Ricerche sperimentali nell' Oltrepò Pavese (Valle Padana) sugli aspetti epidemiologici delle ruggini del frumento

Experimental researches in Oltrepò Pavese (Padana Valley), on wheat rust epidemiological aspects related to the climatic conditions Our experimental researches began in 1976 in Oltrepò Pavese, one of the most important seedwheat growing environment in the Padana Valley. Wheat rust epidemiology, on the cv San Pastore, was studied in relation to the following climatic conditions: temperature and rain. Therefore, after having illustrated the modalities of observation and survey of the three rusts, we studied the infection behaviour on plants in field and hence the infection behaviour on the single leaves. In the end, knowing, by statistical analysis, the relations between infections and climatic parameters, it was possible to define as follows. By comparing the three rusts infections in our environment, we noted that San Pastore wheat has been more affected by Puccinia striiformis West. with maximum infection points of 26,4 % on the leaves. We noted the greater development of this infection from the fourth to the sixth observation, in correspondence with average values of T° max rising from 23,7° to 26,4°C; in the same period, precipitations varied with a daily average from 3,0 to 1,7 mm. Both P. striiformis and P. recondita Rob. ex Desm. appeared when the average of the T° max was 20,6°C, and in lack of rain. P. recondita had a development rising from the fourth to the sixth observation showing, with regard to P. striiformis, lower demands of humidity and relatively greater demands of temperature; in fact, it reached a maximum point of infection of 26,4 % on the leaves, assuming a more gradual development than P. striiformis. P. graminis Pers. appeared much later, as it needs higher T° max, followed by rains. Indeed, it appeared with average T° max of 23, 8 °C and with average daily rains of 0,4 mm, rising above all at the sixth observation with 26,4° C and 1,7 mm, respectively. So, we can affirm that the actual experimental investigations point out and confirm what has been already met by other Authors, that is: a) among the three rusts considered, P. striiformis and P. recondita show to begin their development at the same time, in climatic conditions characterized by T° max relatively mild and high environmental humidity; b) P. striiformis shows, afterwards, the highest infections percentages; c) P. graminis appeared much later reaching modest infection percentages.