فصلنامه بیماریهای گیاهی
سال پنجاه و دوم شماره 3 (پاییز 1395)

Annual survey for monitoring of reaction of commercial wheat cultivars to stripe rust disease is very important after their introduction and extensive cultivation. The host materials surveyed included the standard differential cultivars for stripe rust along with 24 and three respectively commercial bread and durum wheat cultivars. This study was accomplished in selected wheat fields of six regions of Fars province including Zarghan, Marvdashat, Fassa, Mammassani, Darab and Eghlid during 2003- 2005 and in two stripe rust nurseries in Zarghan and Mammassani during 2003- 2013. The results showed that the resistance of 12 cultivars including Chamran, Shirodi, Shiraz, Darab 2, Falat, Star, kavir, Zarin, Shahriar, Alvand, Alemot and Bahar was overcome by stripe rust during or before the last decade. Yavarous and several recently introduced cultivars including Zareh, Mihan, Siravan, Chamran 2, Ophogh, Behrang and Shabrang have conferred moderately to intermediate resistance reaction to the disease. The cultivars Sivand, Parsi, Pishgham, Marvdasht and Aflak showed a range of moderately resistance to moderately susceptible reaction. The response of Pishtaz varied from moderately susceptible to resistance. Nicknejad has shown to have high level of resistance since its long time introduction. Decrease or changes in the resistance of some of the cultivars can be attributed to changes in stripe rust races, weather conditions and environmental factors. In this regard among the differential cultivars, virulence was almost present for Yr2, Yr6, Yr7, Yr9, Yr17, Yr25, Yr26, Yr27, YrA and YrSU. Current research indicates that annual survey on responses of commercial wheat cultivars to stripe rust together with monitoring of pathogen virulence factors in Fars province are very necessary. These information not only can effectively aid in giving on-time warning to replace susceptible cultivars and to use effective control measures to reduce the loss of the disease, but also can play an important role in short and long time wheat breeding programs.

Effects of aqueous extracts of plantain, castor, marigold and eruca on egg hatching and the mortality of second stage Juveniles (J2) of Meloidogyne incognita, was studied in vitro. Also the effects of their green manures (12 g/kg soil) and Paecilomyces lilacinus alone and in combination on the root-knot nematode and growth parameters of infected tomato (CV Early Urbana) in sterilized mixed soil and non-sterilized farm soil were studied, under greenhouse conditions. The results of in vitro test showed that all plants extracts increased the mortality of J2, and plantain and eruca reduced the egg hatching, significantly, and they had not negative effect on P. lilacinus. The result of greenhouse test in sterilized soil revealed that in the presence of the nematode, marigold- fungus spore suspension caused 140.5% increase in the shoot height of tomato plants. In addition, marigold treatments caused 11.4-11.8 and 20.1-23.1 folds and caster 10.0-10.1 and 10.0-17.7 folds in fresh and dried shoot weight, respectively. In non-sterilized soil, caster treatments with 47.9-67.5% and 32.4-140.5% increases in fresh and dried shoot weights have the highest effects. The nematode gall index in both tests was 4.2-5.0. Except for the treatment of plantain-fungus spore suspension with 84% decrease, the other treatments in sterilized soil test caused increases in the final population and reproduction factor of nematode. In non-sterilized soil, all treatments reduced gall and egg masses, but only plantain treatments and some of marigold and caster treatments reduced the reproduction factor of the nematode.

Effect of 10% aqueous extracts of inhibitory plants viz. Plantago major, Ricinus communis, Eruca sativa and Tagetes sp. on Meloidogyne incognita activity and Pseudomonas fluorescens CHA0 was studied. The results showed that the extracts increased 31-42% mortality of the second stage juveniles and decreased 37.5-60.0% egg hatching of the nematode, but did not inhibit the bacterium growth. The combined effects of green manures of plants (12 g/kg of soil) and bacterium (cfu108) on activity of the nematode and growth parameters of tomato (Early Urbana) were studied in 3.5 kg pots, containing sterilized mixed or non-sterilized farm soils. The results showed that in presence of the nematode and in sterilized soil, marigold-bacterium with 66.2 and 60.9% increases, and in non-sterilized soil castor with 29.1 and 18.3% increases in shoot fresh and dry weights, respectively, had the highest impacts. Plantain-bacterium decreased 95.9 & 86.0% of eggs/g of root and 92.9 & 95.2% of nematode reproduction factor in sterilized or non-sterilized soils, respectively. In addition, plantain decreased 93.9 & 84.5% of eggs/g of root and 90.7 & 95.9% of nematode reproduction factor, respectively. The results of the greenhouse test on usage of eruca green manure and bacterium in 12 kg pots, containing sterilized mixed soil, showed that in the presence of nematode, eruca with 15.0, 2.2 and 48.3% increases in shoot fresh, shoot dry and fruit weights, respectively had the greatest impact. Moreover, eruca-bacterium decreased 55.2 and 52.4% of egg or gall/g root, respectively and 65.5% of reproduction factor.

In order to identify the plant parasitic nematodes in Ramsar forests, 90 samples of soil and root of trees were collected in October 2012. Nematodes were extracted, fixed and transferred to anhydrous glycerin, and identified. 27 nematode species belonging to 16 genera were identified. The species Crossonema dryum, C. menzeli, Ogma fagini, and O. murrayi are recorded or described from Iran for the first time. C. dryum by having 20-44 short scales on body annuli at midbody and different shape of scales on body of fourth-stage juvenile (J4); C. menzeli by presence of 55-65 digitate or slender scales on body annuli at midbody, 8-10 µm long; O. fagini by having less than 10 longitudinal rows of scales on body annuli and a convex-conoid posterior region, and O. murrayi by having eight longitudinal rows of triangular scales on body annuli and a head with two equal annuli; can be differentiated from closely related species

Grapevine fanleaf virus belongs to the genus Nepovirus in the family Secoviridae. It causes an important disease of grapevine worldwide. To determine the genetic diversity of GFLV in Southern Iran, samples of grapevine and weeds were collected from vineyards in Fars and Kohgiluyeh-Boyer Ahmad provinces. ELISA using specific antibody of GFLV showed that grapevine, bermudagrass, knotweed, Johnson grass and raspberry plants are natural reservoir hosts of GFLV. In mechanical inoculation of different isolates of GFLV to Chenopodium quinoa, mosaic, leaf malformation and sharpening of leaf edges were developed in inoculated plants. Complete length of GFLV coat protein gene amplified in RT-PCR using specific primers was subjected to RFLP analysis using TaqI endonuclease. It was shown that GFLV isolates belong to 11 haplotypes. Phylogentic analysis based on the nucleotide sequence of the coat protein gene showed that Iranian isolates of GFLV have distinct position in phylogentic tree. Moreover, evidence of divergent evolution was observed between isolates from northwest, northeast and south of Iran. It confirms that genetic makeup of GFLV may be affected by geographical isolation.

Rhizoctonia solan AG-2 and AG-4 are main pathogens in ornamental plants in Shiraz but their sources of inoculum is not known. During 2013 and 2014 soil samples from different parts of Shiraz landscape, nurseries, sources of animal fertilizers, compost, vermin compost ,soil mix and Shiraz vicinities from cultivated and virgin soils were collected and assayed using sugar beet seeds as bait and plated on PDA supplemented with 100ppm PCNB and Chloramphenicole and 50ppm Hymexazole. 218 isolates of Rhizoctonia were recovered of which 193 multinucleate and 25 binucleate.Anastomosis groups of 50 multinucleate isolates were determined using 18 AG testers and the following AGs with their frequencies were found: Tweleve AGs included AG-4(36%), AG-2 (18%), AG-1-1A (18%), AG-2-IIIB(6%), AG-3, AG-2-2 and AG-13 ( 4%), AG-2-C, AG=5, AG-7 and AG-11(2%) in field soil and AG-BI (2%) in virgin soil. No Rhizoctoniawere recovered from in front of soil mix, animal fertilizers and composts used for potting and nurseries..It was concluded that transplants from nurseries are the main sources of inoculums.

This study was conducted to identify cereal cyst nematodes (CCNs), distribution and disease incidence, population density and preparing map of distribution based on interpolation using geographic information system (GIS), as well as determination of relationship between climatic factors with population density of dominant species. Totally 280 soil and root samples were randomly collected from 140 wheat fields of Isfahan province during 2012-2014. The soil samples were processed for cyst extraction and number of cysts, second stage juveniles (J2) and eggs inside each sample were counted. Species was identified based on morphological and morphometric features and molecular characters. Analysis was performed by Arc GIS software using interpolation technique for determination of raster maps of population density of J2, eggs and direction of disease progression. After preparing the raster maps, direction and the correlation of J2 and eggs populations with some climatic factors and altitude determined by GIS using Pearson's correlation coefficient. Heterodera filipjevi was the only species of cereal cyst nematodes found in Isfahan province, and 56.4% of soil samples were contained H. filipjevi with an average population of 6.02 eggs and J2/g of soil. Based on interpolation of population density, Ardestan, Natanz, Kashan, Aran va Bidgol, Mobarekeh, Naein and Isfahan districts had the most mean population density of H. filipjevi, respectively. Population density of the nematodeshowed direct correlation with the long term mean of temperature and inverse correlation with the long term mean of precipitation, relative humidity percent and altitude.

Tomato big bud (TBB) is an economically important disease of tomato (Lycopersicon esculentum Mill.) in various regions of the world. In 2013 surveys of Zanjan province (Iran) tomato fields, symptoms of TBB disease were observed. The disease agent was successfully transmitted by grafting from a naturally symptomatic tomato in Zanjan to tomato and eggplant and from tomato to periwinkle via dodder (Cuscuta campestris Yank.) transmission. In inoculated plants phytoplasma-type symptoms were produced. Expected length DNA fragments of nearly 1,800 and 1,250 bp were respectively amplified from naturally infected tomato and experimentally inoculated plants in direct polymerase chain reaction (PCR) using phytoplasma primer pair P1/P7 or nested PCR using the same primer pair followed by R16F2n/R16R2 primers. Virtual restriction fragment length polymorphism (RFLP) of nested PCR products (1.2 kbp) showed that Zanjan TBB (ZTBB) phytoplasma is related to subgroup A in 16SrVI (clover proliferation) phytoplasma group. Phylogenetic analysis of full length 16S rDNA classified ZTBB with 16SrVI-A subgroup. This is the first report of biological and molecular characterization of a phytoplasma associated with TBB disease in Zanjan province.

Bermudagrass southern mosaic virus (BgSMV)and Maize dwarf mosaic virus (MDMV) are closely related potyviruses varying in geographical distribution and the existence of an additional 90- nucleotide stretch in the 5 'region of coat protein gene. .In the present study, the effect of temperature on disease severity of both viruses was assessed. A factorial experiment was conducted laid out in a completely randomized design with two factors, temperature at three levels (25, 30 and 35°C) and inoculation at three levels (MDMV, BgSMV and buffer) each in six replications. Eleusine compressa, a common host of both viruses, was inoculated mechanically and disease severity, length of incubation period, plant height, and plant weight were measured 30 days post inoculation. Disease severity of MDMV was not significantly affected by temperature change but that of BgSMV increased with increasing temperature. Incubation period of MDMV inoculated plants decreased with increasing temperature. Bioinformatics analysis showed presence of a coiled-coil region in CP of both viruses. This region was longer in BgSMV extending into extra amino acids in amino terminal region. Extra amino acid stretch may contribute to the adaptation of this virus to higher temperatures.

Gibberella fujikuroi the cause of rice Bakanae disease and foot rot is one of the important seed-borne diseases in Guilan province. Three Fusarium species including Fusarium proliferatum, Fusarium verticillioides and Fusarium fujikuroi have been reported as the casual agents of rice Bakanae disease from all over the world. These three species belonged to three mating population A, C and D that have previously been reported from Guilan province (Hosein nejad et al. 2008). These Fusarium species makes symptoms on seedlings in nurseries and plants on the field. The study of pathogenicity of different isolates were done by collecting 42 isolates of infected samples from rice infected fields in Guilan province due to 2012-2013. Morphological identification of species carried out based on valid identification literatures (Leslie & Summerell 2006, Gerlach & Nirenberg 1982) and two species viz F. verticillioides and F. fujikuroi were identified. Frequency of F. verticillioides and F. fujikuroi was 88.4 and 11.6 respectively. The plant stems were inoculated by spore suspension of pathogens with 106 conidia/ml on the Sepidroud cultivar seedlings and percentage of death tillers was evaluated. The results showed that F. verticillioides isolates were more virulent than F. fujikuroi and cluster analysis of isolates from pathogenicity viewpoint, characterized four different groups. All isolates of F. verticillioides were in the group with high pathogenicity.