| Mulberry(Morus alba L.)is an importantly native cash tree in China.The Sichuan Basin is one of the most traditional cocoon industries with a current mulberry plantation of 133,000 hectares for a 7.0 billion RMB economy,which contributes great significance to the livelihood of local growers.Therefore,the selection of local suitable varieties is the premise to ensure the economic benefits of sericulture.Studies have shown that the growth and survival of mulberry trees depends on arbuscular mycorrhizal fungi(AMF)for taking up soil nutrients.By combing the mycorrhizal physiological and ecological approaches with high-throughput gene sequencing techniques,this present research studied the community composition and diversity of AMF in both mulberry soil(0-10 and 10-30 cm depths)and their affecting factors.The field sites are locating in the Gao and Ningnan County(450 km apart)in Sichuan,southwest China,where is one of the traditionally important sericulture industries in China.Three mulberry varieties in the Gao County(Baiyou,Chuansang 98-1 and Qiangsang 1)and Ningnan County(Fengtian 5,Hongya,and Yunsang 1)were respectively selected with similar management(fertilization,irrigation,pruning,and etc.).Plant root and soil samples at 0-10 and 10-30 cm depth were collected to determine their root AMF colonization,soil pH,soil organic carbon(SOC),available nitrogen(AN),available phosphorus(AP),available potassium(AK),urease,sucrase,and glomalin-related soil protein(GRSP).The principal co-ordinates analysis and Permutational multivariate analysis of variance were applied to establish AMF community composition from the virtual taxa that were detected using the Illumina MiSeq high-throughput gene sequencing.The AMF community composition was then related to all generated soil variables for locating the driving factors how edaphic properties could affect the AMF community composition and functioning.The main results were as follows:(1)Formation of AMF was success in all the six tested mulberry trees and the percentage of root AMF colonization as well as soil GRSP content were differed among mulberry varieties.In general,the mycelium colonization of mulberry in the field was about 30～50%,the vesicular colonization was 15～30%,and arbuscular colonization was 10～15%.Root AMF colonization was significantly higher in Chuansang 98-1(53%±3.3);and soil GRSP at both the 0-10 and 10-30 cm depths was significantly highest in Qiangsang 1,higher in Chuansang 98-1,and lowest in Yunsang 1.(2)Soil chemical properties significantly differed among mulberry orchards in the Gao County and Ningnan County.Soil pH,AP,AK,activity of urease and sucrase were significantly higher in the Ningnan County than in the Gao County,while the opposite was true for the alkaline N.Soil AP and AK were obviously different among different cultivars.The principal component analysis showed that SOC,AP,AK and the total GRSP significantly affected soil fertility,which patterned as the following significant order:Fengtian 5>Yunsang 1>Hongya>Qiangsang 1>Baiyou>Chuansang 98-1.(3)AMF resources were rich in the mulberry orchards in both the Gao County and Ningnan County.The AMF community position was consisted of seven AMF genera,namely Ambispora,Archaeospora,Claroideoglomus,Gigaspora,Glomus,Paraglomus and Scutellospora.Glomus and Paraglomus were the most dominant genera with a relative abundance of 61%and 35%,respectively.(4)Relative abundance of Glomus and Paraglomus,numbers of soil AMF virtual taxa(VT)as well as AMF diversity indexes were significantly different among cultivars At 0-10 cm soil depth,the relative abundance of Glomus and Paraglomus were highest in Chuansang 98-1(45%,28%)and Qiangsang 1(39%,36%)orchards,but lowest in Hongya orchard(14%,21%).However,at 10-30 cm soil depth,the relative abundance of both Glomus and Paraglomus were significantly increased in Hongya orchard.In addition,the number of detected VT were highest in Qiangsang 1 orchard and lowest in Hongya orchard.But AMF diversity indexes were the opposite to VT numbers,which appeared lowest in Qiangsang 1 orchard,but highest in Hongya orchard.Furthermore,the AMF diversity of Fengtian 5,Hongya,Yunsang 1 and Qiangsang 1 orchards were decreased with soil depth,but were increased with soil depth of in Chuansang 98-1 and Baiyou orchards.(5)The principal co-ordinates analysis as well as PERMANOVA(Permutational multivariate analysis of variance)analysis displayed substantial differences in the AMF community composition between the Gao County and Ningnan County and among Qiangsang 1,Baiyou and Chuansang 98-1,but were less different among Fengtian 5,Hongya and Yunsang 1.In addition,the permutational multivariate analysis of variance showed that significantly higher AMF community position in Qiangsang 1 than in Baiyou,Fengtian 5,Hongya and Yunsang 1,in Baiyou than in Hongya and Yunsang 1,but was similar between Chuansang 98-1 and Yunsang 1.(6)Hellinger transformation-based redundancy analysis(tbRDA)and Monte Carlo permutation tests showed that cultivar was the main influencing factor of AMF community.A single soil factor had no significant influences on AMF community,but the interaction among soil factors had significant influences on AMF community,among them soil AP,AK,SOC and T-GRSP were the main influencing factors.(7)The structural equation model(SEM)showed that mulberry cultivars had significantly direct effects on soil AP,AK and T-GRSP,and T-GRSP had significantly direct effects on SOC.In addition,cultivars showed significant indirect effects on SOC.With the increase of soil AP,the diversity of AMF decreased significantly.The increase of SOC could reduce the soil AMF abundance,which indicated that with the increase of T-GRSP content,the AMF abundance would have significant indirectly decrease.Soil AK had insignificant direct positive effect on AMF abundance and insignificant indirect negative effect on AMF diversity. |
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