Monitoring of the field application of Metarhizium anisopliae in Brazil revealed high molecular diversity of Metarhizium spp in insects, soil and sugarcane roots

Natasha Sant′Anna Iwanicki,Ana Beatriz Riguetti Zanardo Botelho,Italo Delalibera Júnior,Alessandro Alves Pereira,Rafael De Andrade Moral,Maria Imaculada Zucchi,Janayne Maria Rezende

doi:10.1038/s41598-019-38594-8

Abstract

The use of Metarhizium against sugarcane spittlebugs in Brazil is one of the most successful and long lasting biological control programs using entomopathogenic fungus in the world. However, studies to monitor the fate of this fungus on the sugarcane agroecosystem are rare, especially with respect to its persistence, efficacy in pest control and impact on the local populations of Metarhizium. The present study aimed at documenting the efficacy and persistence of M. anisopliae strain ESALQ1604 in a sugarcane field by using microsatellite molecular markers. The species diversity of Metarhizium was characterized in insects, soil and sugarcane roots in a sprayed and an unsprayed plot. Although the infection rates were not very high (≤ 50%), the applied strain was recovered from spittlebugs after 7, 30 and 60 days’ post-application, but accounted for only 50%, 50% and 70.5% of all insects killed by M. anisopliae, respectively. All haplotypes from spittlebug were associated with a single subclade of M. anisopliae. The highest haplotype diversity was found in soil (h = 0.989) and in the smallest in spittlebug (h = 0.779). Metarhizium robertsii, M. anisopliae, M. brunneum; one taxonomically unassigned lineage was found in soil and only M. brunneum and M. anisopliae were isolated from roots. This study revealed the great diversity of Metarhizium spp. in the sugarcane agroecosystem and the importance of the local population of M. anisopliae on spittlebugs management.

Highlights

Sugarcane (Saccharum spp.) is one of the key crops for the Brazilian economy
The applied strain ESALQ1604, represented by the multilocus microsatellite haplotype (MMH) 152 (Fig. 1), was recovered only from insects collected in the sprayed plot on all post-application dates except on day 90 (Fig. 2)
We have shown that strain ESALQ1604 of M. anisopliae can persist infecting spittlebugs on sugarcane for up to sixty days after the application in the field

Summary

Introduction

Sugarcane (Saccharum spp.) is one of the key crops for the Brazilian economy. the sugar and sugarcane-ethanol industry represent 12% of the country’s Gross domestic product (GDP) and employs 4.5 million workers annually[1]. There is a significant number of companies expanding business opportunities in new biorefineries, investing in R & D of bioplastics[5] and developing studies on bioelectricity In this promising scenario for the sector, the government has introduced incentives and programs to increase the efficiency in sugarcane production. Nymphs extract water and nutrients from the roots, causing stress that predisposes plants to steam-cracking and deterioration, while adults feed and inject toxins into leaf which cause necrosis of the leaves[7] These damages change the physical quality of sugarcane used as raw material in the industry, by reducing the sugar content in stems and increasing the fiber content[8]. In Brazil, M. anisopliae is the fungal species with the highest number of product registrations[11], as well as being the entomopathogen most widely commercialized by companies and produced on a large scale by sugarcane mills for controlling spittlebugs (adults and nymphs).

Objectives

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Results

Conclusion