Evaluation of new rubber tree clones in the field for resistance to black crust and anthracnose and identification ofpathogens causing drought in rubber trees

• Grant number: 23/11027-9
• Support Opportunities: Regular Research Grants
• Start date: October 01, 2025
• End date: September 30, 2028
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Ana Carolina Firmino
• Grantee: Ana Carolina Firmino
• Host Institution: Faculdade de Ciências Agrárias e Tecnológicas. Universidade Estadual Paulista (UNESP). Campus de Dracena. Dracena , SP, Brazil

Abstract

Despite the expansion of the rubber tree plantation area (Hevea brasiliensis Muell. Arg.) in recent years, factors such as phytosanitary problems are limiting the development of the crop. These diseases include black crust and anthracnose. The first disease is associated with different fungi such as Cladosporium spp. and Phyllachora huberi, and the second is caused by Colletotrichum spp. Both diseases mainly affect the leaves, and can cause premature leaf fall, in addition to affecting branches, petioles and new shoots. Anthracnose can also cause damage to the tapping panel. Chemical control of rubber tree foliar diseases in the field is limited due to the low quantity of registered products and operational difficulties for applications on adult plants; other strategies, such as biological control, still require further studies. In this context, the use of resistant clones seems to be a promising strategy for the control of black crust and anthracnose. Thus, this study will seek to evaluate the behavior of clones recently developed in Bahia and São Paulo, such as those from the IAC500 series, over a three-year period against these foliar diseases, evaluating their resistance characteristics in the field. Since climatic conditions influence the pathogen population and the severity of the disease, the causal agents in the study area will be identified, in addition to evaluating under which climatic conditions the disease occurs with greater intensity, through correlations with climatic data. In addition to foliar diseases, the frequency of plants with symptoms of drought and death, caused by vascular pathogens, has recently been increasing significantly. Many samples with these symptoms are being received at the phytopathology clinic of UNESP/Campus de Dracena, which has generated some concern, since the only information we have is that L. theobromae is the only pathogen associated with these symptoms in rubber trees. Considered a weak parasite, since it does not have an active penetration capacity and mainly uses wounds to infect plants, this fungus causes symptoms of graft and bark rot, which can lead to plant drying. These characteristics mean that L. theobromae is considered a pathogen of little importance in rubber trees, resulting in little information about the disease. Therefore, this study also aims to determine which species of fungi occur and which are prevalent in areas where plant deaths due to vascular problems are occurring. To this end, collections, isolation and molecular analyses will be performed, using partial sequences of the ITS, ¿-tubulin and ¿-elongase genes. The isolates will be characterized pathogenically by inoculation into different clones of rubber trees, which will also allow a brief selection of resistant clones. The results obtained will provide a better understanding of the etiological and epidemiological aspects of the disease, providing support for the development and adoption of appropriate control methods for diseases in rubber trees in Brazil. (AU)