Genetic variation in survival, growth, and stem form of Pinus leiophylla in Brazil and South Africa and provenance resistance to pitch canker

Pinus leiophylla is a relatively common pine that occurs in the mountains of western and central Mexico. Between 1987 and 1990, Camcore, North Carolina State University, sampled 11 populations and 309 mother trees of the species to determine patterns of genetic variation in survival, growth and stem form. Fifteen provenance/progeny trials were established in southern Brazil and South Africa across a wide range of sites and assessed at 3, 5 and 8 years of age for height, diameter and stem form. Results indicated that average productivity ranged from 5 to 19m(3) ha(-1) y(-1) depending on the site and that performance was not as competitive as P. patula, (South Africa) and P. taeda (Brazil) controls. Provenances from central Mexico (Michoacan) were statistically better in productivity than those from the southern part of the country (Oaxaca), which in turn were superior to those from the northern part of the country (Durango). However, provenances from northern Mexico exhibited superior survival to seed sources from other locations in Mexico when grown on cold sites (winter minimums -10 to 5 degrees C) in South Africa and superior stem form across all locations. Seedlings from the original 11 provenances were screened for resistance to the pitch canker fungus (PCF; Fusarium circinatum). Results indicated that generally P leiophylla is as susceptible to PCF as P patula (stemkill = 85%) with the exception of two fast-growing, moderately resistant populations from Michoacan, La Pinalosa (stemkill = 44%) and Ario de Rosales (stemkill = 73%). The future potential of P leiophylla might be in hybrid combination with P. patula in the seasonally dry areas of southern Africa where fires are common and pitch canker is a problem.