Abstract
The aim of the present study was to evaluate structural and biochemical aspects related to the interaction of resistant (RRIM 937, IAC 502 and 507) and susceptible (RRIM 600) rubber tree clones with C. tamarillo. For such analysis, ultrathin sections of the leaf limb were embedded in historesin and differently stained to verify structural alterations and presence of starch grains, arginine, lipids, tannins and lignins. The total proteins and activity of the enzymes peroxidase and (PAL) were quantified. Stomatal density was also analyzed under a scanning electron microscope. Data indicated alterations in the cell content of resistant clones inoculated with the pathogen, as well as greater lignin and lipid accumulation in these samples. For tannins, there was no difference between inoculated and non-inoculated clones. Arginine was found at greater quantities in IAC 502 and 507. Starch grains were not detected in any of the analyzed samples. Protein level and stomatal density were lower in resistant clones. Peroxidase activity was more expressive in resistant clones. PAL activity, there was no significant difference between clones. The lignin and lipids, total protein, peroxidase activity and stomatal density may be related to the resistance of rubber tree clones to anthracnose.
Highlights
The use of resistant materials is considered ideal to control diseases since they can be applied to large areas and have low environmental impact
The present study aimed to evaluate structural and biochemical resistance mechanisms that may be involved in the interaction of rubber trees with C. tamarillo, complementing the understanding of this pathosystem
Changes were detected in the epidermis and palisade parenchyma of clones inoculated with C. tamarillo, which may be justified by mucilage or pectin accumulation (Figure 1)
Summary
The use of resistant materials is considered ideal to control diseases since they can be applied to large areas and have low environmental impact. There is evidence that resistance of rubber trees to anthracnose, caused by fungi belonging to the genus Colletotrichum, is qualitative since different resistance degrees have been reported among the tested clones. A recent study developed by Antonio et al [3], in the region of Votuporanga City, São Paulo State, Brazil, identified different disease severity levels among 22 clones tested in the field, and the most resistant clones were IAC507 and IAC505, followed by IAC502, RRIM937, PB235 and PB311, which presented moderate symptoms. Based on the development of infection by C. gloeosporioides in different rubber tree clones, that author reported longer latent period and shorter sporogenesis resulting in lower disease severity for resistant clones, in contrast to shorter incubation period, earlier sporogenesis and greater disease severity for susceptible clones [4]. Magalhães et al [5], noticed those same aspects for
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