Оценка резистентности природных популяций вредителей зерновых запасов к фосфину

Dependence of mortality of rice weevils Sitophilus oryzae from the natural (synanthropic) and laboratory populations on phosphine concentration was experimentally studied and mathematically described. The index of resistance to phosphine in beetles of the natural population was 2.5.

Thirteen laboratory populations (six mass cultures and seven isofemale lines) of Drosophila bipectinata were established from files collected from six different geographic localities (four in the north and two in the south) in India. These mass cultures and isofemale lines were maintained in food bottles in the laboratory for varying number of generations by transferring about 50 files (females and males in equal number) in each generation. After several generations, all the laboratory populations were analysed chromosomally to determine the frequency of different inversions. The results indicate that all the laboratory populations remained chromosomally polymorphic due to the persistence of inversions which were originally present ion the populations. The quantitative data on the frequency of inverted gene orders and the level of inversions heterozygosity in laboratory populations are compared with those in corresponding natural populations. This comparison clearly shows that there is a considerable increase in the frequency of inverted gene orders and the level of inversion heterozygosity in laboratory populations when compared with corresponding natural populations. This is most likely to be due to selective advantage of inversion heterozygotes under stringent competition in laboratory populations. Thus heterotic buffering is associated with chromosome inversion of Drosophila bipectinata.

Gene arrangement frequencies of different chromosome types of three inversions, IIL-2, III-35 and III-2 are reported in some natural and laboratory populations of Drosophila nasuta. In general, the frequencies of inversion heterozygotes for these inversions are in excess of what is expected under Hardy-Weinberg equilibrium in both natural and laboratory populations. This suggests that these inversion heterozygotes are heterotic to the species as far as viability is concerned. Similar to what occurs in the cosmopolitan species, chromosomes with standard gene sequences are more frequent than inverted gene sequences in this species. The scarcity of inversion homozygotes is due to reduced viability of their carriers, which probably have lethal or sublethal combinations of alleles in the inverted sections of their chromosomes. Further, the inversion frequencies in laboratory populations follow the frequencies in natural populations.

Hermaphroditism is relatively common among coastal and reef-associated tropical marine fishes (Reinboth, 1970; Thresher, 1984; Sadovy and Shapiro, 1987). However, the western Atlantic mangrove killifish, Rivulus marmoratus, appears to be unique among hermaphrodites in its pattern of sexual allocation and reproduction. In laboratory populations, fish are reported to be either primary males that develop directly and produce only sperm, hermaphrodites that produce both sperm and ova, or secondary males that arise from hermaphrodites following loss of female function (Harrington 1975). In natural populations, primary males are reported to be rare (Harrington, 1975; but see Davis et al., 1990; Turner et al., 1992a), and secondary males have not been verified (Harrington, 1971). No pure females have been reported from either natural or laboratory populations (Harrington, 1975; Soto et al., 1992). On the basis of previous laboratory and field data, most individuals in this species are assumed to be obligate self-fertilizing hermaphrodites (Harrington, 1971; Davis et al., 1990; Soto et al., 1992). Results from studies of tissue transplants and allozymes confirmed this assumption (Harrington, 1975; Vrijenhoek, 1985). However, recent molecular studies (Turner et al., 1991, 1992b) have shown much richer genetic variation in natural populations of R. marmoratus than did earlier techniques. We examined gonadal development in R marmoratus to clarify the pattern of sexual allocation in this species and to confirm whether it is, in fact, an obligate selffertilizing species (Judson and Normark, 1996).

The response of Rhyzopertha dominica and Sitophilus oryzae (both phosphine-resistant) in mixed-age cultures to phosphine at fixed concentration-time products (CT) of 10,500 to 168,000 microliters litre 1 h (ppm h) with either constant, rising or falling concentrations for 7 days was studied at 27 (+/- 2) degrees C. At lower CT products, rising concentrations of phosphine led to significantly fewer survivors of R dominica and S oryzae. Conversely, exposure to falling concentrations of phosphine resulted in significantly more survivors. The influence of changing concentrations of phosphine was more pronounced in S oryzae than in R dominica. In the latter, at the lower CT products of 21,000 and 42,000 microliters-1 h, the adult stage proved to be most tolerant, contrary to the accepted belief that the egg or pupal stage are always more tolerant to phosphine. The results indicate that application of phosphine in rising concentrations is more effective than in constant or falling concentrations.

Agriculture commodities infested by insect pest are being controlled by various methodologies for countering their drastic affects. One of the earliest methods is the use of insecticide against red flour beetle (Tribolium castaneum) insects have developed resistance against these insecticides, there for in the present research we were examine the mortality effect of two plants extracts (kaniar and shahtra) and spinetoram (radiant) against red flour beetle to compare the efficacy of these insecticide. The lethal effect of kaniar, shahtra and spinetoram were be evaluated using 6 concentrations 2.5, 5, 7.5, 10, 12.5 and 15 with 3 replications. The filter paper was used for bioassay evaluating the mortality after 24, 48, 72, and 96 hours. Statistical analysis was carried out for (ANOVA) using statistics 8 software. Mean of significant treatments were compared using Tukey HSD test. Mortality analysis showed that highest mortality was observed in case of spinetoram (radiant) (97%) at 150 ppm after 96-hour exposure following the plant extract Kaniar (70%) at 15% concentration after 96-hour exposure and shahtra (57%) at 15% concentration after 96-hour exposure, high repelancy was obtained by the plant extract, Shahtra (100%) after 60 minutes exposure followed by Kaniar (93%) after 60 min exposure. The results concluded that both the plants are highly effective than the insecticide against Tribolium castaneum and they can be safely used against stored product pests in commodities to conserve the food grains for future use without residual effects and other side effects related to health and food quality.

Adjustment of a population's gene pool to maintain maximum fitness is to be expected following changes either in selective forces, in genetic variability, or in both. New genetic combinations may evolve when genic complexes are derived from unrelated genomes as in laboratory populations of Drosophila with chromosomes of diverse origins (mesoevolution of Dobzhansky, 1954; Dobzhansky and Pavlovsky, 1957; Dobzhansky and Spassky, 1962). But the fact that no laboratory population is static and fixed in its genetic composition (except an isogenic strain) is demonstrated by the evolution of new adaptive complexes when natural selection has an opportunity to act on any genetic variation which has not yet attained equilibrium, even when that variation is a sample from a single welladapted natural population (Buzzati-Traverso, 1955; Lewontin, 1958; Strickberger, 1963). These experiments on laboratory populations derived from natural populations serve to illustrate clearly the dynamic poise of those populations and the rapid deterministic nature of the selective process in establishing new genetic equilibria. On the basis of laboratory population results from earlier work, Spiess (1961) described the outcome of gene arrangement frequency changes with strains of Drosophila persimilis from Timberline (10,000 feet elevation in the Yosemite area) as unexpected responses indicating the extreme novelty of population cage conditions for Timberline genotypes compared with the more expected responses of flies

Storage pests are a significant factor contributing to rice crop losses, adversely affecting both the quantity and quality of stored rice. This study was carried out to assess the current status of storage insect pests, storage methods, and management practices in Fogera district, Ethiopia, during the 2022 cropping season. The assessment was conducted based on interviews, visiting the individual households, and collecting a representative sample of rice grains from each store among 200 randomly selected farmer households. Data on the socio-economic characteristics, storage structures, durations of rice storage, pest management practices, relative abundance, grain damage, weight loss, and germination percentage were collected and analyzed using descriptive statistics. The result of the study showed that rice weevil (Sitophilus oryzae), lesser grain borer (Rhyzopertha dominica), red flour beetle (Tribolium castaneum), and angoumois grain moth (Sitotroga cerealella) insect pests were found in the surveyed areas. Among these, rice weevil and lesser grain borer predominantly occurred, and the majority of the respondents perceived them as the most common and damaging pests of rice. Most farmers used traditional storage structures like Gota (32%), Shirfa (27%), polypropylene bags (25%), and fertilizer bags (12%) for storing rice, which were susceptible to insect pest infestations, resulting in 2.26% grain damage. Farmers applied various storage insect pest control methods, including physical, chemical, and cultural practices, with chemical (29%) being the most commonly used. They repeatedly use insecticides that pose risks to both the environment and human health. Therefore, the study recommended the adoption of improved storage technologies to protect grains from pests, minimize insecticide use, and preserve grain quality. Additionally, training on effective storage methods, pest management, and healthy rice preparation is essential. These findings serve as a foundation for developing sustainable pest management methods in the study area, ultimately improving food security and farmer livelihoods.

Anastrepha fraterculus (Wied.) is known as the South American Fruit Fly. In order to develop efficient control strategies, we need deep knowledge on its biology along with periodical studies on population dynamics. Citogenetic studies on natural populations of this pest fly made it possible to reveal the presence of double minute chromosomes (DMs) in several natural populations of this insect. Cytogenetic studies performed in our insect laboratory, allowed the genetic analysis through a genealogical methodology. The establishment of families made it possible the genetic studies allowing the rigorous identification, characterization and confirmation of new chromosomal variants, frequently missinterpreted when the materials analyzed only come from nature. Double minute chromosomes -considered a type of chromosomal rearrangement- are extra chromosomal gene copies. This study sought to answer: What role do DMs chromosomes play in laboratory populations of the pest derived from natural populations? How are they transmitted from one generation to another? To answer our questions, we analyzed for 25 generations, two laboratory populations derived from Tucuman (T) and Buenos Aires (BA -tester) guava,. Data were recovered from cytological analysis of ganglia preparations revealed with H33258. The natural population from BA didn’t carry DMs. Results showed DMs in flies of both laboratory populations. DMs were transmitted from parents to progenies through 25 generations and their transmission was randomized in number. DMs are the cytological expression of resistance mechanisms used by the pest as a response to environmental stress. DMs in BA strain marked the change to the laboratory environment. A. fraterculus is a model insect for the study of cancer.

Population genetic variations of Helicoverpa armigera (Hiibner) over different major cotton growing regions were analyzed by DNA polymorphism amplified with four simple repetitive sequence primers. The results showed that the laboratory population had relatively lower genetic variation than natural populations. The genetic variation between natural populations was not significant and genetic variation existed in the same location from different years, indicating frequent migration among natural cotton bollworm populations. Cluster analysis indicated that individuals from Chaoyang of Liaoning Province (CY), Gaotang of Shandong Province (GT) and Dafeng of Jiangsu Province(DF) were more mixed each other, which suggested that CY population might have higher gene flow with GT and DF populations, especially with GT population. It supports the theory that the cotton bollworm in Northeast China came from Shandong and Hebei Provinces. This result also demonstrated that the molecular makers in this study are sensitive to detect population genetic structure changes.

Drosophila melanogaster from Australia, Europe and North America enter an adult ovarian dormancy in response to short days and low temperatures. The independent effects of temperature and day length in the determination of dormancy have been examined only in one long-established laboratory line (Canton-S). In all other studies of natural or laboratory populations, dormancy has been assessed at either a single short day or a single moderately low temperature. Herein, we determine the relative roles of temperature, photoperiod, and their interaction in the control of ovarian dormancy in D. melanogaster from two natural populations representing latitudinal extremes in eastern North America (Florida at 27 degrees N and Maine at 44 degrees N). In both natural populations, temperature is the main determinant of dormancy, alone explaining 67% of the total variation among replicate isofemale lines, whereas photoperiod has no significant effect. We conclude that ovarian dormancy in D. melanogaster is a temperature-initiated syndrome of winter-tolerant traits that represents an adaptive phenotypic plasticity in temperate seasonal environments.

Deterministic and stochastic evolutionary processes drive adaptation in natural populations. The strength of each component process is determined by the population size: deterministic components prevail in very large populations, while stochastic components are the driving mechanisms in small ones. Many natural populations, however, experience intermittent periods of growth, moving through states in which either stochastic or deterministic processes prevail. This growth is often countered by population bottlenecks, which abound in both natural and laboratory populations. Here we investigate how population bottlenecks shape the process of adaptation. We demonstrate that adaptive trajectories in populations experiencing regular bottlenecks can be naturally scaled in time units of generations; with this scaling the time courses of adaptation, fitness variance, and genetic diversity all become relatively insensitive to the timing of population bottlenecks, provided the bottleneck size exceeds a few thousand individuals. We also include analyses at the genotype level to investigate the impact of population bottlenecks on the predictability and distribution of evolutionary pathways. Irrespective of the timing of population bottlenecks, we find that predictability increases with population size. We also find that predictability of the adaptive pathways increases in increasingly rugged fitness landscapes. Overall, our work reveals that both the adaptation rate and the predictability of evolutionary trajectories are relatively robust to population bottlenecks.

Dispersal is a key component of life history that influences individual fitness, population dynamics and range expansion. Morphological traits that are functionally related to dispersal may change through the spatial sorting of phenotypes at population range edges and invasion fronts. Generally, since larger invertebrates are expected to have greater dispersal capacity, larger body size and mass is expected to evolve in dispersers. Yet, different study systems exhibit a range of trait‐specific and sex‐specific responses to spatial sorting. Furthermore, a persistent issue in this field is that spatial sorting can be challenging to separate from natural selection and population dynamics. To address this, here we investigated the responses of dispersal and morphological traits to simulated spatial sorting into disperser and non‐disperser red flour beetles (Tribolium castaneum) using a controlled laboratory dispersal system that isolated spatial sorting from natural selection and allowed sex‐specific dispersal traits to evolve independently. After seven generations of spatial sorting, the time taken to disperse decreased in dispersers and increased in non‐dispersers, with males dispersing more quickly than females. In contrast to expectations that dispersers would increase in body mass and size, we found the opposite. Body mass and morphology diverged such that dispersers became smaller and narrower, while non‐dispersers became larger relative to the randomly selected controls, but femur length did not change. The trait responses across generations were also sex specific. Divergence between male dispersers and non‐dispersers was more substantial than females, both in dispersal and in some morphological traits. We hypothesize that small individuals were more biomechanically efficient at dispersing through the dispersal apparatus and were therefore the ones that dispersed more readily. We suggest that key differences in dispersal modes across biological systems may impact the morphological and phenotypic trait changes from spatial sorting processes in range expansions and biological invasions.

Information on the molecular basis of resistance and the evolution of resistance is crucial to an understanding of the appearance, spread, and distribution of resistance genes and of the mechanisms of host adaptation in natural populations. One potential important genetic constraint for the evolution of resistance is fitness cost associated with resistance. To determine whether host resistance to parasite infection is associated with fitness costs, we conducted simultaneous quantitative trait loci (QTL) mapping of resistance to parasite infection and fitness traits using the red flour beetle (Tribolium castaneum) and the tapeworm parasite (Hymenolepis diminuta) system in two independent segregating populations. A genome-wide QTL scan using amplified fragment length polymorphism (AFLP) markers revealed three QTL for beetle resistance to tapeworm infection. These three QTL account for 44-58% variance in beetle infection intensity. We identified five QTL for fecundity and five QTL for egg-to-adult viability, which accounted for 36-57% and 36-49%, respectively, of the phenotypic variance in fecundity and egg-to-adult viability. The three QTL conferring resistance were colocalized with the QTL affecting beetle fitness. The genome regions that contain the QTL for parasite resistance explained the majority of the variance in fecundity and egg-to-adult viability in the mapping populations. Colocalization of QTL conferring resistance to parasite infection and beetle fitness may result from the pleiotropic effects of the resistance genes on host fitness or from tight linkages between resistance genes and adverse deleterious mutations. Therefore, our results provide evidence that the genome regions conferring resistance to tapeworm infection are partially responsible for fitness costs in the resistant beetle populations.

A free-living nematode was isolated from soils of coastal areas of Northern Sri Lanka using an insect-baiting technique. The morphometrics and the potential of the nematode to control the insect pest, red flour beetle ( Tribolium castaneum ) and white grubs ( Phyllophaga ephilida ) were evaluated. The female nematode had a mean body length of 720 µm longer than male (607 µm) with an annulated cuticle and narrow stoma with rhabditoid esophagus. Female with monodelphic, dextral, reflexed with post uterine sac and protuberance vulva at the mid-body, showed sexual dimorphism with male which had a single and reflexed testis. The identification of the nematode was confirmed as Acrobeloides cf. longiuterus (Nematoda: Cephalobidae). The propensity of this nematode to kill insect pests was subsequently tested against T. castaneum and P. ephilida under laboratory conditions. In Petri dish trials, the nematode caused significant mortality of larvae, pupae and adults of T. castaneum within 48 hours. LC 50 for larvae ranged from 3.8-5.9 infective juveniles (IJs)/larva 1.1 and 7.1 IJs/insect for pupae and adults respectively. In soil-based bioassays, the LC 50 for T. castaneum larvae was 69.46 IJs/larva, LT 50 (Larvae) under the exposure time assay was 4.43 hours, whereas in pot experiment mortality of P. ephilida was recorded 69% . The experimental results showed that A. cf. longiuterus is a potential biocontrol agent and further studies are suggested in this regard