02879nam a2200277 a 450000100080000000500110000800800410001910000190006024500810007926000520016030000090021250000190022152021350024065000180237565000150239365000220240865000210243065000210245165000100247265000220248265000250250465300220252965300200255165300190257165300110259015632931999-04-23       1978    bl uuuu  m   00u1 u    #d1 aDIAS, J. C. A.  aInheritance of resistance to Septoria nodorum (Berk) Berk. in a wheat cross.  aLincoln, Nebraska: University of Nebraskac1978  a59p.  aTese Mestrado.  aInheritance of sedling resistance to Septoria nodorum (Berk.) Berk. was studied in the cross of spring wheat, Toropi, with a hard red winter wheat, Centurk 78, at the University of Nebraska-Lincoln greenhouse, Lincoln, Nebraska. Percent necrosis per square centimeter of leaf area and number of lesions per square centimeter of leaf area were symptom parameters measured. Analyses od variance of the symptom expressions in the parents, F1, F2 and backcrosses to each parent were calculated. The genetic variation obtained though the frequency distribution for each generation and parents was studied. Heritability in the broad sense was calculated for each character studied. The heritability in the broad sense was relatively high, especially in the second test for both characters. The genetic variances of the F2 progenies were greater than the genetic variances within the parents. In order to obtain better information to support the finding of this study, the tests made with F2 plants should be followed up by head-row tests. These tests were not made in this study due to limitations of time. The lack of significant dominance effects the absence of heterosis for both symptom parameters studied in this experiment provide evidence that dominance may be lacking in loci controlling either susceptibility or resistance to Septoria nodorum in this cross. Very positive transgressive segregation for resistance or susceptibility was not evident in this research. From the results of this experiment it can be concluded that quantitative factors are involved in the inheritance of resistance to Septoria nodorum. Therefore, efficient breeding procedures which allow the accumulation of favorable genes for resistance through some recurrent selection system should be effective in the improvement of high-yielding lines highly resistant to Septoria nodorum. Since the pricipal problem in conducting recurrent selection in a self-pollinated crop is the large number of crosses necessary in the recombination phase of the selection cycle, simple seed descent methods could be used, as suggested by Brim (1966) and Compton (1968).  ahybridization  aCruzamento  aDoença de Planta  aDoença Fúngica  aSeptoria Nodorum  aTrigo  aTriticum Aestivum  aVariedade Resistente  aDisease resitance  aFungal diseases  aPlant diseases  aWheats