Photoperiodic Response Research Articles

A Crop Simulation Model for Tef (Eragrostis tef (Zucc.) Trotter)

Tef is an Ethiopian staple grain that provides both food security and income for smallholders. As tef is nutritious and gluten free, it is also gaining popularity as a health food. A tef model was calibrated based on the Decision Support System for Agrotechnology Transfer’s (DSSAT) NWheat model and included parameter changes in phenology, photoperiod response, radiation use efficiency, and transpiration efficiency for both standard and elevated atmospheric CO2, based on published literature for tef and other C4 species. The new DSSAT-Tef model was compared with tef field experiments. DSSAT-Tef accurately simulated phenology and responded to changes in N supply and irrigation, but overestimated growth and occasionally yields. Simulation-observation comparisons resulted in an RMSE of 2.5 days for anthesis, 4.4 days for maturity, 2624 kg/ha (49.6%) for biomass, and 475 kg/ha (41.0%) for grain yield. Less data were available for N uptake, and the model simulated crop N uptake with an RMSE of 45 kg N/ha (46.2%) and 15 kg N/ha (37.3%) for grain N. While more data from contrasting environments are needed for further model testing, DSSAT-Tef can be used to assess the performance of crop management strategies, the suitability of tef for cultivation across growing environments, and food security.

Photoperiodic and clock regulation of the vitamin A pathway in the brain mediates seasonal responsiveness in the monarch butterfly

Seasonal adaptation to changes in light:dark regimes (i.e., photoperiod) allows organisms living at temperate latitudes to anticipate environmental changes. In nearly all animals studied so far, the circadian system has been implicated in measurement and response to the photoperiod. In insects, genetic evidence further supports the involvement of several clock genes in photoperiodic responses. Yet, the key molecular pathways linking clock genes or the circadian clock to insect photoperiodic responses remain largely unknown. Here, we show that inactivating the clock in the North American monarch butterfly using loss-of-function mutants for the circadian activators CLOCK and BMAL1 and the circadian repressor CRYPTOCHROME 2 abolishes photoperiodic responses in reproductive output. Transcriptomic approaches in the brain of monarchs raised in long and short photoperiods, summer monarchs, and fall migrants revealed a molecular signature of seasonal-specific rhythmic gene expression that included several genes belonging to the vitamin A pathway. We found that the rhythmic expression of these genes was abolished in clock-deficient mutants, suggesting that the vitamin A pathway operates downstream of the circadian clock. Importantly, we showed that a CRISPR/Cas9-mediated loss-of-function mutation in the gene encoding the pathway's rate-limiting enzyme, ninaB1, abolished photoperiod responsiveness independently of visual function in the compound eye and without affecting circadian rhythms. Together, these results provide genetic evidence that the clock-controlled vitamin A pathway mediates photoperiod responsiveness in an insect. Given previously reported seasonal changes associated with this pathway in the mammalian brain, our findings suggest an evolutionarily conserved function of vitamin A in animal photoperiodism.

Effect of T-photocycle and wavelength on photoperiodic induction in Indian weaver bird (Ploceus philippinus)

ABSTRACT Photoperiodic responses of a photosensitive species depend on the species-specific critical day length (CD), determined by the entrainment of the endogenous circadian rhythm of photoinducibility. We examined the entrainment pathway of the circadian photoperiodic system of photosensitive weaver birds. Birds were subjected to T = 22,24 and 26 h photocycles, with 11- and 12-h photophase to study the photoperiodic induction and synchronization of bird’s circadian system with reference of different light wavelengths. Two experiments were performed on adult male weaver birds. In experiment 1, birds were exposed to T = 22 and 26 h LD-cycles, having 11-h photophase with red and blue light wavelength, while in experiment 2, birds were exposed to T = 22, 24 and 26 h LD-cycles, having 12-h photophase with red and blue light wavelength. Observations on change in body mass and testis size were recorded at monthly intervals. There was a significant effect of red light wavelength on photoperiodic induction of testicular growth in the birds exposed to T = 22 h (11L:11D and 12L:10D) and T = 26 h (11L:15D and 12L:14D; both wavelength), but not when exposed to T = 24 h (12L:12D) photophase. Further, body mass regression was faster in birds of T = 26 h photophase (12L:14D) under blue wavelength. Thus, the above results are indicative of the influence of light wavelength on the endogenous programming that times seasonal responses in body fattening and testicular growth-regression of Indian weaver bird.

Identification of diapause-associated proteins in migratory locust, Locusta migratoria L. (Orthoptera: Acridoidea) by label-free quantification analysis

Maternal photoperiodic response is a key factor that affects offspring diapause in migratory locust, Locusta migratoria L. (Orthoptera: Acridoidea). Although many aspects of insect diapause have been studied, little is known about the molecular mechanisms of maternal photoperiodic response that influence diapause regulation. To gain insight into the possible mechanisms of maternal photoperiod influence on diapause regulation, proteomics data by label-free quantification analysis were generated from non-diapause and diapause eggs. A total of 175 proteins were differentially expressed between diapause and non-diapause eggs. Among them, 24 proteins were upregulated, and 151 proteins were downregulated. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichments were performed on all differentially expressed proteins (DEPs) and showed that peroxisome, insect hormone biosynthesis, and longevity regulating pathway may be related to diapause of migratory locust. Furthermore, we used qRT-PCR to verify some results of the proteomic analysis. Proteins such as hexamerin-like protein 4, juvenile hormone epoxide hydrolase 1 (JHEH1), cytochrome P450 and heat shock protein (HSP) 20.7 were predicted to be involved in diapause. This study provides an important reference for future research that will explore the mechanisms of diapause induced by maternal effects in migratory locust.

Photoperiod-sensitivity genes (Ppd-1): quantifying their effect on the photoperiod response model in wheat.

Coupling anthesis date to the most suitable environmental conditions is critical for wheat (Triticum aestivum L.) adaptation and yield potential. Development to anthesis is controlled by temperature and photoperiod. Response to photoperiod is chiefly modulated by Ppd-1 genes, but their effect on the quantitative response to photoperiod of (i) time to anthesis and (ii) pre-anthesis phases remains largely unknown. A photoperiod-sensitive spring cultivar, Paragon, and near-isogenic lines of it carrying different combinations of Ppd-1a insensitivity alleles were tested under a wide range of photoperiods, including switches in photoperiod at the onset of stem elongation. Using multimodel inference we found that Ppd-1a alleles reduced photoperiod sensitivity of (i) emergence to anthesis and (ii) emergence to onset of stem elongation, both in a less than additive manner, while threshold photoperiod and intrinsic earliness were unaffected. Sensitivity to current photoperiod from onset of stem elongation to flag leaf and from then to anthesis was milder than for previous phases and was not related to variability in Ppd-1. However, 'memory' effects of previously experienced photoperiod on the duration from onset of stem elongation to flag leaf were related to variability in Ppd-1. The characterization and quantification provided here of the effects on development of Ppd-1 allelic combinations should help increase accuracy of genotype-to-phenotype models in predicting wheat phenology.

Positional Cloning of the Flowering Time QTL qFT12-1 Reveals the Link Between the Clock Related PRR Homolog With Photoperiodic Response in Soybeans.

Flowering time and maturity are important agronomic traits for soybean cultivars to adapt to different latitudes and achieve maximal yield. Genetic studies on genes and quantitative trait loci (QTL) that control flowering time and maturity are extensive. In particular, the molecular bases of E1-E4, E6, E9, E10, and J have been deciphered. For a better understanding of regulation of flowering time gene networks, we need to understand if more molecular factors carrying different biological functions are also involved in the regulation of flowering time in soybeans. We developed a population derived from a cross between a landrace Jilincailihua (male) and a Chinese cultivar Chongnong16 (female). Both parents carry the same genotypes of E1e2E3HaE4 at E1, E2, E3, and E4 loci. Nighty-six individuals of the F2 population were genotyped with Illumina SoySNP8k iSelect BeadChip. A total of 2,407 polymorphic single nucleotide polymorphism (SNP) markers were used to construct a genetic linkage map. One major QTL, qFT12-1, was mapped to an approximately 567-kB region on chromosome 12. Genotyping and phenotyping of recombinant plant whose recombination events were occurring within the QTL region allowed us to narrow down the QTL region to 56.4 kB, in which four genes were annotated. Allelism and association analysis indicated Glyma.12G073900, a PRR7 homolog, is the strongest candidate gene for qFT12-1. The findings of this study disclosed the possible involvement of circadian clock gene in flowering time regulation of soybeans.

Diversity of photoperiodic responses in oats

The article presents the results of an evaluation of the earliness and photoperiodic response (PPR) in the long-day oat accessions of various geographic origin. The material for this study were 139 oat accessions from the global collection of plant genetic resources maintained by the Vavilov Institute (VIR), which included landraces, breeding cultivars, and lines. In addition, the donors of low sensitivity to photoperiod developed at VIR were tested. A preliminary field study of the oat collection for early maturity and growing plants in the vegetation experiment was carried out according to the VIR Guidelines. The early accessions from VIR’s oat collection identified in the field showed a great diversity of their photoperiodic responses during the vegetation experiment in a photoperiod facility. By origin, most of the accessions described in the vegetation experiment as earliness and weakly responsive to photoperiod were from Brazil (66 %); others from the USA, Portugal, Turkey, Colombia and Australia. Most of the Russian cultivars studied (77 %) were sensitive to a short photoperiod. Among donors with different photoperiodic responses, Skorospely 1 and Skorospely 2 were weakly responsive to photoperiod, while Srednespely 1 and Srednespely 2 showed medium responses. Many years of field studies and vegetation experiments with the oat genetic diversity from the VIR global collection have resulted in identifying genotypes characterized by earliness and weak photoperiodic responses. These accessions are of special value for breeders and currently being used to develop new early and productive oat cultivars.

Variability of the photoperiod response in guar (Cyamopsis tetragonoloba (L.) Taub.) genotypes of different geographic origin

Variability of the photoperiod response in guar (Cyamopsis tetragonoloba (L.) Taub.) genotypes of different geographic origin

Different as night and day: Behavioural and life history responses to varied photoperiods in Daphnia magna.

Nearly all animal species have utilized photoperiod to cue seasonal behaviours and life history traits. We investigated photoperiod responses in keystone species, Daphnia magna, to identify molecular processes underlying ecologically important behaviours and traits using functional transcriptomic analyses. Daphnia magna were photoperiod‐entrained immediately posthatch to a standard control photoperiod of 16 light/ 8 dark hours (16L:8D) relative to shorter (4L:20D, 8L:16D, 12L:12L) and longer (20L:4D) day length photoperiods. Short‐day photoperiods induced significantly increased light‐avoidance behaviours relative to controls. Correspondingly, significant differential transcript expression for genes involved in glutamate signalling was observed, a critical signalling pathway in arthropod light‐avoidance behaviour. Additionally, period circadian protein and proteins coding F‐box/LRR‐repeat domains were differentially expressed which are recognized to establish circadian rhythms in arthropods. Indicators of metabolic rate increased in short‐day photoperiods which corresponded with broadscale changes in transcriptional expression across system‐level energy metabolism pathways. The most striking observations included significantly decreased neonate production at the shortest day length photoperiod (4L:20D) and significantly increased male production across short‐day and equinox photoperiods (4L:20D, 8L:16D and 12L:12D). Transcriptional expression consistent with putative mechanisms of male production was observed including photoperiod‐dependent expression of transformer‐2 sex‐determining protein and small nuclear ribonucleoprotein particles (snRNPs) which control splice variant expression for genes like transformer. Finally, increased transcriptional expression of glutamate has also been shown to induce male production in Daphnia pulex via photoperiod‐sensitive mechanisms. Overall, photoperiod entrainment affected molecular pathways that underpin critical behavioural and life history traits in D. magna providing fundamental insights into biological responses to this primary environmental cue.

Phenotypic and genetic analysis to identify secondary physiological traits for improving grain yield in wheat considering anthesis time variability

Identification of secondary traits in mapping populations is usually hindered by the strong effect of anthesis time. Thus, considering the variability in time to anthesis in combination with an accurate phenotyping of mapping populations and available molecular tools is a possible way for recognising secondary traits to improve yield potential. The aim of this work was to identify secondary traits to perform indirect selection for grain yield (GY) in a bread wheat mapping population consisting of 124 doubled haploid lines, derived from the cross between two soft red winter wheat genotypes with contrasting photoperiod response. Genomic regions linked to different traits were analysed under two environments. The population showed a strong effect of time to anthesis over GY, as expected. A large variability in GY was observed but only two QTLs were detected on chromosome 5A for this trait, which co-localized with QTLs of time to anthesis. GY variation was partially associated with above-ground dry matter at maturity (AGDM) and to a lesser extent with harvest index (HI). Detected QTLs for grains per m2 (GN), grain weight, AGDM and HI explained between 25 and 61% of the GY additive genetic variance. GN, defined as the product between spike dry weight at anthesis (SDW) and fruiting efficiency (FE), was the main numerical component that explained most of the variation in GY. Five QTLs were detected for SDW, which did not co-localize with QTLs of time to anthesis and captured ca. 50% of the additive genetic variance, while there was a weak relationship between NG and FE. When genotypes were filtered by similar anthesis time and plant height, SDW was identified as a promising secondary trait to be targeted for indirect selection of GY.

Earliness per se variation in Argentine bread wheat varieties and mapping of QTLs in a recombinant inbred line population

The occurrence of flowering time in wheat is affected not only by the vernalization and photoperiod response, but also by earliness per se (EPS). The effects of this trait facilitate the fine tunning of the life cycle for regional adaptation within mega environments. To contribute to the knowledge of the wheat germplasm grown in Argentina and to the understanding of the genetic basis underlying variation in EPS, this study aimed to characterize EPS in a set of modern local bread wheat varieties and to develop a biparental recombinant inbred line (RIL) population based on parental contrasting for EPS. The variation observed in flowering time, which was measured under satisfied vernalization and photoperiod demands and assignment of chromosomic regions by QTL analysis, constitutes the first genetic dissection of EPS control in Argentine wheat adapted materials, providing valuable information for regional adaptation in breeding programs. Based on EPS variation analysis, Baguette Premium 11 (late-heading variety) and BioINTA 2001 (early-heading variety) were selected to develop the mapping population. Six QTLs for EPS were detected in the biparental RIL population and QTL QEps.imj-5D1, in chromosome 5D, showed the greatest effect on EPS and is the first QTL to be reported in this chromosome.

Identification and mapping of a photoperiod response gene (QPpd.zafu-4A) on wild emmer wheat (Triticum turgidum L.) chromosome 4AL

Heading date (HD) is an important agronomic trait, influencing directly or indirectly yield and quality traits. Previous experiments showed that the chromosome arm substitution line (CASL) 4AL of wild emmer in the background of Chinese Spring (CS) was about 18–22 days later in HD than CS. In this study, CASL4AL flowered roughly 20 days earlier than CS grown under long day (LD) with short day (SD) vernalization, but failed to flower when planted under controlled SD conditions. The above results suggest CASL4AL carries an extremely sensitive photoperiod response gene. CASL4AL showed a major difference from CS in restricted young spike development, remaining at the double-ridge stage and floret-primordium differentiation stage much longer than CS under SD. To map this gene, the F2 population from cross between CS and CASL4AL were explored in two consecutive years. In 2016, a HD related QTL flanked by M576 and wmc468 with a LOD score (8.5) was detected. In 2017, this QTL was repeatedly detected with a higher LOD score (10.03), and therefore named as QPpd.zafu-4A. A total of 27 genes were annotated and possible candidate was discussed. This work lays a foundation for map-based cloning of QPpd.zafu-4A and elucidating its molecular mechanism in affecting HD.

Testosterone does not mediate variation in basal metabolic rate and activity in relation to reproductive condition and photoperiod in white-footed mice (Peromyscus leucopus).

The photoperiodic response of many temperate zone rodents, including white-footed mice (Peromyscus leucopus), is a heritable life-history trait with underlying physiological variation. Previous studies of intact male P. leucopus utilized two wild-derived bidirectional selection lines, a short photoperiod responsive (R) line selected for reproductive suppression in short-day conditions (SD) and a nonresponsive (NR) line selected for reproductive maturity in SD. NR mice in SD had greater food intake, but also higher levels of locomotor activity, and basal metabolic rate (BMR) than R mice. We hypothesized that testosterone may be a key mediator of this metabolic difference, as it is likely to be significantly reduced in R SD mice. Male P. leucopus from either line in SD were castrated and given either an implant containing testosterone (T) or a sham control (C). They were then tested for variation in metabolic rate and activity in SD, thermoneutral conditions. T mice had significantly higher levels of food intake, testosterone, and seminal vesicle dry weight than C mice. Seminal vesicle dry weight was significantly and positively correlated with average testosterone level, indicating an effect of the T implants. There was no statistically significant difference among treatment groups in BMR and average daily metabolic rate, suggesting that differences in testosterone alone are not the cause of differences in metabolic rate between selection lines.

Rapid Isolation of Loss‐of‐Function Mutations for Dominant Traits: A Case Study Using Photoperiod Sensitivity Trait in Pima Cotton

In its natural state, cotton (Gossypium spp.) is a perennial that flowers only under short‐day conditions. Early selection efforts eliminated this photoperiod requirement, allowing cotton cultivation to shift predominantly to annual growth under long summer daylengths throughout the world. Photoperiod sensitivity persists in many wild cottons and remains a major barrier to the introgression of beneficial alleles into elite breeding material. Identification of the variation and genetic factors underlying photoperiod response in cotton is needed to fully harness the genetic diversity of wild cotton and broaden the cultivated germplasm pool. Genetic variants, especially loss‐of‐function mutations in dominant genes conferring photoperiod sensitivity, would be highly valuable in this regard. After mutagenizing pima cotton (G. barbadense L.) seeds heterozygous for the major photoperiod response gene Gb_Ppd1 with γ rays, we identified plants no longer sensitive to photoperiod. Genetic analysis of BC1F1 plants derived from backcrossing the mutants with their photoperiod‐insensitive parent confirmed the loss‐of‐function mutations were allelic with Gb_Ppd1. Characterization of the mutants with molecular markers confirmed that all but one were deletions of Gb_Ppd1. Further, genotyping localized Gb_Ppd1 to a 12‐Mb region on chromosome D10. The newly identified genomic region and loss‐of‐function mutants may help assist with the identification and functional validation of candidate genes for photoperiod response in cotton, facilitating the valuable introgression of genetic diversity into cotton breeding programs.

Critical Photoperiod Measurement of Soybean Genotypes in Different Maturity Groups

Soybean [Glycine max (L.) Merr.] is a photoperiod‐sensitive crop, and the photoperiod response determines the ecological adaptability of soybean genotypes. Critical photoperiod is the dividing daylength between photoperiod sensitivity and photoperiod insensitivity phases and is one of the most important indicators of photoperiod sensitivity. However, the appropriate experimental treatment and calculation method for quantifying the critical photoperiod are poorly documented. To characterize the photoperiod response of genotypes, 72 soybean genotypes belonging to 14 different maturity groups (MG 0000–MG X) were included, and five photoperiod treatments of 12‐, 14‐, 16‐, 18‐, and 20‐h daylength were conducted in the consecutive 3 yr from 2015 to 2017. The piecewise linear regression model based on the median function was used to determine the critical photoperiod. The results showed that the photoperiodic responses of soybean genotypes were significantly different among various MGs. The critical photoperiod of MG 0000 was 16.4 h d−1, whereas those of MG 000 to MG I, MG II to MG III, MG IV, MG V to MG VIII, and MG IX to MG X were 15.7 to 15.8, 15.3, 14.7, 13.4 to 13.7, and ≤12 h d−1, respectively. A significant negative linear relationship between the critical photoperiod and relative maturity group (RMG) was found. It is of particular importance for the quantification of soybean photoperiod response and precise prediction of the developmental process. More importantly, the critical photoperiod obtained in this study will help breeders to synchronize the flowering time of parents from distant geographic origins and break the reproductive isolation among different ecotype cultivars.

Responses to nitrogen conditioning in ‘Albion’ strawberry (Fragaria X ananassa Duch.) for off-season plasticulture production are primarily qualitative rather than quantitative

The nature (qualitative vs. quantitative) of growth responses to nitrogen during photoperiod conditioning of ‘Albion’ strawberry (Fragaria x ananassa Duch.) plants for late summer / early fall off-season field production was evaluated in New Jersey, USA. For two different planting dates (14 June and 6 July), plants were conditioned in the greenhouse under ND (natural daylength), LD (natural daylength supplemented with 24 h incandescent radiation (Phillips Duramax Soft White A19 60 W) or LD7W (natural daylength supplemented with 24 h incandescent radiation (C9, 7 W bulbs) followed by elevated nitrogen (800 ppm) for 0–4 weeks. Plants were then established in field plasticulture. Flowering in July was enhanced by LD conditioning; however, these effects did not persist and have an impact on plant productivity. Qualitative responses to N included crown branching, runner production, fruiting precocity and early season yield. Results confirm the previous observation that conditioning plants prior to off-season plasticulture production in the Northeast US is not necessary if plants are established in the field by early July. The LD7W light treatment was more effective than the LD light treatment in eliciting photoperiod responses especially when nitrogen levels were low. Thus, the lower wattage bulbs may be an effective tool for managing photoperiod responses for off-season production when needed (later planting dates) with this cultivar.

Growth and Flowering Response of <i>Patrinia rupestris</i> in Response to Different Cold Durations and Photoperiods

This study aims to examine the effects of cold durations and photoperiods on dormancy break, growth, and flowering of Patrinia rupestris native to Korea. First, we monitored the growth and flowering phenology of plants growing in an open field from March to October, 2018. For the dormancy breaking experiments, P. rupestris was maintained at 4°C for 0, 3, 6, 9, and 12 weeks under short-day conditions andfor cold treatment. The plants were then transferred to long-day conditions (9 h + 4h night interruption) in room chamber set at 25°C. To determine photoperiodic responses, P. rupestris was maintained under short- (9 h, SD), middle- (12 h, MD), and long-day (16 h, LD) conditions in room chamber set at 25°C following natural chilling accumulation. In open field conditions, P. rupestris blooms in the late summer from August to September with attractive yellow flowers. Time to first flower significantly decreased following 9 or 12 weeks of cold storage compared with the plants subjected to 3 or 6 weeks of cold storage. P. rupestris required ≥9 weeks of chilling treatment to achieve ≥33% flowering. Plant height was the highest in the LD condition (50.1 cm) compared with the SD (16.7 cm) and MD (16.1 cm) conditions. All plants grown under LD conditions flowered, but not all plants grown under SD and MD conditions did (0% flowering) after 16 weeks of forcing. P. rupestris demonstrated both obligate vernalization and long-day flowering responses.

Molecular Basis of Natural Variation in Photoperiodic Flowering Responses

Plants exhibit different flowering behaviors in response to variable photoperiods across a wide geographical range. Here, we identify MYC3, a bHLH transcription factor, and its cis-element form the long-sought regulatory module responsible forcis-regulatory changes at the florigen gene FLOWERING LOCUS T (FT) that mediate natural variation in photoperiodic flowering responses in Arabidopsis. MYC3 is stabilized by DELLAs in the gibberellin pathway to suppress FT through binding the ACGGAT motif and antagonizing CONSTANS (CO) activation. Changing photoperiods modulate the relative abundance of MYC3 and CO, thus determining either of them as the predominant regulator for FT expression under different day lengths. Cis-regulatory changes in the MYC3 binding site at FT are associated with natural variation in day-length requirement for flowering in Arabidopsis accessions. Our findings reveal that environmental and developmental signals converge at MYC3 suppression of FT, an elementary event underlying natural variation in photoperiodic flowering responses.

Seasonal Development of Plant Bugs (Heteroptera, Miridae): Subfamily Bryocorinae

Data on seasonal development of plant bugs from subfamily Bryocorinae (Miridae) are reviewed and analyzed. All of the species of bryocorines whose seasonal development has been studied so far belong to the tribe Dicyphini, owing to the latter’s economic importance as agents of biological control in greenhouses. Macrolophus melanotoma, M. pygmaeus, and Nesidiocoris tenuis have homodynamic seasonal development and the lower developmental threshold of about 8–9°C. If food is available, they can remain active all year round and produce annually a varying number of generations, depending on the local climatic conditions. To survive adverse low-temperature winter conditions these species use various natural protected microhabitats and can overwinter at different developmental stages. The other two bryocorines studied (Dicyphus errans and D. hesperus) exhibit heterodynamic seasonal development and overwinter in the state of adult diapause. Induction of this diapause is controlled by a long day-type photoperiodic response. Also, the nymphal growth rate of D. errans is affected by day length and this quantitative photoperiodic response ensures that nymphs of this species reach the diapausing stage (adult) in appropriate time, which is crucial for successful overwintering. The threshold photoperiod for induction of winter adult diapause varies with latitude in D. hesperus, only nymphs being sensitive to day length in this species. Pilot experimental studies should precede any planned introduction of a biocontrol agent, as these may reduce the risk of invasions. During the early stages of settling in a new area, it is seasonal adaptations controlling development of bug populations in their natural environments that are particularly important. In greenhouses, higher efficiency of biocontrol measures can be achieved with southern multivoltine populations of homodynamic species, especially if these grow rapidly as immatures, have high reproduction rates at the adult stage, and easily switch to novel prey. Under field conditions, polyphagous heterodynamic univoltine species and populations with deep obligate diapause are more likely to naturalize successfully.

Temperature alters the hypothalamic transcription of photoperiod responsive genes in induction of seasonal response in migratory redheaded buntings

We investigated the temperature effects on hypothalamic transcription of genes involved in the induction of photoperiodic response in redheaded buntings. Birds were exposed at 22 and 38 °C to 13-h long photoperiods (LP), with controls at 22 °C on 8-h short photoperiods (SP). At 22 °C, compared to SP, we found higher tshb, eya3 and dio2 and low dio3 and gnih mRNA expressions after a week of LP; concomitant with testis recrudescence this confirmed buntings’ responsiveness to LP-induced photostimulation. tshb, dio2 and gnrh mRNA levels were further increased by 2.5 weeks of LP at 38 °C. Temperature sensitive trpm8, but not trpv4, bdnf or adcyap1 also showed LP-induced expression at 22 °C. Concomitant changes in dnmt3b and tet2 mRNA expressions further suggested epigenetic modification of temperature influence on photoperiodic responses. These results demonstrate the role of temperature in hypothalamic molecular regulation of the photoperiodic gonadal response in seasonally breeding birds.