Tobacco streak virus in sunflower (Helianthus annuus)

Tobacco streak virus (TSV) was isolated from a plant of sunflower (Helianthus annuus) showing severe necrosis and chlorosis in the leaves. The virus was identified as TSV by serology and, to some extent, by host range. The type of symptoms varied with the host plant in which the virus had been propagated in successive transfers. Test plants inoculated with the virus propagated inNicotiana rustica produced symptoms which very much differed from those brought about by the virus from eitherN. clevelandii orChenopodium amaranticolor.The significance of the host-mediated variation in symptoms is discussed.Samenvatting Tabaksstrepenvirus (TSV) werd geïsoleerd uit zonnebloem (Helianthus annuus) die sterke necrose en chlorose van de bladeren vertoonde. De identiteit van het virus werd vastgesteld op grond van serologische reacties en, tot op zekere hoogte, de symptomatologie. Het type symptoom op de toetsplanten bleek echter sterk afhankelijk te zijn van de plant waarvan het inoculum afkomstig was. Was het virus verschillende malen achtereen vermeerderd inNicotiana rustica dan waren de symptomen op de toetsplanten zeer verschillend van die, welke werden veroorzaakt door virus vermeerderd inN. clevelandii ofChenopodium amaranticolor. De betekenis van deze door de waardplant bewerkstelligde variatie in symptomen wordt besproken.     

Genotype-isolate interaction for resistance to black stem in sunflower (Helianthus annuus)

Two experiments were undertaken to determine the partial resistance of sunflower genotypes to seven isolates of Phoma macdonaldii . In the first experiment, 28 genotypes, including recombinant inbred lines and their parents, M6 mutant lines developed by gamma irradiation, and some genotypes from different geographical origins, were used. The experiment consisted of a split-plot design with three replications, each with 12 seedlings per genotype per isolate, in controlled conditions. Seven days after inoculation, plantlets were scored on a 1–9 scale for percentage necrotic area. Highly significant differences were observed among genotypes, isolates and their interactions. The presence of a differential interaction between genotypes and P. macdonaldii isolates was confirmed in a second experiment using 12 genotypes representing large variability for partial resistance to P. macdonaldii isolates, as identified in the first experiment. Inbred lines B454/03, ENSAT-B5 and LC1064C were the most susceptible sunflower genotypes, whereas two American lines SDR19 and SDR18 presented high partial resistance to all P. macdonaldii isolates studied. The least and most aggressive isolates were MA6 and MP3, respectively. Isolates interacted differentially with sunflower genotypes. This study identified two genotypes (AS613 and PAC2) presenting specific resistance to isolate MP8. The results also showed a wide range of isolate-nonspecific partial resistances among the lines tested. The information presented here could assist sunflower breeders to choose parents of crosses for breeding of durable resistance to phoma black stem disease.     

Prohexadione-calcium induces sunflower (Helianthus annuus) resistance against the root parasitic weed Orobanche cumana

Prohexadione-calcium (PHDC) is a plant growth retardant that inhibits gibberellin biosynthesis and transiently alters the spectrum of flavonoids and their phenolic precursors. In this study, root chamber and pot experiments were conducted to evaluate the effects of PHDC on Orobanche cumana seed germination and induction of sunflower resistance to this root parasitic weed. Root chamber experiments indicated that PHDC did not interfere with the progress of Orobanche seed germination, but retarded O. cumana tubercle formation and development. In pot experiments, control of O. cumana by PHDC depended on its dose, method of application and sunflower cultivar. In sunflower cv. HA89, PHDC at 10 mg LS⁻¹ (litre soil) as two drenches or at 1 m m as two foliar sprays significantly reduced the total number and dry matter of O. cumana without influencing flower, leaf and root development. In sunflower cv. Albena, PHDC at 20 and 30 mg LS⁻¹, but not at 10 mg LS⁻¹, as two drenches significantly reduced O. cumana infection. Sunflower cv. HA89 was less susceptible to O. cumana and more inducible by PHDC than sunflower cv. Albena. The biochemical analysis of root extracts revealed a significantly higher accumulation of free phenolics in sunflower cv. HA89 after PHDC soil drench, but not in Albena. No significant lignification was observed after PHDC treatments. The results suggest that PHDC reduces O. cumana infection in sunflower by inducing host resistance, not by directly interfering with the parasite. Free phenolics play an important role in sunflower response to the parasite.     

Association of the western flower thrips (Frankliniella occidentalis) with cultivated sunflower (Helianthus annuus) in Israel

In 1992 and 1993, sunflower (Helianthus annuus L.) crops in Israel were heavily damaged by the western flower thrips (WFT),Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Adult females appear in the heads of sunflower just as the latter begin to blossom; the population decreases towards completion of anthesis. The damage to kernels is greatest at the periphery of the heads, where flowers appear first, and lowest at the center. Fields sown early in the season (in March) are usually the ones infested most by WFT and suffering the greatest damage. Fields sown one month later are less infested, since predatory bugs of the genusOrius are very active at that time.     

Resistance of sunflower (Helianthus annuus L.) to terminal bud attack bySclerotinia sclerotiorum (Lib.) de Bary

Resistance of sunflowers to terminal bud attack bySclerotinia sclerotiorum was studied by microscopical observations of infection processes and by genetical analyses of trials showing natural infections. Electron microscope studies showed that there were no differences in leaf morphology between susceptible and resistant genotypes, and that both were contaminated by ascospores. Only on the susceptible genotype was considerable ascospore germination observed, followed by mycelial development and leaf penetration. On the resistant genotype, there was little ascosopore germination and no further development. The genetical studies of percentage natural attack observed on eight inbred lines representing a range of reactions, and the hybrids from a factorial cross of these lines, indicated that inheritance is mainly additive, with few interactions.     

Waterhemp (Amaranthus tuberculatus) control under drought stress with 2,4‐dichlorophenoxyacetic acid and glyphosate

Waterhemp (Amaranthus tuberculatus) is a common and troublesome weed in cropping systems throughout the United States. With the potential for future periods of low rainfall or drought, the need for improved weed control under drought stress is necessary. Drought stress typically reduces herbicide efficacy by reducing the foliar uptake of herbicides and their translocation. The objectives of this research were to determine the efficacy of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and glyphosate, applied alone or when tank‐mixed, on waterhemp under varying levels of drought stress, the effect of the timing of drought stress in relation to herbicide application and the absorption and translocation of each herbicide in drought‐stressed waterhemp. At reduced herbicide rates, 2,4‐D had a greater level of control of waterhemp under drought stress, compared to glyphosate. The level of herbicide efficacy was lower when the amount of water that was applied to the plants was reduced. The level of waterhemp control was greatest when drought stress occurred before the herbicide application and when the plants were watered to saturation after the application, compared to when drought stress occurred after the herbicide application or restricted watering levels occurred throughout the entire study. Glyphosate absorption and translocation were reduced in the drought‐stressed plants, but 2,4‐D absorption and translocation were not altered. The absence of a reduction in 2,4‐D translocation in the drought‐stressed weeds has not been previously reported. Applying herbicides prior to a rainfall event could increase the weed control level, even if the weed is stressed. Determining how and why 2,4‐D absorption and translocation levels, compared to those of glyphosate, are unaffected by drought stress in waterhemp can aid in improving the control of drought‐stressed weeds with other postemergence herbicides.     

Soil‐less bioassays for early screening for resistance to imazapyr in sunflower (Helianthus annuus L.)

BACKGROUND: Rapid and efficient diagnostic tests for early screening of herbicide resistance are convenient alternatives to field screening methods. There is a need for a quick, reliable and cost‐effective method for rapid diagnosis of imidazolinone resistance in sunflower (Helianthus annuus L.). RESULTS: Two seed germination bioassays were developed. Seeds from three sunflower inbred lines differing in resistance to imidazolinones were germinated either on solid culture medium or placed in plastic pots filled with commercial perlite. After 8 days incubation under controlled conditions, both assays successfully distinguished susceptible genotype from the resistant and intermediate ones. The susceptible genotype showed arrested root growth at all herbicide treatments (root length < 1 cm). The resistant genotype developed a complete root system even when exposed to the highest dose of herbicide. However, no definite differences were observed for the intermediate and resistant genotypes with respect to root growth under the different herbicide treatments. CONCLUSION: The simple and rapid screening assays described in the present study were useful in discriminating imidazolinone resistance at the seedling stage. Therefore, these bioassays could be potential tools for early screening of imidazolinone resistance genes from large sunflower populations. Copyright © 2009 Society of Chemical Industry     

Effect of planting date on broomrape (Orobanche cernua Loefl.) infections in sunflower (Helianthus annuus L.)

Field studies were conducted in 1988 and 1989 to determine the phenology and growth of broomrape in sunflower as affected by crop sowing dates. The parasitic weed attachment was observed in sunflower plants with 6–7 leaves; later it was found throughout the vegetative and flowering period of the crop. O. cernua seedlings with shoot development extensive but subterranean were mainly observed at the early heading stage of sunflower. At this stage they were beginning to reduce sunflower plant growth as compared with non–parasitized plants. The emergence of broomrape began at the early flowering stage of the crop and was particularly abundant throughout this and the achene–filling stage. Generally, broomrape infection was much less at the first than at the second or third sunflower sowings, and caused less reduction in yield. The duration of the broomrape emergence period increased as sowing date was delayed. Since sunflower yield was higher at earlier sowing dates, early sowing may be recommended for sunflower crops in broomrape–infested areas under mild mediterranean climates. Effet de la date de semis sur les infections d'orobanche (Orobanche cernua Loefl.) en culture de tournesol (Helianthus annuus L.) Des études de plein champ ont été conduites en 1988 et 1989 pour déterminer comment la phénologie et la croissance des orobanches en culture de tournesol étaient affectées par les dates de semis de la culture. Le rattachement de 1'adventice parasite a été observeé chez les plantes de tournesol avec 6–7 feuilles; plus tard il était observé tout au long des périodes végétatives et de floraison de la culture. Des plantules d'O. cernua avec un développement de la tige important mais souterrain ont été principalement observées au stage bourgeon précoce du tournesol. A ce stade elles ont commencé & réquire la croissance du tournesol en comparaison avec des plantes non parasitées. La levée de 1'orobanche a commencé au début du stade de la floraison de la culture et a été particuliérement abondant pendant celle–ci et le stade remplissement des akénes. Généralement, l'infection d'orobanche a été beaucoup moins forte au premier qu'au second et troisiéme semis et a causé des baisses de rendement plus faibles. La durée de la période de levée des orobanches a augmenté quand le semis a été retardé. Puisque le rendement en tournesol a été plus élevé pour les dates de semis précoces, un semis précoce peut être recommandé pour le tournesol en zones infestées par les orobanches sous les climats méditerranéens. Die Bedeutung des Saattermins der Sonnenblume (Helianthus annuus L.) für den Befall mil der Sommerwurz (Orobanche cernua Loefl.) In Feldversuchen wurden 1988 und 1989 die PhÄnologie und das Wachstum der Sommerwurz in Sonnenblumenkulturen untersucht. Der Befall der Sonnenblumenpflanzen wurde im 6- bis 7-Blatt-Stadium festgestellt, aber auch später in der gesamten vegetativen und generativen Phase der Kulturpflanze. Keimpflanzen der Sommerwurz mit einer kräftigen, aber unterirdischen Sproßentwicklung wurden überwiegend im frühen Stadium der Blütenentwicklung der Sonnenblume beobachtet. In diesem Stadium begann die Wachstumshemmung der Sonnenblume. Zu Beginn der Blüte der Sonnenblume lief die Sommerwurz auf und war während dieses Entwicklungsstadiums und der folgenden Samenbildung besonders häufig anzutreffen. In der ersten Aussaat der Sonnenblume war der Befall allgemein geringer als in der zweiten oder dritten. Mit späterem Saattermin verlängerte sich die Keimungsperiode der Sommerwurz. Nachdem die Sonnenblume bei früherer Saat einem höheren Ertrag brachte, wird für mild-mediterrane Gebiete mit Befall von Sommerwurz eine frühe Aussaat empfohlen.     

Effect of incorporation method and soil type on selectivity of metribuzin in sunflower (Helianthus annuus L.)

In field experiments, sunflower (Helianthus annuus L. cv. Hybrid 894) showed sufficient tolerance to metribuzin to permit use of this herbicide to control selectively several broad-leaved weeds, including wild mustard (Sinapis arvensis L.). Metribuzin, at rates up to 0.3 kg ai ha⁻¹, applied pre-emergence to sunflower and soil incorporated to a depth of 2.5 cm with a spike tooth harrow, did not injure sunflower plants growing in clay loam soil containing 5.3% O.M. A similar treatment injured sunflowers planted in a fine sandy loam soil with 4.5% O.M. Results from controlled-environment studies supported the field results. Metribuzin as a postplant, shallow incorporation treatment offers a practical method for the selective control of wild mustard and other broad-leaved weeds in sunflowers grown on clay loam soils. Effet de la méthode d'incorporation et du type de sol sur la sélectivité de la métribuzine chez le Tournesol (Helianthus annuus L.) Au cours d'essais au champ, la métribuzine a été suffisamment bien tolérée par le tournesol (Helianthus annuus L. cv. Hybrid 894) pour pouvoir être utilisée pour le contrôle sélectif de plusieurs dicotylédones, y compris la moutarde sauvage (Sinapis arvensis L.). La métribuzine, jusqu'à la dose de 0,3 kg ma ha⁻¹, appliquée en pré-levée et incorporée à la profondeur de 2,5 cm avec une herse à dents, n'a pas été phytotoxique pour le tournesol cultivé sur un sol limonoargileux contenant 5,3% de matière organique. Un traitement similaire s'est montré phytotoxique pour les tournesols dans un sol fin limonosableux avec 4,5% de matière organique. Les résultats d'études en conditions contrôlées concordent avec les observations au champ. La métribuzine administrée en traitement de postsemis à faible profondeur offre une possibilité pratique de contrôle sélectif de la moutarde sauvage et d'autres dicotylédones chez le tournesol cultivé sur les sols limono-argileux. Einfluss von Einarbeitungsmethode und Bodentyp auf die Selektivität von Metribuzin in Sonnenblumen (Helianthus annuus L.) In Feldversuchen zeigten Sonnenblumen (Helianthus annuus L. cv. Hybride 894) gegenûUber Metribuzin eine genügend höhe Toleranz, um den Einsatz dieses Herbizids zur selektiven Bekämpfung verschiedener breitblättriger Unkräuter, incl. Ackersenf (Sinapis arvensis L.), zu ermöglichen. In tonigem Lehm mit 5,3% organ. Substanz bewirkte Metribuzin in Dosierungen bis zu 0,3 kg ai ha⁻¹ preemergent in Bezug auf Sonnenblume appliziert und in eine Tiefe von 2,5 cm eingehackt, an der Kultur keine Schäden. In feinem sandigen Lehm mit 4,5% organ. Substanz wurden die Sonnenblumen durch eine ähnliche Behandlung geschädigt. Ergebnisse von Untersuchungen unter kontrollierten Umweltbedingungen bestätigten die Feldresultate. Metribuzin, nach der Aussaat flach eingearbeitet, ermöglicht auf tonigen Lehmböden eine selektive Bekämpfung von Ackersenf und anderen breitblättrigen Unkräutern.     

Benzothiadiazole Activates Resistance in Sunflower (Helianthus annuus) to the Root-Parasitic Weed Orobanche cuman

ABSTRACT The study was conducted to evaluate the potential of induced resistance to infestation of sunflower (Helianthus annuus L.) by the parasitic weed Orobanche cumana Wallr. Treatment of sunflower seeds with 40 ppm of benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH) for 36 h completely prevented infection in root chambers. In pot studies using 2.86 x 10(-4) g of Orobanche seeds per gram of soil as inoculum, the total number of O. cumana shoots was reduced by 84 and 95% in the 60-ppm BTH treatment in the first and second trial, respectively. Evaluation of the disease incidences revealed that attachment of O. cumana at the sunflower root and the stage of early penetration was reduced in the BTH-treated plants. Chemical analysis of root extracts revealed synthesis of the phytoalexin scopoletin and of hydrogen peroxide in the BTH-treated sunflower roots, but no increase in lignification. Western blot analysis demonstrated accumulation of the pathogenesis-related protein chitinase in roots and stems of induced resistant plants. These results show that the phenomenon of induced resistance is not restricted to viral, bacterial, and fungal disease and demonstrate the great potential of this protection strategy as an effective component of future plant production systems.     

Effects of chloroacetamides and phytosynthesis-inhibiting herbicides on growth and photosynthesis in sunflower (Helianthus animus L.) and Amaranthus hybridus L.

The effects of the chloroacetamide herbicides acetochlor, alachlor and propachlor and the pho-tosynthesis-inhibiting herbicides linuron, prometryn and terbutryn on sunflower (Helianthus annuus L.) and atrazine-sensitive and -resistant Amaranthus hybridus L. biotypes were investigated under laboratory conditions. Sunflower tolerated all three chloroacetamides in pre-emergence applications of 1.5–5.0 kg a.i. ha^?1 in growth assays. Sunflower also survived doses of 0.5–1.0 kg a.i. ha^?1 of linuron, prometryn and terbutryn, although growth reduction and chlorosis of treated plants was observed. These three herbicides inhibited photosynthetic electron transport in in vitro Hill reaction and fluorescence assays and, with terbutryn, photosynthesis recovered upon transfer of the leaves from herbicide solutions to water. The practical significance of these results for the control of weeds in sunflower cultivation in Spain are discussed. Effets d'herbicides chloroacétamides et d'herbi-cides inhibiteurs de la photosynthèse sur la crois-sance et la photosynthèse du tournesol (Helianthus annuus L.) et de Amaranthus hybridus L. Les effets des herbicides chloroacétamides acétochlor, alachlor et propachlor ainsi que des herbicides inhibiteurs de la photosynthèse linuron, prometryne et terbutryne, ont étéétudiés sur le tournesol (Helianthus annuus L.) et sur des biotypes sensibles et résistants d'Amaranthus hybridus L. en conditions de laboratoire. La croissance du tournesol n'était affectée par au-cun des trois chloroacétamides appliqués en prélevée (1,5–5,0 kg m.a. ha^?1). Le linuron, la terbutryne et la prometryne (0,5–1,0 kg m.a. ha^?1) occasionnaient des réductions de croissance et des chloroses sur le tournesol mais les plantes survivaient. Ces trois herbicides in-hibaient le transport d'électrons photosyn-thétique observé par des mesures de fluorescence et, in vitro par la réaction de Hill. Dans le cas de la terbutryne, la photosynthèse reprenait après transfert des feuilles des solutions d'herbicides dans 1'eau. La signification pratique de ces résultats pour la lutte contre les mauvaises herbes du tournesol en Espagne est discutée. Wirkung von Chloracetamiden und Photosyn-these-hemmenden Herbiziden auf Wachstum und Photosynthese der Sonnenblume (Helianthus annuus L.) und Amaranthus hybridus L. Die Wirkung der Chloracetamid-Herbizide Acetochlor, Alachlor und Propachlor und der Photosynthese-hemmenden Herbizide Linuron, Prometryn und Terbutryn auf die Sonnenblume (Helianthus annuus L.) und Atrazin-empfindliche sowie-unempfindl Amaranthus-hybridus-Biotypen wurde unter Laborbedin-gungen untersucht. In Wachstumstests tolerierte die Sonnenblume alle 3 Chloracetamide bei Vorauflaufanwendung von 1,5 bis 5,0 kg AS ha^?1. Auch Dosen von 0,5 bis 1,0 kg AS ha^?1 von Linuron, Prometryn und Terbutryn wurden vertragen, aber der Wuchs war beeinträchtig, und Chlorosen wurden beobachtet. Diese 3 Herbizide hemmten den photosynthetischen Elektronentransport bei Versuchen zur Invitro-Hill-Reaktion und Fluoreszenz, und bei Terbutryn stellte sich die Photosynthese nach Überführen der Blätter von der Herbizidlösung auf Wasser wieder ein. Die praktische Bedeutung dieser Ergebnisse für die Unkrautbekämpfung in Sonnenblumenkulturen in Spanien wird diskutiert.     

Microscopical studies of the effect of metalaxyl on the interaction between sunflower,Helianthus annuus L. and downy mildew,Plasmopara halstedii

The mode of action of the fungicide metalaxyl againstPlasmopara halstedii, the causal agent of sunflower downy mildew, was studied following its application before, during and after artificial contamination of seedlings. The development of the fungus within the treated seedlings was examined microscopically and compared to that occuring in untreated genetically susceptible or resistant genotypes. Hypersensitive-like reactions and necrotic zones leading to the inhibition of fungus growth within the hypocotyl were observed for the three modes of application. This suggests that sunflower defence mechanisms activated by genetical resistance are also involved in the control of downy mildew by metalaxyl.     

Effect of broomrape (Orobanche cumana Wallr.) on some agro-morphological and biochemical traits of Tunisian and some reference sunflower (Helianthus annuus L.) accessions

Journal of Plant Diseases and Protection - Orobanche cumana Wallr. is an important new problem for sunflower crop in Tunisia. Little information is available on the behavior of sunflower to O....     

干旱胁迫下高粱叶温与叶片水分状况的关系

根据叶片温度可以反映植物体内水分状况及气孔运动等一系列生理变化的特征,研究干旱胁迫下高粱叶片温度与水分状况变化间的关系,分析高粱抗旱反应机制。采用4个不同抗旱性高粱品种,在盆栽条件下,分别在拔节期、开花期和灌浆期进行干旱胁迫,以正常灌水为对照,胁迫7 d后测定高粱叶片自由水含量、离体叶片失水速率、相对含水量等水分状况,利用远红外热成像仪测定叶片温度变化。结果表明,干旱胁迫下,高粱叶片自由水含量、束缚水含量、相对含水量和离体叶片失水速率等水分状况在不同生育时期均呈下降趋势,吉杂305（高度抗旱品种）的下降幅度显著小于吉杂127（高度干旱敏感品种）（P＜0.05）,锦杂106（中等抗旱品种）和锦杂103（干旱敏感品种）介于二者之间。叶温差与自由水含量和相对含水量显著相关（P＜0.05）,与束缚水含量极显著相关（P＜0.01）。叶片温度变化可以反映高粱叶片的水分状况,叶温差可以作为高粱抗旱性筛选的一个重要指标,应用远红外热成像技术在高粱抗旱性的鉴定上具有可行性。     

干旱胁迫下3个油菜品种地上、地下部生长特征与抗旱性的关系

为了探索干旱胁迫下不同抗旱性油菜品种的地上、地下部生长特征与抗旱性的关系,通过土柱栽培试验,对油菜品种DR1、DR2和DR3在不同水分处理条件下不同土层根量、地上部生物量、冠层覆盖面积及抗旱性之间的关系进行研究。结果表明：3个品种在水分胁迫和正常供水条件下产量和根系生物量在品种间均达到显著性差异,3个品种的抗旱能力大小依次为：DR1>DR3>DR2;不同水分处理下油菜的根系主要分布于0~30 cm土层,占根系总量的70%以上;在干旱胁迫下,3个品种DR1、DR2和DR3的总根量分别减少了22.53%、24.17%和24.53%,但仍表现出抗旱性强的品种DR1的根系总量最大,达到12.07 g,其次为品种DR3和DR2;在大于30cm的土层中,DR1的根系量占到总根量的31.5%,这表明根系垂直分布量的多少对抗旱性的影响较大,同时植株冠层面积、总生物量、根系干重与抗旱性的直接通径系数分别为0.5861、0.4514、0.5715,说明除了根系外,大的冠层面积可减少地表蒸发有利于作物抗旱。     

黄淮海地区夏玉米对干旱和涝渍的生理生态反应

利用黄淮海地区多站点的夏玉米水分控制试验,探讨旱涝对夏玉米发育进程、光合能力、干物质分配、叶面积扩展、产量结构及最终产量的影响,进而分析旱涝对夏玉米生长过程的影响机制。结果表明:干旱减缓了夏玉米营养生长阶段的发育速率,但加快了生殖生长阶段的发育进程,而涝渍对夏玉米发育进程的影响较小;夏玉米全生育期土壤湿度距适宜湿度减小1%,其叶片最大光合速率将下降0.3 mol·m~(-2)·s~(-1),比叶面积上升8×10-6hm~2·kg~(-1);夏玉米全生育期土壤相对湿度下降1%,其地上总干重和穗干重均下降0.55%,而产量将减少155kg·hm~(-2);干旱不仅使玉米灌浆时间变短,而且使叶片光合能力下降;营养生长阶段干旱使干物质更多地分配向茎秆,导致叶面积扩展乏力,生殖生长阶段干旱减少干物质向贮存器官的分配而影响产量构成;尽管干旱使叶片变薄而促进其扩展,但仍不足以减缓干旱的整体负面影响,最终导致玉米减产;而涝渍主要使玉米叶片光合能力下降,并导致干物质向穗的分配减少而减产。     

干旱胁迫对向日葵种子萌发的影响及其抗旱性鉴定

利用PEG溶液模拟干旱胁迫,对18个向日葵资源材料种子萌发期的形态、生理生化指标进行测定和比较,筛选与向日葵萌发期抗旱性相关的指标,并采用隶属函数法对供试材料进行抗旱性综合评价。结果表明:向日葵种子萌发期的发芽势、发芽率及发芽指数均受到抑制;相对胚根长度、相对胚芽长度、相对胚芽干重、相对发芽率、相对发芽势、相对发芽指数、相对MDA含量及相对ATP含量与综合抗旱能力D值呈显著正相关,这些指标均可作为萌发期抗旱性鉴定指标;供试18个向日葵材料中株系88抗旱性最强,D值为1.49,可以作为下一步寻找抗旱基因的基础材料。本研究完善了向日葵种子萌发期抗旱性的鉴定方法,对向日葵育种有一定的实践意义与参考价值。