玉米抗禾谷镰孢菌穗粒腐病种质资源鉴定

穗粒腐病是玉米主产区普遍发生的穗部真菌性病害,发掘优异的抗性种质资源和选育优良抗病品种,是防治玉米穗粒腐病最为经济有效的措施。本研究采用针刺果穗注射接种法,在北京通州和小汤山两个试验点,对国内外324份玉米自交系种质资源进行禾谷镰孢菌抗性鉴定。综合2个试验点的抗性评价结果,鉴定到了9份禾谷镰孢菌穗粒腐病表现高抗的自交系,分别为OQ603、百黄混、PI 539921、Mo17、PI 406119、F321、X178、B09和PHG39。有48份自交系对禾谷镰孢菌的穗粒腐病抗性,在2个试验点均为抗级以上(包括高抗和抗)。从不同种质类群自交系的抗性分布情况来看,P群种质整体上表现出较强的抗性,Iodent群和X群次之,而在其他类群中抗性分布趋势并不明显。这些自交系的鉴定,丰富了我国玉米穗粒腐病抗性种质资源,也为抗病育种和理论研究奠定了基础。

Exploring differentially expressed genes associated with fertility instability of S-type cytoplasmic male-sterility in maize by RNA-seq

The germplasm resources for the S-type male sterility is rich in maize and it is resistant to Bipolaris maydis race T and CI, but the commercial application of S-type cytoplasmic male sterility （CMS-S） in maize hybrid industry is greatly compromised because of its common fertility instability. Currently, the existence of multiple minor effect loci in specific nuclear genetic backgrounds was considered as the molecular mechanism for this phenomenon. In the present study, we evaluated the fertility segregation of the different populations with the fertility instable material FIL-H in two environments of Beijing and Hainan, China. Our results indicated that the fertility instability of FIL-H was regulated by multiple genes, and the expression of these genes was sensitive to environmental factors. Using RNA sequencing （RNA-seq） technology, transcriptomes of the sterile plants and partially fertile plants resulted from the backcross of FIL-HxJing 724 in Hainan were analyzed and 2 108 genes with different expression were identified, including 1 951 up-regulated and 157 down-regulated genes. The cluster analysis indicated that these differentially expressed genes （DEGs） might play roles in many biological processes, such as the energy production and conversion, carbohydrate metabolism and signal transduction. In addition, the path- way of the starch and sucrose metabolism was emphatically investigated to reveal the DEGs during the process of starch biosynthesis between sterile and partially fertile plants, which were related to the key catalytic enzymes, such as ADP-G pyrophosphorylase, starch synthase and starch branching enzyme. The up-regulation of these genes in the partially fertile plant may promote the starch accumulation in its pollen. Our data provide the important theoretical basis for the further exploration of the molecular mechanism for the fertility instability in CMS-S maize.

Study on the Mitochondrial Genome of Sea Island Cotton(Gossypium barbadense) by BAC Library Screening

The plant mitochondrial genome displays complex features, particularly in terms of cytoplasmic male sterility （CMS）. Therefore, research on the cotton mitochondrial genome may provide important information for analyzing genome evolution and exploring the molecular mechanism of CMS. In this paper, we present a preliminary study on the mitochondrial genome of sea island cotton （Gossypium barbadense） based on positive clones from the bacterial artificial chromosome （BAC） library. Thirty-five primers designed with the conserved sequences of functional genes and exons of mitochondria were used to screen positive clones in the genome library of the sea island cotton variety called Pima 90-53. Ten BAC clones were obtained and verified for further study. A contig was obtained based on six overlapping clones and subsequently laid out primarily on the mitochondrial genome. One BAC clone, clone 6 harbored with the inserter of approximate 115 kb mtDNA sequence, in which more than 10 primers fragments could be amplified, was sequenced and assembled using the Solexa strategy. Fifteen mitochondrial functional genes were revealed in clone 6 by gene annotation. The characteristics of the syntenic gene/exon of the sequences and RNA editing were preliminarily predicted.

玉米细胞质雄性不育及其育性恢复基因的研究进展

玉米是杂种优势利用最成功的作物之一,采用细胞质雄性不育（CMS）进行玉米杂交种生产已成为杂种优势利用的有力工具。CMS是由于细胞质和细胞核的基因表达产物的不协调而产生的不育性,可被核基因组中的恢复基因恢复。根据育性恢复专效性,玉米CMS材料主要分为T、C和S三种类型。综述了这三种类型不育及其恢复基因的研究进展,分析了在不育化制种中的应用情况。

玉米穗腐病原菌禾谷镰孢的分离鉴定与致病力测试

利用形态学和分子鉴定技术,从玉米穗腐病病穗上分离并鉴定到17个禾谷镰孢菌株。以玉米自交系X178、593和B73为材料,对其中5个产孢能力强的菌株通过玉米发芽抑制试验进行致病力测试。结果表明,菌株FG14对测试自交系的平均发芽抑制率达54.10%;FG7最低,仅有23.22%,两者相差2.3倍。选用5个菌株在田间分别接种B73和LH59果穗,两个自交系对菌株FG14和FG21的抗性评价均为感,FG7为中抗。种子发芽和田间接种鉴定结果均表明,禾谷镰孢菌株间致病力存在显著差异。试验明确不同菌株对穗腐病抗性鉴定的影响,获得的菌株为玉米种质的穗腐病抗性筛选提供理论参考。