The Impact of Inoculation of Two Strains of Rhizobacteria on Radionuclide Transfer in Sesbania Grandiflora

Transfer factors of some naturally-occurring and artificial radionuclides from an agricultural soil to rhizobacteria-treated Sesbania grandiflora, a small leguminous tree, were studied. Two plant growth promoting rhizobacteria (PGPR) strains (SCR17 and PCE2) were used to carry out an agricultural experiment in pots in semi-arid region (Syria). The results showed the bacterial strain (SCR17) increased the transfer and accumulation of 238U and 40K in Sesbania grandiflora, while both bacterial strains showed no effect on the accumulation of 234Th, 226Ra, 210Po and 210Pb in the treated plants. The transfer factor of 137Cs from soil to rhizobacteria-treated Sesbania grandiflora was negligible. The values of the transfer factors of 234Th, 226Ra, 210Po and 40K were found to be within the global values, while the values of the transfer factors of 238U and 210Pb were found to be relatively higher. This study highlights the importance of using Phytoremediation by PGPR strains for radionuclides-contaminated soils. Therefore, this method is a promising technique for the restoration and rehabilitation of contaminated sites with radionuclides, as it is low cost, easy to apply, and environmentally friendly.

Transcriptional interactions during barley susceptible genotype infection with Cochliobolus sativus

A systematic sequencing of expressed sequence tags (ESTs) was used to obtain a global picture of the assembly of barley genes differentially expressed during the hypersensitive reaction of a susceptible genotype in response to an incompatible Cochliobolus sativus pathovar. To identify a large number of plant ESTs, which are induced at different time points, an amplified fragment length polymorphism (AFLP) display of complementary DNA (cDNA) was ulilized. Significant transcriptional changes in the host plant occurred already 4 h post inoculation. Four hundred and fifty six ESTs have been generated, of which 17 (c. 53% up-regulated, 47% down-regulated) have no previously described function. On one hand, the majority of EST-annotations showed protein synthesis, but genes related to signal transduction pathway were also identified. This study provides novel global catalogue ofgene regulations involved in C. sativus-barley interaction not currently represented in EST databases.

Heterogeneity in the ITS of the ribosomal DNA of Pyrenophora graminea isolates differing in xylanase and amylase production

Xylanase and amylase have gained increasing interest because of their various biotechnology applications. In this research, the restriction of PCR-amplified internal transcribed spacers (ITS) of ribosomal DNA (rDNA) was used to confirm the genetic variation among 22 isolates of Pyrenophora graminea differing in their xylanase and amylase production. The fingerprints generated from the six restriction digestions of the rDNA ITS region showed high levels ofintraspecific variation within the P. graminea population. Neighbour-Joining diagram, based on Nei's genetic distances, showed that isolates formed two phylogenetic groups. No apparent association could be observed between xylanase and amylase production and genetic diversity among the twenty-two isolates.

Molecular and xylanolytic variation identified among strains of Pyrenophora graminea

The inter-retrotransposon amplified polymorphism (IRAP) was used to confirm the genetic variation among 22 strains of Pyrenophora graminea differing in their xylanase production. A total of 162 bands were scored of which 151 (93.21%) were polymorphic. The molecular parameter used showed that P. graminea strains reside in four phylogenetic groups. There was observed the resolution between clustering strains and their xylanase production. Hence, the described approach presented here constitutes no prior assumption about the characterization of P. graminea strains differing in xylanase production.

Effect of additional carbon source and moisture level on xylanase production by Cochliobolus sativus in solid fermentation

The fungus Cochliobolus sativus has been shown to be an efficient producer ofxylanase from an industrial point ofview. The addition of extra carbon sources and the initial moisture content of the solid-state fermentation were found to have a marked influence on the xylanase production by C. sativus Cs6 strain. Xylan and starch resulted in an increased xylanase production (1469.4 and 1396.56 U/g, respectively) after 8 days of incubation. Optimal initial moisture content for xylanase production was 80%. The cultivation systems can easily be modified to enhance the productivity of the enzyme formation by C. sativus Cs6, which will facilitate the scale up processes for mass production.