Impact of climatic conditions on outbreaks of bacterial spot on tomato and pepper caused by Xanthomonas vesicatoria and Xanthomonas euvesicatoria

Seed-borne bacterial pathogens of tomato and pepper are of major concern worldwide. Xanthomonas vesicatoria (Xv) and Xanthomonas euvesicatoria (Xe), the causal agents of bacterial leaf spot, and Clavibacter michiganensis subsp. michiganensis (Cmm), the causal agent of tomato bacterial canker, are worldwide distributed, but the occurrence of the latter is usually erratic. In order to evaluate the risk of seed transmission and the relationship between seed contamination and disease outbreak, an extensive field trial has been put in place in 2013 for each pathosystem. Three artificially contamination levels were considered, composed of 100 seedlings each. Disease outbreaks were weekly monitored during the growing season until harvesting and disease was quantified by means of AUDPC. Seeds were produced from each plot and analysed in order to assess their contamination level. Preliminary results of our studies showed that disease quantity caused by Xv, Cmm or Xe was directly correlated to the percentage of initial infection, according to AUDPC values obtained. Contamination rate of seed produced in diseased fields was not always correlated with disease quantity observed. A microbial consortium, a bacterial antagonist and a plant polyphenol were assayed to assess their potential efficacy in seed disinfection: naturally contaminated tomato and pepper seeds were treated and sown. Pepper and tomato seedlings were inspected and analysed for the presence of bacterial spot. Preliminary results obtained show that none of the above mentioned treatments was able to eradicate the pathogen from seeds

Breeding progress in grain yield of winter wheat cultivars grown at different nitrogen levels in semiarid conditions

The objectives of this study were to estimate the progress in wheat genetic yield potential, associated with changes in some agronomic traits, under different N rates. Twenty-four cultivars of winter wheat (T. aestivtum L.) representing most of the cultivars released in Serbia from 1955 to 2006 were analyzed. The cultivars were grown for four years (2005-2008) in field trails with two levels of agronomic inputs (low nitrogen-N-45 and high nitrogen-N-110). Data were collected on 1000-kernel weight, kernels per spike, kernels per square meter, spikes per square meter, plant height, harvest index, heading time and grain yield. Mean difference between the two fertilization levels was 0.44 t ha(-1). The average rate of increase in yield potential per year of release, estimated from the slope, was 41 kg ha(-1) year(-1) and it was significantly different from zero (P lt = 0.01). It was 35 kg ha(-1) year(-1) or 0.55% at the low level of N input, and 46 kg ha(-1) year(-1) or 0.68% at the high level of N input. This suggests that modern cultivars are better adapted to high N input. Our results suggested that individual contribution of the most of analyzed traits may vary depending on the genotype as well as environmental conditions

Uticaj izvora inokuluma Tilletia spp. i uslova sredine na učestalost zaraženih klasova

The influence of inoculum source on the incidence of common bunt, caused by fungi from the genus Tilletia, was estimated based on the frequency of bunt infected wheat spikes in our agroecological conditions. The cultivar Novosadska rana 5 was sown in a random split plot design with four replicates at Rimski Šančevi on three sawing dates in 1999/2000 and 2000/2001. The following variables were evaluated: I – control, II – soilborne inoculum (4 g teliospores/1 l soil), III – seedborne inoculum (2 g teliospores/1 kg seeds), IV – seedborne inoculum + soilborne inoculum (4 g teliospores/1 l soil + 2 g teliospores/1 kg seeds). Correlation and regression analysis were used to evaluate the effect of temperature and precipitation on the frequency of infected spikes. The frequency of bunt infected spikes depended on the source of Tilletia spp. inoculum, and difference in infection frequencies between variables II and III, as well as III and IV, were determined for the assessed infection parameters. When teliospores are the only source of inoculum in soil, 60 days after sawing (r>+0.52) is a critical period in which temperature influences the development of infection. The highest number of plants was infected in the first, while less were infected in the second ten days (decade) after sawing (r>0.41), when temperature was the optimal 5.0-6.0ºC. The initial 60 days after sawing were also critical for disease development when teliospores on seeds were the only source of inoculum (r>+0.50). The highest number of plants was infected in the third and fewer in the fifth decade after sawing (r>0.41), when temperature was the optimal 5.0- 6.0ºC. When infection was caused by teliospores on seeds and in soil, the critical period lasted 120 days after sawing (r>0.42), with a maximum frequency of infection found at the optimal temperatures for the period of 4.0- 5.0ºC.Uticaj izvora inokuluma na pojavu glavnice pšenice koju prouzrokuju gljive roda Tilletia u našim agroekološkim uslovima praćen je, između ostalih, ispitivanjem parametra infekcije: stepen zaraženosti klasova. Sorta Novosadska rana 5 je sejana po split plot metodu u tri roka setve sa 4 ponavljanja na lokalitetu Rimski Šančevi tokom 1999/2000. i 2000/2001. godine. Ispitivane su sledeće varijante: I – apsolutna kontrola, II – zemlja infestirana teleutosporama (4 g teleutospora/1 l zemlje), III – seme infestirano teleutosporama (2 g teleutospora/1 kg semena) i IV – zemlja infestirana teleutosporama + seme infestirano teleutosporama (4 g teleutospora/1 l zemlje + 2 g teleutospora/1 kg semena). Izvršena je korelaciona i regresiona analiza ispitivanog parametara infekcije u odnosu na temperaturu i padavine. Stepen zaraženosti klasova je zavisio od izvora inokuluma Tilletia spp., a uočene su razlike u nivou infekcije između varijanti II i III, kao i III i IV. Kasniji rokovi setve (drugi i treći) su uticali značajno na ispitivani parametar infekcije, ali između njih nisu utvrđene značajne razlike. Kritični period u kom temperature utiču na ostvarivanje infekcije u uslovima kad su teleutospore u zemlji jedini izvor inokuluma traje 60 dana nakon setve (r>+0,52). Najveći broj biljaka je zaražen u prvoj i nešto manje u drugoj dekadi posle setve (r>0,41), pri čemu je optimalna temperatura u tom periodu iznosila 5,0-6,0ºC. Prvih 60 dana nakon setve je, takođe, kritičan period za ostvarivanje infekcije u uslovima kad su teleutospore na semenu jedini izvor inokuluma (r>+0,50). Najveći broj biljaka je zaražen u trećoj i nešto manje u petoj dekadi posle setve (r<-0,45), pri čemu je optimalna temperatura u tim dekadama iznosila 6,0-7,0ºC. U uslovima kad infekciju pšenice ostvaruju teleutospore prisutne na semenu i u zemlji kritičan period traje 120 dana posle setve (r>+0,42), pri čemu je maksimalna infekcija ostvarena pri optimalnoj temperaturi 4,0-5,0ºC

Uticaj Trichoderma spp. na klijavost semena soje i potencijalni antagonistički efekat na Sclerotinia sclerotiorum

Trichoderma species have been registered as species with important plant growth promoting potential and antagonistic effect against various phytopathogens. Trichoderma isolates originating from different soil types from the Vojvodina region (Serbia) were screened using dual culture test for their antagonistic effect against the pathogen Sclerotinia sclerotiorum. All tested isolates had high radial growth inhibition (RGI) factors of the pathogen and high colonization percentage. Growth promoting activity of Trichoderma isolates on soybean seeds was tested under glasshouse conditions. Soybean seeds were coated with suspensions of different Trichoderma isolates and seed germination percentage, root and shoot length were measured. According to data analysed in Statistica 10, using Duncan’s test, there were no significant effects on shoot length among the tested isolates, compared to the control. The four tested Trichoderma isolates showed significant positive effects on germination, root length and vigour index, while two isolates exhibited no significant effect on any of the measured parameters.Vrste roda Trichoderma su poznate po svom antagonističkom efektu na veliki broj fitopatogenih organizama kao i po stimulativnom efektu za rast biljke. Izolati Trichoderma spp. testirani u ovom istraživanju su izolovani iz različitih tipova zemljišta u Vojvodini (Srbija). Test dvojnih kultura je korišćen za testiranje antagonističkog dejstva izolata na patogena Sclerotinia sclerotiorum. Svi testirani izolati su imali visok RGI (faktor inhibicije porasta micelije patogena) i visok procenat kolonizacije patogena. Stimulativni efekat rasta Trichoderma izolata na seme soje je testiran u uslovima staklenika, i sedmog dana su mereni dužina korena, izdanka i klijavost semena tretiranih suspenzijom različitih izolata Trichoderma spp. Svi podaci su analizirani primenom Duncan testa u programu Statistica 10, i ukazuju da nije bilo statistički značajne razlike u dužini izdanaka tretiranih semena i kontrole. Četiri izolata su statistički značajno uticala na povećanje dužine korena, klijavosti i vigor indeksa u odnosu na kontrolu, dok dva izolata nisu statistički značajno uticala ni na jedan od merenih parametara

Metode za detekciju Phytophthora fragariae var. rubi na malini

Phytophthora fragariae var. rubi (Wilcox & Duncan), a causal agent of raspberry root rot, is a serious soil-borne pathogen listed by EPPO as an A2 quarantine pest. Root samples were collected from badly diseased raspberry plants showing a variety of characteristic and often dramatic symptoms during surveys carried out in western Serbia in 2002. Identification of the causal agent was performed in collaboration work with the Scottish Crop Research Institute (S.C.R.I.), Dundee, UK. Necrotic roots were plated on selective French bean agar (incorporating ampicilin, ryfamicin, bavistin and hymexasol). Detection of isolates was based on cultural and morphological features compared with referent cultures. DNA was extracted directly from the sampled roots using extraction buffer (200 mM Tris- HCl pH 8.5, 250 mM NaCl, 25 mM EDTA, 0.5% SDS), purified by multi spin separation columns [Thistle Scientific (Axygen)] or in 24:1 mixture of chlorophorm- iso-amyl alcohol and amplified by nested PCR (ITS 4 and DC 6 for first round, DC 1 and DC 5 for second round). Diluted DNA extracts were also amplified by conventional PCR with modified ”universal” Phytophthora primers (ITS 6, ITS 7 and ITS 8, Cooke et al., 2000) and digested with Msp1. Digestion patterns of the universal primers PCR product from infected roots matched those of Scottish strains. P. fragariae var. rubi occured on 8 out of 14 sites. Our results indicate that nested PCR (ITS 4 and DC 6 for first round, DC 1 and DC 5 for second round) or digestion of the ”universal” Phytophthora primers PCR product for detection of P. fragariae var. rubi are more sensitive and less time-consuming and therefore recommended for use.Phytophthora fragariae var. rubi (Wilcox & Duncan), prouzrokovač truleži korena maline, je veoma značajan zemljišni patogen A2 karantinskog statusa u EPPO. Uzorci korena su sakupljeni sa jako zaraženih biljaka maline koje su ispoljavale čitav niz karakterističnih i često dramatičnih simptoma tokom pregleda koji su vršeni u zapadnoj Srbiji 2002. godine. Identifikacija prouzrokovača je izvršena u saradnji sa Scottish Crop Research Institute (S.C.R.I.), Dundee, UK. Nekrotični korenčići su unošeni u selektivnu French bean podlogu, koja je sadržala ampicilin, rifamicin, bavistin i himeksazol. Detekcija dobijenih izolata je vršena posmatranjem kulture i morfoloških karakteristika i poređenjem sa autentičnim kulturama. DNK je ekstrahovana direktno iz uzorkovanih korenova pomoću ekstrakcionog pufera (200 mM Tris-HCl pH 8,5, 250 mM NaCl, 25 mM EDTA, 0,5% SDS), prečišćena Multi spin separacionim kolonama (Thistle Scientific (Axygen) ili 24:1 mešavinom hloroforma i izoamil alkohola i amplifikovana nested PCR (ITS 4 i DC 6 za prvi krug, DC 1 i DC 5 za drugi krug). Rastvoreni DNK ekstrakti su takođe amplifikovani putem konvencionalnog PCR sa modifikovanim „univerzalnim” Phytophthora prajmerima (ITS 6, ITS 7 i ITS 8, Cooke i sar., 2000) i digestirani sa Msp1. Digestioni paterni proizvoda univerzalnih prajmera iz zaraženih korenova su se poklapali sa škotskim izolatima. P. fragariae var. rubi se javila na 8 od 14 lokaliteta. Naši rezultati ukazuju da su nested PCR (ITS 4 i DC 6 za prvi krug, DC 1 i DC 5 za drugi krug) i digestija produkta univerzalnih Phytophthora prajmera u cilju detekcije P. fragariae var. rubi senzitivnije i zahtevaju manje vremena, pa ih stoga preporučujemo za korišćenje

Smanjenje bolesti ozimog stočnog graška u združenoj setvi u polju

A field experiment was conducted at the experimental field of the Institute of Field and Vegetable Crops in Novi Sad to investigate the effect of forage winter pea and winter oat intercropping on ascochyta blight and powdery mildew infections. Seeding rations of pea and oat in Treatment 1 (50:50%) and Treatment 2 (75:25%, respectively) reduced ascochyta leaf infection by 32.5% and 12.8%, and powdery mildew infection by 12.3% and 17.5%, respectively, compared to pea monoculture used as a control (Treatment 3). The same seeding rations in Treatment 1 and 2 reduced ascochyta blight on pea plants by 37.2% and 18.3%, respectively. However, there were no significant differences between the treatments in reducing powdery mildew on plants. The effects of different treatments on the average number of pods per plant, seed per pod, shriveled pods and seed weight were analyzed using Spearman’s correlation coefficient. Negative but not statistically significant effects on those measured parameters were registered in Treatments 2 and 3, while Treatment 1 showed positive effects on all parameters except shriveled pods. According to all data obtained in this research, the intercropping mixture of pea and oat at 50:50% seeding ratio had the best effect on the measured parameters while the intercropping mixture of pea and oat at 75:25% seeding ratio had low to moderate effect in comparison with pea monocrop.Poljski ogled je postavljen na oglednom polju Instituta za ratarstvo i povrtarstvo u Novom Sadu kako bi se istražio uticaj smeše ozimog stočnog graška i ozimog ovsa na pojavu antraknoze i pepelnice. Smeše graška i ovsa u Tretmanu 1 (50:50%) i Tretmanu 2 (75:25%) smanjile su antraknozu lista za 32.5% i 12.8%, a pepelnicu za 12.3% i 17.5% u odnosu na monokulturu graška, koja je uzeta za kontrolu (Tretman 3). Navedene smeše u Tretmanima 1 i 2 su smanjile pojavu antraknoze celih biljaka za 37.2% i 18.3%. Međutim, između tretmana nije uočena značajnija razlika u pojavi pepelnice na celoj biljci graška. Uticaj tretmana na prosečan broj mahuna po biljci, šturih mahuna po biljci, zrna po mahuni i mase semena analizirani su Spearman-ovim koeficijentom korelacije. Negativne ali ne statistički značajne korelacije sa merenim parametrima su registrovane u Tretmanima 2 i 3, dok je Tretman 1 imao pozitivan efekat na merene parametre sa izuzetkom šturih mahuna. Prema dobijenim rezultatima u sprovedenom istraživanju, združena setva ozimog stočnog graška i ozimog ovsa u smeši 50:50% je imala najbolji efekat na istraživane parametre dok je združeni usev graška i ovsa u smeši 75:25% imao slab do srednji uticaj u poređenju sa kontrolom, odnosno monokulturom graška