Identification Of Pathogen Of Phyllostachys Meveri Black Rot And Its Control

Phyllostachys meyeri McClure is a kind of bamboo with great advantages featuring good ability of adaptation,lower cost and investment.It has a short growth period and strong abilities in keeping water and soil.The stem has been exported to countries and regions such as Japan,Korea and Southeast Asia after being processed into products including various craftworks and fishing pole,bring remarkable benefits to the planter and export-oriented enterprises.This kind of bamboo is mainly located in Yuhang,Deqing and other towns,covering an area of about 6000 hm~2.From the beginning of this century,about a third of the bamboos in the forest have suffered blacking and rotting in the base of the stem.The average disease incidence is 20-30% and the most severe is more than 80%.The less-disease bamboos will have several rotting scars at the base of the stem,thus imposing negative impact on the export. And those worst-disease bamboos will suffer wilting or even shoot-retreat leading to enormous economic losses.To our knowledge,this is the fast report to this kind of disease.It was considered as a new bamboo disease and has been named Phyllostachys meyeri Black Rot.A fungus was consistently isolated from symptomatic tissues on PDA. The fungus was identified as Fusarium sp.,of which the morphological characteristics were basically the same as that of Fusarium equiseit(Corda)Sacc.Further identification of the fungus was carried out through applying several molecular characterization techniques.Although the results indicate that the isolates have including Tox5 gene,no PCR amplification was observed from the pathogen isolates using the F.equiseti species-specific primers Feq-F/P,and FEF1/R1, indicating that the pathogen isolates were different from common F.equiseti isolates. The ITS sequence of the pathogen isolates ODF52,OHF02 and ODR03 was 468 bp which was compared with those available from GenBank.The closest match indicated about 96.4%and 95.9%similarity,with strains identified as F.buharicum and F.beomiforme,but neither of these was similar in morphological characteristics to F.equiseti,and the reported closest matching F.equiseti isolate indicated only up to 91.3%similarity.Phylogenetic analysis of ITS sequence and SSR demonstrated the evolutionary relationships between the pathogen isolates and the F.equiseti isolates came from Switzerland,Mexico,UK and Thailand were far away.It is concluded that the pathogen represents a variety of F.equiseti according to the comprehensive results of morphology and molecular characteristics and it has been named Fusarium equiseti var.meyeri.The study of biological characteristics of the pathogen isolate ODF52 has clarified the effect of medium,illumination,temperature,pH value,humidity,and carbon and nitrogen source on the mycelial growth,pigment variation,sporulation and conidial germination.The isolate ODF52 was growing fastest on Oatemeal Agar (OA)medium and produced the most number of conidia on Potato Sucrose Agar (PSA)medium.Under whole illumination,isolate ODF52 could produce pigment while under whole darkness it could promote conidia formation.Mycelium grew between 4 and 36℃,and optimum growth was at 28℃.Maximum and minimum for conidia germinate were 30℃and 15℃,and the optimum was at 20℃.The lethal temperature of mycelium and conidia were at 52℃and 48℃respectively,both lasting 15 min.The mycelium could grow and the conidia could germinate under pH 3-12,and the optimum pH for mycelium growth was 6 while conidia germination 5 to 6.Conidia could not germinate when the relative humidity was lower than 90%.The optimum carbon and nitrogen source for the mycelial growth were glucose and yeast, respectively,and the best carbon and nitrogen ratio was 50:1.For sporulation,the best source of carbon and nitrogen were fructose and peptone.Studies on the fungicides test in laboratories,patches and pilot-scales showed that 70%Thiophanate-Methyl WP,40%Pentachloronitrobenzene-Carbendazim WP and 50%Carbendazim WP were the most effective and economic fungicides to control the disease,and they could be used alternatively.The optimum control period, the control times and application methods were identified.In forests with water source,the fungicides should be sprayed before the bamboo shoots out while m those lacking water,poisoned soil could be spread before shoot-out.It's best to control for successive twice in the first and the second year of its shoot-out in those areas suffering serious disease and those have suffered for a long period.The antagonistic effects and mechanism of Pythium oligandrum isolate Rcul, Trichoderma harzianum isolates T6,T9,T10,T25,T34 and Bacillus subtilis isolates B1,B3 against pathogen isolate ODF52 were preliminary studied.The result indicated that P.oligandrum isolate Rcul could cause the degradation and separation of ODF52 mycelium,but the secretions of P.oligandrum Rcul(＜8kD)had no remarkable effect on the pathogen ODF52.T.harzianum isolate T34 suppressed the growth of pathogen in the process of mycoparastism and contributing antibiotics.B. subtilis isolates B1 and B3 could inhibit the growth of pathogen with an obvious zone of inhibition.