Culture media influence on vegetative growth and in vitro conidia production of Argentina wheat isolates of Pyricularia oryzae.

SANABRIA, ANALIA; CONSOLO, FABIANA; MARTINEZ, SERGIO IVAN; PERELLO, ANALIA EDITH

Santa Catarina Florianopolis

Congreso; 5th International Symposium on Fusarium Head Blight and 2nd International Workshop on Wheat Blast; 2016

Universidade de Passo Fundo

Culture media influence on vegetative growth and in vitro conidia production of wheat isolates of Pyricularia oryzae from different geographical origin was studied. Four monoconidial isolates from wheat blast tissue samples collected from Argentina, Bolivia, Brasil and Paraguay were tested on solid media, V8 agar, Rice polish agar (RA) and Oat meal agar (OMA) under two different light regimes (12h light-darkness and 24h darkness). Agar blocks (5 mm diameter) were cut from actively growing margins of each colony and centrally inoculated on plates. The cultures were incubated 25 ± 2°C. Growth of the isolates was measured from the circumference of the agar plug to the leading edge of mycelial growth at 2-day intervals. Four replications were maintained for each isolate tested. The morphocultural characteristics to study variability of isolates were: cultural texture, colour, conidia shape and sizes, sporulation and growth rate. Mean diameter and rate of colony growth in cm/24 hr were also determined. Size of conidia (length and width) were measured using a micrometer in microscope. Results revealed that isolates showed variation among them in mycelial growth, pigmentation or conidial production in different culture media and light regime tested. Significantly variation in growth rate among isolates was seen in all media. PyPaG and PyBr isolates shown the highest growth rate on OMA ranging from 0.71 to 0.79cm/day while isolate PyBol had the slower growth rate on V8 (0.47 cm/day). The growth rate of the isolates on OMA was faster than V8 or RA. Thus, OMA resulted a favorable media for the fungus growth with a significant highest growth rate of all the isolates under both light conditions. In all isolates, the shape of the conidia was typically pyriform and 2-septate with basal appendages. Differences in spore size was seen among the isolates tested. The isolate PyBol had the longest (24.00µ ? 48.00µ) and width conidia (9.60µ -19.20µ). The lowest conidial length was for isolate PyArg22 (12.00µ ? 19.20µ). Maximum variation in the length:wide (L:W) relationship ranged from 1.7:1 to 3.8:1 on RA media under 12h light-12h darkness for PyArg22 and PyBol isolates respectively, and 1.7:1 to 2.9:1 on V8 and darkness incubation for PyArg22 and PyBra respectively. Interestingly under continuous darkness conidia were shorter according the L:W relationship and the visual appearance. The L:W relationship resulted variable under the 12 h light-12 h darkness condition. Under darkness, some isolates not shown sporulation. Isolate PyArg22 produced the highest conidial production in all media tested with a maximum shown in OMA. These results could help to understand the in vitro requirements for development of the pathogen, from which no previous information is available in Argentina. Moreover, to contribute with the knowledge about the behavior of the fungus and its handling to produce mass inoculum for future experiments.