Fungi associated with Paraeucosmetus pallicornis causing apparent symptoms of toxicity in rice grains and rice seedlings

Abstract

OkInfestation of rice grains in the field by Paraeucosmetus pallicornis (Dallas)\ud (Hemiptera: Lygaeidae) causes the rice to become broken and bitter, and the bran\ud to become unpalatable for consumption by poultry. This article offers the\ud hypothesis that the insect can carry fungi producing toxic substances, which in turn\ud cause these symptoms. On adult insects collected in four regencies in South\ud Sulawesi Indonesia we identified Aspergillus sp and on two samples, we also found\ud Gliocladium sp. Both the Aspergillus sp. and Gliocladium sp. isolates from\ud different regions showed different cultural characteristics, suggesting different\ud species in each genus associate with the insect. Aspergillus sp. isolated from rice\ud grains was similar to that isolated from the insect, providing evidence that the\ud Aspergillus sp. was transferred from insect to rice grains. Inoculation of these two\ud genera into seeds by immersion and seedlings by spraying with concentration of\ud 10??, 10 , and 10 spores/ml showed that only Aspergillus sp. had an impact on the\ud incidence of damage to seedlings which consisted of symptoms of apparent\ud toxicity. Comparison of treatments with the Bone isolate and Bantaeng isolate of\ud Aspergillus sp. indicated that the incidence of symptoms indicative of toxicity in\ud seedlings infected by Aspergillus through seed treatment was 7.4% per one Log\ud spores concentration for Bone isolate and 2.9% per one Log spores concentration\ud for Bantaeng isolate. The incidence in seedling inoculated by Aspergillus sp.\ud through spraying was 6.9% per one Log spores concentrationfor Bone isolate and\ud 13.5% per one Log spores concentration for Bantaeng isolate. This research\ud confirmed the occurence of an association between Aspergillus fungus and insect\ud pest of P. Pallicornis in causing toxiciy symptoms in ric