Phenological development and biomass allocation in Silene vulgaris (Moench) Garcke

Silene vulgaris (Moench) Garcke, grown from seed or from crown buds, exhibited three dis tinct growth phases; establishment, reproduc tive and post-reproductive. The establishment phase was characterized by rapid accumulation of shoot biomass, high relative growth rates (RGRs) and leaf area ratios (LARs). The sexual reproductive phase was characterized by a rapid increase in floral and seed biomass, minimal root development, and declining RGRs and LARs. In the post-reproductive phase, root and crown biomass increased rapidly concomitant with the development of regenerative buds; low RGR and LAR values occurred during this phase. Although similar growth phases were identified in both the first (grown from seed) and second years (grown from crown buds) of growth, LARs and RGRs were lower in the second than in the first year. In the second year of growth, plants exhibited a continual increase in below-ground biomass throughout growth, including the flowering period, a feature which was absent in the first year of growth.     

Uptake, translocation and fate of 2,4-D and chlorsulfuron in Silene vulgaris (Moench) Garcke

Experiments were conducted to examine the up take, translocation and metabolism by S. vulgaris of two distinctly different herbicides: 2,4-D, a phenoxyalkanoic acid with growth regulator activity to which this species exhibits complete tolerance, and chlorsulfuron, a sul-fonylurea to which S. vulgaris is highly sensitive. Despite their structural dissimilarities 2,4-D and chlorsulfuron was readily absorbed by S. vulgaris with 65 and 69%, respectively, of the applied dosage being absorbed within 72 hours after treatment. Approximately 35% of the 2,4-D and 10% of the chlorsulfuron label was translocated out of the treated leaf after 72 hours. Neither herbicide accumulated in the terminal bud. Seventy-two hours after treatment 63% of the recovered ¹⁴C remained as unaltered 2,4-D in S. vulgaris, while in tomato, a 2,4-D sensitive species, 65% of the recovered ¹⁴C remained as intact herbicide. In S. vulgaris approximately 86% of the radioactivity remained as intact chlorsulfuron 72 hours after treatment compared to 12% in the tolerant wheat. The tolerance of S. vulgaris to 2,4-D could not be accounted for by limited absorption, translocation nor metabolic degradation of the herbicide. The sensitivity of S. vulgaris to chlorsulfuron would appear to be related to the inability of this species to metabolize the herbicide molecule.     

紫花苜蓿下胚轴愈伤组织诱导及再生植株的研究

以培养4～5d的紫花苜蓿无菌苗的下胚轴为材料,改良SH(SH大量元素+MS微量元素+MS铁盐+UM有机)+水解酪蛋白(CH)2000 mg/L为基本培养基,对紫花苜蓿愈伤组织诱导和植株再生进行了研究。愈伤组织诱导和继代培养基分别为2,4-D 1.0 mg/L+KT 0.5 mg/L+蔗糖30 g/L及2,4-D 0.05 mg/L+BA0.5 mg/L+蔗糖30 g/L,将获得的愈伤组织转入正交设计的培养基上进行筛选,得到了愈伤组织分化率相对较高的培养基配方:基本培养基+KT 0.4 mg/L+蔗糖20 g/L,其分化率为73.0%。获得的再生芽在生根培养基上(1/2MSO)培养约10d便能获得具有根和叶的再生植株。本试验结果为下一步将来自蓝藻的Na⁺/H⁺ an-tiporter基因转入苜蓿,获得转基因耐盐苜蓿奠定了基础。     

Hypersensitive reaction in alfalfa (Medicago sativa) induced by alfalfa mosaic virus

Alfalfa (Medicago sativa) cv. Beaver was screened for resistance to alfalfa mosaic virus (AIMV). A1MV infection in clonal plants was tested by double-antibody sandwich ELISA 4 and 8 weeks after inoculation with purified A1MV (1 mg/ml in 0025 M phosphate buffer, pH 7 0). Twelve clones showed a hypersensitive reaction 3–4 days after inoculation and the infection was restricted to the inoculated leaves. All the plants of hypersensitive clones consistently produced local lesions when inoculated with purified AIM V. In contrast, plants inoculated with AIMV in crude sap remained symptomless, although AIMV was detectable in inoculated leaves. The remaining 16 clones were susceptible to AIMV and showed systemic infection.     

Infection process of Colletotrichum destructivum O'Gara from lucerne (Medicago sativa L.)

The infection process of Colletotrichum destructivum, a cause of anthracnose in lucerne (= alfalfa, Medicago sativa) was studied by light microscopy. At the onset of the host-pathogen interaction, the fungus produced large, multilobed, multiseptate infection vesicles with elongated neck regions. Each infection structure packed the lumen of the initially-infected epidermal cell and remained confined within its walls for 48 h. Subsequently, narrow, invasive secondary hyphae radiated from the multilobed vesicles, grew through the walls of host cells and rapidly colonized the surrounding tissues. Acervuli emerged on the surface of colonized leaves 96 h after inoculation. These observations are discussed in relation to the infection process and specificity of a genetically closely-related isolate of Colletotrichum destructivum causing anthracnose in cowpea (Vigna unguiculata).     

Paraphoma root rot of alfalfa (Medicago sativa) in Inner Mongolia,China

Root rot symptoms were observed in fields of alfalfa in Chifeng city, Inner Mongolia, China in 2016. Disease incidences of seven alfalfa varieties planted in 2014 ranged from 56% to 95%, while incidence of Gongnong No. 1 planted in 2016 was 8%, 31% and 76% in 2016, 2017 and 2018, respectively. Paraphoma isolates were consistently recovered from black necrotic root tissues of diseased plants with a frequency of 77.1%. Based on morphological characters and phylogenetic analysis of rDNA internal transcribed spacer (ITS), elongation factor 1-α (EF1-α) and β-tubulin (TUB), this fungus was identified as Paraphoma radicina. Glasshouse pathogenicity experiments showed that P. radicina significantly reduced above- and below-ground biomass of alfalfa plants 2 months after inoculation. Paraphoma radicina infected 70% of the plants inoculated with a root dip in conidia, and these symptoms were consistent with the symptoms in the field. Paraphoma radicina was successfully reisolated from disease roots of the inoculated alfalfa plants. This is the first report of P. radicina as the causal agent of alfalfa root rot in China.     

Effect of alfalfa mosaic virus isolates on forage yield of lucerne (Medicago sativa) in Britain

The effect of alfalfa mosaic virus (A1MV) on lucerne forage yield was investigated in experimental plots in which all plants were indexed for freedom from seed-borne A1MV. Plants which were artificially inoculated with A1MV were tested for successful infection prior to transfer to the plots. Inoculated plots yielded 14-8-22-8% (fresh weight) and 15.0 18.1% (dry weight) less than uninoculated plots. Isolate A1MV-I reduced the yield of five lucerne cultivars and yield was decreased by several A1MV isolates in cv. Vertus. Yield decreases tended to be greatest at the first harvest and progressively smaller at the second and third. Despite aphicide treatments and a cereal barrier crop, ELISA indexing showed natural infection developed in control plots. Most known infected plants failed to produce symptoms and yield decreases were associated with predominantly symptomless infection.     

Competition between vegetative plants of wild oat (Avena fatua L.) and wheat (Triticum aestivum L.)

Competition between wild oat (Avena fatua L.) and wheat (Triticum aestivum L.) was studied in two experiments; a replacement series model and a technique for separation of root and shoot systems. Wild oat and wheat in association resulted in a relative yield total very close to unity showing that the two species were‘crowding for the same space’(or competing for the same resources) and were‘mutually exclusive'. Wild oat was more competitive than wheat, as shown by its aggressivity relative to wheat, relative yields, shoot dry weights and other plant attributes. The greater competitive ability of wild oat was predominantly due to its greater root competitive ability, while the two species had similar shoot competitive ability. Root competition had a much greater effect on the relative performance of the two species than did shoot competition. The effects of root and shoot competition were additive.     

Physiological effects of buthidazole on Zea mays L., Amaratithus retroflexus L., Medicago sativa L. and Agropyron repens(L.) Beauv.*

Buthidazole (3-[5-(1,1-dimethylethyl)-1,3.4-thiadiazol-2-yl]-4-hydroxy-l-methyl-2-imidazolidinone) at concentrations of 10^?6-10^?4M did not affect germination of corn (Zea mays L.,‘Pioneer 3780’), redroot pigweed (Amaranlhus retroflexus L.), alfalfa (Medicago saliva L., ‘Vernal’), and quackgrass (Agropyron repens(L.) Beauv.) seeds. Stressing the seeds obtained from mature corn plants treated either pre-emergence or pre- plant incorporated with buthidazole at several rates by accelerated ageing and cold treatments further indicated that this herbicide did not affect germination. Total photosynthesis and dark respiration of corn plants 12 days after pre-emergence application and of redroot pigweed, alfalfa, and quackgrass plants after postemergence application of buthidazole at several rates were measured with an infrared CO₂ analyser. The results suggested that buthidazole was a rapid inhibitor of photosynthesis of the sensitive redroot pigweed and quackgrass plants, with less effect on corn and alfalfa. Buthidazole did not affect respiration of the examined species except for a transitory increase in corn and alfalfa 12 days after pre-emergence or 4 h after postemergence treatment with buthidazole at 0.56 or 1.12 and 2.24 kg/ha, respectively. A long-term inhibition of quackgrass respiration 96 h after treatment with buthidazole at 1.12 and 224 kg/ha was also evident.     

Inter- and intraspecific competition of fat-hen (Chenopodium album L.) and groundsel (Senecio vulgaris L.)

The responses of Chenopodium album L. and Senecio vulgaris L. to inter- and intra-specific competition were investigated in both additive and replacement series experiments under glasshouse conditions. When grown with tomato the two weed species had similar effects on shoot dry weight at low densities but 5. vulgaris showed more competitive effect at higher densities. Weed density did not affect the concentrations of N, P, K, Ca or Mg in tomato shoots but dry matter and total amounts of nutrients were reduced increasingly with the increase in density of both weeds. The concentration of nutrients in the shoots of the weeds was not affected by density but dry matter yield and total nutrient accumulation per plant fell as the density increased. The concentrations of N, P, K and Mg in the shoots were higher in C. album than S. vulgaris but that of Ca was lower. In a replacement series experiment the two weed species behaved differently. With C. album, both dry matter yield and total nutrient per plant were reduced as its proportion in the mixture increased but, with S. vulgaris, dry matter per plant increased with its proportion in the mixture. One plant of C. album grown with five S. vulgaris gave a higher shoot dry weight than when present in higher proportions or in a pure stand. In a pure stand of six plants the shoot dry weight per plant of C. album was 26% of that of one plant grown with five S. vulgaris. In comparison, the shoot dry weight of one S. vulgaris in pure stand was 120% of that of one plant grown with five C. album. The reduction in growth of C. album was associated with a greater reduction in its ability to accumulate K than other elements. The competition index (CI) of C. album in terms of dry weight decreased with its proportion in the mixture but the reverse was true for S. vulgaris. The relative competitive ability index (RCAI) of C. album was almost 3–5 times that of S. vulgaris. The results showed that differences between the weeds in inter- and intraspecific competition were closely related to the growth of their root systems. Compétition inter- et intraspécifique du chénopode (Chenopodium album L.) et du senecon (Senecio vulgaris L.) Les réponses du chénopode (Chenopodium album L.) et du sénecon (Senecio vulgaris L.) à la compétition inter- et intra-spécifique ont étéétudiées en serre lors d'expériences à séries additives ainsi qu'à séries de remplacement. Quand elles étaient cultivées avec des tomates, les deux mauvaises herbes avaient des effets similaires sur la matière sèche des parties aériennes à faibles densités, mais S. vulgaris se montrait plus compétitif à fortes densités. La densité des mauvaises herbes n'affectait pas les concentrations en N, P, K, Ca et Mg dans les parties aériennes de la to-mate. Par contre, la matière séche et les quantités totales de nutriments étaient d'autant plus réduites que la densité des deux mauvaises herbes était élevée. La concentration en nutriments dans les parties aeriennes des mauvaises herbes n'était pas affectée par leur densité mais le rendement en matière sèche et l'accumulation totale de nutriments par plante décroissaient lorsque la densité augmentait. Les concentrations en N, P, K et Mg dans les parties aériennes étaient plus élevées chez C. album que chez S. vulgaris mais celle de Ca était plus basse. Dans une expérience à séries de remplacement, les deux espèces de mauvaises herbes se comportaient différemment. Chez C. album, le rendement en matière sèche ainsi que la quantité totale de nutriments par plante diminuaient lorsque sa proportion dans le mélange augmentait mais, chez S. vulgaris, la matière sèche par plante augmentait avec sa proportion dans le mélange. Un pied de C. album cultivé avec 5 pieds de S. vulgaris produisait davantage de matière sèche aérienne que lorsqu'il était présent en proportions plus importantes ou en culture pure. Dans une culture pure de 6 plantes, la matière sèche aérienne par pied de C. album représentait 26% de celle d'une plante cultivée avec 5 pieds de S. vulgaris. En comparaison, la matière sèche aérienne par pied de S. vulgaris en culture pure représentait 120% de celle d'une plante cultivée avec 5 pieds de C. album. La réduction de croissance de C. albumétait associée à une réduction de sa capacitéà accumuler K, qui était plus marquée que pour les autres éléments. L'Indice de Compétition de C. album en terme de matière sèche diminuait avec sa proportion dans le mélange, mais l'inverse était vrai pour S. vulgaris. L'Indice Relatif d'Aptitude à la Compétion de C albumétait presque 3,5 fois plus élevé que celui de S. vulgaris. Les résultats montraient que les différences entre les mauvaises herbes en ce qui concerne la compétition inter- et intra-spécifique étaient étroitement liées à la croissance de leur système racinaire. Inter- und intraspezifische Konkurrenz des Weißen Gänsefußes (Chenopodium album L.) und des Gemeinen Greiskrauls (Senecio vulgaris L.) Die inter- und intraspezifische Konkurrenz von Chenopodium album und Senecio vulgaris wurde sowohl in additivem als auch substitutivem Versuchsansatz im Gewächshaus untersucht. In Mischbeständen mit Tomate hatten beide Unkrautarten bei geringer Pflanzendichte eine ähnliche Wirkung auf die Sproß-Trockenmasse, doch Senecio vulgaris war bei hohen Dichten konkurrenzstärker. Die Unkrautdichte hatte keinen Einfluß auf den N-, P-, K-, Ca- oder Mg-Gehalt der Tomatensprosse, aber die Trockenmasse und der gesamte Nährstoffgehalt nahm mit zunehmender Dichte der beiden Unkräuter ab. Der Nährstoffgehalt in den Sprossen der Unkräuter wurde durch die Pflanzendichte nicht beeinflußt, aber die Trockenmasse und der gesamte Nährstoffgehalt nahm mit zunehmender Dichte der beiden Unkräuter ab. Der N-, P-, K-und Mg-Gehalt war bei Chenopodium album höher als bei Senecio vulgaris, doch der Ca-Gehalt war niedriger. In einem substitutiven Versuchsansatz verhielten sich die beiden Unkrautarten verschieden. Bei Chenopodium album wurden sowohl die Trockenmasse als auch der gesamte Nährstoffgehalt pro Pflanze im selben Maße reduziert, wie sein Verhältnis im Mischbestand zunahm; bei Senecio vulgaris stieg die Trockenmasse pro Pflanze mit seinem Anteil im Mischbestand an. Chenopodium album entwickelte bei einem Mischungsverhältnis von l Pflanze zu 5 Senecio-vulgaris-Pflanzen eine höhere Sproß-Trockenmasse als bei höheren Verhältnissen oder im Reinbestand. In einem Reinbestand von 6 Pflanzen war bei Chenopodium album die Sproß-Trockenmasse pro Pflanze 26 % der Masse einer Pflanze, die mit 5 Senecio-vulgaris-Pflanzen wuchs. Bei Senecio vulgaris dagegen war die Sproß-Trockenmasse pro Pflanze im Reinbestand 120 % der Masse einer Pflanze, die mit 5 Chenopodium-album-Pflanzen wuchs. Mit der Wuchshemmung ging bei Chenopodium album eine Abnahme seiner Fähigkeit, K und andere Nährstoffe aufzunehmen, einher. Der Konkurrenzindex von Chenopodium album, bezogen auf die Trocken-masse, nahm mit seinem Anteil in den Mischbeständen ab, während bei Senecio vulgaris das Gegenteil der Fall war. Die relative Konkurrenzfähigkeit von Chenopodium album war fast 3.5mal so groß wie die von Senecio vulgaris. Die Unterschiede der inter- und intraspezifischen Konkurrenz der beiden Unkrautarten stand in enger Beziehung zur Entwicklung ihres Wurzelsystems.     

Selection of sorghum (Sorghum bicolor (L.) Moench) varieties resistant to the parasitic weed Striga hermonthica (Del.) Benth

Pot and field experiments were performed in Burkina Faso in 1987 and 1988 to evaluate the resistance of selected ‘low-stimulant’ sorghum (Sorghum bicolor (L.) Moench) varieties to the parasitic weed (Striga hermonthica (Del.) Benth. In a pot experiment, the variety IS-7777 supported the lowest number and had the latest emergence of Striga, compared with the other varieties tested. The varieties IS-14825, IS-6961, IS-7739, IS-14928 and IS-14975 also had signifi cantly lower numbers of emerged Striga per pot than the resistant control Framida. The resist ance of IS-7777 was confirmed in field experi ments, as was that of IS-7739, IS-6961 and IS-14928. However, the yield potential of these poorly adapted varieties was low in Striga-infested fields. The varieties IS-14975, IS–14825 and Seguetana Niarabougou exhibited a low susceptibility associated with a grain yield equivalent to that of the other varieties in farm fields infested by Striga. As Seguetana is already grown by Sahelian farmers, its use could be recommended in the absence of resistant varieties adapted to Sahelian agroclimatic conditions. The exceptionally high level of restance exhibited by IS-7777 could be exploited in studies on the genetics and mechanisms of resistance of the host plant to the parasite, as well as in sorghum improvement programmes.     

Inhibitory and promotive allelopathy in rice (Oryza sativa L.)

Studies on allelopathic rice, which inhibits the germination and development of weeds such as barnyardgrass ( Echinochloa spp.) and ducksalad [ Heteranthera limosa (Sw.) Wild.], have been strongly conducted in the USA, the Philippines, Japan, Korea, and other countries since the 1980s. Weed-suppressing rice plants can compete with weeds for light and mineral nutrients by their rapid and thick growth characteristics, and probably also by their allelopathic effects. It was suggested that allelopathic properties were inherited from parents. Different screening methods for finding allelopathic rice simply and rapidly have been proposed. In contrast, stimulative allelopathy in rice, which promotes germination of the dormant and dormancy-awakened seeds of Monochoria vaginalis (Burm. f.) Kunth var. vaginalis , has been investigated by the authors since the 1990s. Rice seeds promoted the germination in the dark and in light under submerged conditions. Our experiments suggested that rice seeds, hulls, plants and straw contain stimulative substance(s) that promote seed germination of M. vaginalis .     

Effects of alachlor on anthocyanin and lignin synthesis in etiolated sorghum (Sorghum bicolor (L.) Moench) mesocotyls

Alachlor, a preemergence herbicide used to control grasses and some broadleaf weeds, was found to inhibit anthocyanin and lignin accumulation in excised sections of mesocotyls from 6 day-old, etiolated sorghum (Sorghum bicolor (L.) Moench) seedlings. Alachlor inhibited anthocyanin and lignin synthesis by 50% at 20 and 28 μM, respectively, with anthocyanin synthesis being inhibited in 1 hr. Other chloroacetanilide herbicides also inhibited anthocyanin synthesis in this system, but all were less active than alachlor. Inhibition of anthocyanin synthesis could not be reversed by compounds from the shikimic acid or phenylpropanoic acid pathways. Anthocyanin synthesis could be restored by removal of alachlor from the incubation solution. Evidence is presented which suggests that alachlor inhibits anthocyanin formation at a point late in the phenylpropanoic acid pathway and not in the shikimic acid pathway.     

Diclofop-methyl tolerance in cultivated oats (Avena sativa L.)

The feasibility of achieving selective wild oat (Avena fatua L.) control in a stand of the Australian oat (Avena sativa L.) cv. Savena I was examined. Diclofop-methyl was applied at rates of 0·4–0·7 kg a.i. ha^?1 at the three- and five-leaf stages of A. fatua (84–132 culms m²). Although all rates of diclofop-methyl caused initial chlorosis and necrosis to the crop, the subsequent control of A. fatua permitted increased crop tillering. Avena fatua control and crop yield response were maximized when diclofop-methyl was applied at the three-leaf stage. Crop grain yield was increased by as much as 32% and 22% during 1984 and 1985, respectively. In the absence of A. fatua competition, crop shoot dry weight at ear emergence was reduced only where diclofop-methyl was applied at 0·6 or 0·7 kg ha^?1. However, final grain yield was not reduced by any treatment. Only 11 of 240 cultivars or lines tolerated diclofop-methyl, and none reached the level attained by Savena I and a closely related Australian line [(Irwin × (West × New Zealand Cape/42)) × West]/24. The nature of the inheritance of diclofop-methyl tolerance was examined (1983–1985) by crossing and backcrossing (BC) Savena I with four diclofop-methyl susceptible, but agronomically superior, lines. Inheritance of diclofop-methyl tolerance appeared to be controlled by two genes, with susceptibility being dominant to tolerance in F₃, BCIF₂ and BCIF₃ lines.     

亚麻荠对小菜蛾形态抗虫性的研究

经亚麻荠叶片表面形态及其表面细胞结构观察发现,亚麻荠叶正面上刚毛密度平均为76.13根/cm2,而背面仅为1.63根/cm2;表皮细胞层较厚,结构紧密,其上有一层较厚的角质层。通过亚麻荠叶片饲喂小菜蛾幼虫明确,小菜蛾幼虫在亚麻荞叶片的正面和背面的取食叶面积差异极显著。表明亚麻荠叶片表面的毛状物对小菜蛾幼虫有一定的拒食作用。     

Potential safeners for protecting sorghum (Sorghum bicolor (L.) Moench) against chlorsulfuron,fluazifop-butyl and sethoxydim*

In greenhouse studies, the efficacy of the herbicide safeners NA(1,8-naphthalic anhydride), R-25788 (N,N-diallyl-2,2-dichloroacetamide), cyometrinil and CGA-92194 [N-(1,3-dioxolan-2-yl-methoxy)imino-benzeneaceto-nitrile] in protecting grain sorghum (Sorghum bicolor (L.) Moench, cv. ‘Funk G623’) against injury from pre-emergence or early post-emergence applications of the herbicides chlorsulfuron, fluazifop-butyl and sethoxydim was examined. NA as a seed dressing at 0·5 or 1·0% (w/w) was the most effective of the four safeners and offered partial to good protection to sorghum against injury from the lower rates of pre-emergence applications of all three herbicides. R-25788 was totally ineffective as a sorghum protectant against fluazifop-butyl injury but it did antagonize partially the injurious effects of the lower rates of sethoxydim and chlorsulfuron on sorghum. Cyometrinil and CGA-92194 offered partial protection to sorghum against injury from the lowest rate of all herbicides but their efficacy against higher rates of the three herbicides was very limited. None of the four safeners was effective in protecting grain sorghum against injury from post-emergence applications of the three herbicides tested.     

Photosynthetic parameters in glyphosate-treated sugarbeet (Beta vulgaris L.)

Variable fluorescence and carbon dioxide exchange rate (CER) were measured in intact leaves of glyphosate-treated sugarbeet plants, to investigate rapid effects on photosynthesis. In one experiment, a significant effect on variable fluorescence and CER was found within 8 h after herbicide application. The effect on stomatal conductance was not significant. In a second experiment, the effects of light or dark conditions during herbicide application and 24 h later were evaluated. Under light conditions glyphosate significantly reduced variable fluorescence after 4 h. However under initial conditions of 24 h darkness, followed by alternating 8 h light/8 h dark, the effect was not significant until 44 h after treatment, by which time the plants had received several hours of light. The eflect on variable fluorescence 8 h after herbidde application correlated positively with plant survival 7 days later.