RESUMO
To understand the genetic mechanisms underlying the endangerment of Pinus koraiensis, we studied the mating system of 49 families of this species in 3 natural populations along its post-glacial colonization route across ~1500 km in northeastern China using the chloroplast simple sequence repeat technique. We analyzed 11 polymorphic loci with clear and repeating bands, and we calculated the multi-locus outcrossing rate (tm), single-locus outcrossing rate, inbreeding index, and fixation index (F). Intra-population variation was not observed, but a large inter-population variation was observed in the outcrossing rate, and the tm increased from 0.767 (the south population) to 0.962 (the north population) along the post-glacial colonization route. The tm values within a population did not change with time over 2 consecutive years. The F values for the 3 populations were <0, which indicates an excess of heterozygotes. The mean effective number of alleles, Shannon diversity index, and Nei's genetic diversity index did not show a south-north pattern. The north population had the highest outcrossing rate but the lowest genetic diversity. The average genetic differentiation of P. koraiensis populations was 0.1251, which was within the average range of woody plants with outcrossing and wind pollination. This study suggests that the current endangerment of P. koraiensis is not related to its genetic structure; perhaps it is mainly caused by man-made and natural disturbances such as deforestation and fire. Therefore, reducing disturbances and enhancing habitats, rather than the genetic aspects, play more important roles in the long-term protection of P. koraiensis.
Assuntos
Variação Genética , Repetições de Microssatélites/genética , Pinus/genética , Alelos , China , Espécies em Perigo de Extinção , Deriva Genética , Geografia , Endogamia , Pinus/fisiologia , PolinizaçãoRESUMO
Brassica crops infected by Plasmodiophora brassicae can produce root galls (clubroots) and be prevented from growing normally. To understand the series of changes that occur in the host root during root gall production, the resistance character of 21 Chinese cabbage lines were identified and then resistant and susceptible lines were used for infection observation. Hydroponic technology system was used for plants growing, and the infection process of P. brassicae in the roots of resistant and susceptible Chinese cabbage was examined based on morphology and microscopic characteristics using micoscope. In susceptible Chinese cabbage, the root hair infection stage occurred over approximately 7 days after inoculation, the cortical infection happened over approximatly 14 days after inoculation, and clubroots formed in approximately 30 days after inoculation. However, in resistant Chinese cabbage, the pathogen could be prevented and maintained in the root hair infection stage. This research provides a foundation for the subsequent studies of cabbage resistance of P. brassicae.