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Pigeonpea [ Cajanus cajan (L.) Millspaugh] is an economically important legume playing a crucial role in the semi-arid tropics. Pigeonpea is susceptible to Helicoverpa armigera (Hübner), which causes devastating yield losses. This pest is developing resistance to many commercially available insecticides. Therefore, crop wild relatives of pigeonpea, are being considered as potential sources of genes to expand the genetic base of cultivated pigeonpea to improve traits such as host plant resistance to pests and pathogens. Quantitative proteomic analysis was conducted using the tandem mass tag platform to identify differentially abundant proteins between IBS 3471 and ICPL 87 tolerant accession and susceptible variety to H. armigera, respectively. Leaf proteome were analysed at the vegetative and flowering/podding growth stages. H. armigera tolerance in IBS 3471 appeared to be related to enhanced defence responses, such as changes in secondary metabolite precursors, antioxidants, and the phenylpropanoid pathway. The development of larvae fed on an artificial diet with IBS 3471 lyophilised leaves showed similar inhibition with those fed on an artificial diet with quercetin concentrations with 32 mg/25 g of artificial diet. DAB staining (3,3'-diaminobenzidine) revealed a rapid accumulation of reactive oxygen species in IBS 3471. We conclude that IBS 3471 is an ideal candidate for improving the genetic base of cultivated pigeonpea, including traits for host plant resistance., Competing Interests: The authors declare no conflict of interest.

Background: Supernatant-secreted proteins in Bacillus thuringiensis (Berliner) (Bt) with insecticidal activity provide an important source of information for discovery of new useful strains and/or entomotoxins. However, physiological variation among isolates might interfere in the detection efficiency of screening procedures on Bt collections. The aim of this study was to assess the magnitude of this variation in a sample of isolates from a tropical Bt collection, which was gauged through the assessment of their temporal patterns of growth and protein secretion in culture supernatants (SNs), as well as of the corresponding toxicity against fall armyworm (Spodoptera frugiperda, JE Smith). Feeding bioassays were performed, with larvae being treated with heated and non-heated total protein extracted from SNs collected at different culture times. Larva mortality and reduction in pupa formation were observed., Results: Intra- and interisolate variations were observed in the temporal patterns of growth, quality and quantity of protein secreted, as well as in insecticidal activity of these SNs, based on larvae mortality and pupation rates. These results suggest that the insecticidal potential of certain isolates can be hidden if comparisons are done on the basis of the same number of cells in the culture and/or the same culturing time., Conclusions: Methods of screening Bt collections on the basis of feeding bioassays can be misleading with regards to identifying more promising isolates for biocontrol purposes if physiological differences are not considered. The consequences and implications of these findings for the development of experimental systems that depend on toxicity bioassays to identify alternative Bt strains and entomotoxins with practical applicability have been discussed., (Copyright © 2011 Society of Chemical Industry.)