Development and survival of the diamondback moth (Lepidoptera : Plutellidae) at constant and alternating temperatures

Survival and development time from egg to adult emergence of the diamondback moth, Plutella xylostella (L.), were determined at 19 constant and 14 alternating temperature regimes from 4 to 40degreesC. Plutella xylostella developed successfully front egg to adult emergence at constant temperatures from 8 to 32degreesC. At temperatures from 4 to 6degreesC or from 34 to 40degreesC, partial or complete development of individual stages or instars was possible, with third and fourth instars having the widest temperature limits. The insect developed successfully from egg to adult emergence under alternating regimes including temperatures as low as 4degreesC or as high as 38degreesC. The degree-day model, the logistic equation, and the Wang model were used to describe the relationships between temperature and development rate at both constant and alternating temperatures. The degree-day model described the relationships well from 10 to 30degreesC. The logistic equation and the Wang model fit the data well at temperatures 32degreesC. Under alternating regimes, all three models gave good simulations of development in the mid-temperature range, but only the logistic equation gave close simulations in the low temperature range, and none gave close or consistent simulations in the high temperature range. The distribution of development time was described satisfactorily by a Weibull function. These rate and time distribution functions provide tools for simulating population development of P. xylostella over a wide range of temperature conditions.

Trichogramma pretiosum parasitism of Pseudoplusia includens and Anticarsia gemmatalis eggs at different temperatures

Egg parasitism of Trichogramma pretiosum strain RV when presented with eggs of Anticarsia gemmatalis and Pseudoplusia includens was investigated at 18, 20, 22, 25, 28, 30 and 32 degrees C. The number of eggs parasitized per day decreased for both hosts as a function of the age of parasitoids, reaching 80% of lifetime parasitism more rapidly as temperature increased; on the 4th day at 32 degrees C and on the 12th day at 18 degrees C. The lifetime number of parasitized P. includens eggs achieved by the parasitoid maintained at 20 degrees C (44.95 +/- 3.94) differed from the results recorded at 32 degrees C (28.5 +/- 1.33). Differently, the lifetime number of A. gemmatalis parasitized eggs did not differ among the temperatures. When T. pretiosum reached 100% of lifetime parasitism, each adult female had parasitized from 28.5 +/- 1.33 to 44.95 +/- 3.94 and from 29.58 +/- 2.80 to 45.36 +/- 4.50 P. includens and A. gemmatalis eggs, respectively. Also, the longevity of these adult T. pretiosum females, for which P. includens or A. gemmatalis eggs were offered, was inversely correlated with temperature. Not only were the survival curves of those adult T. pretiosum females of type I when they were presented with eggs of A. gemmatalis but also with eggs of P. includens, i.e., there was an increase in the mortality rate with time as the temperature increased. In conclusion, T. pretiosum strain RV parasitism was impacted by temperature when on both host eggs; however, the parasitoid still exhibited high survival and, more importantly, high number of parasitized A. gemmatalis and P. includens eggs even at the extremes tested temperatures of 18 and 32 degrees C. Those results indicate that T. pretiosum strain RV might be well adapted to this studied temperature range and, thus, be potentially suitable for use in biological control programs of P. includens and A. gemmatalis in different geographical areas that fits in this range. It is important to emphasize the results here presented are from laboratory studies and, therefore, field trials still need to be carried out in the future with this strain in order to support the full development of the technology intend to use this egg parasitoid in soybean fields worldwide. (C) 2011 Elsevier Inc. All rights reserved.

Germinação de esporos de Polypodium pleopeltifolium: resultados preliminares

Polypodium pleopeltifolium is an epiphytic fern which occurs in cerrado vegetation of the State of São Paulo, Brazil. The species is light sensitive for germination but some spores germinate in the absence of light. Short treatments at 40 or 5ºC and alternating temperatures did not increase the germination in dark conditions. Germination was not affected by IAA but it was reduced by GA3, CEPA and ABA. Red light (short treatments) promoted germination.

Influence of light and temperature on seed germination of Cereus pernambucensis Lemaire (Cactaceae)

The objective of the present study was to evaluate the effects of light and temperature on germination of Cereus pernambucensis seeds, a species of columnar cactus native to Brazil and naturally incident in the restinga. Cereus pernambucensis seeds were incubated under different temperatures, from 5 to 45 °C, with 5 °C intervals, and under alternating temperatures of 15-20 °C, 15-30 °C, 20-25 °C, 20-30 °C, 20-35 °C, 25-30 °C, 25-35 °C, and 30-35 °C, both under continuous white light and dark. The seeds were also incubated in a gradient of phytochrome photoequilibrium at 25 °C. The highest percentage germination in this species was between 25 and 30 °C. The minimum temperature was between 15 and 20 °C and the maximum between 35 and 40 °C. Alternating temperatures did not affect the percentage of seed germination, but it did alter the rate and synchronization indexes. Seeds incubated in the dark did not germinate under any of the conditions tested, indicating that this species when cultivated present light sensitive seeds controlled by phytochrome. The seeds can tolerate a lot of shade conditions, germinating under very low fluence response of phytochrome.

Biological characteristics and thermal requirements of a Brazilian strain of the parasitoid Trichogramma pretiosum reared on eggs of Pseudoplusia includens and Anticarsia gemmatalis

A new strain of the parasitoid Trichogramma pretiosum, was collected in Rio Verde County, State of Goias, Central Brazil, and designated as T. pretiosum RV. This strain was then found to be the most effective one among several different strains of T. pretiosum tested in a parasitoid selection assay. Therefore, its biological characteristics and thermal requirements were studied, aiming at allowing its multiplication under controlled environmental conditions in the laboratory. The parasitoid was reared on eggs of Pseudoplusia includens and Anticarsia gemmatalis at different constant temperatures within an 18-32 degrees C temperature range. The number of annual generations of the parasitoid was also estimated at those temperatures. Results have shown that T. pretiosum RV developmental time, from egg to adult, was influenced by all temperatures tested within the range, varying from 6.8 to 20.3 days and 6.0 to 17.0 days on eggs of P. includens and A. gemmatalis, respectively. The emergence of T. pretiosum RV from eggs of A. gemmatalis was higher than 94% at all temperatures tested. When this variable was evaluated on eggs of P. includens, however, the figures were higher than that within the 18-30 degrees C range (more than 98%), and were also statistically higher than the emergence observed at 32 degrees C (90.2%). The sex ratio of the parasitoids emerged from eggs of A. gemmatalis decreased from 0.55 to 0.29 at 18-32 degrees C, respectively. However, for those emerged from eggs of P. includens, the sex ratio was similar (0.73, 0.72 and 0.71) at 20, 28 and 32 degrees C, respectively. The lower temperature threshold (Tb) and thermal constant (K) were 10.65 degrees C and 151.25 degree-days when the parasitoid was reared on eggs of P. includens; and 11.64 degrees C and 127.60 degree-days when reared on eggs of A. gemmatalis. The number of generations per month increased from 1.45 to 4.23 and from 1.49 to 4.79 when the parasitoid was reared on eggs of P. includens and A. gemmatalis, respectively, following the increases in the temperature. (C) 2009 Elsevier Inc. All rights reserved.

Biologia e exigências térmicas de cinco linhagens de Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) criadas em ovos de Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Artigos científicos defesa fitossanitária.

Seed germination of a rare neotropical canopy tree dormancy and the effects of abiotic factors

The purpose of this study was to examine if germination is a critical phase on Enterolobium glaziovii regeneration. Hence, the germinative response of E. glaziovii seeds was investigated in relation to some of the main environmental factors (temperature, light and water stress) to which its seeds are subjected in the forest, as well as its dormancy and the longevity of its burial seeds. According to our results, its seeds may be regarded as photoblastic neutral. They do not need alternating temperatures to germinate and can germinate under a broad range of water stress. However, only about 10% of E. glaziovii seeds remain viable after one year. In other words, the annual fruiting, instead seed longevity, seems to maintain the long-term seed availability of this species. Consequently, the seed longevity could be a critical phase of E. glaziovii germination.

TEMPERATURE AND SUBSTRATE INFLUENCES ON SEED GERMINATION AND SEEDLING FORMATION IN Callisthene fasciculata Mart. (VOCHYSIACEAE) IN THE LABORATORY1

ABSTRACTCallisthene fasciculata Mart. is a tree belonging to the Vochysiaceae family. Its wood is moderately heavy and resistant and used to make poles, beams, and other structures. The aim of this work was to evaluate seed germination and the initial growth of seedlings of C. fasciculata at different temperatures and in different substrates. Seeds were collected from fruits in the Pantanal de Miranda, Mato Grosso do Sul state, Brazil. In one experiment, the seeds were subjected to constant temperatures of 20, 25, 30 and 35 °C and to alternating temperatures of 20-30 and 25-35 °C (on paper substrate). In another experiment, the seeds were subjected to temperatures of 20 and 25 °C on three substrates (sand, vermiculite and between paper) in a germinator. The experiment had a randomized design, with four replicates of 25 seeds per treatment. The F-values obtained for germination indicated no significant effect of substrate or temperature on the final germination percentage. The analyses revealed no effect of a treatment interaction (temperature x substrate) on either germination or average germination time; however, a treatment interaction effect was observed on the germination speed index. The treatment combinations yielding the best performance were between paper substrate at 20 °C and sand substrate at 25 °C. There was a significant effect of the interaction between temperature and substrate on seedling growth, with increased root growth observed in the between paper substrate at 25 °C and increased aerial component growth in both sand at 20 °C and vermiculite at 25 °C. The between paper treatment at 25 °C yielded the greatest final seedling size. Between paper is the most recommended substrate for the production of seedlings due to its ease of handling and lower probability of contamination.

Effect of light and temperature on germination and early growth of Vochysia tucanorum Mart., Vochysiaceae, in cerrado and forest soil under different radiation levels

Vochysia tucanorum Mart. (Vochysiaceae) is a very widely distributed species in the cerrado and forests in Brazil, from the State of Bahia to Paraná. Its seed germination was analysed under eight treatments using different conditions of light and temperature. Up to 73 days, at least ca. 93% of the seeds germinated in all treatments, except under alternating temperatures of 35°/10°C (62%). Light enhanced germination, except under constant temperature of 25°C when seeds are not photoblastic. At this temperature, the highest percentage of germination was found. Initial vegetative growth was analysed by comparing the effects of shading, by means of different percentages of full daylight (100%, 45%, 10.6%, 4.8%), and soils from cerrado and forest. During 123 days, no mortality was recorded and cotyledons persisted on the seedlings of all treatments. In general, the seedlings of V. tucanorum were found to be more or less indifferent to the soil from cerrado or forest and shading seems to promote height increment. However, total dry mass was larger under a radiation of 45% full daylight and smaller under extreme conditions (100% or 4.8% full daylight).

Germination of seeds of tropical pioneer species under controlled and natural conditions

Seed germination of eight tropical pioneer species (Cecropia hololeuca, C. pachystachya, C. glazioui, Solanum gracillimum, S. granuloso-leprosum, S. tabacifolium, Croton floribundus and Miconia chamissois) was studied. In controlled conditions, alternating temperatures were tested from 5 to 25 °C. Low Red:Far Red ratios (R:FR) were also examined. In the field, germination was evaluated in gaps and under the canopy. With the exception of Croton floribundus, all other species were photoblastic in that higher germination percentages were found under light conditions (S. tabacifolium behaved as a negative photoblastic species at some temperatures). No relationship was found between germination percentage and alternating temperature. Germination was markedly reduced under low R:FR ratios. Alternating temperature is not the main factor affecting field germination. The low R:FR ratio under the canopy seems to be the crucial factor affecting germination.

Germination and morphological characterization of the fruits, seeds, and seedlings of Pilosocereus gounellei

The present work examined the germination and morphology of the fruits and seeds of the cactus Pilosocereus gounellei (xique-xique) and describeb the different stages of seedling growth. Germination tests examined the effects of combinations of two illumination regimes (a 12 hour photoperiod and total darkness) and three temperature regimes (25, 30, and 20-30 ºC) on the seeds of this species. Germination counts were made daily until the 16th day after sowing and the germination percentage and velocity index, and average germination time were evaluated. Descriptions of seed morphology considered both their external and internal aspects. The processes of germination and seedling growth were evaluated during 150 days and eight developmental stages were identified based on morphological changes. The fruits of the xique-xique cactus are 40.67 ± 4.40 mm long and 48.09 ± 3.23 mm in diameter, weigh 53.85 ± 10.03 g, and contain 3713 ± 689.50 seeds. Alternating temperatures of 20-30 ºC together with a photoperiod of 12 hours of light resulted in the highest seed germination rate. The seeds are positively photoblastic and germination is epigeal and fanerocotyledonary. Seedling growth is slow, but at 150 days after sowing the plants had developed epicotyls, large numbers of thorns, and the whole plant averaged 59.56 mm in height.

Physical purity and germination of sugarcane seeds (caryopses) (Saccharum spp.)

Plant breeding is generally done through sexual reproduction even when the species is propagated asexually for commercial exploitation, as for example, in sugarcane. Therefore, the development of procedures to evaluate sugarcane seed viability is important for plant breeding programs. The objective of this research was to develop a methodology for analyzing the viability of sugarcane seeds (Saccharum spp.). Three crosses were used, two biparental crosses and one polycross. For the germination test study, two substrates (paper and sand) and three constant incubation temperatures (25 ºC, 30 ºC and 35 ºC), in the presence of constant light and also an alternating temperatures (20-30 ºC), with 8 hours light (30 ºC) and 16 hours darkness (20 ºC), were studied. Seedlings were evaluated every five days. The results demonstrated that temperature affected sugarcane seed germination with the most favorable conditions being the alternating temperature (20-30 ºC) and the constant temperature of 30 ºC on a paper substrate.

Seed dormancy and germination of Ficus lundellii and tropical forest restoration

We investigated seed dormancy and germination in Ficus lundellii Standl. (Moraceae), a native species of Mexico's Los Tuxtlas tropical rain forest. In an 8-h photoperiod at an alternating diurnal (16/8 h) temperature of 20/30 degrees C, germination was essentially complete (96%) within 28 days, whereas in darkness, all seeds remained dormant. Neither potassium nitrate (0.05-0.2%) applied continuously nor gibberellic acid applied either continuously (10-200 ppm) or as a 24 hour pretreatment (2000 ppm) induced germination in the dark. Germination in the light was not reduced by a 24-h hydrochloric acid (0.1-1%) pretreatment, but it was reduced both by a 24-h pretreatment with either H2O2 (0. 1-5 M) or 5% HCl, or by more than 5 days of storage at 40 degrees C (4.5% seed water content). In a study with a 2-dimensional temperature gradient plate, seeds germinated fully and rapidly in the light at a constant temperature of 30 degrees C, and fully but less rapidly in the light at alternating temperatures with low amplitudes (< 12 degrees C) about the optimal constant temperature. The base, optimal and ceiling temperatures for rate of germination were estimated as 13.8, 30.1 and 41.1 degrees C, respectively. In all temperature regimes, light was essential for the germination of F lundellii seeds.

Factors influencing the germination of myrtle (Lagerstroemia speciosa (L.) Pers. and L-floribunda Jack) seeds

Gibberellic acid and potassium nitrate did not promote the germination of myrtle seeds when tested at 20/30degreesC (16/8h). Germination was promoted considerably by alternating temperatures. The results of an investigation on a two-dimensional temperature gradient plate showed that myrtle seeds germinated most rapidly (within 14 days) and fully (all viable seeds) at 35/22.5degreesC (16/8 h) and similar regimes. Tests on five seed lots of Lagerstroemia speciosa and L. floribunda showed the efficacy of the alternating temperature regime of 35/20degreesC (16/8 h) in promoting germination. Thus we recommend myrtle seeds be tested for germination in this regime for 28 days.

Superação de dormência de sementes de Piptadenia moniliformis Benth

O angico-de-bezerro (Piptadenia moniliformis Benth.) é uma espécie arbórea melífera, de crescimento rápido, característica da caatinga do nordeste brasileiro, onde é muito abundante e com dispersão contígua e irregular. Seus ramos finos, junto com as folhas, servem como alimento para animais. Como suas sementes apresentam dormência por impermeabilidade do tegumento à água, objetivou-se neste trabalho avaliar a eficiência de tratamentos pré-germinativos para superar a dormência de suas sementes visando maximizar e uniformizar o processo de germinação. Foram estudados 28 tratamentos pré-germinativos: imersão em água a 70, 80, 90 ºC e fervente por 1, 2, 3, 4 e 5 minutos e imersão em ácido sulfúrico concentrado por 1, 5, 10, 15, 20, 25 e 30 minutos, além da testemunha. A semeadura foi realizada sobre papel em temperatura alternada de 20-30 ºC, utilizando-se quatro repetições de 25 sementes. Foram avaliadas as porcentagens de germinação das sementes considerando a protrusão da raiz primária, de plântulas normais e de sementes duras e o índice de velocidade de germinação. O delineamento experimental utilizado foi o inteiramente casualizado e as médias comparadas pelo teste de Scott-Knott a 5% de probabilidade. Os tratamentos de imersão em água, independentemente da temperatura e do período de imersão, aumentaram a porcentagem de germinação das sementes, comparativamente ao tratamento controle, mas foram menos eficientes que os tratamentos em ácido sulfúrico nos maiores períodos de imersão. Desta forma, a imersão por 20, 25 e 30 minutos em ácido sulfúrico é recomendada para a superação da dormência de sementes de Piptadenia moniliformis Benth.