Taxonomic description of Pseudomonas rhizovicinus sp. nov., isolated from the rhizosphere of a desert shrub Haloxylon ammodendron

A Gram-negative aerobic bacterium, strain M30-35 ^T, was isolated from the rhizosphere of Haloxylon ammodendron in Tengger desert, Gansu province, northwest China. Our previous research indicated that strain M30-35 ^T can promote the growth of ryegrass (Lolium perenne L.). In this study, strain M30-35 ^T was subjected to a polyphasic taxonomic study. Phylogenetic analysis of the 16S rRNA gene and two other housekeeping genes (gyrB, rpoD) showed that strain M30-35 ^T is a member of Pseudomonas anguilliseptica group. The average nucleotide identity (ANI) scores for strains KMM 3042 ^T and FR1439^T were 76.5% and 83.7%, respectively, and DNA-DNA hybridization (DDH) were 21.6% and 26.6%, respectively, and the rates were less than the threshold range for species determination. The dominant cellular fatty acids of strain M30-35 ^T were C_16:0 (22.7%), summed feature 3 (C_16:1ω7c and/or C_16:1ω6c; 18.5%), summed feature 8 (C_18:1ω7c and/or C_18:1ω6c; 23.1%). The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phospholipid and aminophospholipid and the predominant respiratory quinone was ubiquinone (Q9). On the basis of above data, it can be concluded that strain M30-35 ^T represents a novel species in the genus Pseudomonas, for which the name Pseudomonas rhizovicinus sp. nov. is proposed. The type strain is M30-35 ^T (=?MCCC 1K03247^T?=?KCTC 52664 ^T).

     

三种观赏植物对重金属镉的耐性与积累特性

通过盆栽实验,对镉(Cd)胁迫下3种观赏植物含羞草、白雪姬和树马齿苋的生长、生理和重金属累积与分布情况进行了研究。结果表明:含羞草、白雪姬和树马齿苋的平均耐性指数分别为105.57、81.35和79.88;在100mg.kg-1Cd浓度下三者叶绿素a、b的含量分别为对照的83.74%、69.83%;60.64%、51.26%和60.64%、51.26%;类胡萝卜素的含量和叶绿素a/b值无明显变化;三者在Cd胁迫下均表现出O2.-离子生成速度上升,MDA含量增加,电导率升高的趋势,其中含羞草的变化幅度最低,白雪姬次之,树马齿苋最高。三者对Cd的耐性表现为含羞草白雪姬树马齿苋。3种观赏植物对Cd均具有较强累积能力,在土壤Cd含量为100mg.kg-1时,三者根和地上部分的Cd累积浓度均高于100mg.kg-1。且对Cd积累能力为树马齿苋含羞草白雪姬。含羞草、白雪姬和树马齿苋在土壤Cd污染的治理中有一定的应用价值。     

水稻DH群体籽粒充实度的QTL定位

籽粒充实度较差是当前水稻亚种间杂种优势利用中所面临的最大障碍之一。研究采用籼粳交(圭630×02428)来源的DH群体对水稻籽粒充实度进行QTL分析,检测到1个主效应QTL(qGP-7),该QTL位于第7染色体RZ978～RG404a～RG404c区间的大约26cM的染色体区段上,对籽粒充实度的贡献率为10%～15%。发现了2对"加性×加性"效应的互作QTL,对籽粒充实度的贡献率皆为20%左右,表明QTL的上位性是控制籽粒充实度的重要遗传基础之一。还对亚种间杂交稻育种中"以饱攻饱"的亲本选配策略作了讨论。