Combining Ability and Genetic Effects of Germination Traits of Brassica napus L.Under Waterlogging Stress Condition

Cross combinations from six rapeseed cultivars and lines were evaluated under waterlogging stress condition in order to understand the genetic mechanism of waterlogging tolerance of Brassica napus L.and provide reasonable improvement programs.There were six germination traits investigated on combining ability and heritability using complete diallel crossing method designed for 30 combinations from those six cultivars and lines.The traits included relative root length,stem length,fresh weight per plant,survival rate,electrical conductivity,and vigor index.After flooding treatment,the six traits of parents and F1 were analyzed.The general combining ability（GCA） and special combining ability（SCA） of germination traits were analyzed using Griffing I method.Among 30 cross combinations,the GCA was significantly different among six waterlogging resistance traits.The SCA of these traits was significantly different except the SCA of electrical conductivity.As a representative trait of waterlogging tolerance in rapeseed,relative vigor index had the highest narrow heritability and relatively low broad heritability.The cultivars Zhongshuang 9 and P79 had higher tolerance potential to waterlogging stress.It can be concluded that combining ability and genetic effects of relative vigor index during germination stage could be used to identify the waterlogging tolerance of rapeseed in breeding program.

Seed germination traits of two plant functional groups in the saline deltaic ecosystems

Aims Salt stress resulting from soil salinization is one of the driving forces of the land degradation throughout the world.The modern Yellow River delta is one of the most saline areas in China.Phytoremediation can be an effective way to restore the salinized ecosystems,which requires selecting appropriate plant species.This study explored the germination responses of common plant species from contrasting habitats in the Yellow River delta to varying salinity,offering experimental information for ecosystem restoration in the Yellow River delta.Methods In this study,15 common plant species from the Yellow River delta were divided into two groups(high-salinity and low-salinity groups)by their natural habitats using Canonical Correlation Analysis.Seeds of each species were treated with five salinity levels(0,5,10,20 and 30 ppt),using a randomized complete block design,and germinated seeds were counted and removed daily for 28 days to calculate the final germination proportion and mean time to germination.The germination responses of seeds to salinity treatments were compared between the two groups.Important Findings In relation to salinity,seed germination behavior of the test species was closely related to the salinity level of the habitats over which they were distributed.Species from the habitats with higher salinity had generally higher final germination proportion but shorter mean time to germination than those from the habitats with lower salinity in all of five salinity treatments used.The final germination proportion and mean time to germination of low-salinity group species were more sensitive to salinity than those of high-salinity group species.Selecting the species with high final germination proportion and short mean time to germination is important for restoration of salinized land.

Impact of grazing on germination trait selection in an alpine grassland on the Tibet Plateau

Previous studies indicated that grazing can cause significant changes in abiotic and biotic environment in grassland.However,how these changes impact germination trait selection in grassland has not been well studied.Thus,we aimed to explore whether grazing can significantly change germination trait diversity and composition of grasslands community.We measured the germination traits of species in the laboratory,and compared their performance in grazed and nongrazed grasslands.Then,we compared the community-weighted means of germination traits and functional diversity of grazed and nongrazed grasslands based on these germination traits to know whether grazed and nongrazed grasslands differed in their germination trait structures.At the species level,we found that the changes of abundance in grazed and nongrazed grasslands were not related to species’germination traits.However,at the community level,compared with nongrazed grasslands,species in the grazed grasslands generally exhibited a higher seed germination percentage.Moreover,seed germination response in grazed grasslands was more positively related to alternating temperature than in nongrazed grasslands,and breadth of the germination temperature niche was narrower in grazed than in nongrazed grasslands.Compared with nongrazed grasslands,seed germination trait diversity was increased and germination trait evenness decreased in grazed grasslands.Grazing can change microhabitat conditions,thereby changing germination trait selection by environmental filtering,resulting in a significant difference in germinate trait composition at the community level.