Abstract
Abstract A strategy in the control anthracnose of cashew (Anacardium occidentale L.) is the management of crop phenology and defense mechanisms of this host. In previous studies, under controlled conditions, the seedling reactions of 5 cashew clones (CAP-14, CCP-06, CCP-09, CCP-76 and CCP-1001) to 36 isolates of Colletorichum gloeosporioides Penz. complex (LARS- 905 to 940) was evaluated. However, good field management requires information about the infection process. This research aimed to clarify cytophysiological aspects of three compatible interactions of this pathosystem (isolates LARS-905 and 910 × CCP-76; LARS-910 × CCP-1001) and an incompatible one (LARS-905 × CCP-1001), using infected leaves/stems and microscopy (light, scanning and transmission electron). No significant differences were found prior to penetration. In the susceptible combinations, 36-66 h after inoculation, a thin primary hypha (TPH) formed in the invaded epidermal cell, widening as a large primary hypha (LPH), which filled the cell lumen simultaneously with accumulation of of yellow-brown lignopolysaccharides. Then, a thin secondary hypha (TSH) developed from the LPH, penetrating adjacent cells before the first became necrotic. In the incompatible interaction, the response of the first invaded cell was faster and more intense, with formation of papilla and lignopolysaccharide-protein-silicon complex usually blocking the pathogen.
Highlights
The first Europeans who arrived in Brazil in the 16th century found a land with exotic plant-fruits, such as cashew trees (Anacardium occidentale L.), transporting them by sea to Africa (Mozambique, Angola, Kenya and Madagascar) and Goa (India)
Since 2012 the country’s participation in the world cashew market is decreasing, because of improved technologies provided by incentives from other governments in the market, but due to the strong and prolonged drought in the Northeast region from 2012 to 2016, associated the occurrence of pests and diseases, such as anthracnose (VIDAL, 2016) caused by members of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. species complex, i.e. C. chrysophilum, C. fragariae, C. fructicola, C. gloeosporioides sensu stricto, C. queenslandicum, C. siamense and C. tropicale (COMÉ, 2014; NORSHIE, 2020; VELOSO et al, 2018)
The leaves and stems of cashew seedlings (60-days-old) of the clone CCP-1001 × LARS-905, an incompatible interaction, as well the ones of compatible interactions of the clones CCP76, CCP-1001 and CAP-14 × LARS-910, or CCP-76 and CAP-14 × LARS-905, were investigated by microscopy
Summary
The first Europeans who arrived in Brazil in the 16th century found a land with exotic plant-fruits, such as cashew trees (Anacardium occidentale L.), transporting them by sea to Africa (Mozambique, Angola, Kenya and Madagascar) and Goa (India). In the 20th century, the North American and European acceptance of cashew nuts, boosted its marketing from India to the world. Brazil’s Northeastern semi-arid only entered this international chestnut market in the 1950s, but even more so in the 1970s, mainly in the dry season of the year, after government incentives for the development of cashew nut and juice processing (ALBUQUERQUE; SILVA, 2008). Species complex, i.e. C_chrysophilum, C. fragariae, C. fructicola, C. gloeosporioides sensu stricto, C. queenslandicum, C. siamense and C. tropicale (COMÉ, 2014; NORSHIE, 2020; VELOSO et al, 2018). This reduced the cashew plantation area by 144,000 hectares, leading producers to eradicate the dead cashew trees and to trade their wood (VIDAL, 2016). The losses caused by anthracnose to cashew trees were recognized in all producing countries (KHATOON et al, 2017; MONTEIRO et al, 2015), there was no published research on the cytology, ultrastructure and physiology of the infection process on such a host
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