Resistant structures in the entomogenous hyphomycete, Nomuraea rileyi: an ultrastructural study

1982 ◽  
Vol 60 (8) ◽  
pp. 1569-1576 ◽  
Author(s):  
J. C. Pendland

Three types of resistant or resting structures were found to occur in the entomogenous hyphomycete Nomuraea rileyi when unfavorable conditions (e.g., low humidity) inhibited conidiogenesis. Intrahyphal hyphae, which are regenerative hyphae within deteriorating parent hyphae, were observed in both the disintegrating larval tissue of Anticarsia gemmatalis and the extracuticular fungal mat. Thick-walled hyphae and chlamydospores were found in the external mat, and lipid-filled, thin-walled hyphae were prevalent in the larval tissue. Chlamydospores formed as apical swellings of thick-walled hyphae. Resistant structures remained viable for at least 12 weeks. Upon rehydration, cells resumed metabolic activity and after several days, conidiophores and conidia were produced. Verification of the existence of such structures provides an explanation as to how the fungus survives in the field under adverse environmental conditions.

Author(s):  
L. V. Tashmatova ◽  
О. V. Mantseva ◽  
N. V. Gorbacheva

The basic moments of a process of obtaining apple tetraploids as donors of diploid gametes for apple breeding with polyploidy using are demonstrated. In industrial terms, triploids are of the greatest importance. The manifested effect of heterosis leads to the improvement of many characteristics - higher resistance to diseases, pests and adverse environmental conditions, greater autogamy than in diploids, less pronounced periodicity of fruiting, larger fruits and a convenient crown for harvesting. Triploids are developed as a result of crosses 2n × 3n or 2n × 4n. Tetraploids are necessary for more successful apple breeding with polyploidy using. For industry they are not of great importance but they are of interest as donors of diploid non-reduced gametes and allow to make the selection process more directional. One of the methods of experimental polyploidy is the induction of polyploids using mutagenes. The germs were treated with colchicines at concentrations 0.1% - 0.4% during 24 and 48 hours. According to the morphology the obtained plants were divided into five groups. Colchicine concentrations 0.3% and 0.4% during 48 hours of the treatment had a disastrous impact on the development of germs. As a result of the cytological analysis, tetraploids and chimeras were revealed, which were obtained from the seeds from the open pollination of Orlik and Svezhest (treatment variants – 0,1% colchicines solution and 24 and 48 hours of exposition), as well as from the seeds obtained as a result of the Svezhest × Bolotovskoye crossing. Tetraploids had a normal growth but they differed in large leaves, while chimeras were of low size with normal leaves and internodes.


2008 ◽  
Author(s):  
◽  
Vanesa Eva Dikgolz

En los últimos años el cultivo de soja se ha convertido en uno de los más importantes de nuestro país. Existe una gran diversidad de insectos fitófagos que atacan a los cultivos de soja y bajo determinadas condiciones pueden alcanzar niveles de densidad altos, convirtiéndose en plagas. Entre las principales especies de lépidopteros defoliadores considerados plaga se encuentran: la “oruga de las leguminosas” Anticarsia gemmatalis (Hubner), la “oruga medidora” Rachiplusia nu Guenneé, la “oruga de la alfalfa” Colias lesbias (Fabricius), la “oruga militar tardía” Spodoptera frugiperda (J. E. Smith), orugas del género Helicoverpa y la “gata peluda norteamericana” Spilosoma virginica (Fabricius). De menor importancia son la “oruguita de la verdolaga” Loxostege bifidalis Fabricius, el barrenador menor del tallo” Elasmopalpus lignosellus Séller, orugas del género Agrotis, Eulia loxonepes (Meyrick) y Prodenia ornithogalli (Guenneé). Estos insectos provocan daños en las hojas de la plantas, sobre todo antes de la formación de frutos. Los enemigos naturales de estos insectos están conformados por depredadores, parasitoides y patógenos. Entre los patógenos se destacan los hongos, los cuales se encuentran infectando gran diversidad de insectos y hábitats. Estos organismos son una herramienta útil dentro del manejo integrado de plagas. El principal hongo entomopatógeno relacionado con larvas de lépidopteros defoliadores, en particular de la Familia Noctuidae, es Nomuraea rileyi (Farlow) Samson (Ascomycota: Sordariomycetes: Hypocreales). Hasta el presente han sido realizados varios estudios a nivel mundial acerca del hongo N. rileyi, sobre su virulencia, rango hospedador, citología e inmunidad. En nuestro país se ha encontrado una importante acción del hongo N. rileyi en el control natural de lepidópteros defoliadores de soja, cuando se presentaron condiciones de humedad favorables para su dispersión, llegando a observarse un control del 60 al 90 % de las poblaciones de A. gemmatalis en la provincia de Santa Fe, siendo citada previamente la existencia de epizootias y control natural de esta especie plaga en la provincia de Córdoba. Hasta el presente hay pocos estudios de caracterización de poblaciones de N.rileyi de nuestro país y sobre todo de la región pampeana donde se concentra el 83,68 % del área sojera. Tampoco se han realizado hasta el momento estudios sobre el ciclo parasexual en este hongo por lo que resulta de importancia abordar estas temáticas. El objetivo de este trabajo fue evaluar las diferencias morfológicas, y genéticas de aislamientos nativos del hongo Nomuraea rileyi y evaluar su patogenicidad mediante bioensayos, así como también intentar determinar la existencia de un ciclo parasexual.


1975 ◽  
Vol 19 (3) ◽  
pp. 301-304
Author(s):  
Ann E. Martin

The present study was conducted to investigate the effects of environmental conditions on visual workload. The environmental variables used were temperature, studied at levels of 45°F., WBGT, and 95°F., WBGT; and noise, studied at 83 dBA intermittent noise and 93 dBA continuous noise. Workload was defined as the amount of attention demanded from an operator as measured by performance decrement on a secondary task while performing a primary and secondary task simultaneously. The secondary task was reading random numbers, and the primary task was reading word lists. Significant differences (p<.05) were found between the control condition and all experimental conditions. The low temperature and high temperature-continuous noise conditions were significantly different from the other conditions. Noise and temperature were found to significantly increase workload (p<05).


2018 ◽  
Vol 2 ◽  
pp. 247054701880829 ◽  
Author(s):  
Keila Rebello ◽  
Luciana M. Moura ◽  
Walter H. L. Pinaya ◽  
Luis A. Rohde ◽  
João R. Sato

Default mode network (DMN) plays a central role in cognition and brain disorders. It has been shown that adverse environmental conditions impact neurodevelopment, but how these conditions impact in DMN maturation is still poorly understood. This article reviews representative neuroimaging functional studies addressing the interactions between DMN development and environmental factors, focusing on early life adversities, a critical period for brain changes. Studies focused on this period of life offer a special challenge: to disentangle the neurodevelopmental connectivity changes from those related to environmental conditions. We first summarized the literature on DMN maturation, providing an overview of both typical and atypical development patterns in childhood and early adolescence. Afterward, we focused on DMN changes associated with chronic exposure to environmental adversities during childhood. This summary suggests that changes in DMN development could be a potential allostatic neural feature associated with an embodiment of environmental circumstances. Finally, we discuss about some key methodological issues that should be considered in paradigms addressing environmental adversities and open questions for future investigations.


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