Comparative study on Pseudaulacaspis pentagona resistance of four different cultivars of kiwifruit

Abstract

Background:Kiwifruit is a common and popular fruit around the world. However, white peach scale (Pseudaulacaspis pentagona) [Targioni-Tozzetti], a scale insect with a wide range of hosts, seriously affects the yield and quality of kiwifruit. To investigate the differences in resistance of different kiwifruit cultivars to Pseudaulacaspis pentagona, cellular structure and gene expression assays were used to explain the mechanism. Results :In this study, based on the stability of the rate of injury fruit, we selected four cultivars from fty kiwifruits for in-depth study, including "LC-04285", "CF-3", "DA-7B" and "Hayward". By analyzing the differences in the anatomical structure of the canes of these cultivars, we found that the resistant cultivar "LC-04285" had thicker cuticle, denser epidermis and cortex. The real-time quantitative PCR data indicated that the expression levels of genes related to cuticle synthesis and formation of epidermis and cortex are also higher in "LC-04285". Jasmonic acid (JA) is an important hormone involved in plant defense against many insect pests. In this study, we found that the expression levels of JA receptor COI1 were higher in "LC-04285". However, the expression levels of AcJAZs, which played negative role in JA signaling, were higher in susceptible cultivar "Hayward". Besides, the expression levels of AcICS, AcPAL4, AcPAL5, and AcNPRs, which were involved in salicylic acid (SA) synthesis and SA response, were also higher in "LC-04285". Conclusions:Our results revealed the mechanism of kiwifruit resistance to P. pentagona at the molecular and cellular levels. This study provided useful guidance for breeding insect-resistant kiwifruit in future.P. pentagona was cultured in the insect rearing facility of The Sichuan Provincial Academy of Natural Resource Science. Twelve-hour newborn female eggs of P. pentagona on pumpkin or potato were collected before the test. One-year-old canes (approximately 1.0-1.5 m long and 1-2 cm in diameter), including "LC-04285", "CF-3", "DA-7B" and "Hayward", were collected in winter (middle of December in China). The canes were wrapped in black plastic and held in a cool store at 0-2℃, RH60-70%. The laboratory experiment was set up 1-2 months later (Jan. or Feb.) in a controlled environment room at kiwifruit laboratory, Chengdu. The environmental conditions were 25℃, 70±10% Relative Humidity (RH), with a 14 h light:10 h dark photoperiod regime.The kiwifruit canes were removed from the cold store, marked and cut into 60 cm with removing the bottom of 10 cm. Each cane length was labelled and the buds were cut off. All wounds were sealed with Vaseline. Each cane was gently wrapped 6-9 turns with wool, providing a place for the eggs and crawlers to colonize [56]. Each kiwifruit cultivar had ve replicates. Colonization rate and survival rate measurementThe female eggs (about 200) of P. pentagona were gently transfer to the sites which wrapped turns on branches using stroke pen. The branches were placed at an angle of 30-50 ° to ensure that the eggs would not ...