Study of reproductive barriers in the production of P. elliottii x P. caribaea hybrid seed

Abstract

Since its introduction, the P. elliottii (Pe) x P. caribaea var. hondurensis (Pch) hybrid has played a very important role in the plantation forestry industry due to its displayed improved growth, desirable wood properties (Du Plooy, 1984; Malan, 1995) and high level of tolerance to Fusarium circinatum (Roux et al., 2007). Currently, there is an unprecedented demand for this hybrid in South Africa. Research conducted by the CSIR on pine hybrid improvement indicated that the first generation (F1) Pe x Pch hybrid is difficult to produce as the cross typically results in high abortion rates of cones and low seed yields. The low seed set obtained from the F1 Pe x Pch cross makes the production of seeds in commercial quantities difficult and costly (Slee, 1970). Genetic incompatibilities and poor pollen quality are among the key factors that may be responsible for the high cone abortion rates and low seed yields. The aim of the study was to assess the quality of pollen used in the creation of this hybrid via in vitro pollen germination and microscopy studies.