Americana Var Research Articles

Análisis florístico de un bosque de Abies y el bosque mesófilo de montaña adyacente en Juanacatlán, Mascota, Jalisco, México

Se presenta el análisis florístico de un bosque de Abies y del bosque mesófilo de montaña adyacente, localizados al occidente de Jalisco, México. Se obtuvo una lista de plantas vasculares constituida por 80 familias, 195 géneros y 290 especies, con un índice de diversidad florística de 210.33 especies/km2, el cual es elevado al compararlo con el obtenido en otras áreas boscosas similares. Las familias más diversas por cantidad de especies son Asteraceae (46), Fabaceae (22) y Orchidaceae (18). La flora de la comunidad estudiada es similar a lo descrito para los bosques de oyamel en Nueva Galicia y a los bosques mesófilos de la Faja Volcánica Transmexicana. Cinco especies recolectadas en el área se encuentran bajo alguna categoría de riesgo dentro de la Norma Oficial Mexicana NOM-059-SEMARNAT-2010 ( Abies flinckii , Comarostaphylis discolor subsp. discolor , Juglans major var. glabrata , Ostrya virginiana y Tilia americana var. mexicana ). Los rodales de Abies flinckii son propuestos como área de conservación dado su carácter relictual.

Seed germination of Agave species as influenced by substrate water potential.

BackgroundPlants of Agave spp. perform Crassulacean acid metabolism (CAM) and are highly drought-tolerant, but little is known concerning seed germination under low water availability. The aim of this study was to assess the effect of substrate water potential (ΨW) on seed germination and contrast hydrotime parameters of seven valuable and commercially-important Agave species from different geographical distributions and climatic regions of Mexico. Our hypothesis was that seed germination of Agave species is not affected by low water availability independently of seed biomass and the climate of their distribution area.ResultsSeed germination (at 25°C and in the dark) between 85 and 100% for all species occurred within 80–180 h at -0.03 MPa and 250–430 h at -1.0 MPa. Seed germination at -1.5 MPa declined to less than 50% (p < 0.05) for A. asperrima and A. cupreata but did not change significantly for A. americana var. marginata, A. lechuguilla and A. striata, although they showed the lowest mean base water potential (-2.01 to -2.64 MPa). Seed germination of 40% Agave species, from arid and semi-arid climates in this study, was not affected by the lower ΨW.ConclusionGermination of seeds of Agave species is moderately affected by low water availability, is partially dependent of their ecological distribution, and is independent of seed mass.

Respuestas bioquímico-fisiológicas de especies de Agave a la restricción de humedad

En México se encuentra la mayor riqueza de especies de Agave , distribuidas en ambientes diversos. Para contribuir con el conocimiento en torno a las formas de tolerar las restricciones de humedad se evaluó el efecto de dos potenciales de agua (?) en el sustrato (-0.7 y -3.5 MPa) durante 14 meses, en invernadero, sobre el crecimiento, la distribución de biomasa, el grosor foliar y el contenido de prolina en dos especies del subgénero Littaea ( A. lechuguilla y A. striata ) y seis del subgénero Agave ( A. americana var. marginata , A. angustifolia subsp. tequilana , A. asperrima , A. cupreata , A. duranguesis y A. salmiana ), reconocidas por su importancia económica y ecológica. La menor disponibilidad de humedad inhibió la acumulación de biomasa en las ocho especies; no obstante, el crecimiento (número de hojas y cobertura de planta) pudo mantenerse en aquellas más adaptadas a la aridez o con límites de tolerancia ambiental más amplios como A. angustifolia subsp. tequilana , A. duranguensis , A. lechuguilla y A. salmiana . El ? limitante promovió mayor asignación de biomasa a la raíz a expensas de la de las hojas en algunas especies y la duplicación de la prolina radical en las especies del subgénero Agave . La modificación de la distribución de la biomasa y el incremento del contenido de prolina, como formas de tolerar la restricción de humedad, sólo se presentaron en algunas de las especies estudiadas. En contraste, el mantenimiento del grosor de la hoja (indicador de turgencia) fue una respuesta general al ? limitante. Las especies de Agave presentan respuestas fisiológicas y bioquímicas variadas, que reflejan su amplia tolerancia a condiciones ambientales adversas y explican la distribución ecológica amplia del género.

Research on Characteristics of Plant Electrical Signal under High Voltage Pulse Stimulation

In order to further understand the Agave americana var. marginata electrical signals in High Voltage Pulse Stimulation conditions, a new method is provided in this paper by using wavelet soft threshold noise reduction and the power spectrum analysis. The results show that the level `of its electrical distribution in uV. The plant electrical signal amplitude arithmetic mean increases with the increase of pulse stimulation signal but for a little effect on the natural frequency of the plant, its frequency is mainly distributed in the 0.07813 Hz ~0.1953 Hz.

Anticonvulsant and antioxidant effects of Tilia americana var. mexicana and flavonoids constituents in the pentylenetetrazole-induced seizures.

Tilia genus is commonly used around the world for its central nervous system properties; it is prepared as tea and used as tranquilizing, anticonvulsant, and analgesic. In this study, anticonvulsant activity of the Tilia americana var. mexicana inflorescences and leaves was investigated by evaluating organic and aqueous extracts (100, 300, and 600 mg/kg, i.p.) and some flavonoids in the pentylenetetrazole-induced seizures in mice. Moreover, antioxidant effect of these extracts and flavonoids was examined in an in vitro study by using spectrophotometric technique. Significant activity was observed in the methanol extract from inflorescences. An HPLC analysis of the methanol extract from inflorescences and leaves of Tilia allowed demonstrating the respective presence of some partial responsible flavonoid constituents: quercetin (20.09 ± 1.20 μg/mg and 3.39 ± 0.10 μg/mg), rutin (3.52 ± 0.21 μg/mg and 8.94 ± 0.45 μg/mg), and isoquercitrin (1.74 ± 0.01 μg/mg and 1.24 ± 0.13 μg/mg). In addition, significant but different antioxidant properties were obtained among the flavonoids and the extracts investigated. Our results provide evidence of the anticonvulsant activity of Tilia reinforcing its utility for central nervous system diseases whose mechanism of action might involve partial antioxidant effects due to the presence of flavonoids.

Flora y vegetación del cerro El Águila, Michoacán, México

Con base en trabajo de campo realizado entre 2007 y 2010 en el cerro El Águila, la montaña más alta localizada en los municipios de Lagunillas y Morelia, Michoacán, se registraron 105 familias, 343 géneros, 633 especies y 42 taxa infraespecíficos. Las familias más diversas fueron Asteraceae (153 especies), Fabaceae (53) y Poaceae (34). Los géneros con mayor riqueza de especies fueron Salvia (17), Stevia (12) y Verbesina (11). Las especies de hierbas conforman el 72.4% del total de la flora. Se describe la fisonomía y las especies más abundantes de cinco tipos de vegetación. Los bosques de Pinus-Quercus y Quercus son los tipos de vegetación con mayor número de especies (286 y 383, respectivamente). De acuerdo con la NOM-059-ECOL-2010 se consideran cinco Especies Sujetas a Protección Especial ( Cedrela dugesii, Cupressus lusitanica, Dahlia scapigera, Gentiana spathacea y Laelia speciosa ) y una en Peligro de Extinción ( Tilia americana var. mexicana ). Se enfatiza la importancia de coordinar esfuerzos hacia la conservación del cerro El Águila, cuya flora y vegetación se encuentran amenazadas por los cambios de uso de suelo.

Analysis of expressed sequence tags (ESTs) from avocado seed (Persea americana var. drymifolia) reveals abundant expression of the gene encoding the antimicrobial peptide snakin

Avocado is one of the most important fruits in the world. Avocado "native mexicano" (Persea americana var. drymifolia) seeds are widely used in the propagation of this plant and are the primary source of rootstocks globally for a variety of avocado cultivars, such as the Hass avocado. Here, we report the isolation of 5005 ESTs from the 5' ends of P.americana var. drymifolia seed cDNA clones representing 1584 possible unigenes. These avocado seed ESTs were compared with the avocado flower EST library, and we detected several genes that are expressed either in both tissues or only in the seed. The snakin gene, which encodes an element of the innate immune response in plants, was one of those most frequently found among the seed ESTs, and this suggests that it is abundantly expressed in the avocado seed. We expressed the snakin gene in a heterologous system, namely the bovine endothelial cell line BVE-E6E7. Conditioned media from transfected BVE-E6E7 cells showed antimicrobial activity against strains of Escherichia coli and Staphylococcus aureus. This is the first study of the function of the snakin gene in plant seed tissue, and our observations suggest that this gene might play a protective role in the avocado seed.

Plant diversity of Gadchiroli district of Maharashtra, India: a brief survey

A qualitative survey was carried out during 2005- 2010 of all indigenous and naturalized plants of Gadchiroli district, Maharashtra, India. There are 237 species belonging to 184 genera and 73 families which are listed in this paper. Out of 73 families listed, 63 belong to dicotyledonae and 10 belong to monocotyledonae. Dominant families were Fabaceae (21 genera), Acanthaceae (12 genera) followed by Asteracece (9 genera). The nomenclature system followed in this paper is up to date. Three plants (1.63%) listed in this paper come under Vulnerable (VU) and two (1.09%) comes under Lower Risk (LR) categories. Eleven genera (5.98%) are reported to be endemic to Maharashtra state of India. Only one plant species (Agave americana var. americana) was not native of the area and is cultivated. Voucher specimens of the representative plants are submitted at Medicinal Plants Conservation Center (MPCC), Pune, Maharashtra, and the voucher number is provided along with names of plants.

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF AVOCADO (Persea americana Mill.): A REVIEW

SUMMARYThe results of research on the water relations and irrigation need of avocado are collated and reviewed in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information is given on the centre of origin (Mexico and Central America) and the three distinct ecological areas where avocados are grown commercially: (1) Cool, semi-arid climates with winter-dominant rainfall (e.g. Southern California, Chile, Israel); (2) Humid, subtropical climates with summer-dominant rainfall (e.g. eastern Australia, Mexico, South Africa); and (3) Tropical or semi-tropical climates also with summer-dominant rainfall (e.g. Brazil, Florida and Indonesia). Most of the research reported has been done in Australia, California, Israel and South Africa. There are three ecological races that are given varietal status within the species: Persea americana var. drymifolia (Mexican race), P. americana var. guatemalensis (Guatemalan race) and P. americana var. americana (Antillean, West Indian or Lowland race). Interracial crossing has taken place. This paper summarises the effects of water deficits on the development processes of the crop and then reviews plant–water relations, crop water requirements, water productivity and irrigation systems. Shoot growth in mature trees is synchronised into flushes. Flower initiation occurs in the autumn, with flowering in late winter and spring. Flowers form on the ends of the branches. A large heavily flowering tree may have over a million flowers, but only produce 200–300 fruits. Fruit load adjustment occurs by shedding during the first three to four weeks after fruit set and again in early summer. Water deficits during critical stages of fruit ontogeny have been linked to fruit disorders such as ring-neck. Reproductive growth is very resistant to water stress (compared with vegetative growth). Avocado is conventionally considered to be shallow rooted, although roots extend to depths greater than 1.5 m. The majority of feeder roots are found in the top 0.60 m of soil and root extension can continue throughout the year. Leaves develop a waxy cuticle on both surfaces, which is interrupted by stomata on the abaxial surface (350–510 mm−2), many of which are blocked by wax. Stomata are also present on the sepals and petals at low densities (and on young fruit). During flowering, the canopy surface area available for water loss is considerably increased. Stomatal closure is an early indicator of water stress, which together with associated changes in leaf anatomy, restricts CO2 diffusion. There have only been a few attempts to measure the actual water use of avocado trees. In Mediterranean-type climates, peak rates of water use (in summer) appear to be between 3 and 5 mm d−1. For mature trees, the crop coefficient (Kc) is usually within the range 0.4–0.6. The best estimate of water productivity is between 1 and 2 kg fruit m−3. Soil flooding and the resultant reduction in oxygen level can damage roots even in the absence of root rot. Avocado is particularly sensitive to salinity, notably that caused by chloride ions. Rootstocks vary in their sensitivity. Both drip and under-tree microsprinklers have been/are successfully used to irrigate avocado trees. Mulching of young trees is a recommended water conservation measure and has other benefits. A large proportion of the research reviewed has been published in the ‘grey’ literature as conference papers and annual reports. Sometimes, this is at the expense of reporting the science on which the recommendations are based in peer-reviewed papers. The pressures on irrigators to improve water productivity are considered.

Analysis of Sesquiterpene Distributions in the Leaves, Branches, and Trunks of Avocado (&amp;lt;i&amp;gt;Persea americana&amp;lt;/i&amp;gt; Mill.)

Avocado is a commercially valuable fruit crop cultivated in tropical and subtropical climates throughout the world. Taxonomists recognize three horticultural races of avocado, consisting of Mexican (Persea americana var. drymifolia), Guatemalan (P. americana var. guatemalensis), and West Indian (P. americana var. americana) varieties. Published research that attempted to differentiate among the horticultural races by using leaf chemistry found that sesquiterpene content was only useful for discrimination of pure Mexican from Guatemalan and West Indian, but not to distinguish between Guatemalan and West Indian races. This study presents a sampling method for analysis of sesquiterpenes from avocado leaf, branch and trunk samples. Our results indicate that sesquiterpene content from leaves and small diameter branches (2.5 cm) was highly variable; however, sesquiterpenes were much less variable within wood from larger diameter branches and trunk samples, providing information representative of avocado varietal differences. In addition to chemotaxonomic applications, information on sesquiterpene content of avocado wood is needed for identification of host-based attractants for a new avocado pest, the redbay ambrosia beetle (Xyleborus glabratus). This insect vectors a fungal pathogen that causes laurel wilt, a lethal vascular disease that currently threatens avocado production in south Florida, USA. Females of X. glabratus identify appropriate host trees based on emissions of terpenoids, particularly α-copaene. Our results are discussed in terms of how proximo-distal distributions of sesquiterpenes may function as host-location cues by this invasive wood-boring pest.

Flavonol glycosides found in hydroethanolic extracts from Tilia cordata, a species utilized as anxiolytics

Tilia species, among which is Tilia cordata Mill. (Tiliaceae), have been used in folk medicine as anxiolytic. The hydroethanolic extract was analyzed by using liquid chromatography with mass spectrometry HPLC-DAD-ESI-MS/MS in negative ion mode, and its chemical composition was compared to flavonoids reported as anxiolytics. The major flavonoids found were: quercetin-3,7-di-O-rhamnoside, kaempferol-3,7-di-O-rhamnoside and kaempferol 3-O-(6"-p-coumaroyl glucoside) or tiliroside. The anxiolytic activity of the genus Tilia has been attributed to the presence of quercetin and kaempferol derivatives, while the anxiolytic activity of T. americana var. Mexicana was attributed to tiliroside, which was also found among the major constituents of this species.

A further species of Agave L., A. salmiana Otto ex Salm-Dyck (subsp. salmiana) var. salmiana (Agavaceae), naturalised in the Eastern Cape Province of South Africa

Agave salmiana Otto ex Salm-Dyck subsp. salmiana var. salmiana, the typical variety of this large-growing Mexican species, is here recorded as having become established in South Africa's Eastern Cape Province. A description and key that can be used to distinguish it from A. americana L. subsp. americana var. americana and A. americana subsp. americana var. expansa (Jacobi) Gentry, both of which are large-growing and more widely naturalised in southern Africa, are provided. A comprehensive chronological synonymy summarises the complex nomenclatural and taxonomic histories of the species.

Diarrhena obovatain the Potomac River Watershed: A New Invader?

Diarrhena obovata (Gleason) Brandenburg is a woodland grass primarily of the central United States in the Mississippi River drainage (Brandenburg et al. 1991). Isolated occurrences of D. obovata in the Appalachian and Piedmont regions of the mid-Atlantic states have been found in the last several decades, and the species is or has been considered to be a rare native species in Pennsylvania (Rhoads and Klein 1993); in West Virginia, Virginia, and New York (NatureServe 2011); and (as Diarrhena americana Beauv.) in Maryland (Maryland Natural Heritage Program 2003). The taxonomic concept of D. obovata was first recognized by Gleason (1952a, 1952b) as Diarrhena americana Beauv. var. obovata Gleason. Brandenburg et al. (1991) elevated var. obovata to species rank by proposing the new combination D. obovata, after discovering consistent morphological differences between D. americana var. americana and var. obovata that corresponded to largely allopatric ranges for the two taxa. Most recent floristic authors (e.g., Barkworth et al. 2007, Brandenburg 2007, Rhoads and Block 2007, Weakley 2011) follow Brandenburg et al. (1991) in recognizing D. obovata as a distinct species. D. americana (in the narrow sense of Brandenburg et al. [1991], and as is used in this paper, unless otherwise noted) occupies mostly the Ohio River basin in the central Appalachians and interior plateaus, with a disjunct distribution in the Ozark region. Although it overlaps the range of D. americana, D. obovata occurs primarily in the central Mississippi and lower Missouri River drainages of the upper midwestern United States (Brandenburg et al. 1991, Barkworth et al. 2007, Brandenberg 2007). The former treatment of D. obovata under D. americana (in the broad sense) occasionally has created ambiguity about which one of the two taxa has been represented when D. americana has been recorded in literature and databases. D. obovata apparently was first reported in Maryland, as D. americana (in the broad sense) without note of variety, by Rodney Bartgis in 1988 (Maryland Natural Heritage Program, unpublished data), several years prior to the recognition of D. obovata as a species by Brandenberg et al. (1991). At the time of Bartgis’ report, Brown and Brown (1984) had listed D. americana as potentially occurring [only] for Maryland. Shortly after this discovery, Bartgis showed me this occurrence along the Potomac River near Plummers Island in Montgomery County. In ensuing years, additional records of Diarrhena, reported as D. americana (in the broad sense), were made from along the Potomac and the Chesapeake and Ohio (CO Wiegand and Becker 1995). In 1995, I reported a colony of D. americana (in the broad sense) from along the CO Accepted March 24, 2012. DOI: 10.2179/11-044

Effect of root competition and shade on survival and growth of nine woody plant taxa within a pecan [Carya illinoinensis (Wangenh.) C. Koch] alley cropping system

Suitability for production of woody floral stems in a pecan [Carya illinoinensis (Wangenh.) C. Koch] alley cropping was determined for nine shrub species in northwest Florida. Treatments included partial shade without root competition, partial shade with root competition, and full sun. Only three species had high rates of survival for all treatments throughout both years of the study: Callicarpa americana L. (American beautyberry), C. americana var. Lactea (white American beautyberry), and Crataegus marshallii Eggl. (parsley haw). For C. americana, plant growth index increased through time and was similar among the three treatments, indicating that this species grew equally well in sun or shade irrespective of root competition from the tree crop. C. americana var. Lactea had similarly high rates of survival and grew largest in partial shade without root competition (81.7 cm) compared to partial shade with root competition (67.2 cm) and full sun (57.0 cm). C. marshallii had 100 % survival in partial shade without root competition, with one mortality in partial shade with root competition (91.7 % survival) and one in full sun (91.7 % survival). Growth index did not increase over time and was similar among all three treatments. Other species tested had low rates of survival in all treatments throughout both years of the study and included: Ilex glabra L. (inkberry), Ilex myrtifolia Walt. (myrtle-leaf holly), Hydrangea paniculata Seibold var. ‘Tardiva’ (panicle hydrangea), Hydrangea quercifolia Bart. (oakleaf hydrangea), Lyonia lucida (Lam.) K. Koch, and Salix matsudana Koidz. F. tortuosa Rehd. (corkscrew willow). No species produced sufficient flowers, fruits or ornamental stems during this establishment period to allow a florist evaluation of the stems for use as woody floral stems.

Agave americana L. (subsp. americana) var. expansa (Jacobi) Gentry (Agavaceae) naturalized in South Africa

The Mexican Agave americana L. subsp. americana var. expansa (Jacobi) Gentry, a distinctive variety of the widely cultivated, blue-leaved century plant, is here recorded as having become established in South Africa. A description and key that can be used to distinguish it from A. americana (subsp. americana) var. americana, which is more widely naturalized in South and southern Africa, is provided.

Heptadecanols from the leaves of Persea americana var. americana

From the leaves of Persea americana var. americana, eleven heptadecanol derivatives were identified. Their structures were elucidated on the basis of spectroscopic analyses. The absolute configurations were determined by chemical reaction, NOESY experiment and further comparison of the optical rotation value with the literature value. Additionally, the ratios of the contents of six heptadecanol derivatives in leaves, immature fruits, mature fruits and seeds of P. americana were estimated by LC–MS in multiple reaction monitoring (MRM) mode.

Seed germination temperatures of eight Mexican Agave species with economic importance

AbstractThe genetic diversity of Agave plants is threatened by clonal commercial reproduction and climatic change. Sexual reproduction is uncommon and research on seed germination is scarce. The present study evaluated the seed germination of Agave lechuguilla, Agave striata, Agave americana var. marginata, Agave asperrima, Agave cupreata, Agave duranguesis, Agave angustifolia ssp. tequilana and Agave salmiana at constant temperatures (10, 15, 20, 25, 30, 35 and 40°C). Initial imbibition (after the first 12 h) was significantly variable among species, positively correlated with seed weight (r = 0.6560, P &lt; 0.001) and increased with temperature (from 35% at 10°C to 66% at 40°C). Temperature affected maximum imbibition (83–150%) for A. asperrima, A. lechuguilla, A. salmiana and A. striata; other species averaged 110%. Most germination kinetics best fitted a logistic model, whereas only a few treatments fit a Weibull model. The time to germination onset diminished (P &lt; 0.05) from 125–173 h at 15°C to 68–84 h at 25°C, and then ascended to 84–196 h at 35°C. The mean germination rate and seed germination percentage after 312 h peaked at 25°C (0.50–0.95% seeds/h and 85–99%, respectively) and fell (P &lt; 0.05) to near zero at 10 and 40°C. Temperatures of 10, 35 and 40°C were partially lethal to A. asperrima, A. duranguensis and A. salmiana seeds. The time to germination onset, seed germination percentage after 312 h and mean germination rate are best described by a Gaussian distribution, with its optimum at approximately 25°C. Thus, optimum temperatures are related to the ecological characteristics of each species area.

Reduction of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes with electrolyzed oxidizing water on inoculated hass avocados (Persea americana var. Hass).

This study was intended to evaluate the bactericidal effect of electrolyzed oxidizing water (EOW) and chlorinated water on populations of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes inoculated on avocados (Persea americana var. Hass). In the first experiment, inoculated avocados were treated with a water wash applied by spraying tap water containing 1 mg/liter free chlorine for 15 s (WW); WW treatment and then spraying sodium hypochlorite in water containing 75 mg/liter free chlorine for 15 s (Cl75); WW treatment and then spraying alkaline EOW for 30 s (AkEW) and then spraying acid EOW (AcEW) for 15 s; and spraying AkEW and then AcEW. In another experiment, the inoculated avocados were treated by spraying AkEW and then AcEW for 15, 30, 60, or 90 s. All three pathogen populations were lowered between 3.6 and 3.8 log cycles after WW treatment. The application of Cl75 did not produce any further reduction in counts, whereas AkEW and then AcEW treatment resulted in significantly lower bacterial counts for L. monocytogenes and E. coli O157:H7 but not for Salmonella. Treatments with AkEW and then AcEW produced a significant decrease in L. monocytogenes, Salmonella, and E. coli O157:H7 populations, with estimated log reductions of 3.9 to 5.2, 5.1 to 5.9, and 4.2 to 4.9 log CFU/cm², respectively. Spraying AcEW for more than 15 s did not produce any further decrease in counts of Salmonella or E. coli O157:H7, whereas L. monocytogenes counts were significantly lower after spraying AcEW for 60 s. Applying AkEW and then AcEW for 15 or 30 s seems to be an effective alternative to reduce bacterial pathogens on avocado surfaces.

Effects of host plant on the development, survivorship and reproduction of Dysmicoccus neobrevipes Beardsley (Hemiptera: Pseudoccocidae)

The effects of four host plants ( Agave sisalana, Ag. americana var. marginata, Ananas comosus Baili and An. comosus Smooth Cayenne) on the biology of the mealybug Dysmicoccus neobrevipes Beardsley were studied in the laboratory at 26 ± 1 °C, 75–90% RH and 14:10 (L:D) photoperiod. The development, survivorship, longevity, reproduction and life table parameters of D. neobrevipes differed among the host plants. The shortest developmental period (from the first instar nymph to adult) was recorded on An. comosus Smooth Cayenne (22.4 days for females and 21.3 days for males), whereas the longest was recorded on An. comosus Baili (25.6 days for females and 24.7 days for males). The highest survivorship was found on An. comosus Baili (98% for both females and males) and the lowest was on Ag. americana var. marginata (39.6% for females and 50% for males). Meanwhile the sex ratio and fecundity were highest and the pre-lay period was shortest on Ag. sisalana. The longest longevity of females was 62.5 days on An. comosus Baili, whereas the other host plants did not differ significantly with grand mean longevities of 51.0 days for females, while the longest and shortest longevities of males were 4.6 days and 2.3 days on Ag. americana var. marginata and Ag. sisalana, respectively. Values for net reproductive rate, intrinsic rate of increase and finite rate of increase were highest on Ag. sisalana, whereas the mean generation time was shortest on An. comosus Smooth Cayenne. The results indicated that Ag. sisalana is the most suitable host for D. neobrevipes among the four tested plants. When reared on Ag. sisalana, D. neobrevipes had a short developmental period (females 22.7 days and males 23.8 days), high reproduction (418 nymphs/female) and a high intrinsic rate of increase (0.106). Results of this study indicated that host plant can largely influence the population dynamics of D. neobrevipes, and our findings are useful in understanding the roles of host plants in integrated management of this pest, including exploitation of these host plants in push-pull control.

The foliar chemical profile of criollo avocado, Persea americana var. drymifolia (Lauraceae), and its relationship with the incidence of a gall-forming insect, Trioza anceps (Triozidae)

Abstract The role of phytochemical diversity in plant defense was studied using the specialist herbivore Trioza anceps Tuthill (avocado gall-forming insect), and the volatile fraction of the foliar chemicals of its host, the creole avocado (Persea americana var. drymifolia (Schect. & Cham.) Blake). Two hypotheses were tested: a) plant defense is determined by phytochemical diversity, and b) plant defense is determined by single compounds or specific blends of compounds. Simple and multiple regressions and a size and shape analysis (which considers the compounds relative and absolute concentrations within the leaf blend) were used to test these hypotheses. Simple regressions of gall incidence and chemical diversity and the tree origin elevation and latitude were very weak. The linear multiple regression to explain gall incidence with 33 foliar compounds and geographical data produced a model with low predictive power (R2 = 0.13). The size and shape analysis showed intraspecific variation in leaf chemical profiles among five tree groups, classified by the number of galls per 10 cm2 of leaf. Discriminant analysis separated clearly the tree groups’ chemical profiles through specific compounds. These results suggest that the gall incidence is associated with specific chemical profiles, rather than to high or low foliar phytochemical diversity.