Spodoptera frugiperda,also known as fall armyworm(FAW),is an invasive crop pest that can feed on a variety of host plants,posing a serious threat to food security.There are two sympatric strains of FAW that are morpho...Spodoptera frugiperda,also known as fall armyworm(FAW),is an invasive crop pest that can feed on a variety of host plants,posing a serious threat to food security.There are two sympatric strains of FAW that are morphologically identical but described with different food preferences:the“rice strain”(SfR)and the“corn strain”(SfC).A few genetic loci exist to identify these two strains.Mitochondrial and Z-chromosome-linked haplotypes are the most used,but the biggest part of the genome displays little polymorphism between strains that could explain their adaptation to different plants.We have previously observed consistent transcription differences between the strains in both laboratory and natural populations.Therefore,we wonder if there are effects from host-strain-associated loci,maternally or paternally inherited,on FAW performance that could explain the divergence between the two FAW strains.To test this hypothesis,we first produced two F1 hybrid generations(SfR♀×SfC♂,SfC♀×SfR♂).These reciprocal hybrids should be heterozygous for all chromosomes except for the maternally inherited mitochondrial and sexual W chromosomes.To evaluate whether plant preference is determined by these genetic loci,we cultivated the two hybrids and the two parental strains in triplicate on an artificial diet and recorded several phenotypic traits such as weight over time,survival rate,emerging rate,developmental time,and sex ratio.Then,the same performance experiment was carried out on corn plants.Surprisingly,on the artificial diet,the two hybrid genotypes were both more performant than the two parental strains in terms of survival rate,pupal emerging rate,and developmental time,whereas they were intermediate to the inbred parental strains in pupal weight.On the corn plant diet,both hybrid genotypes outperformed the two parental strains in larval weight.Although these asymmetrical results revealed that mitochondrial or sex-linked haplotypes alone cannot explain the performance differences,they suggested a heterosis effect in FAW.A reduction of the female number for the CR genotype and the decreased F1 offspring reproduction in both hybrids suggested the possibility of Haldane's rule,which might be explained by the dominance model.展开更多
基金supported by funding from SPE department of INRAE for NN and by the scholarship from China Scholarship Council(CSC)under the collaborative program of CSC&Agreenium(CSC NO.202008440426,https://en.agreenium.fr/page/agreenium)for LLWe are also grateful to Gaetan Clabots,Raphael Bousquet,and Dylan Valenza for maintaining the insect collections of the DGIMI laboratory in Montpellier,France+2 种基金We also want to thank Antony Champion for providing the corn plants and Laetitia Leclerc and Anne-Sophie Petitot for helping take care of the plants in IRDWe appreciate the help from Sylvia Abdelmalek in setting up the experiment with corn plantsWe acknowledge Emmanuelle d'Alencon and Kiwoong Nam for their reviews and comments on an earlier version of the manuscript.
文摘Spodoptera frugiperda,also known as fall armyworm(FAW),is an invasive crop pest that can feed on a variety of host plants,posing a serious threat to food security.There are two sympatric strains of FAW that are morphologically identical but described with different food preferences:the“rice strain”(SfR)and the“corn strain”(SfC).A few genetic loci exist to identify these two strains.Mitochondrial and Z-chromosome-linked haplotypes are the most used,but the biggest part of the genome displays little polymorphism between strains that could explain their adaptation to different plants.We have previously observed consistent transcription differences between the strains in both laboratory and natural populations.Therefore,we wonder if there are effects from host-strain-associated loci,maternally or paternally inherited,on FAW performance that could explain the divergence between the two FAW strains.To test this hypothesis,we first produced two F1 hybrid generations(SfR♀×SfC♂,SfC♀×SfR♂).These reciprocal hybrids should be heterozygous for all chromosomes except for the maternally inherited mitochondrial and sexual W chromosomes.To evaluate whether plant preference is determined by these genetic loci,we cultivated the two hybrids and the two parental strains in triplicate on an artificial diet and recorded several phenotypic traits such as weight over time,survival rate,emerging rate,developmental time,and sex ratio.Then,the same performance experiment was carried out on corn plants.Surprisingly,on the artificial diet,the two hybrid genotypes were both more performant than the two parental strains in terms of survival rate,pupal emerging rate,and developmental time,whereas they were intermediate to the inbred parental strains in pupal weight.On the corn plant diet,both hybrid genotypes outperformed the two parental strains in larval weight.Although these asymmetrical results revealed that mitochondrial or sex-linked haplotypes alone cannot explain the performance differences,they suggested a heterosis effect in FAW.A reduction of the female number for the CR genotype and the decreased F1 offspring reproduction in both hybrids suggested the possibility of Haldane's rule,which might be explained by the dominance model.
