Colonization of exopolysaccharide-producing Paenibacillus polymyxa on peanut roots for enhancing resistance against crown rot disease

The effect of Paenibacillus polymyxa (syn. Bacillus polymyxa) which produces an exopolysaccharide (EPS) on control of crown rot disease caused by Apergillus niger of peanut was investigated. In an invitro assay, two strains of P. polymyxa (B5 and B6) were tested against A. niger. Both strains showed inhibitory effect against A. niger. Growth, protein and biopolymers production of bacteria were evaluated. The biopolymers were purified with several precipitation steps using ethanol and cetyltrimethyl-ammonium bromide. Carbohydrate analysis using various color reactions, infrared spectroscopy, and high performance liquid chromatography (HPLC) revealed that the biopolymer is ahomopolysaccharide, which is consisting of various sugars such as glucose, galactose, mannose and xylose. When these strains of P. polymyxa were applied to seed and sowed in soil infested with A.niger, they significantly suppressed crown rot disease development and decreased survival of the A. niger pathogen. Over a period of 60 days, the population of bacteria was greatly increased. The bacterium colonized plant roots and were able to migrate downward with the root as it elongated. Scanning electron microscopic analysis of one month plants from seeds previously inoculated with P.polymyxa revealed dense colonization on the roots. Moreover, significant increases in activities of plant defense enzymes include -1,3-glucanase and chitinase were recorded in treated roots compared with untreated. In vivo, two trials were conducted in 2005 and 2006 seasons to define the effect of bacterium treatment on crown rot disease control and pod yield. Plants grown from peanut seeds previously treated with P. polymyxa displayed significant resistance to the crown rot disease triggered by A. niger. Coating seeds with bacterium decreased infection by A. niger, Aspergillus counts in the rhizosphere, pods and seeds as well as increased root colonization with bacteria. The yield of  bacterium-treated peanut plants was significantly higher than untreated control plants. These results showed that P.polymyxa is potentially a biocontrol agent for use in controlling of A. niger in roots and seeds of peanut plants

Septoria-like pathogens causing leaf and fruit spot of pistachio

Several species of Septoria are associated with leaf and fruit spot of pistachio (Pistacia vera), though their identity has always been confused, making identification problematic. The present study elucidates the taxonomy of the Septoria spp. associated with pistachio, and distinguishes four species associated with this host genus. Partial nucleotide sequence data for five gene loci, ITS, LSU, EF-1a, RPB2 and Btub were generated for a subset of isolates. Cylindroseptoria pistaciae, which is associated with leaf spots of Pistacia lentiscus in Spain, is characterised by pycnidial conidiomata that give rise to cylindrical, aseptate conidia. Two species of Septoria s. str. are also recognised on pistachio, S. pistaciarum, and S. pistaciae. The latter is part of the S. protearum species complex, and appears to be a wide host range pathogen occurring on hosts in several different plant families. Septoria pistacina, a major pathogen of pistachio in Turkey, is shown to belong to Pseudocercospora, and not Septoria as earlier suspected. Other than for its pycnidial conidiomata, it is a typical species of Pseudocercospora based on its smooth, pigmented conidiogenous cells and septate conidia. This phenomenon has also been observed in Pallidocercospora, and seriously questions the value of conidiomatal structure at generic level, which has traditionally been used to separate hyphomycetous from coelomycetous ascomycetes. Other than DNA barcodes to facilitate the molecular identification of these taxa occurring on pistachio, a key is also provided to distinguish species based on morphology