Aphids cause significant yield losses in agricultural crops worldwide. Medicago truncatula, a model legume, cultivated pasture species in Australia and close relative of alfalfa (Medicago sativa), was used to study the defence response against Therioaphis trifolii f. maculate [spotted alfalfa aphid (SAA)]. Aphid performance and plant damage were compared among three accessions. A20 is highly su...

Tagosodes orizicolus is one of the main plagues of rice in tropical America causing two types of damages, the direct one, feeding and oviposition effect, and an indirect one, by the transmission of the "Rice hoja blanca virus". During 2006-2007 we carried out research under greenhouse conditions at Fundaci6n Danac, Venezuela, in order to determine the mechanisms of antixenosis, antibiosis and t...

Sitophilus zeamais (Motsch.) (Coleoptera: Curculionidae) has a global distribution and is one of the most important post-harvest pests maize (Zea mays L.). Some Mexican races could be novel source resistance against S. to improve commercial maize, generating lines, varieties, hybrids with pest. These are original from center origin have been exposed selection pressure other for thousands years,...

The English grain aphid, Sitobion avenae, is a major pest species of wheat crops; however, certain varieties may have stronger resistance to infestation than others. Here, we investigated 3 classical resistance mechanisms (antixenosis, antibiosis, and tolerance) by 14 wheat varieties/lines to S. avenae under laboratory and field conditions. Under laboratory conditions, alatae given the choice b...

Antibiosis-based resistance to two insect pests of rice, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) and Marasmia patnalis Bradley (Lepidoptera: Pyralidae), was compared in 11 F1 hybrids and their parental lines. Our objective was to determine whether hybrids show heterosis (hybrid vigor) for insect resistance or susceptibility. Heterosis is deÞned as the amount by which a hybrid exceeds...

Resistance categories (antibiosis and tolerance) of four sorghum (Sorghum bicolor (L.) Moench) hybrids to biotype I greenbug, Schizaphis graminum (Rondani), were determined in environmental growth chamber and field studies. Greenbug weight and fecundity were lower on ‘Cargill 607E’ compared with ‘Cargill 797’. Percentage of leaf damage area was significantly less on two resistant hybrids (Cargi...

The development of superior soybean, Glycine max (L.) Merr., cultivars exhibiting resistance to insects has beenhindereddue to linkagedrag, a commonphenomenonwhen introgressing alleles from exotic germplasm. Simple-sequence repeat (SSR) markers were used previously to map soybean insect resistance(SIR)quantitative trait loci (QTLs) ina ÔCobbÕ PI229358population, and subsequently used tocreatene...

This work aimed to characterize 20 isolates obtained from upland rice plants, based on phenotypic (morphology, enzymatic activity, inorganic phosphate solubilization, carbon source use, antagonism), genotypic assays (16S rRNA sequencing) and plant growth promotion. Results showed a great morphological, metabolic and genetic variability among bacterial isolates. All isolates showed positive acti...

The " discovery " of penicillin by Fleming in 1928 and its dramatic production, urged on by the necessities of war, heralded a new era of therapeutics. It has changed the pattern of disease the prognosis of infections, the expectation of life, indeed, it has changed the whole human ecology. Before the discovery of penicillin, there were many early descriptions of the characteristics and propert...