SNP-based analysis reveals unexpected features of genetic diversity, parental contributions and pollen contamination in a white spruce breeding program

Accurate monitoring of genetic diversity levels of seedlots and mating patterns of parents from seed orchards are crucial to ensure that tree breeding programs are long-lasting and will deliver anticipated genetic gains. We used SNP genotyping to characterize founder trees, five bulk seed orchard seedlots, and trees from progeny trials to assess pollen contamination and the impact of severe roguing on genetic diversity and parental contributions in a first-generation open-pollinated white spruce clonal seed orchard. After severe roguing (eliminating 65% of the seed orchard trees), we found a slight reduction in the Shannon Index and a slightly negative inbreeding coefficient, but a sharp decrease in effective population size (eightfold) concomitant with sharp increase in coancestry (eightfold). Pedigree reconstruction showed unequal parental contributions across years with pollen contamination levels between 12 and 51% (average 27%) among seedlots, and 7–68% (average 30%) among individual genotypes within a seedlot. These contamination levels were not correlated with estimates obtained using pollen flight traps. Levels of pollen contamination also showed a Pearson’s correlation of 0.92 with wind direction, likely from a pollen source 1 km away from the orchard under study. The achievement of 5% genetic gain in height at rotation through eliminating two-thirds of the orchard thus generated a loss in genetic diversity as determined by the reduction in effective population size. The use of genomic profiles revealed the considerable impact of roguing on genetic diversity, and pedigree reconstruction of full-sib families showed the unanticipated impact of pollen contamination from a previously unconsidered source.

Prevalence of microscopic fungi in bee pollen

One of the problems with storing bee products – pollen – is their microbiological pollution. With high levels of pollen contamination by microscopic fungi, toxins synthesized by the fungi of some genera can have a negative impact on human health. During the experiment, the prevalence of microscopic fungi in pollen was evaluated, and their genera and species were identified. Pollen samples were collected at different times of the year – spring and summer – in order to ascertain the abundance and diversity of different fungal genera and species. The dilution method (CFU/g) was used to determine the number of fungal strains per sample and their amount. The total number of fungal strains in the pollen collected in spring ranged from 1.3 to 5.7 × 10–3 CFU/g, in summer –1.0 to 5.8 × 10–3 CFU/g. In the pollen, 11 genera and six species of fungi were identified. The number of fungal genera and species in pollen collected in spring and summer varied insignificantly. In spring, ten genera and six species of fungi were isolated from pollen, and in summer 11 genera and six species were identified. Penicillium and Alternaria fungi dominated the bee pollen.

EFFECTS OF POLLEN CONTAMINATION AND KERNEL WEIGHT ON KERNEL STRUCTURE OF MAIZE IN OPEN AND SELF POLLINATION TREATMENTS

In small plot experiments conducted in maize, the mostly used pollination methodsare open and self-pollination treatments. Comparative studies using thesetreatments are abundant in scientific literature; however studies on the effect ofcross pollination and kernel weight on kernel biochemical properties in differenttreatments are limited. In this study, we conducted a comparative experiment toinvestigate the effect of pollen contamination and mean kernel weight on kernelbiochemical composition of ten different maize genotypes by using two differentpollination methods.Open and self-pollination treatments were applied aspollination methods. Eight different traits; kernel weight, cross pollination rate,protein, oil, carbohydrate, oleic acid linoleic acid and carotenoid content weremeasured. Regression analyses were performed to understand the effects of crosspollination and mean kernel weight on biochemical constituents of maize kernel indifferent treatments. Results showed that the major biochemical traits, such asprotein, oil and carbohydrate content were significantly affected by pollencontamination but minor traits were not. When data were combined (n=60) theeffect of pollen contamination in different treatments was not clearly understood.When data (n=30) of each treatment were separately analyzed, it was found thatcross pollination rate had significant effect on the most of biochemical constituentsin open pollination. Overall, results suggested that pollen contamination had aneffect on major biochemical traits in maize and hand pollination could be used forpreventing of unwanted effect of pollen contamination in small plot experiments.However, it should be considered that the effects of hand pollination on kernelweight affect the some biochemical traits in maize.