Host Fruit Research Articles

Diversity of Colletotrichum species causing cherry postharvest anthracnose in China

Cherry postharvest anthracnose (CPA) is an important fungal disease that endangers cherry production. To characterize the pathogen diversity, 43 Colletotrichum isolates were isolated from 175 cherry fruits. The multi-locus phylogenetic analysis (ACT, CAL, CHS-1, GAPDH, HIS3, ITS, TUB2) revealed that strains of the C. gloeosporioides species complex (CGSC) associated with CPA included C. aenigma, C. fructicola, C. gloeosporioides, C. siamense, and strains of the C. acutatum species complex (CASC) included C. fioriniae, C. godetiae, C. salicis. There were significant differences in biological characteristics between CGSC and CASC. The mycelium growth rate, sporulation and conidial germination ability of CGSC was significantly higher than that of CASC. However, CASC was more adaptable to low temperatures. CGSC was more pathogenic than CASC toward cherry fruits. On other tested hosts, all species showed pathogenicity only on wounded condition and the pathogenicity of CGSC and CASC to other host fruits was significantly different too. C. aenigma and C. siamense exhibited significantly higher pathogenicity towards grapes and blueberries compared to C. gloeosporioides and C. fioriniae, while the pathogenicity to cherry tomatoes was reversed. In general, CGSC was more pathogenic than CASC to testes hosts. Our results showed that there were seven species of two species complex of Colletotrichum responsible for CPA in China, and the biological characteristics and pathogenicity of different species were significantly different.

Effectiveness of Diachasmimorpha longicaudata in Killing Ceratitis capitata Larvae Infesting Commercial Fruits in Dryland Agroecosystems of Western Argentina

Ceratitis capitata (Wiedemann) (medfly) strongly affects Argentinean fruit production and export. Augmentative biological control using the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) is currently applied to this problem. The ability to find and parasitize medfly larvae on a wide diversity of fruit host species is a key issue that needs to be analyzed. This research assessed the effect of the physical features of fruit on the preference of foraging D. longicaudata females and the influence of varying release density on parasitoid performance as a pest mortality factor in three fruit species. Trials were performed inside field cages under semi-arid environmental conditions in Argentina’s central-western fruit-growing region. Sweet orange, peach, and fig were tested. The fruits were inoculated with third-instar larvae of the Vienna-8 temperature-sensitive lethal medfly strain. Naïve, 5 d-old mated D. longicaudata females were released in cages at 20, 40, 80, and 160 parasitoid densities. The highest levels of medfly mortality and parasitoid emergence were recorded in fig and peach, although D. longicaudata also induced mortality in orange, a fruit with few physical features favorable to parasitism. The medfly mortality in all fruit host species significantly increased with an increased number of parasitoid females released into the field cages. Diachsmimorpha longicaudata has high potential as a medfly biocontrol agent.

Electroantennographic and behavioral responses of Bactorcera dorsalis (Diptera: Tephritidae) adults to the volatiles of plum fruits.

Fruit volatiles play a crucial role in the host localization by the oriental fruit fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae). This study focused on identifying the fruit volatiles from Sanyue plum and Sanhua plum (Prunus salicina Lindl.), which are 2 varieties of the same species, and examined their impact on the behavior of B. dorsalis by using a Y-olfactometer. A total of 35 and 54 volatiles from Sanyue plum and Sanhua plum were identified, respectively. Among these, 23 volatiles elicited electroantennographic (EAG) responses by B. dorsalis adults, showing concentration-dependent effects in males and females. Ethyl butyrate, butyl acetate, butyl hexanoate, ethyl caproate, ethyl hexanoate, and hexyl acetate significantly attracted B. dorsalis compared to liquid paraffin, while nonaldehyde was avoided. There was no significant difference in the behavioral responses of both sexes to sorbitol esters, hexyl isobutyrate, and 1-tetradecene compared with the control liquid paraffin group. Interestingly, (3Z)-C-3-hexenyl acetate significantly attracted females, but not males. The above findings suggest that plum fruit volatiles are likely to facilitate the localization of host fruit by B. dorsalis adults and may even aid in mate-finding. This study opens up new avenues for exploring novel plant-based attractants that might be of value for the integrated management of B. dorsalis.

Citrus Fruits Produce Direct Defense Responses against Oviposition by Bactrocera minax (Diptera: Tephritidae).

Plants perceive and orchestrate defense responses when herbivorous insects are ovipositing. Fruits, as a crucial reproductive organ in plants, have rarely been researched on the responses to insect eggs. Here, we found that oviposition by the specialist insect Bactrocera minax in navel oranges activated the lignin synthesis pathway and cell division, causing mechanical pressure that crushed the eggs. Transcriptome and metabolome analyses revealed an enrichment of oviposition-induced genes and metabolites within the lignin synthesis pathway, which was confirmed by histochemical staining. Furthermore, hydrogen peroxide (H2O2) accumulation was observed at the oviposition sites. Plant defense-related hormones jasmonic acid (JA) and salicylic acid (SA) exhibited rapid induction after oviposition, while indole-3-acetic acid (IAA) activation occurred in the later stages of oviposition. Additionally, secondary metabolites induced by prior egg deposition were found to influence larval performance. Our studies provide molecular evidence that host fruits have evolved defense mechanisms against insect eggs and pave the way for future development of insect-resistant citrus varieties.

Influence of Anastrepha host fruit size over parasitism by Diachasmimorpha longicaudata in open-field augmentative releases

ABSTRACT Fruit size can act as a physical barrier providing refuge for larvae of pest Anastrepha species against parasitoid attack. Therefore, the aim of this study was to evaluate the influence of fruit size in six fruit species infested by Anastrepha larvae on the parasitism of Diachasmimorpha longicaudata after its augmentative release. About 1500 parasitoids were weekly released in disturbed wild vegetation patches. Fruit sampling was performed at the Coastal Lowlands of the Soconusco Region, southeastern Mexico, between June 2021 and October 2022. Overall, 310 ripe fruits belonging to grapefruit, creole mamey (large-size fruits), sweet orange, creole mango, wild guava (medium-size fruits), and wild hog plum (small-size fruit) were collected. The length, frontal width, lateral width and pulp thickness of all sampled fruits were measured. Such physical characteristics are indicators of the fruit size. Fruit collection was performed 48 h after release. Results indicated an inverse correlation between fruit size and parasitism, with a significant r 2 value higher than 75%. Host larvae in all fruits were parasitised only by D. longicaudata. The highest mean parasitism, which exceeded 90%, was recorded on hog plum and the lowest, below 20%, on Citrus spp. and mamey. Results corroborated the influence of host fruit size on parasitism levels by D. longicaudata regardless of its large-scale, open-field releases. Augmentative releases of D. longicaudata can be focused on wilderness areas with prevalence of medium-size to small-size Anastrepha host fruits. This would encourage long-term sustainable conservation of released parasitoid populations.

Advancing rational pesticide development against Drosophila suzukii: bioinformatics tools and applications-a systematic review.

Drosophila suzukii (Matsumura, 1931) is a widespread agricultural pest responsible for significant damage to various soft-skinned fruit hosts. The revolutionary potential of bioinformatics in agriculture emerges from its ability to provide extensive information on pests, fungi, chemical resistance, implications of non-target species, and other critical aspects. This wealth of information allows researchers to engage in projects and applied research in diverse agricultural domains that face these challenges. In this context, bioinformatics tools play a fundamental role. The negative impact of pests on crops, resulting in substantial economic losses, has highlighted the importance of in silico methods. To achieve this, we conducted a systematic search in scientific databases using as keywords "Drosophila suzukii," "biopesticides," "simulations computational," and "in-silico." After applying the filters of relevance and publication date, we organized the articles and prioritized those that directly addressed that matched the keywords and the use of bioinformatics tools. Additionally, we included studies focusing on in silico assays of biopesticides, such as molecular docking. Our review aimed to present a collection of recent literature on biopesticides against Drosophila suzukii, emphasizing bioinformatics methods. Through this work, we strive to contribute to the literature of new perspectives on the development and efficiency of biopesticides, along with to advance research that may improve pest control strategies. In the results of the systematic review, we found 2734 articles related to the selected keywords. Six of these articles directly address Drosophila suzukii and the use of bioinformatics tools in the search for alternatives in pest control. In the selected studies, we observed that two articles tend to focus on phylogenetic approaches, searching for gene sequences, amino acids, and constructing phylogenetic trees. The other three articles used molecular modeling and docking of receptors such as GABA and TRP with plant-derived and synthetic compounds to study intermolecular interactions. However, we identified gaps in these studies that could lead to further research in the biorational development of biopesticides using bioinformatics tools.

Comparative Biology of Guava Fruit Fly <i>Bactrocera correcta</i> (Bezzi)

Fruit flies are polyphagous insect pests, infesting various fruits and vegetables. The host preference and biology of guava fruit fly Bactrocera correcta (Bezzi) were studied on 17 hosts. Biological parameters such as incubation period, maggot and pupal period, maggot and pupal weight, pupal recovery, adult emergence, total fecundity and adult longevity were studied. All biological parameters were significantly influenced by the host fruits. The results showed that the total developmental period was longer on pomegranate (26.7± 2.1 days), ber (26.1± 2.4 days) and custard apple (25.1± 1.5 days); while shorter period was observed on sweet banana (20.1± 1.6 days). Pupal recovery was maximum on sweet banana (93.33%) and lowest on mango (Totapuri) (42%). The adult emergence was also more on sweet banana (90%) and survived for longer period. Sweet banana was preferred for oviposition followed by guava, papaya, and sapota.

Development of Biological Control Tools against Bactrocera zonata (Saunders) (Diptera: Tephritidae) in Citrus Orchards in Egypt

The peach fruit fly Bactrocera zonata, is a harmful insect that infests various fruit crops and vegetables worldwide, including Egypt. Its presence leads to significant damages and losses. To minimize the negative impact of pesticide residues on human health and the environment, a study was conducted to examine the seasonal behavior of Bactrocera zonata on navel orange trees. This investigation involved the utilization of sex attractants and the monitoring of fruit samples. The research was conducted over two consecutive seasons, namely 2020 and 2021. By utilizing sex attractants, pheromone (mass trapping) it was discovered that the number of male Bactrocera zonata captured and infested increased during the Autumn period, specifically in October, in both seasons. Additionally, it was observed that Bactrocera zonata males exhibited a single peak of activity each season. Fruit samples were monitored to assess fruit infestation, and it was found that infestation was positively correlated with the maturity of the fruits. The weekly count of males captured in the fly traps, along with the infestation rate of this pest, indicated that these traps could serve as a useful tool for predicting the infestation rates of Bactrocera zonata in their host fruits. Conclusion The implementation of mass trapping techniques utilizing pheromone-based tools will result in a reduction of infestation by the end of the second season of 2021.

Foraging behavior of Ganaspis brasiliensis in response to temporal dynamics of volatile release by the fruit–Drosophila suzukii complex

The lineage G1 of Ganaspis brasiliensis is a larval parasitoid of the worldwide pest Drosophila suzukii and one of its most effective natural enemies in the native area. Because of its high degree of host specificity, G. brasiliensis G1 is considered a suitable species for introduction in areas invaded by D. suzukii following a classical biological control approach. Indeed, the release of the parasitoid is currently implemented in the USA and Italy. G1 females attack only host larvae developing in ripening fresh fruits on the plant and not larvae that develop in decaying fruits. To date, virtually no information is available on the cues regulating the foraging behavior of G1. In this study, we therefore aimed to find out whether chemical cues are exploited by G1 females to: (i) locate host fruits; (ii) locate suitable host larvae within infested fruit; (iii) discriminate between infested fresh fruits and infested rotting ones. We used a model system composed of blueberries and D. suzukii tested in two-choice olfactometer bioassays (with D. suzukii-infested fruits, healthy fruits, and pure air as odor targets), followed by the collection and the characterization of volatile organic compounds (VOCs) released by the tested targets. The results showed a clear time-dependent choice made by G1 females of infested versus healthy fruits related to the concomitant development of D. suzukii larvae and fruit degradation. Attraction to infested fruits was recorded during the early stages of infestation, followed by a repellent phase coinciding with fruits largely degraded by larval feeding. We found that the attractiveness of G. brasiliensis G1 towards fruits infested by young larvae was associated with the detection of VOCs released by the infested blueberries, and host’s cuticular hydrocarbons. Conversely, the repellence of older and deteriorated fruits hosting developed D. suzukii larvae was associated with the detection of a fermentation compound produced by microorganisms likely carried inside the fruit by the flies. The response of G1 females to the temporal dynamics of chemical cues emitted by the fruit–host larvae complex was consistent with the high degree of specificity of the parasitoid towards the ripening host fruits and towards D. suzukii.

How plant and insect host characteristics affect pepper weevil Anthonomus eugenii parasitism efficacy by the pteromalid Jaliscoa hunteri

The pepper weevil Anthonomus eugenii (Cano) (Coleoptera: Curculionidae) is an economically important pest of both field and greenhouse pepper crops, Capsicum annuum Linnaeus (Solanaceae) in North America. Among its natural enemies is the parasitoid wasp Jaliscoa (= Catolaccus) hunteri (Crawford) (Hymenoptera: Pteromalidae), whose potential control of A. eugenii appears promising but is currently unclear. We conducted controlled environment trials to quantify A. eugenii offspring emergence following exposure to J. hunteri, examining how parasitoid exposure period, weevil host life stage, pepper cultivar, fruit size and abscission status affect weevil-natural enemy dynamics. In pepper cultivar comparison trials, we identified a significant reduction in weevil offspring emergence from three different cultivars of ornamental peppers infested by A. eugenii, but no difference among them. In trials comparing wasp exposure period and weevil larval instar, pepper plants of one cultivar (Blaze) were exposed to A. eugenii adults, and subsequently to J. hunteri wasps for either three or seven days, when offspring weevils were either at the L1 or L3 instar. Offspring emergence was significantly reduced up to 62% when L3 but not L1 weevils were exposed to wasps for 7 days. Following this longer exposure period, significantly greater weevil suppression occurred in small (71.7%) versus large fruit (62.5%), with an additional 15.1% weevil suppression resulting from attached relative to abscised fruit. These results highlight the potential for J. hunteri as a biological control agent of A. eugenii on pepper crops, with particular value in commercial greenhouse production where wasp retention rates can be high.

D-Limonene Is the Active Olfactory Attractant in Orange Juice for Bactrocera dorsalis (Insecta: Diptera: Tephritidae).

The oriental fruit fly, Bactrocera dorsalis (Hendel), poses a significant threat to the global fruit industry, causing damage to diverse fruits like citrus, mango, and guava. Chemical pesticides have limited effectiveness, and pesticide residues and pesticide resistance are pressing issues. Therefore, it is essential to develop environmentally friendly pest control methods to address this problem. Behavior-modifying chemicals, including male attractants and intersex protein baits, play a critical role in the control of B. dorsalis. The mature host fruit serves as both an oviposition site and food source under natural conditions, making it a potential attraction source for oriental fruit flies. Orange, Citrus sinensis, is a main host of B. dorsalis, and commercial orange juice is a common attractant for the egg laying of B. dorsalis. Although it can both attract and elicit oviposition behaviors in B. dorsalis adults, its active components are still unclear. This study utilized analytical chemistry, behavioral tests, and electrophysiology to identify the active components of commercial orange juice that attract B. dorsalis, with the aim of providing a reference for the development of behavior-modifying chemical-based techniques to control B. dorsalis. Five compounds with a high abundance were identified via a GC-MS, including D-Limonene, butanoic acid ethyl ester, β-myrcene, linalool, and α-terpineol. Behavioral and electrophysiological experiments uncovered that D-Limonene was the active substance that was the main attractant in the mixture of these five substances, evoking a strong electrophysiological response in adult B. dorsalis. D-Limonene strongly attracts adult B. dorsalis only when they are sexually mature, and the attraction is not rhythmic. Olfaction plays a leading role in the attraction of D-Limonene to adult B. dorsalis, and Orco-/- mediates the perception of D-Limonene by B. dorsalis. Overall, D-Limonene is one of the key attractant compounds for B. dorsalis in the volatile compounds of commercial orange juice, offering possible support for the development of behavior-modifying chemical-based technology to control B. dorsalis in the future.

Unravelling genetic diversity of whitefly species on different host plants from New Delhi

Aim: This study investigates the genetic diversity and distribution of different species of whiteflies on 20 host plants vegetables (cucumber, summer squash, pumpkin, tomato, brinjal, okra), field crops (sunflower, lettuce, field bean, lobia), commercial crops (cotton, tobacco), ornamentals (chrysanthemum, bellflower, marigold), fruit crops (lemon), trees (mulberry, wild tamarind, ficus), and others (wild brinjal) in New Delhi. Methodology: Genetic diversity was assessed through mitochondrial cytochrome oxidase-I gene-based molecular markers. Results: Phylogenetic analysis revealed that whitefly Bemisia tabaci was the most prevalent pest species across the crops reported in this study. The other whitefly species, viz., Dialeurodes sp., Singhiella simplex, Aleuroclava sp., Tetraleurodes acaciae, Trialeurodes vapororium, and Aleurodicus floccissimus were reported as pests of different horticultural crops. Interpretation: Genetic diversity of B. tabaci revealed that the genetic groups Asia II-1 and Asia II-7 were most prevalent, while Asia I was the minor one. Understanding the species composition and genetic diversity of whiteflies will help in devising appropriate control strategies. Key words: Hosts, Molecular markers, mtCOI, New Delhi, Phylogenetic analysis, Whitefly diversity

On the impact of re-mating and residual fertility on the Sterile Insect Technique efficacy: Case study with the medfly, Ceratitis capitata.

The sterile insect technique (SIT) can be an efficient solution for reducing or eliminating certain insect pest populations. It is widely used in agriculture against fruit flies, including the Mediterranean fruit fly (medfly), Ceratitis capitata. The re-mating tendency of medfly females and the fact that the released sterile males may have some residual fertility could be a challenge for the successful implementation of the SIT. Obtaining the right balance between sterility level and sterile male quality (competitiveness, longevity, etc) is the key to a cost-efficient program. Since field experimental approaches can be impacted by many environmental variables, it is difficult to get a clear understanding on how specific parameters, alone or in combination, may affect the SIT efficiency. The use of models not only helps to gather knowledge, but it allows the simulation of a wide range of scenarios and can be easily adapted to local populations and sterile male production. In this study, we consider single- and double-mated females. We first show that SIT can be successful only if the residual fertility is less than a threshold value that depends on the basic offspring number of the targeted pest population, the re-mating rates, and the parameters of double-mated females. Then, we show how the sterile male release rate is affected by the parameters of double-mated females and the male residual fertility. Different scenarios are explored with continuous and periodic sterile male releases, with and without ginger aromatherapy, which is known to enhance sterile male competitiveness, and also taking into account some biological parameters related to females that have been mated twice, either first by a wild (sterile) male and then a sterile (wild) male, or by two wild males only. Parameter values were chosen for peach as host fruit to reflect what could be expected in the Corsican context, where SIT against the medfly is under consideration. Our results suggest that ginger aromatherapy can be a decisive factor determining the success of SIT against medfly. We also emphasize the importance of estimating the duration of the refractory period between matings depending on whether a wild female has mated with a wild or sterile male. Further, we show the importance of parameters, like the (hatched) eggs deposit rate and the death-rate related to all fertile double-mated females. In general, re-mating is considered to be detrimental to SIT programs. However, our results show that, depending on the parameter values of double-mated females, re-mating may also be beneficial for SIT. Our model can be easily adapted to different contexts and species, for a broader understanding of release strategies and management options.

Phytophthora species causing root and crown rot on castor bean (Ricinus communis) in Brazil

AbstractCastor bean (Ricinus communis) is a crop of great economic importance in Brazil. It is used for producing oil used in the manufacture of cosmetics and biodiesel. The genus Phytophthora contains pathogens with a wide range of host plants, including ornamentals, fruit and vegetable crops. Among the symptoms induced by Phytophthora species are collar and root rot. This study aimed to identify Phytophthora species causing collar and root rot in castor bean seedlings in the Federal District and test their pathogenicity. Samples of symptomatic plants were collected in four satellite cities in Distrito Federal, Brazil. Fourteen isolates were obtained, and they were initially identified through the morphology of reproductive structures. The isolates were subjected to molecular characterization using phylogeny of the sequences from the ITS region and the Cytochrome Oxidase II gene. Ten isolates of the pathogen were tested for pathogenicity on seedlings of two castor bean accessions and species known to be hosts of P. nicotianae. The isolates were identified as P. nicotianae (12 isolates) and P. palmivora (two isolates). In the pathogenicity test, all isolates were capable of causing disease in castor beans. The isolates of P. nicotianae and P. palmivora varied in pathogenicity to other plant species. This is the first report of P. nicotianae causing collar and root rot in castor bean in the Central‐West Region of Brazil. It is also the first report of P. palmivora causing diseases in castor beans in South America.

Life history and overwintering in multi‐ and univoltine species of family Tephritidae in a subtropical region of northwestern Argentina

AbstractAmong phytophagous insects, life history often evolves as a strategy to cope with seasonality in host plant availability. Whereas specialization often leads to dormancy, aestivation, or longevity, polyphagous species bridge between periods of host availability by exploiting alternative host plants. The aim of the present work was to characterize the life histories of four species of specialist and generalist uni‐ and multivoltine frugivorous fruit flies – Ceratitis capitata Wiedemann, Anastrepha fraterculus Wiedemann, Rhagoletis blanchardi Aczel, and Rhagoletotrypeta pastranai Aczel (all Diptera: Tephritidae) – inhabiting in sympatry in Las Yungas phytogeographical province in Tucumán (northwestern Argentina). For this purpose, infested host plant fruits were sequentially collected during two consecutive years, and flies recovered from these fruits were subjected to demographic experiments to establish longevity and overwintering mechanisms. The results indicated that life cycles were tightly related to host fruit availability, where multivoltine species sequentially exploit different host plants over the year, whereas univoltine species must undergo pupal dormancy to reach the next host fructification period and may extend the duration of dormancy when climatic conditions are acyclic and unpredictable. The present study may broaden knowledge about diapausing Tephritidae in subtropical regions and may contribute to an increased conceptual basis for the improvement of pest control strategies, such as the sterile insect technique (SIT).

Conserved cold tolerance of Rhagoletis species from different host fruits and elevations in Colorado, USA

AbstractUnderstanding and characterizing how insects tolerate low temperatures is important for predicting their overwintering survival and subsequent geographic spread. This study characterized the cold tolerance of two members of the Rhagoletis genus (Diptera: Tephritidae) in Colorado, USA. Pupae were collected from the infested fruits in late summer and early fall. For the first time, we show that the rosehip fly Rhagoletis basiola Osten Sacken is freeze‐avoidant; overwintering pupae could supercool to temperatures as low as −26°C and survive. Interestingly, the temperature at which ice forms (supercooling point; SCP) did not vary between R. basiola at high (c. 2900 m above sea level [m a.s.l.]) and lower (c. 1650 m a.s.l.) elevations. We also report the apple maggot R. pomonella Walsh infesting an unusual host fruit, the Dolgo crabapple, in close proximity to infested hawthorn trees. R. pomonella infesting hawthorn fruits and crabapples had similar SCPs and survived temperatures as low as −21°C. Pupae from both host fruits also survived prolonged exposure (2 weeks or more) to mild low temperatures (0 to −5°C). Further study into the mechanisms underlying the impressive and conserved cold tolerance of R. pomonella and R. basiola is an interesting avenue for future research.

Identity, Pathogenicity, and Genetic Diversity of Lasiodiplodia Species Associated with Stem-End Rot of Avocado in China.

Stem-end rot (SER) causes brown necrotic lesions in the pulp near the base of the fruit pedicel and is one of the most devastating postharvest diseases of avocados in all avocado-growing regions of the world. China's avocado industry is growing very rapidly, and the planting area is expanding, but little is known about the pathogens and genetic diversity of avocado SER. To determine the causal agents of SER, avocado fruits were sampled from the main avocado-producing areas in China during 2020 and 2021. Fungal isolates were obtained from SER symptomatic avocado fruits and identified by morphology combined with phylogenetic analysis of internal transcribed spacer (ITS), translation elongation factor 1-α (EF1-α), and β-tubulin (TUB2) gene sequences. All 101 isolates belonged to Lasiodiplodia spp.; four Lasiodiplodia species were identified, namely, L. pseudotheobromae (59.41%), L. theobromae (24.75%), L. mahajangana (7.92%), and L. euphorbiaceicola (1.98%); and six others are classified as Lasiodiplodia sp. (5.94%). There were only slight morphological differences in colonies and conidia of these four species of Lasiodiplodia. The pathogenicity tests showed symptoms of SER, and 92.08% of the isolates exhibited a high level of virulence on avocado (disease index >70), related to the disease severity on avocado fruits. All tested isolates grew well under the temperature ranging from 23 to 33°C. There was a significant difference in mycelial growth between the four species of Lasiodiplodia after treatment with high or low temperatures. The growth of L. pseudotheobromae was the fastest at 13 to 18°C but was the lowest at 38°C (P < 0.05). The red pigment could be produced by all tested isolates after culturing for 7 days at 38°C. The mycelial growth rate was the fastest on PDA medium, and the slowest on the OMA medium but promoted spore formation (P < 0.05). In addition, the genetic diversity of pathogenic Lasiodiplodia species associated with SER collected from avocado, mango, guava, and soursop fruits was determined. A total of 74 isolates were clustered into four main ISSR groups by the unweighted pair-group method with arithmetic mean analysis, and the classification of this group was related to the host. Extensive diversity was detected in the Lasiodiplodia populations. The diverse geographical origins and host species significantly influenced the population differentiation, and most of the genetic variation occurred within populations (P < 0.001). This is the first study to identify the major pathogens of avocado SER in China, survey their occurrence and pathogenicity, and include a comparative analysis of genetic diversity with Lasiodiplodia spp. causing SER on other fruit hosts. Collectively, the Lasiodiplodia species complex affecting avocado showed high pathogenicity and diversity, while L. pseudotheobromae was the most frequently isolated species in China. The results of this study provide insights into the aspects of the epidemic of SER disease caused by Lasiodiplodia species, which will help in developing strategies for the management and control of SER in avocado.

The Variation of Oviposition Preference and Host Susceptibility of the Oriental Fruit Fly (Bactrocera dorsalis Hendel) (Diptera: Tephritidae) on Commercial Mango Varieties

The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), is a serious fruit pest in South Asia; however, studies of their oviposition behavior on different host fruits in Sri Lanka are insufficient. Thus, the present study was conducted to determine the oviposition preference and host susceptibility of B. dorsalis on four commercial mango varieties (Karutha kolumban (Kc), Willard (Wld), Vellai kolumban (Vc), and Betti amba (Ba)) under controlled laboratory conditions. The comparative preference and host susceptibility of B. dorsalis to four mango varieties were tested by a series of choice and no-choice experiments. The preference for the oviposition was evaluated by observations, and the host susceptibility was investigated by incubating the above-tested fruits separately until the pupation and the emergence of adults. The gravid females of B. dorsalis showed a significantly different host preference and susceptibility among the four mango varieties tested. Among four mango varieties, “Kc” showed a significantly high oviposition preference and pupae and adult emergence of B. dorsalis. Study findings are useful to design control measures for B. dorsalis to prevent their damage to the commercial mango varieties in Sri Lanka.

Quantitative genetic analysis of attractiveness of yeast products to Drosophila.

An attractive perfume is a complex mixture of compounds, some of which may be unpleasant on their own. This is also true for the volatile combinations from yeast fermentation products in vineyards and orchards when assessed by Drosophila. Here, we used crosses between a yeast strain with an attractive fermentation profile and another strain with a repulsive one and tested fly responses using a T-maze. QTL analysis reveals allelic variation in four yeast genes, namely PTC6, SAT4, YFL040W, and ARI1, that modulated expression levels of volatile compounds [assessed by gas chromatography-mass spectrometry (GC-MS)] and in different combinations, generated various levels of attractiveness. The parent strain that is more attractive to Drosophila has repulsive alleles at two of the loci, while the least attractive parent has attractive alleles. Behavioral assays using artificial mixtures mimicking the composition of odors from fermentation validated the results of GC-MS and QTL mapping, thereby directly connecting genetic variation in yeast to attractiveness in flies. This study can be used as a basis for dissecting the combination of olfactory receptors that mediate the attractiveness/repulsion of flies to yeast volatiles and may also serve as a model for testing the attractiveness of pest species such as Drosophila suzukii to their host fruit.

Genome-wide analysis of the PG gene family in Penicillium expansum: Expression during the infection stage in pear fruits (Pyrus bretschneideri)

Penicillium expansum is a necrotrophic plant pathogen that has a broad range of fruit hosts and is responsible for blue mold rot. This rot has a significant impact on the fruit industry, causing economic losses during storage, transport, and sale. Polygalacturonase (PGs) enzymes are essential for pathogenic fungi to break down pectin, as they hydrolyze the polygalacturonic acid chain along the oxygen bridge. This enzyme has been identified in decayed tissue and is linked to multiple soft rot diseases. This study encompasses a thorough examination of the PGs gene family within the genome of P. expansum, utilizing a genome-wide analysis approach. As a result, a total of seven PG genes were successfully found. These genes were phylogenetically divided into four distinct clades. The gene structural characteristics of each group exhibited a fundamental level of conservation. Furthermore, the gene architectures and motif compositions exhibited robust evidence in favor of the credibility of the phylogenetic relationship. Motif analysis reveals that most of the motifs predicted had Glycosyl hydrolases family 28 conserved domains (PF00295). Analysis of RNA-seq data and the PG genes identified by RT-qPCR were mostly upregulated. Hence, comprehending the characteristics of PePGs holds significant scientific importance and will offer comprehensive insights into the PG superfamily in P. expansum and will make a valuable contribution to the ongoing validation of functional genes.