Screening Of Maize Germplasm Resources Resistant To Spodoptera Frugiperda(Lepidoptera:Noctuidae) And Study On Maize Insect Resistance

As an important food crop,feed crop and industrial raw material,corn plays an important role in our country’s economic development.There are many pests on corn in the world,which seriously affect the yield of corn.Damage by insects is one of the most important problems in corn production.Improving insect resistance of crops by genetic breeding is an effective method to control pests.Some maize varieties themselves have good endogenous insect resistance genes.Through hybridization and breeding,excellent varieties with insect resistance and high yield can be obtained,which can be better promoted and applied commercially.Spodoptera frugiperda is a newly emerged invasive pest in recent years.Compared with several more serious pests on maize,such as the Asian corn borer,there are few studies on the identification and evaluation of insect-resistant germplasm resources and the resistance of different maize varieties,and it is difficult to apply the research results.In order to prevent the large-scale outbreak of this pest,it is necessary to screen and identify insect resistant and high-yield germplasm resources for promotion and application in a timely manner,so as to sustainably control the damage of Spodoptera frugiperda.In this study,the methods and standards of field resistance identification of maize to Spodoptera frugiperda were explored through field experiments,and the field resistance evaluation of existing maize materials was carried out to screen out maize materials with different field resistance.Through laboratory experiments,the effects of maize materials on the growth and development of Spodoptera frugiperda were analyzed,and the differences in utilization,transformation and feeding selectivity of Spodoptera frugiperda fed with different maize materials were clarified.Based on field and laboratory experiments,the evaluation system of maize resistance to Spodoptera frugiperda was improved.The main research results are as follows:1.Identification,evaluation and screening of field resistance of maize materials to Spodoptera frugiperdaThe method for identification of the field resistance to Spodoptera frugiperda was established through field experiments: Two 2nd instar larvae of Spodoptera frugiperda were inserted into the heart leaves of each plant during the period of the trumpet stage of maize.The evaluation standard of resistance at seedling stage was Davis Scale,and the evaluation standard of resistance at ear stage was 5 grades.The insect resistance of existing maize germplasm resources was evaluated to screen maize materials with different resistance to Spodoptera frugiperda.In this study,201 maize materials from Xindu and 292 maize materials from Xichang were identified.8 resistant materials and9 highly sensitive materials were identified through field insect resistance test at seedling stage in Xindu.A total of 15 resistant materials and 16 highly sensitive materials were identified through field insect resistance test at seedling stage in Xichang.5 resistant materials,17 medium resistant materials and 27 highly sensitive materials were identified by ear stage investigation.2.The growth and development of Spodoptera frugiperda larvae on different maize materials are differentThere were significant differences in food intake and body weight of the 3rd instar larvae,survival rate and body weight of the 6th instar larvae,pupal weight and pupation rate when the 2nd instar larvae were fed with different maize materials.The weight,food intake,pupation rate and pupa weight of the larvae fed with better resistant maize materials(such as H30)were lower.The results indicated that the resistance of different maize materials would affect the growth and development of Spodoptera frugiperda larval and pupal stages.Factor analysis was conducted to study the suitability of different materials to the growth and development of Spodoptera frugiperda.The results showed that the comprehensive fitness score of sensitive materials to the growth and development of Spodoptera frugiperda was higher than that of resistant materials,which meant the sensitive materials were more suitable for the growth and development of Spodoptera frugiperda than the resistant materials.Maize materials showed different degrees of resistance in various indexes.The resistance of maize to Spodoptera frugiperda may be a comprehensive resistance of many aspects,and the highly sensitive and resistant materials showed obvious consistency in many aspects.3.The nutrient utilization ability of Spodoptera frugiperda larvae to different maize materials was differentWhen the 3rd instar larvae of Spodoptera frugiperda were fed with different maize materials,the relative growth rate,food utilization rate and food conversion rate of Spodoptera frugiperda larvae fed on sensitive materials were generally higher than those of resistant materials,while the relative food intake and approximate digestibility of the larvae were lower than those fed on resistant maize materials.Compared with resistant materials,sensitive materials were more suitable for the growth,development and nutrient accumulation of Spodoptera frugiperda.However,for the low-resistant and low-sensitive materials,the correlation between the feeding and digestibility of larvae and the resistance of the materials was not significant.That is,the field resistance of the materials can affect the nutrient utilization and growth ability of larvae to a certain extent,but it is not a single decisive factor,and there may be other factors acting together.4.Feeding selectivities of Spodoptera frugiperda larvae to different maize materials was differentThe feeding selectivity of Spodoptera frugiperda larvae to different maize materials was not completely the same.The 3rd instar larvae showed significant differences in food consumption and feeding selectivity to different materials,which tended to feed on sensitive materials in general,but less resistant materials.The field resistance of different materials might affect feeding preference of different instars to a certain extent,but there might be other factors affecting the feeding preference.In summary,this study established the methods and standards for the identification of maize resistance to Spodoptera frugiperda in the field.The existing maize germplasm resource materials were identified,evaluated and screened for insect resistance in the field.The effects of different maize materials on the growth and development of Spodoptera frugiperda in the field were explored from three aspects: adaptability of growth and development,nutritional effect and feeding selectivity.The insect resistance of maize materials was clarified and the evaluation system of maize resistance to Spodoptera frugiperda was improved.The results of this study are of great significance to the screening and application of maize germplasm resources resistant to insects and the comprehensive management of Spodoptera frugiperda.