Development of Oryzophagus oryzae (Costa Lima) in rice cultivars

Abstract

Insect-resistant cultivars are essential for improving the management of pests such as Oryzophagus oryzae (Coleoptera: Curculionidae), which significantly decreases flooded rice yields. However, the degree of benefit brought to the crop varies with the type of resistance. This study aimed to evaluate the resistance of rice cultivars to O. oryzae, inferring about antixenosis and antibiosis effects on the development of larvae and adults. Under natural infestation conditions, a biennial experiment was carried out using a latin square design, with six treatments (cultivars) and plots with 30 plants (five rows of six plants equidistant 20 cm) irrigated with water depth of 15 cm. The number and weight of larvae by size, as well as the number, weight, emergence rate, and sex ratio of adults, were evaluated using standard soil, plant and root samples. Except for adult sexual ratio, the cultivars differed (p ≤ 0.05) for the other variables, whose relationship evidenced antibiosis effects at the larval stage, making possible to conclude that: the BRS Firmeza cultivar has resistance to O. oryzae due to antixenosis and/or antibiosis effects; BRS Ligeirinho is susceptible to this insect species, resulting in a relatively higher number of well-developed larvae and adults; and IRGA 417 shows an antibiosis action, restricting the adult emergence rates. The weight of adults gives a greater accuracy to the evaluation of the harmful effects of rice cultivars on the O. oryzae development.

Morphoanatomical and biochemical factors associated with rice resistance to the South American rice water weevil, Oryzophagus oryzae (Coleoptera: Curculionidae)

“…From this perspective, the present study investigated the factors potentially involved in rice resistance to O. oryzae. Understanding the mechanisms involved in rice plant-RWW interactions, which are not yet completely characterized 21 , is essential for the successful development of elite cultivars that are resistant www.nature.com/scientificreports/ to insects, since the degree of resistance of a cultivar is related to the effectiveness of plant defensive traits against herbivory 24,27 . Based on preferences for adult feeding and oviposition, a lack of antixenosis was found among the evaluated cultivars, including 'Dawn' , which is known to be resistant to RWW 19,31 .…”

“…Six commercial rice cultivars were selected as treatments in the 2-year choice field experiment (Supplementary Table S1 ). The experimental design was a Latin-square (six treatments and six replications) to provide an equal probability of natural RWW infestations in all treatments 21 . Each plot measured 4.56 m 2 with five rows of rice spaced 30 cm apart, where each row had 20 plants spaced 20 cm apart (100 plants total).…”

“…Larvae dislodged from each root samples during sampling procedures in each plot were counted and transferred to 2.9 × 11.5 cm polypropylene tubes containing approximately 40 mL water. The tubes were kept in a climate-controlled room (25 ± 2 °C) for up to two days to record the individual larval weight following the method of Lima et al 21 .…”

“…The effect of rice cultivars on production of F1-generation adult offspring of larvae was determined according to Lima et al 21 . Four additional core samples were collected from each plot at 30 DAF and transferred into 30 × 50-cm plastic buckets (30 L) containing ~ 7 L water.…”

“…The effects of resistant host plants on arthropods are broadly classified as antixenosis (or non-preference) and antibiosis 15 ; tolerance, a third category of plant resistance, does not disrupt the behavior or biology of herbivores, but rather refers to the ability of a plant to withstand herbivory without decline in yield or quality 15,16 . Antixenosis and antibiosis against RWW species have been identified in various genotypes of rice [17][18][19][20][21] .…”