磷酸二氢钾对苜蓿幼苗体内根瘤菌运移及定殖的影响

试验以WL343HQ紫花苜蓿(Medicago sativacv.WL343HQ)及3株青色荧光蛋白(CFP)标记根瘤菌株Rzhizobium LH3436f(3436f)、Ensifermeliloti 12531f(12531f)和Rzhizobium GN5f(gn5f)为材料,添加不同浓度磷酸二氢钾(KH2PO4)于3株标记根瘤菌菌液内,分别筛选出3个有利于各标记根瘤菌生长的KH2PO4浓度,并分别将选定浓度的KH2PO4与相应的标记根瘤菌组合接种于苜蓿幼苗根部。检测根瘤菌侵入根系后在苜蓿幼苗体内运移及定殖的动态变化和对苜蓿幼苗生长的影响,探讨KH2PO4促进根瘤菌运移和定殖的适宜浓度及根瘤菌运移和定殖的效果。结果表明:50mg/L KH2PO4促使3436f长期稳定的大量定殖于苜蓿根系,定殖数量最高达到27075.12cfu/g,显著高于其他处理(P0.05),并快速运移至上部茎和上部叶中,数量分别为19.20cfu/g、9.94cfu/g;50mg/L KH2PO4促使12531f大量定殖于根系,也可运移至上部茎,数量为53.45cfu/g;200mg/L KH2PO4促使gn5f稳定定殖于根系和茎内,接种45d时下部茎内仍有定殖,数量为33.29cfu/g。添加KH2PO4接种可明显提高苜蓿单株结瘤数和单株根瘤重,增加苜蓿叶片数、株高、根长、地上鲜重和根鲜重,显著促进了标记根瘤菌侵染根系并进入苜蓿体内运移和定殖。结合苜蓿体内根瘤菌运移和定殖以及苜蓿生长各指标优化状况,筛选出标记根瘤菌株与KH2PO4的优良组合为3436f+50 mg/L KH2PO4,12531f+50 mg/L KH2PO4和gn5f+200mg/L KH2PO4,为苜蓿接种目标根瘤菌并促使其在体内运移和定殖至种子,构建目标根瘤菌与苜蓿良种种子共生体奠定基础。

Effects of KH2PO4 on rhizobia migration and colonization in alfalfa seedlings

WL343 HQ alfalfa (Medicago sativa cv.WL343 HQ)and 3 cyan fluorescent protein (CFP)-labeled rhizobia,Rzhizobium LH3436f (3436f),Ensifermeliloti 12531f (12531f),and Rzhizobium GN5f (gn5f)were used as materials.Different concentrations of KH2PO4solution were added to 3 strains of rhizobia to screen out the different suitable concentrations for the growth of rhizobia.The growth of inoculated alfalfa seedling root with the most suitable rhizobia strains suspensions combination of KH2PO4solution's concentrations and the la-beled rhizobia was observed to test the effects of rhizobia's dynamic changes of migration and colonization of al-falfa seedlings in the plants after rhizobia invade the roots.The appropriate concentrations of KH2PO4for pro-moting the colonization of rhizobium and the effects of rhizobia migration and colonization were studied as well. The results showed that 3436f was promoted a long-term and stable colonization in the alfalfa root system in the 50 mg/L KH2PO4with a colonization density up to 27 075.12 cfu/g,which was significantly higher than other treatments (P<0.05).In the upper stem and leaf,the densities were 19.20 cfu/g and 9.94 cfu/g,respectively;50 mg/L KH2PO4promoted 12531f to colonize in root system largely,and also promoted 12531f to migrate the upper stem,with a quantity of 53.45 cfu/g.200 mg/L KH2PO4promoted the stable colonization of gn5f in root and stem.And after 45 days'inoculation,it could still colonize in lower stems with the density of 33.29 cfu/g. And adding KH2PO4could significantly increase the number of root nodule and root nodule weight of single plant,improve the leaf number,plant heights,root length,fresh weight and fresh weight of root,and significant-ly promoted ability of the infection of the root system by the marker rhizobia and the migration and colonization of rhizobia.According to the rhizobia's migration and colonization in alfalfa seedlings,and with reference to the optimum conditions of alfalfa seedling growth,the proper combination of labeled rhizobia strains and KH2PO4 concentrations in seedling stage was:3436f+50 mg/L KH2PO4,12531f+50 mg/L KH2PO4,and gn5f+200 mg/L KH2PO4.This could provide the foundation for inoculating of target rhizobia and promoting the migra-tion and colonization to seeds,and establishing a target symbiosis of rhizobium and seedlings.