Maize and Oat Antixenosis and Antibiosis Against <I>Delphacodes kuscheli</I> (Homoptera: Delphacidae), Vector of “Mal de Rio Cuarto” of Maize in Argentina

Abstract

"Mal de Rio Cuarto" (MRC) is the most important virus disease of maize, Zea mays L., in Argentina. Several maize lines show different levels of resistance to MRC in the field; however, no studies have been conducted to investigate resistance mechanisms against its insect vector, Delphacodes kuscheli Fennah (Homoptera: Delphacidae). Oat, Avena spp., is the main overwintering host of D. kuscheli and main source of populations that infest maize. Although oat varieties resistant to the greenbug, Schizaphis graminum (Rondani) (Homoptera: Aphididae) are commercially available, their effect on D. kuscheli is unknown. We conducted laboratory experiments to test for the presence of antixenosis and antibiosis resistance mechanisms on six maize lines with different levels of field resistance to MRC, and seven commercial oat cultivars that include two S. graminum-resistant varieties. We did not find antibiotic effects of maize lines on D. kuscheli longevity and survivorship patterns, but we obtained antixenotic effects from the LP2 line (field moderate) due to reduced settling preference and feeding. Oat 'Bonaerense Payé and 'Suregrain INTA' showed both antixenosis and antibiosis, with significantly less settling preference, oviposition in the no-choice test, and reduced total fecundity in comparison with the other varieties studied. The S. graminum-resistant 'Boyera F. A.' and 'Tambera F. A.' did not showed a consistent pattern of resistance versus D. kuscheli across all experiments. Our results indicate the presence of potential sources of insect resistance in the maize lines and oat cultivars tested that may be used in MRC integrated pest management programs.

Modeling population dynamics of yeast-like symbionts (Ascomycota: Pyrenomycetes: Clavicipitaceae) of the planthopper Delphacodes kuscheli (Hemiptera: Delphacidae)

“…It was shown that this model is a particular case of a generalized von Bertalanffy model (Day 1966). Only for peak oviposited females, apart from its weight we added the weight represented by the number of mature oocytes calculated as: WE (t=38) = 20 • W (t=4) , where 20 represents the mean maximum number of eggs deposited during peak reproduction (Costamagna et al 2005) and W (t=4) the weight of an individual young egg.…”

Wheat Antixenosis, Antibiosis, and Tolerance to Infestation by <I>Delphacodes kuscheli</I> (Hemiptera: Delphacidae), a Vector of “Mal de Río Cuarto” in Argentina

“…Nevertheless, their resistance to infestation by D. kuscheli has scarcely been studied. Antixenotic and antibiotic resistance to D. kuscheli of oat cultivars, carrying resistance to greenbug, Schizaphis graminum (Rondani), has been reported previously (Costamagna et al 2005).…”

“…The telomeric region of the 6A chromosome probably carries genes that enable the plant to tolerate biotic stresses. Nonetheless, the Þrst report of resistance against D. kuscheli in oats indicates an absence of antixenosis and antibiosis in commercial greenbugresistant oat cultivars (Costamagna et al 2005). Stress signaling pathways are not independent, ABA, ethylene, jasmonic acid, and salicylic acid are produced by plants under stress, and when exogenously applied, they switch on a number of genes that respond to environmental or biotic stress (Yamaguchi-Shinosaki and Shinosaki 2006).…”

Natural Variation in Maize Defense against Insect Herbivores

“…Maize antixenosis has been demonstrated in the westem corn rootworm (Bemklau et al 2010), planthoppers (Costamagna et al 2005), and European com borer (Robinson et al 1978). In some instances, trade offs in maize antixenosis have been identified, whereby the activation of a defense mechanism against one herbivore or pathogen makes the plant more attractive than another (Ballhom2011).…”