Avalia??o de resistência de clones de eucalipto às infec??es naturais de Cryphonectria cubensis, com nova metodologia

摘要

A new methodology is presented for susceptibility or resistance evaluation of Eucalyptus grandis clones, at five years of age, naturally infected by Cryphonectria canker in the state of Amapá, Brazil. The adopted parameters were frequencies of disease incidence, mortality, frequencies of lesions and cankers considering trunk position, depth, and size. These parameters are directly or indirectly related to the expression of defense mechanisms at bark and xylem levels. A disease index in percentage (IDIN) was calculated for each clone. To facilitate comparing IDIN's of the genotypes, the IDIN of the most susceptible clone was divided by a factor to allow it to be equal to 100. The IDINs values of the other genotypes were also divided by the same factor. The clones were grouped into the categories HS (highly susceptible), MS (moderately susceptible), MR (moderately resistant), and HR (highly resistant). Each category included clones whose average of IDIN was significantly different from the other averages, according to the test of average contrast.