Changes in the adult sex ratio of six duck species breeding populations over two decades

Despite all efforts,long-term changes in the adult sex ratios of breeding duck populations are still unclear;this uncertainty is especially true for male-bias populations,which are often under the scrutiny of researchers lacking convenient results for the active protection of endangered species.Species with male-bias populations are usually strongly affected by a decline in population size that leads to a higher extinction risk.In this study,we examined our long-term data of the abundance of breeding populations in six duck species(Mallard Anas platyrhynchos,Gadwall Mareca strepera,Red-crested Pochard Netta rufina,Common Pochard Aythya ferina,Tufted Duck Aythya fuligula,and Common Goldeneye Bucephala clangula)from fishponds in South Bohemia,Czechia,between 2004 and 2022.This evidence was used to assess long-term changes in the adult sex ratio in these breeding populations and investigate the possible effects of the NAO index(North Atlantic Oscillation index)on them,indicating climate conditions in winter.We determined a long-term decrease of the proportion of females in the breeding season in two of the six examined species:Common Pochard and Red-crested Pochard,which is driven by the long-term increase in the number of males in contrast to the decreasing or stable number of females likely caused by different migration behaviours between females and males.In the case of Common Pochard,in breeding populations,we estimated 60-65%of males in the early 2000s rising to 75-80%in the early 2020s.However,we establish no significant effects linked to climate conditions of the previous winter in these species as a crucial cause of the changes of the proportion of females in the breeding population.

Structure of Allozymatic Diversity of Ten Temperate and Adapted Exotic Breeding Populations of Maize (Zea mays L.)

Ten temperate and adapted exotic breeding populations of maize were studied with electrophoretic techniques. Three isozyme systems coded by nine allozyme loci were used for evaluating the genetic variability within and among populations. The results revealed that 78.57% of allozyme loci were polymorphic. Low allelic variation with a mean number of 1.84 alleles per locus per population was detected. But, these populations still maintained higher level of heterozygosity; moreover, the exotic populations had greater gene diversity than the temperate populations. All the populations were non-panmictic with negative Wright＇s fixation indexes （-0.091— -0.424）. The tropical BS 16 was typified by maximum allelic richness, percent of polymorphic loci and heterozygosity. More than 93% of the gene diversity maintained within populations, and the genetic differentiation among populations was low （0.002—0.191）. Multivariate analysis demonstrated that the tropical BS29 diverged from other populations in the reverse direction. The temperate BS9 and tropical BS16 were divergent each other, and highly differentiated from other temperate and tropical populations, consequently, these two populations would be analogically postulated as potential germplasms to establish new heterotic groups for temperate maize breeding programs.

Genetic diversity and elite gene introgression reveal the japonica rice breeding in northern China

Abundant genetic diversity and rational population structure of germplasm benefit crop breeding greatly.To investigate genetic variation among geographically diverse set of japonica germplasm,we analyzed 233 japonica rice cultivars collected from Liaoning,Jilin and Heilongjiang provinces of China,which were released from 1970 to 2011 by using 62 simple sequence repeat（SSR） markers and 8 functional gene tags related to yield.A total of 195 alleles（N_a） were detected with an average of 3.61 per locus,indicating a low level of genetic diversity level among all individuals.The genetic diversity of the cultivars from Jilin Province was the highest among the three geographic distribution zones.Moreover,the genetic diversity was increased slightly with the released period of cultivars from 1970 to 2011.The analysis of molecular variance（AMOVA） revealed that genetic differentiation was more diverse within the populations than that among the populations.The neighbor-joining（NJ） tree indicated that cultivar clusters based on geographic distribution represented three independent groups,among which the cluster of cultivars from Heilongjiang is distinctly different to the cluster of cultivars from Liaoning.For the examined functional genes,two or three allelic variations for each were detected,except for IPA1 and GW2,and most of elite genes had been introgressed in modem japonica rice varieties.These results provide a valuable evaluation for genetic backgrounds of current japonica rice and will be used directly for japonica rice breeding in future.

Microsatellite analysis of genetic diversity and population structure of freshwater mussel（Lamprotula leai）

Lamprotula leai is one of the most commercially important freshwater pearl mussels in China, but there is limited data on its genetic diversity and population structure. In the present study, 119 individuals from four major geographical populations were investigated using 15 microsatellite loci identified via cross-species amplification. A total of 114 alleles were detected, with an average of 7.6 alleles per locus（range： 2 to 21）. Among the four stocks, those from Hung-tse Lake and Poyang Lake had the lowest（0.412） and highest（0.455） observed heterozygosity respectively. The polymorphism information content（PIC） ranged from 0.374 to 0.927（mean： 0.907）. AMOVA showed that 12.56% and 44.68% genetic variances were among populations and within individuals, respectively. Pairwise Fst ranged from 0.073 to 0.146, indicating medium genetic differentiation among the populations. In aggregate, our results suggest that inbreeding is a crucial factor accounting for deviations from Hardy–Weinberg equilibrium at 12 loci. Moreover, the genetic distance among four stocks ranged from 0.192 to 0.890. Poyang Lake and Hung-tse Lake were clustered together, joined with Dongting Lake and Anqing Lake. Given that specimens from Hungtse Lake showed the highest average allele richness, expected heterozygosity and PIC, this location may be the source of the highest quality germplasm resources and the stock from this area may be the best for future breeding efforts.

Effects of SPNE on Growth,Development and Correlated Traits of Five Drosophila melanogaster Strains

Five homozygous strains of Drosophila melanogaster were used as the experimental materials and treated with SPNE （ Special Plant Nutritional Element）. D. melanogaster larvae were incubated at 18 ℃ in Drosophila culture medium with SPNE addition. The results showed that larva emergence, pupa emergence and adult emergence in SPNE treatment were earlier than that in control. SPNE treatment accelerated the growth and development, shortened the life cycle, significantly increased the quantity of offspring and slightly improved the weight of D. melanogaster, which confirmed that SPNE posed significant effects on D. melanogaster. This study laid foundation for the breeding of D. melanogaster and other insects and provided new materials and a new approach for broadening the application of SPNE.