Reaction of dwarf cashew clones to Colletotrichum gloeosporioides isolates in controlled environment

Abstract

The cashew (Anacardium occidentale L.) crop is an important source of income for the population of the Brazilian Northeast, and anthracnose disease caused by Colletotrichum gloeosporioides leads to significant production loss. However, there is little information on either the host resistance or the variation in the aggressiveness of the pathogen under controlled environment. The reaction of commercial (CCP-06, CCP-09, CCP-76 and CCP-1001) and one non-commercial (CAP-14) dwarf cashew clones was assessed against 36 isolates of this fungus controlled environmental conditions. All the isolates, including those from hosts other than cashew, were able to cause lesions on leaves and stems of most clones, albeit to different degrees. Clone CCP-06 was the most susceptible, while clone CCP-1001 showed a level of resistance to a number of the isolates, including isolate 905, while isolates 910 and 912 were aggressive to all clones. Injury increased the susceptibility of the clones to all isolates, indicating that resistance also might be associated with structural barriers that hinder penetration. Ripened cashew apples (8-week-old), of commercial clones were susceptible to isolates 905 and 910. Immature pseudo-fruits (2-week-old), with exception of clone CCP-76 which was susceptible to both isolates showed resistance against these isolates, suggesting the presence of structural and chemical barriers. Developed nuts (8-week-old), however, were more resistant than immature nuts (2-weekold) to both isolates, probably due to their thicker exocarp cuticle and reduced number of stomatal pores. Key words: Anacardium occidentale, anthracnose, resistance, aggressiveness Reação de clones de cajueiro-anão a isolados de Colletotrichum gloeosporioides em ambiente controladoRESUMO: A cultura de caju (Anacardium occidentale L.) é uma fonte de renda importante para a população do Nordeste brasileiro, sendo a antracnose causada por Colletotrichum gloeosporioides a doença que mais conduz a perdas de sua produção. Entretanto, há pouca informação para a resistência desse hospedeiro ou para a variação na agressividade do patógeno em ambiente controlado. A reação de clones comerciais (CCP-06, CCP-09, CCP-76 e CCP-1001) e um não comercial (CAP-14) de cajueiros anão-precoce, contra 36 isolados desse fungo, foi avaliada sob condições controladas. Todos os isolados, incluindo os provenientes de diferentes hospedeiros, foram capazes de causar lesões sobre folhas e hastes da maioria dos clones, ainda que em graus diferenciados. O clone CCP-06 foi o mais suscetível, enquanto o clone CCP-1001 foi resistente a mais isolados, incluindo o 905, enquanto os isolados 910 e 912 foram agressivos a todos os clones testados. A injúria mecânica das folhas aumentou a suscetibilidade dos clones a todos os isolados, indicando que a resistência pode também estar associada a barreiras estruturais que impedem a penetração. Os pseudofrutos amadurecidos (8 semanas) dos clones comerciais avaliados, foram suscetíveis a ambos os isolados testados (905 e 910), mas...

Cytological aspects of compatible and incompatible interactions between cashew (Anacardium occidentale L.) seedlings and isolates of Colletotrichum gloeosporioides (Penz.) complex

“…The detached leaves or stem segments were inoculated and incubated, as described by López and Lucas (2010a). At intervals after inoculation (12, 18, 24, 30, 38, 48, 72, 96, 114, 132, 158 and 182 h), tissues beneath inoculation droplets of twelve young stem segments (ca.…”

“…Two groups of five stem segments and five leaves (abaxial surface) were placed inside plastic boxes (20 cm × 12 cm × 4 cm), on filter paper moistened either with an aqueous solution of 0.6 mM cycloheximide or with SDW. The samples were immediately inoculated with isolate 905 of C. gloeosporioides and incubated as described by López (1999) and López and Lucas (2010a). The third group of samples were treated with cycloheximide but not inoculated (control), to observe later the possible occurrence of phytotoxicity.…”

“…According to López and Lucas (2010a), after assessing the reaction of one non-commercial (CAP-14) and four commercial dwarf cashew clones (CCP-06, CCP-09, CCP-76 and CCP-1001), in controlled environmental conditions, against 36 isolates of Colletotrichum, it was found that all the strains, including those from hosts other than cashew, were able to cause lesions on leaves and stems of most clones, albeit to different degrees. The isolates were obtained from anthracnose lesions of cashew and associated host plants in Brazil, and had been previously identified (by cultural, morphological and partial sequences of their 28S ribosomal DNA characters) as members of the C. gloeosporioides complex (López and Lucas, 2010b).…”