CONTRIBUTION CONCERNING THE METHODOLOGY OF ASSESSING AGGRESSIVENESS OF HELMINTHOSPORIUM TURCICUM PAS. THAT PRODUCES HELMINTHOSPORIOSIS OR NORTHERN CORN LEAF BLIGHT PUBLISHEDGheorghe Popescu, Floarea Adam, D. Jurca
Helminthosporium turcicum Pass. is the main leaf parasite of corn that encounters problems for plant inbreeders, and the cultivators suffer average loses in comparison with other continents as is North America where the loses are sometimes very important. In the experimental field from Şagu (Arad County area), we have realised a comparative crop with eight corn hybrids produced by “Afumaţi Pioneer Research Centre” of “Pioneer Dupont Company” during 2006. This comparative crop is analysed under the aspect of Helminthosporium turcicum attack. For the data registered during 10-12 September, we have a repetition with 10 plants, and after eliminations, there remained 116 plants that have entered in experimental calculus. Observation phenophase is ten leaves. Classical study methodology refers to the aggressiveness as referring to corn plants, and the new study methods are having in view to establish these parasitic features at the leaves level, following this the aggressiveness for a hybrid is the average from the plants and leaves level. This method appreciate more accurate the hybrids comportment with very important aspects for inbreeders and corn cultivators. PR 37D25 hybrid is considered by “Pioneer Dupont Company” as tolerant for Helminthosporium turcicum and Ostrinia nubilalis being considered good as control variant. Fungus aggressiveness for PR 39D81, PR 38R92, PR 38A24, PR 37D25, PR 37M34, PR 37 W05, PR 35P12, PR 36R67 hybrids is average being comprised between 43.19% (control variant) and 87.1% in case of extra-early hybrid PR 39D81 at plants level. At leaves level the fungus aggressiveness is almost a half (40.7-59.2%), and on hybrids level the amplitude variability is 34.93-60.75%, after the new study method. Is very important to include the corn hybrids on a scale as resistant, medium resistant, or tolerant and sensitive, and is also important to compare them with the aggressiveness values from the plants level. Analysed hybrids are not containing major genes (Ht1, Ht2, Ht3, and HtN), minor, or their combinations. The tolerance of PR 37D25 is genetically controlled, but not with resistance genes.
Helminthosporium turcicum; Drechslera turcica; aggressiveness; resistance; Zea may