Chloroplast DNA variation and pollen contamination in a Pinus brutia Ten. clonal seed orchard: implication for progeny performance in plantations

Abstract

Pollen contamination is one of the important factors affecting the yield, adaptability, and genetic quality of the seed produced from seed orchards in forest tree breeding programs. Incoming pollen from the forests surrounding the seed orchard is a major concern in tree breeding because it contributes to losses in the expected genetic gains from seed orchard crops. The genetic variation and the level of pollen contamination in a 16-year-old Pinus brutia Ten. first-generation clonal seed orchard was studied using chloroplast microsatellite markers (cpSSRs). In total, 23 alleles and 36 unique allelic combinations (haplotypes) were detected based on the 6 cpSSR loci analyzed. The haplotypic diversity of the clones in the seed orchard was found to be 0.849. Out of 300 embryos analyzed, 87 were not compatible with any male parent within the seed orchard. Thus, 29% of the embryos were sired by pollen sources outside the orchard (i.e. apparent contamination). Microsatellite-based analysis revealed that the estimated contamination rate was 39.3%. Background pollination at this level will cause losses of 20% in the expected genetic gains. Our findings are valuable for the assessment of the intended seed orchard function, i.e. provision of genetically improved seed. It may be worthwhile to use pollen management strategies like strobilus stimulation, controlled pollination, and supplemental mass pollination to decrease pollen contamination and increase the genetic quality of the seeds produced.

Pollen contamination and mating patterns in a Prosopis alba clonal orchard: impact on seed orchards establishment

“…These contamination values are within the range recorded in the literature for both wind and insect pollinated orchards. Bilgen & Kaya (2014) reported that 29% of the embryos of Pinus brutia were sired by pollen sources outside the orchard. Feng et al (2010), Torimaru et al (2009) and Buiteveld et al (2001) estimated contamination rates of 25%, 51% and 70% for Pinus koraiensis, Pinus silvestris, and Quercus robus, respectively.…”

“…Failures in the recognition of parental trees within the studied orchard can be explained by: (i) natural regeneration of individuals from outside (e.g., seeds carrying unrelated genotypes) establishing within the clonal orchard; (ii) mutational events (such as inversions) in the offspring, whose rate is fairly high in SSR regions of the genome; (iii) scoring mistakes; and (iv) pollen flow from outside the orchard (Plomion et al 2001, Bilgen & Kaya 2014. Some of these causes can be easily ruled out in our case.…”

“…An accurate estimation of seed orchard reproductive patterns are necessary. Parental analyses have become an important method for providing a detail description of genetic diversity and pollination patterns inside the seed orchards mainly in anemophilous tree species (Hansen 2008, Torimaru et al 2009, Feng et al 2010, Bilgen & Kaya 2014, Ebrahimi et al 2018).…”

Estimation of Pollen Contamination and Mating System in Pinus Merkusii Seedling Seed Orchard Using Allozyme Markers

“…Pollen contamination influences the genetic worth of seed orchard and therefore determines the quality of seed production, which may include reduction of genetic gain (Grattapaglia et al 2014, Funda et al 2016, Gonzaga et al 2016). Studies of wind-pollinated orchards show that between 25 and 80% of seeds produced usually result from pollen contamination (Kaya et al 2006, Torimaru et al 2009, Bilgen & Kaya 2014. In young orchards, where pollen production is limited, the contamination rate could be even higher.…”

“…Genetic markers (biochemical and molecular) have been used to determine mating system parameters and estimate pollen contamination in seed orchards (Fernandes et al 2008, Torimaru et al 2009, Feng et al 2010, Kaya & Isik 2010, Bilgen & Kaya 2014. Biochemical markers such as allozymes were popularly used in the 1980s and 1990s because they are easy to use, cost effective and exhibit simple Mendelian inheritance (Firas et al 2015).…”