Judith K Brown

Ur-Rehman, Z., H.-W. Herrmann, U. Hameed, M.S. Haider, and J.K. Brown. 2013. First detection of Cotton leaf curl Burewala virus and cognate Cotton leaf curl Multan betasatellite and Gossypium darwinii symptomless alphasatellite in symptomatic Luffa cylindrica in Pakistan. Plant Dis. 97:1094 //dx.doi.org/10.1094/PDIS-12-12-1159-PDN.Disease Note (short report)

Abstract:

To explore the effectiveness of insect derived protease inhibitors in protecting plants against insect feeding, anti-trypsin, anti-chymotrypsin and anti-elastase protease inhibitor (PI) genes from Manduca sexta L. were expressed in transgenic cotton (Gossypium hirsutum L.). From 198 independent transformants, 35 elite lines were further analyzed. Under the control of the 35S promoter of CaMV, PI accumulated to approximately 0.1% of total protein, depending on the tissue analyzed. Using cell-flow cytometry, DNA content/ nuclei of transgenic and non-transformed cotton were identical. On cotton plants expressing PIs, fecundity of Bemisia tabaci (Genn.), the sweetpotato whitefly, was reduced compared to controls. Expression of these protease inhibitors may reduce the developmental rate of B. tabaci and other insects, and provide a strategy for cotton protection. © 1995 Springer-Verlag.

Abstract:

Biochemical properties of the predominant esterases found in two distinct populations, presently considered to be different biotypes of the whitefly Bemisia tabaci, were investigated. General esterases, previously established as diagnostic markers on native polyacrylamide gels (PAGE) for the 'A' and 'B' biotypes, were characterized with respect to molecular masses, isoelectric points (pIs), isomeric relationships, and substrate specificities. One previously unidentified band in the 'B' biotype was detected on native gels when ethylenediaminetetracetic acid (EDTA) was added to gel buffers. In each of the 'A' and 'B' biotypes, 12 bands were resolved by isoelectric focusing (IEF), and had pIs ranging from 4.86 to 7.37, and 4.70 to 6.59, respectively. The two bands ('B'1 and 'B'2), used as diagnostic markers on native gels for the 'B' biotype, were identified as a single band (E7) with IEF. An analogous E7 band was resolved in the 'A' biotype with IEF, but corresponded to only one isomer (A6) on native gels. Results of substrate studies revealed most bands on IEF gels had carboxylesterase activity. The E7 esterase in each biotype was identified specifically as acetylcholinesterase (AChE). Ferguson plots revealed these E7 esterases of the 'A' and 'B' biotypes had equivalent charges, but different molecular masses, indicating they are size isomers. Two dimensional (2D) and IEF analyses confirmed this relationship. © 1994.

Abstract:

Bemisia tabaci (Gennadius) adults were collected from poinsettia plants (Euphorbia pulcherrima) in retail nurseries in Cd. Obregon and Navojoa, Sonora, Mexico. A single field sample was collected from broccoli plants in Obregon, Sonora. Both adult whitefly and immature instars were observed on infested leaves. Whiteflies were identified as B. tabaci using morphological characters of the pupae to distinguish them from the greenhouse whitefly; and to specific biotype, by molecular analysis using the mitochondrial cytochrome oxidase I (mtCOI) sequence. Phylogenetic analysis of mtCOI sequences indicated that poinsettias were colonized both by the Q and the B biotype. The Q biotype was found only on poinsettia plants, and one poinsettia sample was infested with both the Q and the B biotype. The B biotype alone was associated with the field-collected broccoli sample analyzed in the study. A more extensive survey is required to determine the extent of the distribution of the Q biotype in Mexico, particularly where ornamental plants are transported from central to northern Mexico. Such plants could serve as the source of the Q biotype, which has been reported to be highly resistant to insecticides including the neo-nicotinoids that are widely used to control the B biotype in much of Mexico. This is the first report of the Q biotype in Mexico.

PMID: 12695565;PMCID: PMC154288;Abstract:

Evolution of resistance by pests is the main threat to long-term insect control by transgenic crops that produce Bacillus thuringiensis (Bt) toxins. Because inheritance of resistance to the Bt toxins in transgenic crops is typically recessive, DNA-based screening for resistance alleles in heterozygotes is potentially much more efficient than detection of resistant homozygotes with bioassays. Such screening, however, requires knowledge of the resistance alleles in field populations of pests that are associated with survival on Bt crops. Here we report that field populations of pink bollworm (Pectinophora gossypiella), a major cotton pest, harbored three mutant alleles of a cadherin-encoding gene linked with resistance to Bt toxin Cry1Ac and survival on transgenic Bt cotton. Each of the three resistance alleles has a deletion expected to eliminate at least eight amino acids upstream of the putative toxin-binding region of the cadherin protein. Larvae with two resistance alleles in any combination were resistant, whereas those with one or none were susceptible to Cry1Ac. Together with previous evidence, the results reported here identify the cadherin gene as a leading target for DNA-based screening of resistance to Bt crops in lepidopteran pests.