Carry over of bruchid,Caryedon serratus (Olivier) (Coleoptera) from field to stores through seeds of Acacia nilotica (L.) Willd. in India

Abstract

A percentage pod damage of 6.8% in Acacia nilotica (L.) Willd. by the bruchid, Caryedon serratus (Olivier) in the field was recorded by examining exit holes on the pods. The mean number of females and males that emerged from 50 pods kept in laboratory were 1.3 and 1.2 respectively. The pods of A. nilotica gathered from the field for seed purposes were found to be infested in small numbers but the bruchid population increased during storage. The infestation of seeds and carry over to stores is not only a danger to uninfested seeds of A. nilotica and other plants, important in social forestry, but the tree also acts as secondary host for the population build‐up of C. serratus which spreads to its primary host, the groundnut, Arachis hypogea (L).     

Low root‐to‐root transmission of a tobamovirus,yellow tailflower mild mottle virus,and resilience of its virions

Tobamoviruses are serious pathogens because they have extremely stable virions, they are transmitted by contact, and they often induce severe disease in crops. Knowledge of the routes of transmission and resilience of tobamovirus virions is essential in understanding the epidemiology of this group of viruses. Here, an isolate of the tobamovirus yellow tailflower mild mottle virus (YTMMV) was used to examine root‐to‐root transmission in soil and in a hydroponic growth environment. Root‐to‐root transmission occurred rarely, and when it occurred plants did not exhibit systemic movement of the virus from the roots to the shoots over a 30‐day period. The resilience of YTMMV virions was tested in dried leaf tissue over time periods from one hour to one year under temperatures ranging from ?80 to 160 °C. Infectivity was maintained for at least a year when incubated at ?80 or 22 °C, or at fluctuating ambient temperatures of 0.8 to 44.4 °C, but incubation under dry conditions at 160 °C for >4 days eliminated infectivity. Exposure of virions to 0.1 m sodium hydroxide or 20% w/v skimmed milk solution for 30 min, treatments recommended for tobamovirus inactivation, did not abolish infectivity of YTMMV.     

Isotope-edited nuclear magnetic resonance: novel methodologies for investigating metabolism

While the use of NMR and stable isotopes in metabolism studies is hardly new, it is only recently that isotope-edited NMR spectroscopy has been applied in kinetic studies of glyphosate metabolism of soil microbes. NMR can detect multiple species simultaneously and non-destructively, yielding valuable information on structural identification of metabolites. T riple R esonance I sotope ED ited spectroscopy (TRIED), [²H]NMR, and [²H–¹³C] INEPT (I nsensitive N ucleus E nhancement through P olarization T ransfer) are three isotope-edited techniques which have been used in combination to examine the microbial degradation of glyphosate (N-phosphonomethylglycine). Using ¹³C- and ¹⁵N-labeled glyphosate, TRIED can detect multiple metabolites in crude matrices at submicrogram levels, an improvement over earlier techniques where milligrams were needed. It can detect 500 nanograms of ¹³C–¹⁵N-labeled compound in a crude sample (1 : 1400 mass ratio), only a few hours work being required. [²H]NMR and [²H–¹³C]INEPT were also used as complementary techniques to further examine metabolites whose ¹³C–¹⁵N bond has been cleaved. The three-isotope-edited methods produced results consistent with both radioactivity and HPLC analyses. Accordingly, we are able to detect minute levels of metabolites in the presence of complex mixtures, minimizing the costs and time of sample purification. ©1999 Society of Chemical Industry     

Seasonal changes in germination response of buried seeds of Orobanche crenata Forsk.

Orobanche crenata seeds, collected in Syria, Egypt and Spain, were buried in the field in Syria (all three seed lots) and Spain (only Spanish seeds) and at regular intervals exhumed and tested for germination, to investigate whether the seeds exhibit an annual dormancy/non-dor- mancy cycle. When exposed directly to the synthetic germination stimulant GR24 for 7 days at 20°C, seeds only germinated in autumn after the first rains and to a limited extent in winter. When the seeds were conditioned for 11 days at 20°C prior to exposure to GR24, germination occurred during summer and autumn, but seeds were dormant in winter and early spring. The observed seasonal pattern in germinability, in relation to rainfall and soil temperature, was largely consistent with the results of an in vitro experiment by Van Hezewijk et al. (1993), investigating the effect of conditioning temperature and conditioning period on germination capacity and the development of secondary dormancy. Moisture and temperature can therefore be considered the major factors regulating induction and alleviation of dormancy in buried O. crenata seeds. There were no basic differences in response owing to site of collection of O. crenata seeds, nor to the location where they were buried. Variations saisonnières des exigences de germination de graines enfouies d'Orobanche crenata Forsk. Des graines d'Orobanche crenata récoltées en Syrie, en Égypte et en Espagne ont été enfouies au champ en Syrie (les 3 lots) et en Espagne (seules les graines d'Espagne) puis ont été exhumées a intervalles régulier pour que leur aptitude à la germination soil évaluée. Le but était de déterminer si les graines possédaient un cycle annuel dormance/non dormance. Quand elles étaient directement exposées au stimulant de germination synthétique GR24 pendant 7 jours à 20°C, les graines ne germaient qu'à l'automne après les premières pluies et peu en hiver. Quand les graines restaient pendant 11 jours à 20°C avant leur exposition au GR24, la germination seproduisait en été et à l'automne mais les graines restaient dormantes en hiver et au début du prin-temps. Les variations saisonnières d'aptitude à la germination, liées aux précipitations et à la temperature du sol, étaient en accord avec les résultats d'une expérience in vitro de Van Hezewijk et al. (1993) concernant l'effet de la température et de la durée pendant laquelle elle est appliquée, sur l'aptitude à la germination et le développement de la dormance secondaire. L'humidité du sol et sa température peuvent ainsi être considérées comme les principaux facteurs qui induisent et lèvent la dormance de graines de O. crenata enfouies. On n'observait pas de différences importantes dues au lieu de récolte ou à l'endroit oü elles étaient enfouies. Jahreszeitliche Änderungen der Keimung von vergrabenen Samen von Orobanche crenata Forsk. Proben von in Syrien, Ägypten und Spanien gesammelten Orobanche-crenata-Samen wurden in Syrien und Proben nur spanischer Herkunft in Spanien im Freiland im Boden ausgelegt und in regelmäßigen Zeitabständen ausgegraben und auf ihre Keimfähigkeit getestet, um zu untersuchen, ob die Samen einen jährlichen Dormanz-Zyklus haben. Beim direktem Auslegen in dem synthetischen Keimungsmittel GR24 öber 7 d bei 20°C keimten die Samen nur im Herbst nach den ersten Regenfällen und in beschränktem Umfang im Winter. Wenn die Samen för 11 d bei 20°C vor dem Auslegen in GR24 vorbehandelt worden waren, keimten sie im Sommer und Herbst, aber im Winter und fröhen Fröhjahr waren sie dormant. Das jahreszeitliche Verhalten der Keimfähigkeit in Abhängigkeit von Niederschlag und Bodentemperatur stimmte weitgehend mit den Ergebnissen eines In-vitro-Versuches von Van Hezewijk et al. (1993) öber die Wirkung einer Wärmevorbehandlung und Vorbehandlungszeit auf die Keimfähigkeit und die Ausprägung sekundärer Dormanz öberein. Bodenfeuchte und -temperatur können deshalb als die wichtigsten Faktoren för die Induktion und Aufhebung der Dormanz von Orobanche-crenata-Samen im Boden angesehen werden. Herkunft und Versuchsort hatten keinen erheblichen Einfluß auf die Ergebnisse.     

Outbreak of MAV-type barley yellow dwarf virus on wheat in the Garhwal Hills in India

A serious outbreak of barley yellow dwarf luteovirus (BYDV, MAV-type) on wheat in the Garhwal Hills, Central Himalayas, India is reported. This is the first conclusive evidence based on serology for the presence of MAV-BYDV in India.     

The response of commercial cucurbit rootstocks to (a)virulent isolates of Meloidogyne incognita

Journal of Plant Diseases and Protection - Meloidogyne incognita is the predominant root-knot nematode (RKN) species infecting cucurbit plants. It causes galling on the roots of plants and...     

Factors Affecting the Release of Ascospores of Anisogramma anomala

ABSTRACT Relationships between environmental factors and release of ascospores of Anisogramma anomala, the causal agent of eastern filbert blight, were examined in four European hazelnut (Corylus avellana) orchards during a 2-year period. In each orchard, Burkhard volumetric spore traps and automated weather-monitoring equipment were deployed for 12-week periods beginning at budbreak, when hazelnut becomes susceptible to infection. Ascospores of A. anomala were released when stromata on the surface of hazelnut branches were wet from rain but not from dew. Release of ascospores ceased after branch surfaces dried. The duration of free moisture on branch surfaces regulated the initiation and rate of ascospore release, but no significant effects of temperature, relative humidity, wind, or light on ascospore release were apparent. Most (>90%) ascospores were captured during precipitation events that exceeded 20 h in duration, which represented about 10% of the total precipitation events each season. Quantitative relationships between the hourly capture of A. anomala ascospores and hours since the beginning of a precipitation event were developed. With the onset of precipitation, the hourly rate of ascospore capture increased until the fifth hour of rain, remained relatively constant between the fifth and twelfth hours, and then declined gradually. During the 12-week spore-trapping periods, the likelihood and rates of ascospore release associated with precipitation were highest at budbreak and then declined through April and May until early June, when the reserve of ascospores in the perithecia was depleted. Large numbers of ascospores were captured in the volumetric spore traps, indicating that ascospores may be commonly dispersed long distances on air currents as well as locally by splash dispersal within the canopy, as reported previously. The results indicate that monitoring seasonal precipitation patterns may be useful for estimating the quantity and temporal distribution of airborne inoculum during the period that the host is susceptible to infection.     

Temperature-dependent development rates of <Emphasis Type="Italic">Bracon vulgaris,</Emphasis> a parasitoid of boll weevil

The duration of development of Bracon vulgaris Ashmead, parasitoid of the boll weevil Anthonomus grandis Boheman, was determined at nine constant temperatures between 18°C and 38°C. Nonlinear regression analysis was used to test the fit of temperature-dependent development rates to the Sharpe and DeMichele and Lactin et al. models. At the highest tested temperature (38°C) all the parasitoid eggs died before hatching and no evidence of development was observed. The high values of R ² for the models of Sharpe and DeMichele (0.8432 to 0.9834), and Lactin et al. (0.9071 to 0.9795) indicated that these models are suitable to estimate the development rate of B. vulgaris as a function of temperature. B. vulgaris showed tolerance to high temperature which is represented by the high value of H _H (change in enthalpy associated with high-temperature inactivation of the enzyme) for the prepupa stage of this insect obtained with the Sharpe and DeMichele model. According to that model, B. vulgaris exhibits thermal stress at 35.7°C, which indicates that maximum thermal stress estimated by this model was close to the real one.