the epidemiology of this disease in Mediterranean cli-mates.
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