| Barley(Hordeum vulgare L.)is a fourth cereal crop in the world,with merits of shorter growth period,high ecological adaptability,tolerance to drought,cold,and salt stresses.It has been global cultivated in the temperate regions.Hulless barley(H.vulgare L.var.nudum)is called “Qingke”in the Qinghai-Tibet Plateau(QTP),and is the only staple cereal crop and an important feed resource with alpine and cold ecology.Stripe(yellow)rust is an important airborne Qingke foliar disease,which prefers to outbreak under cold and moist weather conditions and causes serious yields losses on susceptible varieties.The causal agent is Puccinia striiformis f.sp.hordei(Psh),an obligate fungal pathogen with abundance of virulence variation among its populations.The major resistant varieties are usually overcome due to shifts of dominant physiological races or occurrence of new pathotypes of Psh,causing a great epidemic outbreak on large scale.Development and use of disease resistant varieties is the most economical,effective and environmentally friendly method for strip rust control.However,little was known about present virulence variation among the Psh populations across the barley and Qingke-grown regions.In this study,(1)A set of differential barley varieties was first of all established,wich is suitable for analyzing the virulence variation of Psh in China and detecting the predominant pathotypes;(2)The virulence spectra of 62 Psh isolates collected from the main epidemic regions were tested and their genetic diversity was analyzed to reveal the kinship and inter-regional genetic intercourse between Psh groups and populations from different epidemic regions;and(3)The disease resistance of 700 barley germplasm resources was identified at the seedling stage by using highly virulent pathotypes to clarify their resistance levels to Psh at the seedling stage.The major results of this study are as follows.1.Establishment of a set of barley differential varieties for Psh By inoculating 64 barley varieties with 62 Psh isoaltes at the seedling stage,12 genotypes were selected out to form a set of differential varieties,they are listed in an order from highly susceptible to highly resistant: 1.Shufudamai,2.Bamengdamai,3.Huayuandamai,4.Zangqing320,5.Zangqing25,6.Kangqing2,7.Chaiqing1,8.Kangqing6,9.Zangqing85,10.Zaoshu3,11.I 5,and 12.Mazurka.They were divided into 4 groups as highly susceptible(HS),moderately susceptible(MS),moderately resistant(MR),and highly resistant(HR),with each group including 3 members.This set of barely Psh differential genotypes was suitable for detecting the physiological races or pathotypes of Psh across the stripe rust epidemic areas in the Qinghai-Tibet Plateau and its neighboring regions in China.2.Analysis of virulence of barley strip rust pathogen The 62 isolates derived from epidemic areas of Tibet and Yunnan were clustered into three groups based on their virulence spectrum data on differential varieties,which are low virulence(LV),moderate virulence(MV)and high virulence(HV),with a pathotype averagely detected from 1.88 isolates.Sixteen HV pathotypes were identified,12 of which were collected from Nyingchi in Tibet,indicating that Nyingchi may be the main incolum sources of Psh in the Tibetan epidemic areas.3.Analysis of genetic variation of Psh The genetic diversity of 62 Psh isolates of seven groups derived from Yunnan,Tibet,and Sichuan was evaluated with SRAP molecular markers.Among them,the genetic distance value between two groups of Dali and Kunming was closest of0.0248,and with the highest similarity coefficient 0.9755,indicating that the genetic differences between the two groups were less.On the other hand,the genetic distance value between the two groups of Kardze and Shigatse was highest of 0.0828,with a least genetic similarity coefficient0.9205,showing that significant genetic differences exist between Kardze and Shigatse groups.Besides,less genetic distance between the two populations of Tibet and Yunnan,being regarded as two adjacent epidemic regions,was detected.For example,the genetic distance and similarity coefficients between Lhasa and Kunming groups were 0.0267 and 0.9737,respectively,with significantly positive coherence between genetic and geographical distance values.4.Resistance identification of barley genetic resources at the seedling stage The 700 barley resources were inoculated with mixed five pathotypes at the seedling stage for stripe rust resistance evaluation.Among them,324 items were resistant,which are used as resistant genotypes for further study,and their agronomic traits will be investigated in later tests.They can be used in barley strip rust resistance breeding. |
