Antibiosis In vitro of Trichoderma Strains Metabolic Extract on Mycelial Growth and Reproductive Capacity of Fusarium oxysporum Isolated from Pepper Plants (Capsicum annuum L.).

Aims: To inhibit the mycelia growth inhibition and reproductive capacity of important phyto-pathogen fungus: Fusarium oxysporum by cell-extracts from submerged cultures of Trichoderma. Study Design: A complete randomized experimental design with factorial fix was used. Place and Duration of Study: Laboratory of plant-pathology, Department of Agricultural Parasitology, Universidad Autónoma Agraria Antonio Narro (UAAAN), Mexico, between August 2012 and March 2012. Methodology: Metabolic extract of Trichoderma asperellum produced in liquid medium and Trichoderma dual cultures on F. oxysporum isolated infected plant pepper was evaluated; both strains were subsequently activated in PDA and tested in dual culture and poisoned culture with Trichoderma strains and metabolic extracts against F. oxysporum to determine their growth inhibition potential. Results: Strains Trichoderma were able to inhibit the growth of the plant pathogen, demonstrating to be an attractive alternative for biological control assays. Similar results were obtained with metabolic extracts, where the inhibition was affected up to 29%, the conidiogenesis by 30% and spore viability by 60% at the highest concentration tested. Conclusions: Metabolites produced have the power to reduce the reproductive capacity of F. oxysporum, decreasing sporulation and inhibit the germination of conidia, and this is extremely important, as reducing the quantity and viability of conidia, it is reducing the secondary inoculum of the pathogen.

Cytological characterization of an Aspergillus nidulans mutant from a strain with chromosomic duplication

A development mutant, named V103, was obtained spontaneously from the A strain of A. nidulans. The A strain contains a duplicated segment of chromosome I that has undergone translocation to chromosome II (I ¨ II). It is mitotically unstable and generates phenotypically deteriorated types, some with enhanced stability. The deteriorated variants of A. nidulans show abnormal development, exhibiting slower colony growth, variations in colony pigmentation and changes in conidiophore structure. The alterations observed in the conidiophore include fewer metulae and phialides, further elongation and ramification of these structures, delayed nuclear migration and the presence of secondary conidiophores.

Morphological Characteristics of Conidiogenesis in Cordyceps militaris

Conidial development of Cordyceps militaris was observed from germinating ascospores and vegetative hyphae through light and scanning electron microscopy (SEM). Ascospores were discharged from fresh specimens of C. militaris in sterile water as well as Sabouraud Dextrose agar plus Yeast Extract (SDAY) plates. We observed ascospore germination and conidial formation periodically. Under submerged condition in sterile water, most part-spores germinated unidirectionally and conidia were developed directly from the tips of germinating hyphae of part-spores within 36 h after ascospore discharge, showing microcyclic conidiation. First-formed conidia were cylindrical or clavate followed by globose and ellipsoidal ones. Germination of ascospores and conidial development were observed on SDAY agar by SEM. Slimy heads of conidia on variously arranged phialides, from solitary to whorl, developed 5 days after ascospore discharge. Besides, two distinct types of conidia, elongated pyriform or cylindrical and globose, were observed in the same slimy heads by SEM. Conidia were shown to be uninucleate with 4,6-diamidino-2-phenylindole staining. Conidiogenous cells were more slender than vegetative hyphae, having attenuated tips. Microcyclic conidiation, undifferentiated conidiogenous hyphae (phialides), polymorphic conidia and solitary, opposite to whorled type of phialidic arrangement are reported here as the characteristic features of asexual stage of C. militaris, which can be distinguished from other Cordyceps species.