Field study of the interaction between Orobanche crenata Forsk. and some new lines of Vicia faba L. in Egypt

In Egypt, some newly derived lines of faba bean (Vicia faba L.) as well as Giza 402, all of which had shown a certain resistance against the parasitic weed Orobanche crenata Forsk., were tested in the field. For reasons of comparison, the susceptible cultivars Giza 3 and Reina Blanca were included in this test. Faba bean plants and Orobanche attachments were regularly harvested and examined. The susceptible cultivars completely collapsed before the end of the growing season, whereas others, particularly line 402/294, remained alive until pod formation was completed. It appeared that fewer Orobanche spikes emerged on the new lines and Giza 402. Evidence is given that this was not due to avoidance mechanisms, such as smaller root mass, a deeper root system or lack of germination stimulants. Numbers of Orobanche attachments per unit of lateral root length were found to be low. Hence, it could be concluded that these lines are partially resistant; this resistance must be due to some defence mechanism in their roots. The few Orobanche plants attached grew very fast so that final Orobanche dry weight was similar in resistant and susceptible host plants. Further experiments, including broomrape-free controls, are required to study whether some tolerance mechanism might be involved.     

Field evaluation of the resistance of some faba bean (Vicia faba L.) genotypes to the parasitic weed Orobanche foetida Poiret

Heavy infestation of faba bean fields by Orobanche foetida is an emerging problem in Tunisia. Field trials during three consecutive crop seasons demonstrated the resistance of three genotypes to O. foetida, including the cv. Baraca, selected for resistance to O. crenata, and two Tunisian breeding lines, Bader and XBJ90.03-16-1-1-1. Resistant genotypes displayed a parasitism index two-fold lower than that of the susceptible checks. They carried 2–8 times less of tubercle attachments and 2–3 times less of emerged parasite spikes at pod setting stage and at crop maturity, respectively. Seed-yield losses by parasitism reached 90% for the susceptible checks and were two-fold lower for the resistant genotypes. Parasitism affected negatively the protein/starch ratio of seeds of both susceptible and resistant genotypes. The line XBJ90.03-16-1-1-1 was the best candidate for registration because of better productivity in non-infested fields and production of high-weight seeds.     

A participatory farming system approach for sustainable broomrape (Orobanche spp.) management in the Near East and North Africa

Broomrapes (Orobanche spp.) are aggressive and damaging parasitic weeds which have a tremendous impact on agriculture in East Africa, the Mediterranean region and the Middle East. Despite the availability of technologies to control broomrapes in economically important crops, Orobanche infestation continues to increase, threatening the livelihoods of millions of farmers. Many of the technologies developed have not been effectively disseminated and there has been little or zero adoption by farmers—who continue to use ineffective management practices that exacerbate the problem. The adaptation and dissemination of appropriate management practices are major priorities in broomrape control. However, such work must take into consideration the specific socio-economic characteristics of individual farming systems. Orobanche is a community threat and effective management requires a community-based integrated management approach. Recognizing the central role of farmers in parasitic weed management, a technical cooperation project (TCP) involving FAO, ICARDA and seven countries in the Near East and North Africa (NENA) region was implemented to improve the dissemination of knowledge and skills by using a farmer field school approach: a form of education that uses experiential learning methods to build farmers’ expertise. This paper reviews conventional Orobanche research and development approaches, and highlights weaknesses in the management of the parasitic weed using these approaches as opposed to participatory approaches. The benefits and challenges of participatory farming system approaches in relation to integrated broomrape management (IBM) are also discussed. Lessons learned from achieving community ownership of, and institutional support for, IBM could be applied to other sectors (e.g. public health) in which there is a need for institutional learning and reform. Recommendations are made that include regional collaboration within the framework of a proposed Near East and North Africa Orobanche Management Network (NENAOMAN).     

朱砂根和红凉伞花器官的形态补充描述

朱砂根和红凉伞在最新的分类系统中均隶属于报春花科（Primulaceae）紫金牛属（Ardisia）植物,由于二者在植株形态上存在过渡性状,从而缺乏明显的区分界限,而花部形态是属下划分及种间界定的关键性状,具有较高的分类价值,因此,基于对二者原始形态描述的基础上,分别对其花器官形态与解剖结构进行补充,旨在更加准确地掌握它们在形态性状上的差异。结果表明：朱砂根和红凉伞均为圆齿亚属,主要区别在于叶色的过渡,其余形态无太大的差异性,黑色腺点分布于2种植株的所有器官中,具有较高的观赏价值;朱砂根和红凉伞的花序较多,从外到内不断分化,而花序梗随着花芽的分化逐渐伸长;通过石蜡切片解剖发现,朱砂根和红凉伞花芽分化较早,最小采样花序大小为0.5 mm左右,2种植株均处于花芽分化末期,因此,从外观上不能反映其内部的结构变化;朱砂根的子房膨大有2种类型,当横径>纵径时,子房分化为2室,胚珠和花粉粒成熟,易于受精;纵径>横径时,柱头快速突破花冠裂片高于雄蕊,但子房暂未分室,未见花药明显散粉,导致受精失败和柱头脱落;而红凉伞子房横径和纵径同时生长易于受精,座果率略高于朱砂根。此外,二者通常形成2室子房,本研究还发现朱砂根中具有分化为3室的子房,而红凉伞子房则分隔为完整的4室,后期花器官在外部形态发育过程中没有明显的区别,且二者的花芽分化、开花和坐果等物候期持续时间一致,但朱砂根花芽分化早于红凉伞约7~10 d,这可能与所处的生境不同有关,结果可为物种鉴定及属内分类修订提供参考依据。     

Effects of fungicides on eyespot, caused predominantly by Oculimacula acuformis, and yield of early-drilled winter wheat

The effectiveness against eyespot of nine fungicide treatments, applied at GS 31, was evaluated in early-drilled winter wheat crops. Visual assessments of stem-base diseases were made before fungicide application and at GS 39/55 and 69/70 of cultivars Consort, Savannah and Claire. Competitive PCR was used to quantify Oculimacula acuformis, O. yallundae, Microdochium nivale, Fusarium spp. and Rhizoctonia cerealis. PCR results indicated that O. acuformis was the predominant pathogen causing eyespot in all three crops. Treatments containing cyprodinil were most successful in reducing disease index and DNA of O. acuformis across cultivars. Treatments containing prochloraz were less consistent in eyespot control, significantly reducing the DNA of O. acuformis only in one instance at GS 70 of cultivar Claire. None of the fungicide treatments had any significant effect on brown foot rot or sharp eyespot, or DNA of M. nivale or R. cerealis. The potential for O. acuformis to cause yield loss was indicated by significant negative relationships between yield and eyespot incidence or DNA of O. acuformis at GS 69/70 for each wheat crop. Relationships between DNA of O. acuformis and eyespot incidence or severity at each growth stage were weak but generally improved at the later growth stages of the crops when disease symptoms were easily distinguished. Both molecular methods and visual assessment failed to predict eyespot incidence or pathogen DNA late in season using incidence or DNA of O. acuformis at GS 31. PCR assays, however, accurately identified the stem base pathogens at early growth stages of the crops when the symptoms of their respective diseases were not readily diagnosed.     

多年生稻稻瘟病抗性评价

利用长雄野生稻(Oryzalongistaminata)地下茎无性繁殖特性培育多年生稻(Perennial Rice,PR)已经成功并开始示范推广.多年生稻表现出一定的稻瘟病抗性,但其所具有的稻瘟病抗性来源尚不清楚.本研究通过田间病情调查、接种鉴定以及抗性基因检测等3种方法,对育成的多年生稻23(PR23)、云大24(...     

A review of the biology and control of selected weed species in the genus Oxalis: O. stricta L., O. latifolia H.B.K. and O. pes-caprae L.

This review considers the distribution, weed problems, biology and control of Oxalis stricta, O. latifolia and O. pes-caprae. The rhizomatous O. stricta is a persistent seed-producing weed which invades horticultural crops in North America. Chemical control is generally most effective in situations where soil-applied residual herbicides can be used; in turfgrass however, foliage-applied herbicides provide suppression only. O. latifolia is widely distributed in a range of annual and perennial crops growing in temperate and tropical locations. This pernicious perennial weed reproduces exclusively by asexual structures, underground bulbs, stolons and tubers. The complexities of the perennating system have rendered ineffective a wide range of herbicide families as a means of restricting the spread of O. latifolia. Similarly, cultural methods of control have not been successful. O. pes-caprae also grows and perennates from bulbs. This weed is essentially a problem in cereal crops in Southern Australia and Mediterranean fruit orchards. Cultural and chemical control difficulties and inadequacies are similar to those in O. latifolia. Future research strategies involving weed physiology, herbicide action and cultural control including biological control are discussed in relation to obtaining improved control methods for the selected Oxalis species.     

多年生稻白叶枯病抗性评价

利用长雄野生稻地下茎无性繁殖特性培育多年生稻已经成功,并在生产上进行了示范推广。为明确多年生稻品种（系）对白叶枯病的抗性表现,通过田间病情调查、抗性水平鉴定和水稻白叶枯病抗性基因检测3种方法,对多年生稻品种（系）多年生稻23（简称PR23,下同）、云大24（PR24）、云大25（PR25）、云大101（PR101）、云大107（PR107）及其父本长雄野生稻、母本RD23和F₁（RD23/长雄野生稻）的白叶枯病抗性进行评价。结果表明,长雄野生稻高抗白叶枯病;尽管PR23、PR24、PR25、PR107携带白叶枯病抗性基因Xa1、Xa4、Xa23、xa25的等位基因,但在田间自然发病条件下均易感白叶枯病,说明这几个抗性基因对这4个多年生稻品种（系）不起抗病作用;而PR101在田间自然发病条件下表现为抗白叶枯病,并含有白叶枯病抗性等位基因xa25、Xa27,说明这2个基因可能是PR101抗白叶枯病的基因。本研究结果为明确多年生稻对白叶枯病菌的抗病反应,以及抗白叶枯病育种和多年生稻生产布局提供了一定依据。     

彩色马蹄莲品种对果胶软腐杆菌Pcc抗性的评价方法及鉴定

为探索彩色马蹄莲（Zantedeschia spp.）接种胡萝卜软腐果胶杆菌（Pectobacterium carotovora subsp. Carotovora, Pcc）的适宜方法,鉴定彩色马蹄莲组内品种对软腐病菌Pcc的抗性情况,本研究先以10个彩色马蹄莲品种为试验材料,进行以完整叶片、叶片圆片（叶盘）为接种材料的室内离体接种,以及以主脉、侧脉为接种部位的温室活体植株接种,接种后分别于12、24、36 h 3个时间点,以发病率、病情指数为指标,统计马蹄莲软腐病发病情况;在明确适宜的接种方法和发病时间后,选取包括第1步试验品种在内的34个彩色马蹄莲品种进行Pcc抗性鉴定。结果表明：离体接种的最佳材料为完整叶片,最佳发病观察时间是24 h;活体接种的最佳接种部位为叶片主脉,最佳发病观察时间是36 h;离体鉴定的中抗品种为5个,感病品种为11个,高感品种为18个;而活体鉴定的中抗、感病和高感品种分别为2、17、15个。离体方法鉴定的中抗品种多于活体鉴定,离体方法鉴定的抗性情况更接近田间大规模生产,其原因可能是离体方法鉴定时接种材料的均一性、环境条件的一致性好,更能反应品种本身的抗性情况。     

Resistance of wild rices, Oryza spp., to the brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

Of the 128 wild rices screened, 83 accessions were resistant to the brown planthopper Nilaparvata lugens (Stål). Resistant accessions were non-preferred and significantly more individuals settled on susceptible TN1 plants than on resistant ones. The quantity of food ingested and assimilated by N. lugens on resistant accessions was less than on susceptible TN1. N. lugens caged on resistant accessions had slow nymphal development, reduced longevity and low fecundity. Two wild rice species, Oryza officinalis and O. punctata, reduced the percentage hatchability of N. lugens eggs. A significant reduction in population growth was observed on resistant accessions compared with susceptible TN1.     

中国海南海岛小花蝽（Orius maxidentex Ghauri）的发现及生物学记述

花蝽是一类捕食性半翅目昆虫。花蝽科目前约包含70个属,其中小花蝽属（Orius Wolff, 1811）是最大的属,全世界包含约80种,中国目前有15种。小花蝽属的种类在蓟马的生物防治方面具有极大的应用前景,是生物防治领域研究和利用的热门天敌类群。目前在我国针对蓟马的有害生物综合治理及绿色防控项目中,能够应用的仅东亚小花蝽（O. sauteri）及南方小花蝽（O. strigicollis）。最近在海南发现的海岛小花蝽（Orius maxidentex Ghauri）为中国新记录种,国外分布于泰国、印度、巴基斯坦、伊朗、阿拉伯联合酋长国、苏丹、塞内加尔。本研究对海岛小花蝽的形态学特征和生物学特征进行了描述,拍摄了海岛小花蝽各虫态及生殖器特征图,并对其发育历期、捕食、交配、产卵、孵化、蜕皮、羽化及同类相食的现象进行了简单描述和研究。此外,本研究获得了海岛小花蝽线粒体细胞色素氧化酶亚基I（COI）基因序列,并提交到美国国家生物技术信息中心（GenBank登录号：OL798096）进行序列比对,分子鉴定结果表明与塞内加尔的海岛小花蝽序列高度一致。海岛小花蝽常见于青葙（Celosia argentea）、小蓬草（Conyza canadensis）等杂草,及芒果（Mangifera indica）、豇豆（Vigna unguiculata）和茄子（Solanum melongena）等作物的花及幼叶上。卵产于植物组织中,若虫阶段有5个龄期,成虫和若虫均以蓟马为食,可捕食花蓟马（Frankliniella intonsa）、黄胸蓟马（Thrips hawaiiensis）、棕榈蓟马（T. palmi）、豆大蓟马（Megalurothrips usitatus）、茶黄蓟马（Scirtothrips dorsalis）及美洲棘蓟马（Echinothrips americanus）等。海岛小花蝽在海南岛全年可见,且具有明显的种群优势,是海南蓟马害虫的重要天敌。本研究在实验室条件下,利用美洲棘蓟马（E. americanus）和大豆幼苗进行室内饲养和观察,发现海岛小花蝽在温度(25±2)℃及相对湿度75%±5%条件下,可以取食美洲棘蓟马完成世代发育,卵期(3.66±0.67)d,1龄若虫(1.72±0.65)d,2龄若虫(2.21±0.82)d,3龄若虫(2.62±0.62)d,4龄若虫(2.45±0.74)d,5龄若虫(3.21± 0.82)d。本研究凭证标本保存于中国热带农业科学院环境与植物保护研究所和中国农业大学植物保护学院昆虫标本馆。     

Clonal performance of perennial Oryza sativa/O. rufipogon selections and their combining ability with O. sativa cultivars for survival, stolon production and yield

In Southeast Asia, upland rice (Oryza sativa) is an annual crop typically grown for subsistence on hilly lands that are at risk for soil erosion. If perennial cultivars of upland rice were developed, they would provide farmers with an inexpensive tool to produce a preferred food while conserving soil. O. rufipogon, the undomesticated progenitor of O. sativa, includes perennial and stoloniferous forms. To evaluate the feasibility of developing perennial cultivars by combining genes of O. sativa and O. rufipogon, four trials were conducted in an upland field at IRRI: O. sativa/O. rufipogon F₁ clone and cutting height trial, F₂ family trial, and two O. sativa/stoloniferous-selection factorial mating design trials. Plants were established at the beginning of the rainy season, then subjected to a 6-month dry season and evaluated for survival after 1 year. Of the 2101 cultivar control plants, only three IR47686-1-4-B individuals survived and none produced stolons. The 18 F₁ clones, which were selected from previous trials with less drought stress, ranged in survival from 4.4 to 91.4%. Cutting height at harvest did not affect survival. Survival among the F₂ families ranged from 9.4 to 31.9%. Segregation for stolon presence did not differ from a 3:1 ratio for five of the six F₂ families, suggesting the effect of a single dominant gene. Average yields per plant for the F₂ families were 1/3 to 1/9 of yields for the cultivars. However, by crossing the F₁s to cultivars, yield potential was almost fully recovered. For the full-sib families of the factorial trials, survival ranged from 0.0 to 48.6%. Azucena and IR47686-1-4-B, both japonica cultivars, exhibited greater general combining ability for survival relative to the six other cultivar parents. Thus, the process of developing perennial cultivars of rice should include screening annual cultivars to identify those with the best combining ability for survival. To develop cultivars of perennial upland rice, drought avoidance and/or tolerance from annual upland cultivars must be combined with the capacity for perennial growth from wild perennial species. The frequency of stolonifereous testcross progeny was lower than expected and was affected by the O. sativa parent. Thus, additional genes likely affected stolon penetrance and expression. Analyses of covariance indicated that stolons improved the likelihood of survival for progenies of the factorial trials but the effect was small (b < 0.1), and that yield (g/plant) had a small negative effect on percent survival (b = −0.13 to −0.32). This study demonstrated that it was possible to introgress genes for perennial growth from wild O. rufipogon accessions into domesticated O. sativa. Additionally, strategies for developing perennial cultivars of upland rice were improved.     

Long-term dry preservation of viable mycelia of two mycoherbicidal organisms

The production of large amounts of fungal spores for preservation and formulation are considered constraints to effective use of fungal biocontrol agents. Few successful attempts have been made to store fungal mycelia alone. Late log-phase liquid fermenter cultured isolated mycelia of two Fusarium spp. specific to the parasitic broomrapes (Orobanche spp.) from fermenters were formulated in alginate beads or in ‘Stabileze’ (starch, sucrose, corn oil, and silica) and air-dried. ‘Stabileze’ formulations exhibited <30% loss of mycelial viability for >9 months and retained pathogenicity to the weed for over a year, while mycelia harvested earlier, and conidia from liquid culture exhibited >40% loss of viability. Mycelia from liquid culture yielded >20 times more colony forming units (cfu) of F. arthrosporioides and >2 times more cfu of F. oxysporum than spores at late log phase. Efficient formulation of mycelia should significantly change the economics of biocontrol.     

Effect of host plant resistance and insecticide on brown planthopper Nilaparvata lugens (Stål) and predator population development in the Mekong Delta, Vietnam

Crop yield and populations of brown planthopper Nilaparvata lugens (Stål), whitebacked planthopper Sogatella furcifera (Horvath) (Homoptera: Delphacidae), green leafhopper Nephotettix spp. (Homoptera: Cicadellidae), and hemipteran and spider predators were monitored on rice varieties susceptible, moderately resistant, and highly resistant to N. lugens, under insecticide-treated and insecticide-free conditions. Nilaparvata lugens outbreaks and hopperburned plants were observed only in plots of the insecticide-treated susceptible varieties. In insecticide-free plots, the yield of the susceptible variety was lower than those of resistant varieties in only one of four seasons. In plots of a moderately resistant and a highly resistant variety, populations of N. lugens, S. furcifera, Nephotettix spp., and predators were generally similar, and yields did not differ, under both insecticide-treated and insecticide-free conditions. In insecticide-free plots, predator-N. lugens ratios were generally higher on resistant varieties than susceptible varieties. Two conclusions can'be drawn from our results relevant to the question of what levels of N. lugens host plant resistance are appropriate for farmers who do not overuse insecticides. First, susceptible varieties will not necessarily be damaged by N. lugens, even when N. lugens outbreaks occur in adjacent plots. Second, moderate and high levels of N. lugens resistance do not appear to be incompatible with biological control of N. lugens or other homopteran pests.     

多年生稻育种进展及展望

多年生稻是指头季稻成熟收割后,通过免耕保留稻桩,等到下一个生长季,稻桩地下茎腋芽发出新苗,重新成为可以收割的稻。笔者所在团队以亚洲栽培稻（Oryza sativa）为母本,以来源于非洲的长雄野生稻（O. longistaminata）为父本,通过种间远缘杂交方式培育多年生稻。经过20多年的研究,发现了长雄野生稻地下茎遗传规律,发明了利用长雄野生稻地下茎无性繁殖特性培育多年生稻的方法,创制了一批具有多年生性的育种材料,育成了3个多年生稻品种,创新了以越冬和免耕为核心的多年生稻轻简化生产技术,实现了只需耕种1次即可连续收获4~5年的稻作生产方式。从理论发现、技术发明、品种培育、栽培技术创新到产业化,形成了自成体系、独树一帜的多年生稻研发模式,为农作物尤其是多年生粮食作物的遗传改良与应用提供了借鉴。     

温度对海岛小花蝽5龄若虫捕食茶黄蓟马功能反应的影响

海岛小花蝽（Orius maxidentex Ghauri）是蓟马的重要天敌昆虫,在热带地区,海岛小花蝽是优势天敌,对高温有较强的适应能力,较适合热带地区的害虫防治。目前海岛小花蝽对茶黄蓟马（Scirtothrips dorsalis Hood）的控害情况尚未明确,为了解海岛小花蝽对茶黄蓟马的控制作用,明确不同温度对海岛小花蝽捕食茶黄蓟马功能反应的影响。本研究以海岛小花蝽5龄若虫为例,在16、20、24、28、32℃温度条件下,测定海岛小花蝽5龄若虫对茶黄蓟马2龄若虫和成虫的捕食功能反应。在16~32℃,随着温度的升高,海岛小花蝽5龄若虫随猎物密度的增加,其捕食量有明显的逐级上升趋势;试验温度范围内海岛小花蝽5龄若虫对茶黄蓟马的捕食功能反应均符合Holling Ⅱ型方程。海岛小花蝽5龄若虫对茶黄蓟马2龄若虫的捕食能力与茶黄蓟马成虫的捕食能力并无明显差异,在28~32℃范围内,海岛小花蝽对茶黄蓟马的捕食量显著高于其他试验温度;海岛小花蝽5龄若虫在试验温度32℃,猎物密度为60头时捕食量最大,对茶黄蓟马2龄若虫与成虫的捕食量分别为34.6、34.0头。海岛小花蝽5龄若虫对茶黄蓟马2龄若虫与成虫在32℃时的处理时间最短,分别为0.0119、0.0115 d。海岛小花蝽5龄若虫对茶黄蓟马的捕食量与茶黄蓟马猎物密度呈正相关,但寻找效应与猎物密度呈负相关,在相同的猎物密度下,随着温度的升高,寻找效应逐渐下降,海岛小花蝽5龄若虫对茶黄蓟马表现出较高的寻找效应。当猎物密度大于最大捕食量时,海岛小花蝽5龄若虫取食具有选择性,仅取食茶黄蓟马腹部。海岛小花蝽5龄若虫在较高的温度条件下表现出对茶黄蓟马有良好的控害能力,是热带地区重要的天敌资源。     

The long-term approach to parasitic weeds control: manipulation of specific developmental mechanisms of the parasite

Parasitic weeds pose a tremendous threat to world agriculture, mainly because they are at present almost uncontrollable. The root parasites Striga (witchweed) and Orobanche (broomrape) are vicious pests in both tropical and sub-tropical areas. A thorough understanding of their biology, including detailed knowledge of the specific mechanisms of parasitism, is needed in order to develop novel control methods. Some main developmental steps are described for the root parasites: seed conditioning and germination, haustorium formation, penetration into host tissues, maturation of the haustorium, and seed production. All these stages can be targeted in order to achieve parasite control. For example, based on our findings regarding gibberellin synthesized during seed conditioning, we were able to prevent parasitism by soil application of an inhibitor of gibberellin synthesis. Other developmental stages, such as germination stimulation, the enzymatic penetration of the haustorium into host tissues, and the source–sink relations between host and parasite are also possible targets for control, and the mechanisms involved may be manipulated for specific control of the parasites.     

Donors for Resistance to Brown Planthopper Nilaparvata lugens (Stål) from Wild Rice Species

Out of 1 989 wild accessions sown in seed boxes for screening, only 1 003 wild accessions with good germination were screened against brown planthopper (BPH), Nilaparvata lugens (Stål) under greenhouse conditions. The collection comprised of accessions from 11 wild species and African cultivated rice. The germplasm was screened for BPH following standard seed box screening technique in the greenhouse. As many as 159 accessions were identified as resistant during the year 2012 based on one year screening. A selected set of BPH resistant accessions were screened again during 2013. Based on the two years screening, seven accessions of O. nivara (AA), one accession of O. officinalis (CC), seven accessions of O. australiensis (EE), five accessions of O. punctata (BB and BBCC) and nine accessions of O. latifolia (CCDD) were confirmed to be resistant to BPH. So far no BPH resistance genes have been identified and designated from O. nivara and O. punctata, hence these may act as new sources of resistance.     

Seed treatment of sorghum varieties with brine (NaCl) solution for control of Striga hermonthica in Sorghum

Field trials were conducted in 1997 and 1998 wet seasons to determine the effect of seed treatment of different sorghum varieties with brine (NaCl) on the control of Striga hermonthica in sorghum. The varieties of sorghum used were ICSV 1002, ICSV 1007 (improved resistant varieties from ICRISAT, Mali), BES (a local improved variety), and War-warabashi (a local susceptible variety). Different concentrations of brine at 0.5, 1.0, 1.5, and 2.0 M were used. The results show that the varieties, ICSV 1002 and ICSV 1007 had significantly higher establishment count than the BES and War-warabashi varieties, but had shorter plants. Similarly, the ICSV 1002 and ICSV 1007 and War-warabashi varieties had significantly larger LAI values than the BES variety, although the BES significantly out yielded them. The susceptible War-warabashi variety supported the highest number of Striga emergence than the improved varieties. The effect of brine treatments on plant establishment, growth and yield of sorghum under Striga infestation shows that there was a decrease in crop stands with increase in brine concentration, with the least value at 2.0 M brine treatment, which was damaging at this rate. Plant height and, leaf area index (LAI) of sorghum increased with increasing concentration of brine to a maximum at 1.5 M and declined at 2.0 M brine treatment. The 1.5 M brine treatment produced the highest grain yield. Striga shoot emergence significantly declined with increasing brine concentration reaching the lowest values at 1.5 and 2.0 M brine treatments. The interaction between sorghum varieties and brine concentrations shows that War-warabashi with 1.5 M brine treatment had the tallest plants and largest LAI, while BES and 1.5 M brine produced the highest grain yield. In general, the interaction between the varieties and all the brine concentrations significantly reduced Striga emergence. Irrespective of the sorghum varieties the use of brine at 1.5 M was found optimal for controlling Striga emergence resulting in increased crop growth and grain yield. This implies that which ever variety farmers are using either resistant, tolerant or susceptible, they could easily use brine at 1.5 M to effectively control Striga and increase in grain yield. The mechanism by which brine successfully controlled Striga, is, however, not clear and needs to be investigated.     

Informative ISSR Markers Help Identify Genetically Distinct Accessions of Oryza rufipogon in Yield Improvement

Inter simple sequence repeat(ISSR) polymorphism was used to determine genetic diversity and phylogenetic relationships in 90 genotypes of wild and cultivated species of Oryza from different geographical regions of the world. In all the 17 primers used in ISSR-PCR, a total of 11 464 bands were amplified at 253 band positions/loci. The primer UBC-809 amplified the maximum bands(1 059) at 21 band positions. UBC-810 and UBC-835 amplified the minimum of 391 bands each at 7 and 14 band positions, respectively. The mean polymorphism information content ranged from 0.44 to 0.84 and resolving power ranged from 8.69 to 23.53. Un-weighted pair group method with arithmetic mean dendrogram and population structure based on the 17 primers separated all genotypes into 4 major clusters with a genetic similarity of 53%–100%. The first two clusters consisted of 30 O. rufipogon accessions each. In the third cluster, O. nivara and O. longistaminata grouped as one sub-cluster and all other O. nivara accessions and cultivars grouped as another sub-cluster. The fourth cluster had only five O. rufipogon accessions which can be a source of new genes. Four sub-populations were identified within O. rufipogon and two sub-populations within O. nivara at K = 7. A subset of six primers with high resolving power values were the most informative and grouped all genotypes almost similarly as the 17 primers did. Use of these six highly informative primers in ISSR-PCR is a cost effective and robust method for assessing genetic diversity in large germplasm collections of wild rice species.