Genetic analysis of aphid-resistant materials derived from Stark Saturn flat peach

【Objective】Due to their sessile nature, plants cannot actively avoid adverse environmental factors, such as herbivory by pests. Through long - term evolutionary processes, they have developed unique disease resistance mechanisms. One such strategy is induced defense, exemplified by the production of substantial amounts of callose and suberin. Callose primarily accumulates around sieve tube structures in plants. Under stress conditions, callose deposits form at the edges of sieve pores, creating callose bodies that occlude the pores. This process modulates the transport function of sieve tubes, thereby restricting herbivorous insects access to phloem sap from host plants. Suberin is primarily distributed in the endodermis, exodermis, and epidermis of plant roots. The deposition of suberin enhances the physical barrier properties of cell walls, thereby strengthening the plant's disease resistance capabilities. The green peach aphid (Myzus persicae) is one of the most significant pests threatening peach trees in spring, posing a severe threat to the peach industry. Currently, numerous aphid - resistant resources have been identified both domestically and internationally, including French cultivars such as Rubira,Weeping Flower Peach (WFP), and P1908, as well as domestic varieties like Shouxing peach and prunus davidiana. However, all identified aphid-resistant resources are derived from wild or semi - wild species, posing significant challenges for breeding utilization. Consequently, there is an urgent need for a breeding - friendly material that would facilitate practical application in resistance breeding programs. As an aphid - resistant germplasm derived from cultivated flat peach (Prunus persica var. compressa) varieties, Stark Saturn, have demonstrated high application potential in breeding programs.【Methods】 Six segregating populations, comprising a total of 654 hybrid seedling individuals, were developed. Under greenhouse conditions, each plant was infested with 20 aphids. Phenotypic identification was conducted after the resistant and susceptible phenotypes were fully expressed. Concurrently, vigorous shoots from both susceptible and resistant plants were selected, infested with 20 Myzus persicae individuals, and enclosed in insect-proof bags. Tender stem segments were collected at three time points (0 h, 12 h, and 24 h) after aphid feeding, with three replicates, for histological staining. In the aniline blue staining, callose was specifically stained bright blue, while in the fluorescent yellow staining, suberin was distinctly stained yellow. Finally, the inheritance of aphid resistance in materials derived from the Stark Saturn flat peach was systematically analyzed using an integrated approach combining genetic analysis and polyacrylamide gel electrophoresis (PAGE).【Results】After one week of aphid inoculation when phenotypic manifestation was complete, all plants exhibited two distinct extreme phenotypes: one was aphid - susceptible, characterized by severely curled leaves and heavy aphid infestation; the other was aphid-resistant, which showed no aphid colonization and an absence of leaf curling. No intermediate types were observed. On aphid - susceptible plants, the aphid population increased continuously over one week, reaching five times the initial level on young shoots by day 6, accompanied by severe leaf curling. In contrast, on the aphid - resistant materials derived from Stark Saturn, the aphid population declined steadily after infestation, decreasing to half of the initial level by day 2. After four days, aphids were barely detectable on the resistant plants. Most resistant plants exhibited no leaf curling, with only minor and negligible leaf wrinkling observed in a few individuals. During our assessment, no aphid carcasses were observed on the aphid - resistant plants derived from the Stark Saturn flat peach, indicating that the resistance was typically antixenotic in nature. Notably, no hypersensitive response (HR) spots were observed, differing from the HR phenotype commonly seen in Shouxing peach cultivars. In the aniline blue staining assay, aphid infestation induced callose deposition. Callose levels at 24 hours post - infestation were higher than the initial values in both susceptible and resistant materials. In the fluorescent yellow staining, aphid inoculation triggered suberin deposition in the exodermis of the stem segments, with suberin levels also elevated at 24 hours compared to the initial levels. The genetic segregation analysis revealed that the aphid resistance/susceptibility segregation data from the six populations deviated significantly from the expected mendelian ratios (0∶1 or 1∶1) as determined by χ2 testing, indicating that the aphid resistance trait in Stark Saturn flat peach was regulated by major effect gene. The molecular marker validation results revealed that the marker accuracy rates for the six segregating populations were 90.52%, 73.33%, 71.22%, 88.68%, 71.43%, and 93.48%, respectively, the accuracy of molecular markers across the six segregating populations was inconsistent. These findings would provide molecular evidence supporting the hypothesis that aphid resistance in Stark Saturn is controlled by major effect gene.【Conclusion】The aphid - resistant materials derived from Stark Saturn flat peach exhibit typical antixenosis. Following aphid feeding, no hypersensitive red spots were observed. Concurrently, infestation induced the accumulation of callose and suberin within the plant tissues as part of the defense response against aphids. Both genetic analysis and molecular marker results indicated that the resistance to Myzus persicae in these materials would be controlled by a few major genes, which also suggested the potential for more durable resistance. It seems to be possible to use these valuable materials as breeding resources for breeding new varieties with resistance to aphids in practice.