Identification and marker‐assisted introgression of QTL conferring resistance to bacterial leaf blight in cowpea (Vigna unguiculata (L.) Walp.)

Bacterial leaf blight (BLB), caused by Xanthomonas axonopodis pv. vignicola (Xav), is widespread in major cowpea [Vigna unguiculata (L.) Walp.] growing regions of the world. Considering the resource poor nature of cowpea farmers, development and introduction of cultivars resistant to the disease is the best option. Identification of DNA markers and marker‐assisted selection will increase precision of breeding for resistance to diseases like bacterial leaf blight. Hence, an attempt was made to detect QTL for resistance to BLB using 194 F_2 : 3 progeny derived from the cross ‘C‐152’ (susceptible parent) × ‘V‐16’ (resistant parent). These progeny were screened for resistance to bacterial blight by the leaf inoculation method. Platykurtic distribution of per cent disease index scores indicated quantitative inheritance of resistance to bacterial leaf blight. A genetic map with 96 markers (79 SSR and 17 CISP) constructed from the 194 F₂ individuals was used to perform QTL analysis. Out of three major QTL identified, one was on LG 8 (qtlblb‐1) and two on LG 11 (qtlblb‐2 and qtlblb‐3). The PCR product generated by the primer VuMt337 encoded for RIN2‐like mRNA that positively regulate RPM1‐ and RPS2‐dependent hypersensitive response. The QTL qtlblb‐1 explained 30.58% phenotypic variation followed by qtlblb‐2 and qtlblb‐3 with 10.77% and 10.63%, respectively. The major QTL region on LG 8 was introgressed from cultivar V‐16 into the bacterial leaf blight susceptible variety C‐152 through marker‐assisted backcrossing (MABC).     

黑果枸杞LrDREB1基因克隆及其在非生物胁迫下的表达分析

DREB(Dehydrate responsive element binding factor)转录因子是植物非生物逆境适应中的关键调节因子,该类转录因子具有保守的AP2/EREBP结构域,在低温、高盐等非生物逆境胁迫下,可调控下游逆境应答基因的表达,对增强植物的抗逆能力有重要作用。黑果枸杞具有极强的耐干旱、盐碱能力,为研究黑果枸杞DREB类基因在低温、盐碱响应中的功能,本研究以强抗盐灌木黑果枸杞总RNA为模板,基于前期转录组测序拼接序列,利用RT-PCR方法克隆得到一条DREB基因。该基因含有一个1116 bp的开放阅读框,编码372个氨基酸。系统进化树分析显示,Lr DREB1基因属于DREB亚家族A2组成员,与拟南芥AtDREB2B、AtDREB2E具有较高的相似性。荧光定量PCR结果显示,Lr DREB1受盐胁迫、ABA胁迫和低温胁迫诱导表达,可能参与依赖ABA的信号转导途径,调节黑果枸杞抗盐响应。本研究通过对黑果枸杞LrDREB1基因的克隆、序列分析和表达分析,为研究Lr DREB1的功能及黑果枸杞抗盐机理提供了帮助。     

Production and characterization of hybrids between Cajanus cajan × C. reticulatus var. grandifolius

Cajanus reticulatus var. grandifolius, endemic to Australia and a wild relative of the cultivated species, C. cajan, was successfully crossed with the latter as the female parent. The major wild species characters such as persistent stipules, long pod hairs, pod shattering, brown seeds with grey speckles, and presence of seed strophiole were dominant in the hybrid. For growth and branching habit, and leaflet, flower, pod, and seed size, the hybrid was intermediate between the parents. The meiotic cells of the hybrid were found to have quadrivalents, trivalents, univalents,and showed reduced chromosome pairing as revealed by the increased number of rod bivalents per cell at metaphase-I, and stickiness and precocious movement of chromosomes to poles in the second division. In comparison to the parents, the hybrid had fewer pods and seeds. However,these anomalies in the interspecific hybrid are not significant enough to preclude the gene transfer from C. reticulatus to the cultivated species through a sexual route. This revised version was published online in August 2006 with corrections to the Cover Date.     

Development of a scoring scale for powdery mildew (Golovinomyces cichoracearum (DC.) V.P. Heluta) disease and identification of resistance sources in cultivated and wild sunflowers

Powdery mildew incited by Golovinomyces cichoracearum has become a serious problem on sunflower in India during the past 2–3 years. Genetic resistance in the released cultivars and the parental lines of hybrids is rather limited. Hence, screening of about 420 accessions comprising of wild Helianthus species, interspecific derivatives, core germplasm, inbred lines and few exotic accessions was done under natural field conditions for 2 years and further confirmed by screening under artificial inoculation conditions. PCR analysis using primers specific to powdery mildew causing genera gave a 391 bp band which confirmed the pathogen as G. cichoracearum. Seven different screening methods were tested which induced infection, but dusting of spores on to the healthy leaves proved to be convenient and more effective method of infection. Based on the differential response of the accessions derived from diverse genetic backgrounds, a scale for obtaining reliable estimates of the disease has been devised. Among different cultivar germplasm accessions, the disease severity index (DSI) ranged from 15 to 100 and area under disease progression curve (AUDPC) ranged from 95 to 648. Among the four groups of cultivated sunflower accessions tested, DSI and AUDPC was in the order of exotic lines < interspecific derivatives < inbred lines < core germplasm. Reliable sources of resistance to the pathogen were identified in four annual wild species (H. argophyllus, H. agrestis, H. debilis, H. praecox), six perennials (H. angustifolius, H. atrorubens, H. rigidus, H. salicifolius, H. pauciflorus and H. resinosus), two interspecific derivatives (HIR-1734-2, RES-834-3) and two exotic lines (PI 642072, EC-537925).     

黔油12号双低杂交油菜制种技术研究Ⅲ.父母本不同行比群体经济性状变化及制种产量

为制定黔油12号大面积制种技术方案,明确黔油12号制种时父母本的适宜行比,试验父母本行比共设1:2、1:4、1:6、1:8、1:10、1:126个处理进行研究.结果表明:(1)因行比不同,单位面积上母本不育株数差异较大,行比1:6和1:8的不育株数较行比1:4的分别多124株和342株,行比1:10和1:12的不育株数比行比1:4的分别多461株和551株;(2)考察距父本行不同距离的母本行的经济性状,以距父本行第一行和第二行的全株有效角较多,距父本三行以上的千粒重高,但每角实粒数减少,单株产量随与父本距离加大而降低;不同行比母本群体经济性状以行比1:2～1:6的全株有效角较多,随行比加大,群体的平均每角实粒数减少,千粒重增加,单株产量逐渐降低.(3)在相同面积条件下,制种产量以行比1:6至1:10为佳,其中1:8的产量居第一位,为51.50kg/667m2;1:10的产量居第二位,为51.23kg/667m2;1:6的产量居第三位,为50.03kg/667m2.     

槲蕨水提物对3种杂草的化感效应研究

以槲蕨(Drynaria fortunei (Kunze)J.Sm)为供体植物,分别以黑麦草(Lolium perenneL.)、紫花苜蓿(Medicago sativa Linn.)和紫云英(Astragalus sinicus)为受体,研究不同浓度槲蕨水提物对3种杂草种子萌发和幼苗生长的化感作用.取槲蕨新鲜叶制成0.5 g/mL的水提液,分别用浓度为0、0.1、0.25、0.5 g/mL的水提液来培养3种杂草(黑麦草、紫花苜蓿和紫云英)种子,统计种子萌发率及测量幼苗长度.结果表明:不同浓度的槲蕨水提物对黑麦草、紫花苜蓿和紫云英的发芽率及幼苗生长有显著的抑制效应,但不同浓度水提物对不同杂草的影响存在差异,3种杂草对槲蕨水提物敏感性大小顺序为黑麦草＞紫花苜蓿＞紫芸英.说明槲蕨可作为一种生物除草剂资源加以利用.