Effects of lodging of Echinochloa crus-galli L. on the herbicidal efficacy of MTB-951, a mycoherbicide using Drechslera monoceras (Drechsler) Subram. et Jain (= Exserohilum monoceras [Drechsler] Leonard et Suggs)

MTB-951 is a plant pathogen ( Drechslera monoceras ), which was isolated from native Echinochloa spp. in Japan. The conidia of this pathogen were used as the herbicidal active ingredient to control Echinochloa crus-galli L. The herbicidal efficacy of MTB-951 on E. crus-galli was drastically increased with an increasing water depth of between 1 and 10 cm. The efficacy also was increased when shoots were lodged by pushing down on them with a stainless steel net so that all parts of the weed were submerged. These results suggest that the contact area of the leaf surface of E. crus-galli with water is important for infection and that lodging the shoots of E. crus-galli might be effective in increasing the herbicidal efficacy. In order to find other methods to lodge the weed, we investigated several materials, of which diisononyl phthalate (DINP) was found to be the most effective. Using this material as a model, the effect of lodging on the herbicidal efficacy of MTB-951 was examined. The lodging ratio (ratio of the number of the plants lodged on the water surface to that of the total plants) was increased with an increased amount of DINP, between 0.5 and 8 kg ha⁻¹. The herbicidal efficacy of MTB-951 also was increased by DINP and a positive correlation was observed between the lodging ratio and herbicidal efficacy. These results indicate that lodging, which can increase the contact area between the leaf surface and water, enhances the herbicidal efficacy of MTB-951.     

Effect of δ-aminolevulinic acid on the herbicidal efficacy of foliar-applied MTB-951, a mycoherbicide to control Echinochloa crus-galli L.

The conidia of a plant pathogen ( Drechslera monoceras [Drechsler] Subram. et Jain [=  Exserohilum monoceras [Drechsler] Leonard et Suggs]), MTB-951, which was isolated from native Echinochloa species in Japan, were used as the herbicidal active ingredient. The effects of δ-aminolevulinic acid (ALA) on the efficacy of foliar-applied MTB-951 on Echinochloa crus-galli L. were examined. First, foliar-applied MTB-951 exhibited almost no efficacy when no dew period was provided. However, the efficacy increased depending on the length of the dew period. MTB-951 and ALA exhibited an additive effect on E. crus-galli under 3 day dew conditions, although they exhibited a significant synergistic effect under no-dew conditions. When the leaves of E. crus-galli were immersed in deionized water containing the conidia of MTB-951, cellular electrolyte leakage from the leaves was observed. The ALA increased the electrolyte leakage by MTB-951 synergistically. Also, ALA increased the number of lesions on the leaves of E. crus-galli caused by MTB-951 under light conditions but failed to increase the number under dark conditions. These results suggest that ALA promotes infection with MTB-951 for E. crus-galli through its photodynamic action.     

Effect of temperature on herbicidal properties of MTB-951, a mycoherbicide to control Echinochloa crus-galli L.

MTB-951 is a potential mycoherbicide using a fungal plant pathogen ( Drechslera monoceras ) isolated from native Echinochloa species in Japan. Conidia of this pathogen were used as the active ingredient and the effect of temperature on its properties was examined in a laboratory. The optimum temperature for conidium germination was broad between 15 and 35°C and no difference in the germination ratio existed within this temperature range. Mycelial growth was the fastest at 25°C but was slower outside of the range 15–35°C. When leaves of Echinochloa crus-galli L. were immersed in deionized water containing the conidia, cellular electrolyte leakage from the leaves was observed. However, no electrolyte leakage occurred from leaves of rice ( Oryza sativa L.) under the same conditions. The occurrence of electrolyte leakage from E. crus-galli was dependent on the temperature and was the highest at 25°C. Herbicidal activity of MTB-951 against E. crus-galli was high between 25°C and 30°C, but decreased at 35°C in a glass vessel. In the present study, it was revealed that the physiological and herbicidal properties of MTB-951 depended on the temperature.     

UNTERSUCHUNGEN ZUR BIOLOGIE UND ÖKOLOGIE DER HÜHNER-HIRSE ECHWOCHLOA CRUS-GALLI L. BEAUV.

Summary. 1. Echinochloa crus-galli is a typical grass weed of root crops in warmer regions, germinating late and thus covering the soil at a late stage. It originates in central and east Asia and is now a weed of world-wide importance.
2. High temperatures are necessary for germination which begins in spring, but not before the soil temperature reaches 15° C. Minimum, optimum and maximum germination temperatures of 13° C, 20–30° C and 40° C were found in S.W. Germany.
3. Seeds of E. crus-galli are dormant during the first 3–4 months after harvest. Those developing relatively early in the growing season require rather longer for after-ripening than seeds which mature later.
4. For optimum germination, water saturation of the soil of 70–90% is required.
5. Soil acidity has some influence, and there is an apparent germination optimum around neutrality. Light also induces germination.
6. Seeds can emerge from a relatively wide range of depths. Greatest emergence and the strongest plants resulted from seeds at 2–6 cm, but even from 10 cm a high percentage of seedlings is likely to emerge.
7. Further development proceeds rapidly. The first panicles arc already formed 6–7 weeks after emergence in favourable conditions, but full maturity is possible only if there are high temperatures in late summer.
8. E. crus-galli is a hygrophilous species, with best development on medium heavy soil, sandy loam or loamy sand with sufficient water supply.
9. E. crus-galli is indifferent to the lime content of the soil.
10. Best development occurs with high fertility, and a rich supply of nitrogen is especially important.
Recherches sur la biologie et écologie du panic Echinochloa crus-galli (L.) Beauv.     

Annual cycles of germinability and differences between primary and secondary dormancy in buried seeds of Echinochloa crus-galli

The seasonal changes in percentage of dormant seeds of Echinochloa crus-galli in the field were recorded for 4 years. The lots of seeds were wrapped in nylon fabric, buried 20 cm under the grass sward and exhumed at monthly intervals. The proportion of seeds germinating under light conditions at a constant temperature of 25 °C fluctuated between 0% and 96%, with maxima in May–July and minima in September–November. Small between-year differences in the course of summer dormancy induction and its winter termination were probably caused by variation of weather conditions.
Attributes of dormancy innate to seeds after maturation (primary dormancy) and dormancy induced in buried seeds during the summer (secondary dormancy) were compared by investigating the rate of dormancy termination during storage of (a) dry seeds at 25 °C, (b) imbibed seeds at 5°C and (c) in seeds buried under field conditions during October–June. Percentage of germination increased faster in secondary than primary dormant seeds at both constant 25 °C and 5 °C. The seeds with primary and secondary dormancy also differed in the response to `germination pre-treatment', a 10-day exposure of imbibed seeds at 25 °C that causes germination of the non-dormant fraction of seed materials. After this treatment the time to resuming germination in primary dormant seeds was substantially increased, whereas the secondary dormant seeds were much less affected. Annual variation in the proportion of germinable seeds explains the low efficiency of autumn soil cultivation for decreasing reserves of E. crus-galli seeds in the soil.     

Red rice (Oryza sativa L.) and barnyardgrass (Echinochloa spp.) biotype susceptibility to postemergence-applied imazamox

Pot experiments were conducted to evaluate the level of imazamox tolerance in five red rice ( Oryza sativa L.) and four barnyardgrass (three Echinochloa crus-galli (L.) Beauv. and one Echinochloa oryzoides (Ard.) Fritch) morphologically distinct biotypes collected from rice fields in northern Greece. The susceptibility of barnyardgrass biotypes to propanil was also studied. Red rice biotypes were not controlled by imazamox applied at 40 g ha⁻¹. In contrast, 80 g imazamox ha⁻¹ provided 56–84% red rice control (averaged across shoot number and fresh weight reduction). Not all barnyardgrass biotypes were susceptible to imazamox applied postemergence. However, propanil applied at 2.6 kg ha ⁻¹ controlled the E. crus-galli biotypes well, but propanil applied at rates of 2.6 and 5.2 kg ha ⁻¹ was not effective in reducing the shoot number and fresh weight of the E. oryzoides biotype. Propanil applied at 10.4 kg ha ⁻¹ reduced the shoot number and fresh weight of this biotype by 78 and 85%, respectively. In most cases, a linear equation ( y  = % of control, x  = g ha⁻¹) provided the best fit for regressions between red rice or barnyardgrass shoot number or fresh weight and imazamox rates. The results of this study suggest that postemergence application of imazamox is not effective against all red rice and barnyardgrass biotypes found in the rice fields of Greece and that significant variability regarding herbicide efficacy among biotypes might exist.     

牡丹皮提取物除草活性初步研究

为明确牡丹皮(Cortex Moutan Radicis)的除草活性并初步探索其活性成分分离条件,采用平皿法、土壤喷雾法及茎叶喷雾法测定了牡丹皮不同极性溶剂萃取物对反枝苋Amaranthus retroflexus和稗Echinochloa crus-galli的除草活性。平皿法测定结果显示,在1 mg/mL浓度下,牡丹皮正丁醇萃取物的除草活性最强,对反枝苋幼根和幼茎的抑制率分别为67.88%和65.71%,对稗草幼根和幼茎的抑制率分别为68.72%和71.32%;毒力测定结果表明,牡丹皮正丁醇萃取物对反枝苋幼根和幼茎的IC₅₀分别为12.28 mg/L和19.67 mg/L,对稗草幼根和幼茎的IC₅₀分别为43.35 mg/L和72.79 mg/L。土壤喷雾法和茎叶喷雾法测定结果显示,在5 mg/mL浓度下,牡丹皮正丁醇萃取物对反枝苋和稗草的鲜重抑制率最高,其中土壤喷雾法对反枝苋和稗草的鲜重抑制率分别为81.43%和83.18%;茎叶喷雾法对两种杂草的鲜重抑制率分别为80.83%和83.65%。由此可见,牡丹皮的除草活性成分主要集中在正丁醇...     

Efficacy of four corn (Zea mays L.) herbicides when applied with flat fan and air induction nozzles

Twelve field experiments were conducted over a 4 year (2002–2005) period to determine the influence of the herbicide dose, nozzle type, spray volume, and spray pressure on herbicide efficacy in field corn ( Zea mays L.). The control of Abutilon theophrasti (velvetleaf ), Ambrosia artemisiifolia (common ragweed), Chenopodium album (common lambsquarters), Amaranthus powellii (green pigweed), and Echinochloa crus-galli (barnyard grass) was improved with the use of full herbicide doses compared to half doses of bromoxynil, glufosinate, dicamba, and nicosulfuron. The yield was increased for bromoxynil, glufosinate, and nicosulfuron when the full herbicide dose was used. When applied at the manufacturer's recommended dose, flat fan nozzles, compared to air induction (AI) nozzles, provided better control of A. theophrasti , A. artemisiifolia , and C. album with bromoxynil, A. artemisiifolia and C. album with dicamba, and E. crus-galli with nicosulfuron. Bromoxynil, in relation to weed control, was the only herbicide that was affected by the water carrier volume. By increasing the spray pressure with an AI nozzle, there was an improvement in the control of A. theophrasti , A. artemisiifolia, and C. album with the application of bromoxynil and E. crus-galli with the application of nicosulfuron, with a yield increase with bromoxynil. Overall, this study concludes that the optimum nozzle type, water carrier volume, and spray pressure is herbicide- and weed species-specific.     

A molecular phylogeny of wild and cultivated Echinochloa in East Asia inferred from non-coding region sequences of trnT-L-F

The phylogenetic relationship among 30 accessions belonging to nine species of the genus Echinochloa Beauv. was studied on the basis of the sequence of three non-coding regions ( trn T-L, trn L-F intergenic spacers, and trn L intron) of chloroplast DNA (cpDNA). A strict consensus parsimonious tree of the three most parsimonious trees derived from 25 polymorphic sites (six indels and 19 substitutions) in the total sequences, ranging from 1715–1760 bp, represented five groups: (i) Echinochloa oryzicola Vasing. and Echinochloa stagnina Beauv. from Thailand; (ii) Echinochloa crus-galli Beauv. complex; (iii) Echinochloa crus-pavonis Schult; (iv) Echinochloa colonum Link. and Echinochloa frumentacea Link.; and (v) the African species, Echinochloa obtusiflora Stapf and Echinochloa stagnina . Japanese barnyard millet ( Echinochloa esculenta H. Scholz) and various weedy varieties of E. crus-galli and Echinochloa oryzoides Fritsch had quite similar sequences and formed the E. crus-galli complex, which was characterized by six substitutions. A cultivated form of E. oryzicola (Mosuo barnyard millet) and various morphological and agronomical forms of E. oryzicola were characterized by two indels. Indian barnyard millet ( E. frumentacea ) and its wild counterpart ( E. colonum ) were characterized by five substitutions. Domestication as millets and adaptation to paddy environments as mimic weeds might occur after the divergence of species in the Asian Echinochloa .     

双环磺草酮与氯氟吡啶酯复配的联合除草活性及对水稻的安全性评价

双环磺草酮是一种新型的对羟基苯丙酮酸双加氧酶抑制剂类除草剂,为明确其除草活性以及其与合成激素类除草剂氯氟吡啶酯复配后的除草效果,采用温室盆栽法研究了二者复配的联合作用类型,以及复配药剂在水稻与杂草之间的选择性,并进行了田间药效评价。温室盆栽试验结果表明:双环磺草酮与氯氟吡啶酯复配后使用,对供试杂草稗草、千金子、异型莎草及鸭舌草均呈现加成或增效作用;其中二者按照质量比5:1复配后的除草活性高于双环磺草酮单剂;复配药剂在供试水稻品种与杂草之间的选择性指数在28.72~54.81之间,与两种单剂相比,复配药剂对水稻的安全性均有提高。田间药效试验结果表明:双环磺草酮与氯氟吡啶酯复配扩大了杀草谱,对稗草、千金子、异型莎草及雨久花的株防效和鲜重防效在93.4%~100%之间,且对水稻安全;其中,田间复配用量为双环磺草酮有效成分120 g/hm^2、氯氟吡啶酯有效成分18 g/hm^2时效果最佳,对4种供试杂草的防效为97.1%~100%。     

Herbage mass, nutritive value and palatability of five grass weeds for cattle in the northern Tohoku region in Japan

The objective of this grazing study was to determine the herbage mass, nutritive value and palatability of five grass weed species ( Eleusine indica (L.) Gaertn, Paspalum thunbergii Kunth, Digitaria ciliaris (Retz.) Koeler, Setaria glauca (L.) Beauv. and Echinochloa crus-galli (L.) Beauv. var. crus-galli ) as feeds compared with six forage cultivars ( Lolium perenne L., two Lolium multiflorum cultivars and three Echinochloa crus-galli (L.) Beauv. cultivars). The herbage mass of weed species, with the exception of S. glauca , was most prevalent in August. The total amounts of herbage mass of weed species (except E. indica ) were close to those of the Lolium cultivars, but lower than those of the E. crus-galli cultivars. During the summer, weed species (except E. crus-galli var. crus-galli ) contained favorable levels of total digestible nutrients (TDN), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF) and mineral contents, and exhibited adequate calcium (Ca):phosphorus (P) ratios of 1:2. All weed species had the recommended ratios of potassium (K):(Ca + [magnesium] Mg) < 2.2:1. By autumn, the summertime levels of nutritive values (TDN, CP, ADF and NDF) in the weed species had severely deteriorated, in contrast with those of the forage cultivars. However, they maintained satisfactory mineral content levels and Ca:P and K:(Ca + Mg) ratios (with the exception of E. indica with poor Ca:P ratios and E. crus-galli var. crus-galli with poor P content and Ca:P ratios). All weed species were acceptable to cattle, although there were some differences in palatability among the species.     

稗草生防菌新月弯孢菌Culvularia lunata菌株J15(2)的安全性和致病力

为了确定生防菌新月弯孢菌Culvularia lunata菌株J15(2)的安全性及防除稗草的潜力,研究了该菌株的寄主范围,接种孢子时稗草叶龄、接种后保湿时间、接种浓度对该菌株致病力的影响,土壤带菌对稗草出苗的影响,以及与化学除草剂的相互作用.结果显示,菌株J15(2)只能在稗草上侵染并扩展;接种孢子后保湿24 h,对2叶期稗草抑制率可达55.6%,对1.5叶期稗草抑制率可达100%;保&48h,对2叶期稗草防效提高至91.6%;接种孢子量需达1012孢子/hm2才能较好地抑制稗草生长;土壤带菌亦可抑制稗草生长.该菌与化学除草剂精噁唑禾草灵或二氯喹啉酸混用能显著提高除稗效果,菌株J15(2) 3.3 × 1012孢子//hm2分别与精噁唑禾草灵有效剂量3.83g/hm2二氯喹啉酸有效剂量250.00g/hm2混用,对稗草防效分别为99.5%和88.6%,远高于这两个除草剂单用时的药效.该试验结果表明,菌株J15(2)具有作为微生物除草剂的开发潜力.     

Weed suppression by soil steaming in combination with activating compounds

The aim of this study was to determine the weed suppression potential of soil steaming plus activating compounds (KOH or CaO) to boost soil temperature. Different combinations between the compounds and rates were tested in experiments carried out in the field and in a controlled environment. Treatment effects were assessed on field weed vegetation and on seedbank and seedling emergence of three winter ( Alopecurus myosuroides , Matricaria chamomilla and Raphanus raphanistrum ) and four spring annuals ( Amaranthus retroflexus , Echinochloa crus-galli , Fallopia convolvulus and Setaria viridis ), were assessed on field weed vegetation. Neither maximum soil temperature (from 72 to 85°C) nor duration of high temperature in the 3 h following application consistently affected weed suppression. In the field, no significant effects on total weed density were recorded, but there were some significant effects on individual species. The weed seedbank was clearly suppressed by activated steaming: total seedling emergence was inversely related to increasing KOH rates both in the 0–10 and 10–20 cm soil layers, while for CaO the relationship was significant only in the 0–10 cm layer. Winter annuals were more sensitive to KOH than CaO and spring annuals had a more pronounced species-specific response to treatments. There was a strong negative relationship between compound rate and seedling emergence for all species. Alopecurus myosuroides was the most sensitive to the steam-alone treatment (77% reduction), whereas M. chamomilla and E. crus-galli were the least sensitive. Results from this study indicate that the type and rates of activating compounds for soil steaming must be adjusted to the weed community composition.     

Synthesis and herbicidal activity of new 3-(3-bromothiophen-2-yl)-5-(2,6-difluorobenzyl)oxymethyl-5-methyl-4,5-dihydroisoxazole as a paddy field herbicide

A new compound 3-(3-bromothiophen-2-yl)-5-(2,6-difluorobenzyl)oxymethyl-5-methyl-4,5-dihydroisoxazole was synthesized and the herbicidal activity was assessed under glasshouse and flooded paddy field conditions. This compound demonstrated good rice selectivity and potent herbicidal activity against annual weeds at 125 g ai ha⁻¹ under greenhouse conditions. Soil application of this compound showed the complete control of barnyardgrass to the 4th leaf stage at 250 g ai ha⁻¹. Field trials indicated that this compound, combined with pyrazosulfuron-ethyl, controlled annual and perennial weeds rapidly with good tolerance by transplanted rice seedlings from postemergence and soil application. This compound showed a low mammalian and environmental toxicity in various toxicological tests.     

狭卵链格孢菌毒素细交链孢菌酮酸对稗草细胞膜脂质过氧化作用的影响

为明确狭卵链格孢菌Alternaria augustiovoide菌株AAEC05-3产生的毒素细交链孢菌酮酸(tenuazonic acid,TeA)的作用机制,利用离体试验,研究了TeA对稗草叶片细胞膜脂质过氧化的影响。结果显示,低浓度TeA处理对稗草叶片的细胞膜透性和脂质过氧化影响不大;用高浓度TeA处理稗草叶片24 h后,稗草叶片细胞膜透性和脂质过氧化作用显著增强。TeA浓度为100 μmol/L时,稗草叶片相对电导率和丙二醛(MDA)含量分别增加28.21%和63.58%;脂氧合酶(Lox)活性增高61.59%,且不饱和脂肪酸含量显著降低,亚油酸(18∶2)和亚麻酸(18∶3)分别降低19.56%和17.20%,脂肪酸氢过氧化物在叶片中大量积累。表明TeA可以诱导稗草叶片细胞膜的脂质过氧化作用。     

Chloris polydactyla (L.) Sw., a perennial Poaceae weed: Emergence, seed production, and its management in Brazil

Experiments were conducted to evaluate the plant emergence and seed production of Chloris polydactyla and the efficacy of herbicides for its control. The plants emerged mainly when the seeds were placed on the soil surface at ≤ 3 cm depth. Isolated plants produced a great amount of seeds. The pre-emergence herbicides, acetochlor, atrazine + simazine, s-metolachlor, alachlor, and trifluralin, were effective for C. polydactyla control. The postemergence herbicides, clodinafop-propargil, haloxyfop-methyl, clethodim, fluazifop- p -butil, tepraloxydim, sethoxydim, and quizalofop- p -tefuril showed satisfactory control of the plants at a 20 cm height with six leaves. During the flowering stage (85 cm plant height), only glyphosate was effective in controlling C. polydactyla .     

Physiochemical factors affecting the salt tolerance of Echinochloa crus-galli Beauv. var. formosensis Ohwi

The effects of NaCl-induced stress on physiochemical factors such as inorganic cations, proline, malondialdehyde (MDA) and polyamines were investigated in the gramineous weed, Echinochloa crus-galli Beauv. var. formosensis Ohwi ( E. crus-galli ) and rice ( Oryza sativa L. cv. Nipponbare). Growth inhibition at the 2nd leaf stage under salt stress was more severe in rice than in E. crus-galli . Water content in the 2nd leaves was also more severely decreased in rice, indicating that E. crus-galli was more salt-tolerant. After NaCl treatment, Na⁺ accumulated in the 2nd leaves of both plant species but not in their roots. Proline accumulation in the 2nd leaves was significantly higher in salt stressed E. crus-galli than in rice, suggesting the significance of proline production in the salt tolerance of this weed. Content of MDA of the rice increased more greatly with NaCl treatment than that in E. crus-galli . NaCl treatment affected polyamine metabolism of both plant species, but the response of each plant to salt stress was somewhat different, especially in the leaves. Leaf putrescine and spermidine contents were high in non-stressed plants in salt-sensitive rice, although rather lower in E. crus-galli in response to NaCl concentrations. These results indicate that an increase in proline and changes in polyamines relates to the salt tolerance of E. crus-galli .     

Can rice genetic diversity reduce Echinochloa crus‐galli infestation?

Pot and field experiments were conducted to test whether rice genetic diversity can reduce Echinochloa crus-galli infestation through rice variety mixed-plantings. Two weed-suppressive rice ( Oryza sativa ) varieties, Guodao No. 1 (GD) and PI312777 (PI), and three non-suppressive varieties, Xiushui No. 63 (XS), Zhongjian No. 2 (ZJ) and Chunjiang No. 016 (CJ) were used. Monocultures (GD, PI, XS, ZJ and CJ), two-variety mixtures (GD + XS, GD + ZJ, GD + CJ, PI + XS, PI + ZJ, PI + CJ) and three-variety mixtures (GD + PI + XS, GD + PI + ZJ and GD + PI + CJ) were tested. Effects of herbicide on rice grain yield of non-suppressive varieties were compared between monocultures and mixtures. Pot experiment showed that E. crus-galli germination rate in all mixed-planting except CJ + PI, and E. crus-galli biomass in mixed-planting with GD decreased compared with monocultures. In a field experiment, E. crus-galli density decreased in all mixed-planting models of XS and CJ and ZJ + GD. Echinochloa crus-galli biomass reduction was found in XS + GD, XS + GD + PI, ZJ + GD and CJ + GD. Rice grain yield increased in XS + GD, ZJ + GD, CJ + GD, CJ + PI and CJ + GD + PI. Rice grain yields of non-suppressive varieties under mixtures without herbicides were lower than that in monoculture with full herbicide, but were not significantly different from monocultures with half rate herbicide. Moreover, rice yields of ZJ and CJ under mixtures with half rate herbicides did not decrease compared with monocultures with full rates. The results suggested that rice genetic diversity could reduce E. crus-galli infestation and herbicide utilisation through rice variety mixed-planting.     

Differential susceptibility of barnyard grass (Echinochloa crus-galli var. crus-galli) ecotypes to Exserohilum longirostratum

Ten barnyard grass ( Echinochloa crus-galli var. crus-galli ) ecotypes collected from several locations in Malaysian and Indonesian granaries were tested for variation in their susceptibility to the leaf blight pathogen ( Exserohilum longirostratum ). Four phenological growth stages of the ecotypes were sprayed with E. longirostratum at the rate of 1 × 10⁷ conidia mL⁻¹ under glasshouse conditions. The results of the study showed that plants inoculated with 1 × 10⁷ conidia mL⁻¹ and exposed for 24 h dew periods were severely infected and the percentage dry weight reduction of all ecotypes significantly increased. The 1–2 and 2–3-leaf stage plants were completely killed within 6 days after inoculation. However, susceptibility reactions among the ecotypes were observed at the 4–5-leaf stage, while the 6–7-leaf stage was resistant. The ecotypes, K-02, PK-04, KN-02, CJ-01, and L-01, were the most susceptible ecotypes as indicated by a higher area under disease progress curve value. The apparent disease progress rates for these ecotypes were significantly faster compared to the other ecotypes. The dry weight reduction among the four growth stages was variable. These findings show that the 1–2 and 2–3-leaf stages are the most susceptible, while the 6–7-leaf stage was resistant. This study has confirmed that a variable response to the fungal pathogen occurred within an intraspecific barnyard grass collection.     

Genetic diversity in Echinochloa spp. collected from different geographic origins and within rice fields in Côte d'Ivoire

Summary Diversity studies of Echinochloa spp. are complicated by problems in taxonomy and species identification, caused by the existence of morphologically intergrading types. Six amplified fragment length polymorphism (AFLP) primer combinations and five microsatellites were used to assess variation in 24 samples morphologically identified as E. crus-galli , E. colona and E. crus-pavonis , from Bangladesh, India, Colombia, Costa Rica, Côte d'Ivoire and Philippines. Out of 909 AFLP bands generated, 775 were polymorphic. Genotype diversity for the microsatellites ranged from 0.28 to 0.72. Similarity matrices were calculated using Jaccard coefficient, and input into cluster and principal coordinates analyses. AFLP and microsatellite results were highly correlated. Echinochloa crus-pavonis and E. crus-galli were intermixed, consistent with the view that E. crus-galli occurs as numerous intergrading races in the four countries (Bangladesh, India, Côte d'Ivoire and Philippines). The E. colona samples clustered as a distinct group. In 15 samples of E. crus-pavonis collected from rice fields in a valley in Côte d'Ivoire (over a 2-km distance), four different genotypes were found in a 4 m × 4 m area. These results suggest that AFLPs and SSRs may be useful not only for discriminating genotypes and studying population structure but also for helping to resolve taxonomic relationships in Echinochloa spp.