Resistance Evaluation of Part of Leading Rice Varieties to Rice Blast Disease in Guangxi Province

Qun YAN，Zhiyong LUO，Jin ZHANG，Lijun GAO，Xiaolin CHEN，Hanliang GAO.Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests，Institute of Plant Protection，Guangxi Academy of A-gricultural Sciences，Nanning 50007，China；.Guangxi Seed Administration Station，Nanning 500，China；.Guangxi Academy of Agricultural Sciences，Nanning 50007，China

Resistance Evaluation of Part of Leading Rice Varieties to Rice Blast Disease in Guangxi Province

Qun YAN1*，Zhiyong LUO2，Jin ZHANG3，Lijun GAO1，Xiaolin CHEN1，Hanliang GAO1
1.Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests，Institute of Plant Protection，Guangxi Academy of A-gricultural Sciences，Nanning 530007，China；
2.Guangxi Seed Administration Station，Nanning 530022，China；
3.Guangxi Academy of Agricultural Sciences，Nanning 530007，China

In order to determine the resistance of leading rice varieties to rice blast in Guangxi，three natural rice blast nurseries were established in Cenxi，Sanjiang and Yongfu.The resistance of the 45 leading rice varieties in Guangxi to rice blast was determined under conditions of spray inoculation and natural induction at seedling stage.The results showed that resistance frequencies of the 45 leading rice varieties ranged from 8.33%to 94.44%.Among the 45 tested varieties，there were 8 varieties of which the resistance frequencies were all higher than 80%，accounting for 17.78%；there were 11 varieties of which the resistance frequencies ranged from 50%to 80%，accounting for 24.44%；the resistance frequencies of the remaining varieties were all lower than 50%，accounting for 57.78%of the total tested varieties.The two-consecutive-year determination results showed none of the 45 leading rice varieties showed resistance to rice blast.In 2010，there were 26，12 and 7 varieties that were moderately sensitive，sensitive and greatly sensitive to rice blast respectively，accounting for 57.78%，26.67%and 15.56%of the total tested varieties.In 2011，there were 16，23 and 12 varieties that were moderately sensitive，sensitive and greatly sensitive to rice blast respectively，accounting for 35.56%，51.11%and 13.33%.The overall resistance of the 45 leading rice varieties trended to be decreased year by year.So in rice production，they should be selected properly.

Leading rice varieties；Rice blast；Resistance evaluation；Guangxi

Therefore，in production，corresponding rice blast nurseries should be established in different ecological rice-planted areas so as to monitor the resistance of local leading rice varieties to rice blast.Thus the resistant traits of leading rice varieties will be identified.In addition，the resistancelosing varieties can be found timely. So the establishment of disease nurseries has important guiding significance for effective control of rice blast and secure production of rice.In this study，the natural rice blast nurseries were established in Cenxi，Yongfu and Sanjiang，three different ecological rice-planted areas.Under conditions of spray inoculation and natural induction，the resistance of 45 leading rice varieties in Guangxi to rice blast was determined and evaluated.

Material and Methods

Material

The rice blast strains that were used for artificial inoculation at seedling stage were from Cenxi，Beiliu， Pingnan， Lingchuan， Guiping，Quanzhou，Hepu，Luchuan，Ziyuan and Tianyang.The 36 strains belonged to 12 physiological races，including ZA1（1），ZB5（6），ZB9（3），ZB11（1），ZB13（10），ZB15（2），ZC1（1），ZC9（1），ZD5（7），ZE1（1），ZF1（2）and ZG1（1）. They were provided by the Institute of Plant Protection of Guangxi Academy of Agricultural Sciences.The rice varieties that were sensitive to rice blast in nurseries included Yanhui 559，Guijing No.1， Youzhan No.8， Qiguizhan，Mabayinzhan and Liangyou 6326.

The tested rice varieties were leading varieties in Guangxi Province. They were provided by the Guangxi Seed Administration Station（Table 1）.

Methods

Indoor resistance determination at seedling stage The preparation of rice blast fungal spore suspension，nursing of seedlings and inoculation of pathogenic fungi were all carried out［9］. The investigation was conducted 7 d after the inoculation.According to‘Rule of Field-Resistance Identification for Pyricularia oryza’，the disease degrees of 0-3 were defined as resistance （R），while the disease degrees of 4-9 were defined as sensitivity（S）. The disease degree of the most seriously infected plant was treated as the disease degree of the variety.For each variety，if there was more than one plant sensitive to infection，the variety was considered to be sensitive（S）；if there were none plants infected with rice blast，the variety was considered to be resistant（R）.

Resistance frequency=（No-infecting stain number/Inoculated stain number）×100%.

Table 1 Tested rice varieties

Resistance determination in nurseries under natural induction

Establishment of nurseries The test was carried out during 2010 to 2011.The natural rice blast nurseries were established in Cenxi，Yongfu and Sanjing，respectively.In Cenxi，the nursery was established in Nansha Village，Limu Town.It was located in a small valley base with altitude of 353 m and covered an area of 0.8 hm2.The nursery was surrounded by mountains.There was a year-round flowing creek next to the nursery.The soil in nursery was sandy loam，which had moderate fertility，adequate water，convenient drainage and irrigation and long fog and dew-covered time.In general，the fog and dew would not disappear till 11:00 am.However，the nursery had relatively short sunlight duration，less than 7 h/d.During the whole growth period of rice，the average daily temperature reached 22-26℃.In short，the nursery had geo-graphical and environmental conditions conducive to occurrence of rice blast.This also explained why the rice blast occurred seriously in this area over the years.In Sanjiang，the nursery was located in Zhouping Village，Guyi Town.It had an area of 0.07 hm2，and was also located in a small valley base.The nursery had plenty of water but short sunlight duration.In Yongfu，the nursery was located in Tudong Village，Yongfu Town.It covered an area of 0.09 hm2.In the west of the nursery，there was a hill，which was also an embankment for a reservoir. So the nursery had convenient drainage and irrigation.The sunlight duration of the nursery was also short. This area was also prone to the occurrence of rice blast.

Field management and investigation methods in nurseries Referring to previous study［10］，the field design and cultivation management of the three nurseries were carried out. The nurseries were not sprayed with fungicides.The spraying of fungicides depended on the disease degree in the nurseries.A total of three times of investigation were conducted，including investigation on seedling blast before transplanting，investigation on leaf blast in field at tillering stage and investigation on spike blast at yellow maturity stage.For investigation on seedling blast and leaf blast，the average disease degree of the 20-50 most seriously-infected leaves collected from the representative plants in the incidence center of each plot was treated as the disease degree of the variety.For investigation of spike blast，more than 100 spikes were collected from each plot.The disease degree division，recording standards and resistance evaluation were consistent with those described by Yang et al［11］.

Resistance index=Disease degree of leaf blast×25%+Disease degree of incidence of spike blast×25%+ Disease degree of loss rate of spike blast×50%.

Results and Analysis

Indoor resistance determination of 45 leading rice varieties

The indoor resistance of the 45 leading rice varieties in Guangxi to the 36 rice blast strains from different ecological rice-planted areas was determined at seedling stage.The results showed their resistance frequencies ranged from 8.33%to 94.44%（Table 2）.There were 8 varieties of which the resistance frequencies were all higher than 80%，accounting for 17.78%；there were 11 varieties of which the resistance frequencies ranged from 50% to 80%，accounting for 24.44%；the resistance frequencies of the remaining varieties were all lower than 50%，accounting for 57.78%of the total tested varieties（Fig.1）.The 8 rice varieties of which the resistance frequencies were higher than 80%were all early indicarice.Among the 8 rice varieties，Q You No.6 showed the highest resistance frequency（94.44%），followed by Teyou 5058（86.11%）.The Boyou 998，a light-sensitive late indica rice cultivar， showed the lowest resistance frequency（8.33%）.

Continued（Table 2）

Resistance determination of 45 leading rice varieties in nurseries

The two-consecutive-year determination results showed that the disease degrees of seedling blast and leaf blast all ranged from 6 to 8 in the three natural nurseries.The incidence of spike blast was even up to 100%，and the loss rate of spike blast was also higher than 95%.It was indicated the environments in the three nurseries were all suitable enough for the occurrence of rice blast，and the determination results could truthfully reflect the resistant or sensitive characters of rice varieties.In 2010，there were 26，12 and 7 varieties that were moderately sensitive，sensitive and greatly sensitive to rice blast respectively，accounting for 57.78% ，26.67%and 15.56%of the total tested varieties.In 2011，there were 16，23 and 12 varieties that were moderately sensitive，sensitive and greatly sensitive to rice blast respectively， accounting for 35.56%，51.11%and 13.33%.Combining the two-consecutive-year resistance appearance of the rice varieties，there were 13 varieties moderately sensitive to rice blast，including Zhunliangyou 1383，Ganxi 688，T78 You 2155，Liyou 6602，Teyouhang No.1，Q You No.6，Teyou 5058，Teyou 837，Guodao No.1， Teyou9846，Zhongzheyou No.8，Boyou 781 and Bo III You 273；there were 2 rice varieties highly sensitive to rice blast，including Liushayouzhan 202 and Qiuyou 998.However，none resistant rice varieties were found among the 45 leading rice varieties in Guangxi.Even worse，the overall resistance of the 45 leading rice varieties trended to be decreased year by year（Table 2）.

Conclusions and Discussion

The artificial-inoculation resistance determination and natural-induction resistance determination are two major resistance determination methods.The various rice blast physiological races are usually sprayed on leading rice varieties in room at seedling stage so as to determine the resistance frequencies of rice varieties.In general，the wider the resistance spectrum is，the higher the resistance is，and the longer the resistance will be lasted in field.Chen et al.［12］considered that the indoor resistance rate against blast was positively related to the re-sistance rates against leaf blast and spike blast in natural nurseries.Feng et al.［13］also considered that the incidences of leaf blast and spike neck blast in nurseries were positively related to the indoor in-vitro determination results （P＜0.05）.In this study，the resistance appearances of the 8 rice varieties of which the indoor resistance frequencies were all higher than 80% were basically consistent with the determination results in natural nurseries. The two-consecutive-year determination all showed that the 8 rice varieties had relatively high resistance and they were all moderately sensitive to rice blast.However，Teyou2155and Tianyou 998 were moderately sensitive in 2010，but were sensitive in 2011.For the rice varieties of which the indoor resistance frequencies were lower than 80%，there were no significant correlations between indoor determination results and in-nursery determination results.For example，the indoor resistance frequency of Boyou 998 was lowest（8.33%），but in nurseries，it was moderately sensitive in 2010 and sensitive in 2011；Boyou 679 showed a relatively high indoor resistance frequency（53.78%），but it was sensitive and highly sensitive to rice blast in the two years.These study results were consistent with those of Zhu et al［14］.

In this study，the resistance of the 45 leading rice varieties was generally low in natural disease nurseries.None resistant varieties were found.Instead，most of the rice varieties were sensitive or highly sensitive to，especially the high-quality conventional rice，Liushayouzhan 202 and late rice，Qiuyou 998.These two rice varieties were all highly sensitive to rice blast in the two consecutive years.It is indicated the resistance of leading rice varieties is relatively low in Guangxi.So it is urgent to introduce or breed resistant varieties.Meanwhile，in the production，duly rotation and rational distribution should be carried out.The sensitive varieties should be best promoted in non-endemic areas.If they are planted in endemic areas，the incidence must be monitored and chemical control can be adopted timely so as to prevent the outbreak and spreading of rice blast.

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Responsible editor:Tingting XU

Responsible proofreader:Xiaoyan WU

廣西部分水稻主導(dǎo)品種對(duì)稻瘟病的抗性評(píng)價(jià)

顏 群1*，羅志勇2，張晉3，高利軍1，陳小林1，高漢亮1（1.廣西農(nóng)業(yè)科學(xué)院植物保護(hù)研究所，廣西作物病蟲害生物學(xué)重點(diǎn)實(shí)驗(yàn)室，廣西南寧530007；2.廣西區(qū)種子管理局，廣西南寧530022；3.廣西農(nóng)業(yè)科學(xué)院，廣西南寧530007）

為明確廣西水稻主導(dǎo)品種對(duì)稻瘟病的抗性水平，分別在廣西岑溪、三江、永福設(shè)立了三個(gè)自然誘發(fā)病圃，通過采用苗期室內(nèi)人工噴霧接種和病圃自然誘發(fā)的方法鑒定了45個(gè)主導(dǎo)水稻品種的抗譜及病區(qū)田間抗性。室內(nèi)抗譜測(cè)定結(jié)果顯示，供試的45個(gè)水稻主導(dǎo)品種抗性頻率在8.33%～94.44%之間，抗性頻率在80%以上的有8個(gè)，占鑒定總數(shù)的17.78%；50%～80%之間的有11個(gè)，占總數(shù)的24.44%；50%以下的有26個(gè)，占57.78%兩年病圃鑒定結(jié)果表明，45個(gè)水稻主導(dǎo)品種稻瘟病的抗性水平較差，無中抗水平以上抗性品種；2010年，表現(xiàn)中感的有26個(gè)，占總數(shù)的57.78%，表現(xiàn)感病的有12個(gè)、高感7個(gè)，分別占26.67%、15.56%；2011年，表現(xiàn)中感的有16個(gè)，占總數(shù)的35.56%，表現(xiàn)感病的有23個(gè)、高感6個(gè)，分別占51.11%、13.33%。45個(gè)水稻主導(dǎo)品種總體抗性水平呈逐年下降的趨勢(shì)，在生產(chǎn)上應(yīng)合理使用。

水稻主導(dǎo)品種；稻瘟?。豢剐栽u(píng)價(jià)；廣西

R ice blast is caused by Magnaporthe oryzae （Hebert）Barr.，of which the asexual generation is Pyricularia oryzae （Cooke）Sacc.It is an important destructive disease seriously affecting the improvement of rice yield［1］.Rice blast may occur in the whole growth period of rice.According to different infection periods and positions，the rice blast is divided into seedling blast，leaf blast，knot blast，spike neck blast and grain blast.Among them，spike neck blast generally produces greatest impact on rice yield.Guangxi is located in central and southern subtropical monsoon climate zone.It has warm climate and abundant rainfall，and is very suitable for occurrence and spreading of rice blast.Rice blast occurs every year in varying degrees in various rice-planted areas in Guangxi Province.During 2006-2010，the cumulative incidence area reached 2.88 million hm2［2-6］.The breeding of resistance varieties and utilization of resistance of varieties are all most economical and effective control methods［7］.However，due to the existence of rich genetic diversity and easier variation in pathogenic fungi of rice blast，most of the promoted resistance varieties lose their resistancewithin 3-5 years［8］.

廣西農(nóng)科院基本科研業(yè)務(wù)專項(xiàng)（桂農(nóng)科2013YM20，桂農(nóng)科 2014YZ24）；廣西農(nóng)業(yè)重點(diǎn)科技計(jì)劃項(xiàng)目（2010009）；國家科技支撐計(jì)劃（2012BAD19B03）；廣西創(chuàng)新團(tuán)隊(duì)建設(shè)崗位專家經(jīng)費(fèi)；廣西特聘專家專項(xiàng)經(jīng)費(fèi)。

顏群（1977-），廣西隆安人，副研究員，主要從事植物病理及病害防治研究，E-mail：gxdwb2008@163.com。*通訊作者。

2014-12-25

2015-02-09

Supported by Basic Scientific Research Fund of Guangxi Academy of Agricultural Sciences （GNK2013YM20，GNK2014YZ24）；Guangxi Agricultural Key Scientific and Technological Plan Project （2010009）；National Key Technology Research and Development Program （2012BAD19B03）；Fund for Post Specialists in Innovative Team in Guangxi Province；Special Fund for Distinguished Experts in Guangxi Province.

.E-mail:gxdwb2008@163.com

December 25，2014Accepted:February 9，2015