This programme has been undertaken at Maple for the past 20 years. Most 

 of the breeding work to obtain resistance to rust is carried out on screened grafts 

 and on seedlings that are just beginning to flower. One difficulty, still to be over- 

 come, is the scarcity of male flowers on such materials and thus scarcity of pollen 

 for work within advanced generations. It has now been established with reason- 

 able certainty that resistance to blister rust in white pine is inherited as a polygenic 

 character and the work is carried out with this as a working hypothesis. 



The inclusion of exotic materials with high inherent resistance, such as 

 selected clones of Pinus peuce and P. griffithii in the tree breeding programme has 

 in several cases resulted in marked increases in the proportion of resistant seed- 

 lings. However, it is still unknown how such hybrid material will perform under 

 forest conditions. One shortcut that appears promising is the propagation of 

 resistant seedlings by means of stem cuttings. 



Seeds have recently been collected in plus stands of white pine and seedlings 

 subjected to mass screening for resistance. 



Breeding for resistance to weevil is progressing, in conjunction with the white 

 pine breeding programme. In an area of heavy weevil population, scions of 

 selected white pine materials are top-grafted on to young planted white pine, 

 together with scions from heavily weeviled controls. The results are quite en- 

 couraging but mass selection will remain too slow until sufficient resistant material 

 is available to establish fairly large plantations in areas with heavy weeviling. 



ASPEN-POPLARS 



The production of aspen-like hybrids suitable for growing in southern Ontario 

 continued to be the chief aim of this project. 



The long-standing problem of developing an aspen hybrid with good rooting 

 ability has been solved; results are now satisfactory. The best crosses resulting are 

 being tested for other characteristics required. 



The new tube, produced by the Research Branch, was used to great advantage 

 in germinating and growing aspen-poplar from seed. The growth was much 

 greater than previous production in seed beds. 



HARD PINES 



The development of new types resistant to the pine shoot moth and superior 

 in growth form and growth rate, continued to be the aim of this project. 



Crosses were made of red pines to look for effects of different parents. One 

 of the crosses was made from material from fertilized plots to find out whether 

 larger seeds were produced and what might be the effect on progeny. 



A basic study of the effects of inbreeding jack pine was continued. Five-year- 

 old seedlings obtained from self-pollinated jack pine trees grew slower than seed- 

 lings obtained from mixed pollen on the same parent trees. A substantially greater 

 crop of female flowers was produced on the seedlings originating from mixed 

 pollen. 



SPRUCE 



Controlled pollinations with black spruce, white spruce and several exotic 

 species, started in 1964, were continued. The purpose is to determine the genetic 

 variability of the native spruce species, the genetic relationship of native and 

 exotic species, and the value of certain spruce hybrids. 



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