Whitefly, Bemisia tabaci (Hemiptera : Aleyrodidae) harbors numerous secondary endosymbionts, which are transmitted from mother to offspring by both horizontally and vertically, that have crucial role on host selection, biology, and evolution. Bacteria, Cardinium was identified in B. tabaci as well as in other whitefly population from many different countries by comparing 16S rDNA sequences. Cardinium were detected in all tested indigenous B. tabaci populations of Bangladesh, Myanmar, Nepal, and the Philippines as well as Q1 biotype of Korea. It was absent in B biotype of Korea and Q biotype of China. Cardinium was also detected in three out of five tested Aleurodicus dispersus population as well as in five out of seven Trialeurodes vaporariorum, whereas they were not detected in Tetraleurodes acaciae populatuion. In adition, Cardinium was detected in parasitoid Encarsia formosa attacking B. tabaci. Among the 19 whitefly populations from different countries, present studies identified four phylogenetic groups of Cardinium, thereby demonstrating the high diversity of this genus. Cardinium phylogeny suggests a correlation of geographical range with ecological variation at the species level.

In this study two pairs of primers based on mitochondrial cytochrome oxidase subunit 1 (mtCOI) region and 28S ribosomal RNA (rRNA) gene region were used for identifying very tiny and morphologically indistinguishable parasitoid Encarsia formosa (Gahan) which are specific to this insect. The fragment amplified by these primer pairs were 860 and 650 bp in length. Species specificity test showed that all E. formosa specimens were detected with no cross reactions with other aphelinid species, including E. sophia (Girault & Dodd), E. luteola, E. Inaron and E. Nigricephala. Using phylogenetic cladogram by the sequences analysis of both mtCOI and 28S rRNA genes could be detected in E. formosa accurately in all replicates. Cardinium and Wolbachia secondary endosymbiont were also detected in E. Formosa used by PCR amplification as well as sequence analysis of 16S-23S rDNA gene region. The molecular technique developed here would be useful for rapid and precise species identification, determination of the host spectrum and more effective utilization of E. formosa.

The sweetpotato whitefly, Bemisia tabaci is a species complex that possessed several biotypes including different genotypic clusters within species, which may differ from each other genetically and physiologically but morphologically alike. This study was performed by molecular analysis for easy identification of whitefly and describes its biotype throughout Bangladesh. Whiteflies have been identified from different places of Bangladesh based on mitochondrial cytochrome oxidase subunit I (mtCOI) gene and 16S ribosomal RNA gene sequences analysis. The mtCOI sequences of BW3 (collected from eastern part of Bangladesh) whitefly were diverged by 14.5% and 15.1% compared with B and Q biotypes from Korea and it also diverged by 15.4% and 13.7% from each other compared to BW1 (collected from southern part of Bangladesh) and BW2 (collected from northern part of Bangladesh), respectively within the country. The 16S rRNA sequences of BW3 whitefly were more deviated by 41.5%, 10.7%, 42.7% and 12.6% compared with the country populations from BW1, BW2, B and Q biotypes, respectively. Moreover, it showed high divergences from indigenous whiteflies of southern and northern part of Bangladesh which clustered in a different clade on both mtCOI and 16S rRNA phylogeny. Therefore, till date three genotypic cluster of indigenous whitefly BW1, BW2 and BW3 are identified from Bangladesh.

The experiment was conducted at the Regional Agricultural Research Station,  BARI, Jessore during consecutive two years (2007-08 and 2008-09) to find out  the comparative performance of different intercropped lentil with Mukhikachu  for getting higher yield and economic return. Five treatments comprised of T1=  Sole lentil (30 cm apart continuous seeding), T2 = Sole mukhikachu [(double  row) = 20 cm/55/20 cm x 45 cm], T3= Mukhikachu (double row) + 1 row of  lentil 30 cm apart (33% seeding ratio) between 2 double row of mukhikachu, T4 = Mukhikachu (double row) + 2 rows of lentil 30 cm apart (66%) between 2  double row of mukhikachu and T5= Mukhikachu (double row) + lentil broadcast  (100%). Intercropping systems did not affect the rhizome yield of mukhikachu  significantly but affected the seed yield of lentil. Lentil and mukhikachu  equivalent yield were the highest (5.87 in 2007-08 and 6.09 t/ha in 2008-09, and  27.24 in 2007-08 and 30.45 t/ha in 2008-09, respectively) in treatment T4. This  treatment also gave the highest LER (1.63 in 2007-08 and 1.54 in 2008-09), net  return (Tk. 290508 in 2007-08 and Tk. 368900/ha in 2008-09) with BCR of 4.19  in 2007-08 and 4.88 in 2008-09, respectively. It reveals that lentil could be  grown easily in double row system of Mukhikachu without hampering yield of  Mukhikachu with higher benefit and also enhanced lentil production in the area.   DOI: http://dx.doi.org/10.3329/bjar.v36i4.11757   Bangladesh J. Agril. Res. 36(4): 669-676, December 2011