| Stripe rust is the most important epidemic disease on wheat. Overwintering is the mainly stage of annual cycle of stripe rust. Spring epidemic degree is primarily determined by the amount of overwintering Puccinia striiformis f. sp. tritici(Pst), which is mainly determined by the amount of overwintering inoculum, winter-hardiness of wheat cultivars and conductive weather conditions and so on. So, the aim of this paper was to study on the loci of Pst latent overwintering on wheat, effect of low temperature and winter-hardiness of wheat cultivar on Pst survival, and effect of Pst overwinter on disease incidence of wheat plant in returning green stage based on real-time RT-PCR. The main conclusions were showed as following:(1) Developed RNA extraction method, which was fast, high efficient and stable to extract Pst RNA from urediniospores and wheat leaves. This method overcame the troublesome of Pst urediniospores easily adhere to tube and mortar, and easily fly out during grounding in liquid nitrogen. Therefore, it was kept the initial weight of urediniospores after grounding.(2) Constructed the real-time RT-PCR method to detected viable Pst survival. Both real-time PCR of DNA and RNA could provide reliable measurement of viable Pst in plant tissues in latent stage, however only real-time PCR of RNA rather than DNA was still detected the Pst biomass in the late sporulation stage. Because real-time PCR of DNA level reflected both died and viable Pst, which resulted to over estimation Pst survival. However, real-time PCR of RNA level only reflected viable Pst, which could be used in detecting Pst biomass in the late sporulation stage.(3) Pst survial was decreased in both detached and attached leaves overtime, and less Pst survival was detected in detached leaves compared in attached leaves. Low temperature could kill viable Pst mycelium in latent plant tissues. Viable Pst was killed after incubation at-10°C for 48 h, at-15°C for 30 h in both attached and detached leaves, and at-20°C for 24 h in detached leaves and for 30 h in attached leaves. There was more viable Pst at 8°C amplitude temperature than that 13°C amplitude temperature, and this trend was stronger with the mean temperatures(0,-5 and-10°C) rising.(4) The percentage of viable Pst survival increased with increasing winter-hardiness cultivars at 0°C and-5°C. However, such differences among different winter-hardiness cultivars were decreased at other low temperatures(-10,-15 and-20°C).(5) Pst could overwinter on both wheat leaf and sheath. Pst mainly overwintered on sheath in high altitude regions, and mainly overwintered on leaf in low altitude regions. It increased the percentage of viable Pst under the protecting of outside wheat leaves in low altitude regions, whereas it was no useful for rising percentage of vialbe Pst with outside leaves on wheat plant in high altitude regions.(6) Constructed prediction model of disease incidence of wheat plant in returning green stage,21y=8.174 +0.363x-0.486w+1.280t+0.182t-0.089 d in model, y was disease incidence of wheat plant in returning green stage, x1 was disease incidence of wheat plant before winter, w was winter-hardiness cultivar, t was the daily mean temperature at December to January from meteorological station, and d was the level of remained days of daily mean temperature ≤-5°C. |
