Abundance of 24-methylenecholesterol in traditional African rice as an indicator of resistance to the African rice gall midge, Orseolia oryzivora Harris & Gagné

Rice production is of great importance to food security in Nigeria. The African rice gall midge (AfRGM), Orseolia oryzivora Harris & Gagné, is a major pest of lowland rice in Nigeria and many other Africa countries. Current management efforts are directed at integrating host plant resistance with biological agents. The type and abundance of some phytochemicals are known to affect resistance in host plants, so in this study we measured rice culm hardness, rice culm stickiness and the type and quantity of phytosterols in rice cultivars, and investigated the effects of these factors on resistance to the AfRGM. The study was conducted at 24 ± 2°C, 60 ± 5% relative humidity, and a 12 h light : 12 h dark photoperiod. Three rice cultivars were studied: one Oryza glaberimma cultivar, Tog 7442 (resistant), and two O. sativa cultivars, Cisadane (tolerant) and ITA 306 (susceptible). We found no significant differences in culm hardness and stickiness among the cultivars tested. Using gas chromatography (flame ionization detection) analysis, we identified four major phytosterols: campesterol, 24‐methylenecholesterol, stigmasterol and β‐sitosterol. 24‐Methylenecholesterol was the most abundant sterol in the resistant O. glaberimma cultivar (79.20 μg), whereas β‐sitosterol was most abundant in the two susceptible O. sativa cultivars (Cisadane, 71.27 μg; ITA 306, 66.37 μg). The comparatively high concentration of 24‐methylenecholesterol in this cultivar of O. glaberimma may be an indicator of resistance to AfRGM.     

Screening of certain barley lines for resistance to root rot disease caused by Fusarium graminearum

This investigation was conducted in 2005/2006 and 2006/2007 to test 235 barley lines plus two varieties Giza 127 and Giza 128 for resistance and susceptibility to Fusarium graminearum. All screened barley lines showed varied significant degrees of infestation to root rot pathogen. A screening system is described for identifying barley lines which are effective in controlling resistant or susceptible lines. By detecting small but consistent differences in root rot severity, the bioassay proved effective in large-scale screening for partial resistance: already 335 barley lines and two varieties have been screened. We found five groups (7.12%), 22 barley lines and both varieties are resistant (R) (8.31%); 28 barley lines are moderately resistant (MR) (19.29%); 65 barley lines are moderately susceptible (MS) (27.89%); 94 barley lines are susceptible (S) and (37.39%) 126 barley lines are highly susceptible (HS). The high degree of precision makes this an invaluable tool in the understanding of pathogen aggressiveness, host specialisation and parasitic fitness. Disease scale was strongly negative and had moderate correlation with germination (?0.309?? and ?0.649??) under normal and disease treatment. The correlation between yield and normal and disease treatment during two seasons was strong and negative (?0.834?? and ?0.847??, respectively were detected).     

Influence of olfactory stimulants on resistance/susceptibility of pearl millet, Pennisetum americanum to the rice weevil, Sitophilus oryzae

The orientation responses of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) as influenced by the olfactory stimulants emanating from either resistant or susceptible pearl millet, Pennisetum americanum, kernels were studied using a Y-tube olfactometer. The rice weevils were more attracted towards odours from millet grains than to blank controls and to susceptible entries more than to resistant entries, in general. However, there were exceptions. Odours from some resistant entries caused statistically the same, or even more positive orientations than those from some susceptible entries, and this suggests that the relative resistance of an entry and its olfactory attractiveness may not be strongly related, or that the resistance to infestation might be influenced by factors other than attractiveness. The partial damage of the millet kernel pericarp by abrasion slightly increased the orientational response of the weevils to odours from some susceptible and some resistant entries alike.     

Generation and screening of recombinant inbred lines of rice for yellow stemborer resistance

Based on the results of studies on varietal screening, antixenosis (egg laying preference) and antibiosis (larval survival and adult emergence), rice varieties W1263 and CO43 were selected as resistant and susceptible parents, respectively, for yellow stemborer (YSB) infestation. A mapping population was developed using above parents following single seed descent method. Screening for YSB reaction in F1 and F2, generations under field and glasshouse conditions for both dead hearts and white ears, established the polygenic nature of inheritance for YSB resistance. Field screening for YSB resistance at F9 generation revealed the difference in the reactions among recombinant inbred lines (RILs) between vegetative and reproductive stages. The experiments under field and glasshouse screening of RILs for dead hearts showed significant positive association. However, the reaction was more towards susceptibility in glasshouse screening due to no choice test. Scoring of 250 RILs (F8) for various morphological traits showed wide range of variation indicating the suitability for QTL mapping.     

糯稻品种的抗性评价与利用

我们从1977～1992年计14年,采用网笼育苗接虫鉴定与田间自然诱发,共鉴定国内外水稻品种（包括株系,杂交稻三系）32000多份,筛选出高抗至中抗稻飞虱的材料3247份,占11．44％,并从中评选出产量高,适应性广,糯性好,能抗褐飞虱、白背飞虱、稻瘟病、白叶枯病等多抗性的糯稻新品种,其中以“水源290”及“三五糯”表现最好。在湖南作双季晚稻亩产在420～550kg,作中稻在135～621kg。农民反映糯性好,抗性强,出米率,出酒率,做糍粑,年糕均优于其他糯稻品种。     

辽宁水稻品种抗灰飞虱鉴定及其抗性机制研究

为探明辽宁地区水稻品种对本地灰飞虱Laodelphax striatellus(Fallén)的抗性水平及其抗虫机制,本研究利用改进的苗期集团鉴定法,以IR36为抗虫对照品种、武育粳3号为感虫对照品种,对42份辽宁地区主栽水稻品种和研究待推广品种进行了水稻苗期对灰飞虱抗性鉴定,并从中选取20份不同抗性水平的品种进行了排趋性和抗生性的测定。结果表明:从42份水稻材料中仅筛选出1份抗虫材料辽优5218,中抗品种11份,其余均为感虫或高感品种。在不同水稻类型中,杂交稻的抗虫性普遍较常规稻强,而从水稻株型上看,抗性品种大多为披散型。抗虫机制研究发现,抗虫品种辽优5218和中抗品种港育129兼具排趋性和抗生性,是非常理想的抗性种质资源,中抗品种港源8号和粳优558具有很强的排趋性,也是较为理想的抗性资源,为抗性机制的深入研究提供了材料。但大部分省内主栽主推品种不具备对灰飞虱的抗性,应引起重视。     

空心莲子草DNA溶液浸胚处理水稻的变异系分子检测及耐旱性评价

通过SSR标记检测了以空心莲子草DNA溶液浸胚处理获得的10个农艺性状稳定遗传的水稻变异系,结果表明,10个水稻变异系均整合了供体空心莲子草DNA的部分片段。在此基础上,以8个水稻变异系及2个对照为试验材料,采用二因素裂区设计,并以主成分分析、逐步回归分析等多种统计方法分析了变异系的耐旱性。结果表明,以综合评价指标与耐旱指数相结合的复合评价体系,可增强水稻耐旱评价的可靠性。导入系H8最耐旱,H6和H7较耐旱,均优于巴西陆稻。本研究结果对水稻的耐旱性评价与耐旱品种选育具有重要意义。     

Development of pre-isogenic lines for rice blast-resistance by marker-aided selection from a recombinant inbred population

To increase the available set of near-isogenic lines (NILs) for blast-resistance in rice, we have developed a general method for establishing NILs from populations of fixed recombinants that have been used for gene mapping. We demonstrated the application of this method by the selection of lines carrying genes from the rice cultivar Moroberekan. Moroberekan is a West African japonica cultivar that is considered to have durable resistance to rice blast. Multiple genes from Moroberekan conferring complete and partial resistance to blast have previously been mapped using a recombinant inbred (RI) population derived from a cross between Moroberekan and the highly and broadly susceptible indica cultivar CO39. To analyze individual blast-resistance genes, it is desirable to transfer them individually into a susceptible genetic background. This RI population, and the associated data sets on blast reaction and restriction fragment length polymorphism (RFLP) genotypes, were used for selection of lines likely to carry individual blast-resistance genes and a minimum number of chromosomal segments from Moroberekan. Because skewed segregation in the RI population favored CO39 (indica) alleles, resistant lines carrying 8.7–17.5% of Moroberekan alleles (the proportion expected after two or three backcrosses) could be selected. We chose three RI lines carrying different complete resistance genes to blast and two RI lines carrying partial resistance genes to blast as potential parents for the development of NILs. These lines were subjected to genetic analysis, which allowed clarification of some issues that could not be resolved during the initial gene-mapping study.     

A field screening method to evaluate rice breeding lines for resistance to the hoja blanca virus

A method is presented for rearing large colonies of viruliferous Sogatodes oryzicola, vector of the rice hoja blanca virus (RHBV). These colonies were used for field screening up to 10 000 rice breeding lines per season for resistance to RHBV. Uniform infection of check varieties in the field indicated that the method was adequate. Field release of vectors when plants were 14 days old resulted in satisfactory disease incidence, after 21 days, to distinguish lines segregating for resistance from lines uniformly resistant or susceptible. Various sources of resistance identified earlier continued to be resistant under the screening conditions. Progeny of lines identified as non-segregating resistant continued as non-segregating resistant. Resistant plants from lines segregating for resistance produced progeny lines that were segregating and non-segregating. Ratios of resistant to susceptible plants in F₁ progeny of three-way crosses were consistent with earlier observations that RHBV resistance is a dominant character. The susceptibility of the commercial checks indicates that rice production in RHBV areas of tropical Latin America continues to be at risk from the virus. Virus-resistant commercial cultivars resulting from this method should be available in 2 years.     

Sex ratio bias in the F1 adult progeny of African rice gall midge, Orseolia oryzivora H. and G. (Dipt., Cecidomyiidae)

Abstract:  Against the background of conflicting reports of variable sex ratio distribution in different populations of the African rice gall midge (AfRGM), Orseolia oryzivora Harris and Gagne, the number and sex ratios of F₁ adult progeny produced per female from wild and screen house populations were investigated in the screen house at 27 ± 3°C, 60–70% relative humidity and 12 : 12 h (light : dark) photoperiod. Results indicated the occurrence of a single sex-biased ratio in all the F₁ adult progeny produced per female of this pest. Regardless of the source, whether from wild or screen house population, each mated female AfRGM produced a full complement of either sex only but never both. The difference between the number of eggs laid and F₁ adult progeny that emerged per female from wild and screen house populations was not significant (P > 0.05), indicating consistency in the occurrence of this phenomenon among AfRGM populations. The reason for this could not be ascertained in this study but AfRGM eggs must be fertilized for development and eclosion to occur. No F₂ adults emerged when a cohort of emergents from the same female were allowed to re-infest susceptible seedlings, indicating absence of parthenogenesis.     

Triticum monococcum lines with distinct metabolic phenotypes and phloem‐based partial resistance to the bird cherry–oat aphid Rhopalosiphum padi

Crop protection is an integral part of establishing food security, by protecting the yield potential of crops. Cereal aphids cause yield losses by direct damage and transmission of viruses. Some wild relatives of wheat show resistance to aphids but the mechanisms remain unresolved. In order to elucidate the location of the partial resistance to the bird cherry–oat aphid, Rhopalosiphum padi, in diploid wheat lines of Triticum monococcum, we conducted aphid performance studies using developmental bioassays and electrical penetration graphs, as well as metabolic profiling of partially resistant and susceptible lines. This demonstrated that the partial resistance is related to a delayed effect on the reproduction and development of R. padi. The observed partial resistance is phloem based and is shown by an increase in number of probes before the first phloem ingestion, a higher number and duration of salivation events without subsequent phloem feeding and a shorter time spent phloem feeding on plants with reduced susceptibility. Clear metabolic phenotypes separate partially resistant and susceptible lines, with the former having lower levels of the majority of primary metabolites, including total carbohydrates. A number of compounds were identified as being at different levels in the susceptible and partially resistant lines, with asparagine, octopamine and glycine betaine elevated in less susceptible lines without aphid infestation. In addition, two of those, asparagine and octopamine, as well as threonine, glutamine, succinate, trehalose, glycerol, guanosine and choline increased in response to infestation, accumulating in plant tissue localised close to aphid feeding after 24 h. There was no clear evidence of systemic plant response to aphid infestation.     

水稻品种抗裂颖资源的筛选与初步研究

利用裂颖率指标,对1017份水稻资源进行抗裂颖种质筛选,筛选出13份高抗与高感的种质资源.利用已筛选资源,估算水稻品种(系)裂颖率的广义遗传率为94.8%.纯系选择试验、不同播期试验及不同氮肥施用水平试验的结果表明,水稻品种(系)抗裂颖性状是稳定的可遗传性状,其表达不受环境因素影响.     

水稻品种对褐飞虱持续抗性的筛选技术

通过水稻品种苗期和分蘖期后对褐飞虱的抗性筛选,提出TN_1受害9级时受害1～5级的为抗性品种,TN_19级后苗期10天、分蘖期后24天内保持1～5级的为持抗品种,不具持抗的抗性品种为短期抗性品种。     

Resistance of cabbage (Brassica oleracea capitata group) crops to Mamestra brassicae

Twenty-one cabbage (Brassica oleracea capitata group) varieties, including 16 local varieties and five commercial hybrids, were screened for resistance to the moth Mamestra brassicae L. under natural and artificial conditions in northwestern Spain. Resistance was assessed as the proportion of damaged plants and damaged leaves, leaf feeding injury, and number of larvae present. Correlation coefficients among damage traits showed that a visual scale (general appearance rating) should be a useful indicator of resistance. Most local varieties were highly susceptible to M. brassicae, whereas the commercial hybrids tested were resistant in terms of head foliage consumption and number of larvae per plant. Performance of varieties was similar under natural and artificial infestation although some of them performed differently at each year. Three local varieties (MBG-BRS0057, MBG-BRS0074, and MBG-BRS0452) were highly susceptible at both natural and artificial infestation conditions being MBG-BRS0074 the most damaged variety. Two local varieties (MBG-BRS0402 and MBG-BRS0535) and commercial hybrids were identified as resistant or moderately resistant to M. brassicae. Among them, 'Corazón de Buey' and 'Cabeza negra' were the most resistant and produced compact heads. These varieties could be useful sources of resistance to obtain resistant varieties to M. brassicae or as donors of resistance to other Brassica crops. The possible role of leaf traits, head compactness, and leaf glucosinolate content in relation to M. brassicae resistance is discussed.     

褐飞虱侵害后不同水稻品种根及叶片脱落酸含量的变化

为了解褐飞虱Nilaparvata lugens （Stål）侵害后水稻耐虫性与植物体内源激素关系,应用酶联免疫吸附法（enzyme-linked immunosorbent assay, ELISA）研究褐飞虱若虫侵害分蘖期超级培矮64S/E32和TN1,灌浆期协优963和TN1后根及叶片脱落酸（abscisic acid, ABA）含量变化.结果表明：褐飞虱侵害分蘖期超级培矮64S/E32和TN1后3 d,叶片ABA含量显著上升,ABA含量根冠比（根ABA/叶片ABA）显著下降;侵害后6 d,超级培矮64S/E32叶片ABA含量显著下降,根冠比显著上升;但TN1叶片ABA含量在褐飞虱侵害后3 d和6 d显著上升,根冠比显著下降.褐飞虱侵害灌浆期协优963与分蘖期超级培矮64S/E32变化一致,TN1在褐飞虱侵害后3 d叶片ABA含量显著上升,根冠比显著下降;侵害后6 d,叶片ABA含量、ABA含量根冠比均显著上升.由ABA含量变化百分比可见,分蘖期ABA含量变化幅度较灌浆期大;耐虫品种变化幅度较感虫品种大,持续期较感虫品种短;叶片变化幅度较根部大.褐飞虱侵害后,两种不同生育期两种抗性不同的水稻品种比较,耐虫品种叶片ABA含量先上升（3 d）后下降（6 d）,ABA含量根冠比先下降（3 d）后上升（6 d）;感虫品种叶片ABA含量持续上升（3 d和6 d）,分蘖期ABA含量根冠比持续下降（3 d和6 d）,灌浆期ABA含量根冠比先下降（3 d）后上升（6 d）;耐、感虫水稻品种根部变化规律不明显.这些差别表明不同水稻（耐虫和感虫）品种受褐飞虱侵害后体内ABA含量变化规律不同.本研究结果对深入阐明水稻耐虫品种的机制具有重要参考价值.     

Effects of genotype variation in the cultivated rice species on the biology and galling characteristics of the African rice gall midge,Orseolia oryzivora (Diptera: Cecidomyiidae)

This study assessed the effects of genotype variations in two cultivated rice species: Oryza glaberrima and Oryza sativa on the biology and galling characteristics of the African rice gall midge (AfRGM), Orseolia oryzivora Harris and Gagné. The study was conducted in the screen house at ambient temperature (27 ± 3°C), 70 ± 5% relative humidity and 12:12 h photoperiod. Shoot galling, the most visible response of rice genotypes to attack by the insect, was greatly suppressed, being only 0.7 cm long in the O. glaberrima genotypes compared to 34 cm in the O. sativa species. Larval mortality (70–88%) in the O. glaberrima genotypes was significantly higher at the first instar compared to O. sativa. Gall setting was confirmed to be an irredeemable tiller loss. Even in the susceptible O. sativa genotypes, where many larvae may colonize a tiller, only one survived to the second instar. Resistant and susceptible rice genotypes had significantly different effects on the development and reproductive anatomy of the AfRGM. The female reproductive anatomy which consists of two ovaries, each with a potential complement of 192 eggs was affected by interspecific variation in rice genotypes causing reduced potential fecundity (32); morphological distortion, 60% reduction of egg size of F1 emergent in O. glaberrima compared to emergent from the susceptible O. sativa genotypes.     

Non-specific resistance in brown planthopper resistant indica rice varieties against Plodia interpunctella (Lepidoptera: Phycitidae)

Mechanisms of host plant resistance against insect pests can be manifold. Resistance screenings generally use single target insect pests, but the resistance thus screened may not always be specific to the target insect species. We conducted a test for non‐specific resistance in indica rice varieties with resistance genes against brown planthopper (BPH), by using the Indian meal moth, Plodia interpunctella. The test system was very simple, and only required the non‐pest moth to be reared on rice flour. We compared the survival rate, developmental period and adult weight of the moth on three rice varieties: ‘Nipponbare’, a BPH‐susceptible japonica variety, and ‘Thai Collection 11’ and ‘Pokkali’, two resistant indica varieties. Our results were straightforward and demonstrate that resistance in the two resistant rice varieties is not BPH specific, because development of the moth was retarded and adult body weight was reduced.     

Comparative assessment of feeding damage by pod-sucking bugs (Heteroptera: Coreoidea) associated with cowpea, Vigna unguiculata ssp. unguiculata in Nigeria

Feeding trials were conducted on three (young, mid-fill and mature) developmental stages of cowpea Vigna unguiculata ssp. unguiculata pods in the screenhouse using fourth instar nymphs and adults of Anoplocnemis curvipes (Fabricius), Riptortus dentipes (Fabricius), Mirperus jaculus (Thunberg), Clavigralla tomentosicollis St?l and C. shadabi Dolling. Anoplocnemis curvipes was observed to be the most damaging coreoid species causing a yield reduction of 26.4-51.7% followed by R. dentipes (24.4-29.4%), M. jaculus (21.9-26.9%), C. tomentosicollis (17.9-22.4%) and C. shadabi (15.9-20.4%). The fourth instar nymphs of each pod-sucking bug species caused a significantly higher cowpea yield reduction than their respective adults. Similarly, infestation on young pods compared to mid-fill and mature stages resulted in significantly higher yield reduction. The results suggest that infestation levels of two fourth instar nymphs of A. curvipes or three fourth instar nymphs of the other four pod-sucking bug species per young pod should be adequate for screening of cowpea varieties for resistance to the coreoid bugs.     

水稻外源DNA导入系的分子检测及耐旱性评价

耐旱种质创新对农业节水和培育水稻新品种具有重要意义。本研究以SSR标记检测了以空心莲子草DNA溶液浸胚处理获得的10个农艺性状稳定遗传的水稻变异体,结果表明,10个水稻变异体均整合了供体空心莲子草DNA的不同片段。在此基础上,以8个导入空心莲子草DNA的水稻导入系及2个对照为试验材料,采用二因素裂区设计,并以主成分分析、逐步回归分析等多种统计方法分析了导入系的耐旱性。结果表明,以综合评价指标与耐旱指数相结合的复合评价体系,可增强水稻耐旱评价的可靠性。导入系H8最耐旱,H6和H7较耐旱,均优于巴西陆稻。本研究结果对水稻的耐旱性评价与耐旱品种选育具有重要意义。     

Study of the relationship between the content of the rare earth element Eu in rice plants and in Nilaparvata lugens (Hemiptera: Delphacidae)

Abstract The current study investigated changes in the content of the rare earth element Europium (Eu) in roots, shoots and leaves of rice plants and in Nilaparvata lugens Stål (Hemiptera: Delphacidae) using an Eu marker and hydroponic culture. The results showed that N. lugens infestation significantly reduced Eu content in roots, shoots and leaves of two rice varieties, Shenyou 1 and Xieyou 963. The Eu content in roots, shoots and leaves of the susceptible variety, Shenyou 1, was significantly higher than that in the resistant variety, Xieyou 963. The Eu content of N. lugens fed on Shenyou 1 was significantly higher than of those fed on Xieyou 963. In addition, the Eu level was elevated at a higher density of N. lugens infestation. Eu content in the bodies of N. lugens was related to their weight and honeydew excretion, with a significant positive correlation. Thus, Eu content in the bodies of N. lugens can be considered an index of the amount of phloem sap taken in by N. lugens because the amount of honeydew excretion is proportional to the amount of phloem sap consumed. The ratios of Eu content in N. lugens to that in roots, shoots and leaves of rice plants were elevated at a higher N. lugens infestation density. That ratio was maximal in leaves, was intermediate in shoots and was minimal in roots. There was no significant difference in ratios between the two plant varieties. An Eu marker may be useful in the screening of resistant varieties and in the study of the mechanisms of resistance.