Selection of Pinus spp. in South Africa for tolerance to infection by the pitch canker fungus

Abstract

The increasing threats from pests and diseases demand that the South African forest industry explores options to deploy alternative pine species in plantation development. This is especially true for species, such as Pinus patula Schiede and Deppe ex Schltdl. and Cham., which are highly susceptible to the pitch canker fungus Fusarium circinatum. Losses due to F. circinatum have been confined mostly to nurseries and at field establishment resulting in a significant cost to the industry. Although, the fungus has not as yet resulted in stem and branch infections on established P. patula in South Africa, it has caused pitch canker on other, more susceptible species such as P. radiata D. Don., and P. greggii Engelm. ex Parl. As alternatives to P. patula, on the warmer and cooler sites in South Africa, families of P. elliottii Engelm var. elliottii, P. tecunumanii (Schw.) Eguiluz and Perry, P. maximinoi H. E. Moore and P. pseudostrobus Lindl. were screened for tolerance to infection by F. circinatum in greenhouse studies. Seedlings were wounded and inoculated with spores of F. circinatum. Lesion development following inoculation was used to differentiate the levels of tolerance between families. The results showed that P. maximinoi, P. pseudostrobus, and the low elevation variety of P. tecunumanii are highly tolerant to infection with very little family variation. The narrow sense heritability estimates for these species were less than 0.06. In contrast, P. elliottii showed good tolerance with some family variation and a heritability of 0.22, while the high elevation source of P. tecunumanii showed a high degree of family variation and a heritability of 0.59. These results provide the industry with valuable information on pine species tolerant to F. circinatum that could be used as alternatives to P. patula in South Africa.

Susceptibility of Several Northeastern Conifers to Fusarium circinatum and Strategies for Biocontrol

“…Bearing in mind that the F. circinatum isolate was the same in both studies, this discrepancy could be due to a genetic effect, since Spanish provenances differ genetically from northern and eastern European provenances [52,53]. The effect of genetic variability on the susceptibility to F. circinatum has been previously demonstrated in other pine species [54][55][56][57][58][59]. This finding highlights the importance of testing the susceptibility not only at species level, but also at provenance level across Europe.…”

Re-use of seedling containers andFusarium circinatumassociation with asymptomaticPinus patulaplanting stock

“…Variation in susceptibility to F. circinatum has been found using stem inoculation screening trials at the between species level (Hodge & Dvorak 2000, Mitchell et al 2012b, provenance and family level within species (Hodge & Dvorak 2007, Mitchell et al 2012c and for hybrid combinations of P. patula with species more tolerant of F. circinatum (Roux et al 2007, Mitchell et al 2013. Use of genetically tolerant planting stock and nursery hygiene measures are both important elements of an integrated pest management strategy.…”

Evaluation of the Susceptibility of Several Czech Conifer Provenances to Fusarium circinatum

“…Nevertheless, taking into account that intraspecific genotypic variation has been recognized as a source of resistance to F. circinatum in other pine species [33,35,45,[64][65][66], the genetic effect should not be dismissed. In fact, Martín-García et al [50] found that Romanian provenance of P. sylvestris was not susceptible to F. circinatum and this resistance was related to the high genetic variability of European Scots pine populations [67,68].…”