Table 5— Analysis of variance of infection by Lophodermium 



baculiferum on stands and families of ponderosa pine 



Source of 

 variance 



df 



Mean 

 square 



F 



value 



Block 



4 



0.5673 





Stand 



47 



.2233** 



3.60 



Family in stand 



186 



.0620** 



2.51 



Experimental error 



892 



.0257 





Within plot 



2,644 



.0173 





' 'Significant at the 1 percent level of probability. 



Q 



w 30 



• 



« •• • 

 . * • 



• • 



•• • - 



♦ • •„ • • ' 



• • • • 



Table 6— Variance components for infection of 

 ponderosa pine by Lophodermium 

 baculiferum 



Source 



Variance component 



Stand 



0.0022 



Family in stand 



.0025 



Experimental error 



.0026 



Within plot 



.0173 



DISCUSSION 



Geographic location of seed source had the most effect 

 on the pattern of infection due to this needle cast fungus. 

 The most resistant populations occurred in the north- 

 central portion of the collection area. Susceptibility was 

 most pronounced to the south. What seems to be depicted 

 are gentle north-south clines of susceptibility to L. 

 baculiferum. 



We have no data concerning the level of infection for 

 trees in the stands from which seed was collected. Conse- 

 quently, there is no way of testing whether the variation 

 pattern among stands is due to natural selection keyed to 

 the intensity of the disease or just a chance occurrence. 

 Nonetheless, the pattern of the damage appears to follow 

 the climate of the Northern Rocky Mountains. The ex- 

 treme northern portion of Idaho and adjacent Montana is 

 the wettest part of the area. Usually May and June, and 

 often July, are foggy and rainy. This general area con- 

 tained the stands with the least amount of damage, that 

 is, highest resistance. On the other hand, the stands in the 

 extreme southern portion of the collection were from 

 much drier areas, and their progeny had the greatest 

 amount of damage. 



Thus, it seems reasonable to conclude that resistance to 

 this needle cast fungus is an adaptive trait that has ad- 

 justed to sites according to the amount of damage caused 

 by needle cast. 



From a practical standpoint, L. baculiferum seems to be 

 only a minor problem for ponderosa pine because it shows 

 up only when environmental conditions are favorable and 

 only year-old or older needles are infected. Ponderosa pine 

 in the Northern Rocky Mountains occurs in uniform pure 



• • . • • • 

 •••• 



••• . 2* * 



► ••••• • • • • • 



. . • • • 



• • o» •••• 



• »r 



• • ••• 



• • • a • 



• • • • • 



8 10 12 14 16 18 FT 



(244) (305) (366) (427) (488) (549MCM) 



1985 HEIGHT 



Figure ^-Lophodermium baculiferum infection plotted 

 against 1985 height: A, provenance test; B, family 

 test. 



stands only in the drier habitats where needle cast is likely 

 to occur even less frequently than in the wetter portion of 

 the area. Planting pure ponderosa pine plantations would 

 probably lead to needle cast problems in these wet 

 habitats. This supports the present prevailing forest 

 practice of regenerating mixed stands. 



The relatively high heritabilities for individuals and 

 families indicate that substantial gains could be made in 

 breeding for resistance to this needle cast fungus. For 

 each unit of i (selection intensity), 14 percent gain could 

 be made with family selection and 10 percent for in- 

 dividual selection. With proper seed source management, 

 together with selection of good seed trees for natural 

 regeneration or a fairly large inclusion of resistant trees in 

 seed collected for artificial regeneration, additional 

 resistance is probably not needed, especially if pure stands 

 are not established. However, with a tree improvement 

 program where the main purpose is to produce faster 

 growing trees, knowledge concerning the susceptibility of 

 the selected trees to this needle cast fungus, as well as to 

 other diseases and insects, would be valuable to the tree 

 breeder. It may not be necessary to increase resistance, 

 but it is certain that resistance should not be decreased. 



There appears to be only a slight relationship between 

 relative height and the degree of damage by this needle 

 cast fungus. In this case, the faster growing trees were 

 the most resistant. 



5 



