Biological and molecular characterisation of the two Polish Wheat streak mosaic virus isolates and their transmission by wheat curl mites

Wheat streak mosaic virus (WSMV) is a serious and widespread pathogen in the wheat-producing areas in the USA while, in Europe, it has been considered a minor threat to cereal crops. In the past, WSMV was detected in wheat, triticale and maize plants in Poland by DAS-ELISA. Here, we present the biological and molecular characterisation of WSMV-Sze and WSMV-Sosn isolates collected from western and southern Poland and report their transmissibility by the widespread wheat curl mite (WCM) lineage MT-8. The performed bioassays revealed that the analysed WSMV isolates infect wheat, barley, triticale, rye, oat and maize, but they differ in the symptoms induced on the infected plants. Moreover, they infect Bromus hordeaceus Linnaeus, which is increasingly recognised as a virus reservoir. The full-length genome sequence of both isolates was obtained and compared with the others described to date. The phylogenetic analysis revealed that the Polish isolates are clustered with the earlier described type B isolates of WSMV from Europe and Iran. The recombination analysis revealed the presence of recombinant variants in WSMV population and indicated that the WSMV-Sosn might originated from the intra-species recombination of the WSMV-Sze and WSMV-Cz isolates.

Η χλωρίδα και η βλάστηση του όρους Σαϊτά (Βόρεια Πελοπόννησος)

Βασικός στόχος της διατριβής είναι η καταγραφή της χλωρίδας της και η φυτοκοινωνιολογική μελέτη και καταγραφή των μονάδων βλάστησης του όρους Σαϊτά. Το όρος Σαϊτάς βρίσκεται στη βόρεια Πελοπόννησο και διοικητικά ανήκει στις περιφέρειες Δυτικής Ελλάδας και Πελοποννήσου. Το μεγαλύτερο μέρος του όρους καλύπτεται από ασβεστολιθικούς σχηματισμούς. Στην περιοχή έρευνας του όρους Σαϊτά διακρίνονται δύο γεωτεκτονικές ζώνες ή ενότητες: η ζώνη της Πίνδου και η ζώνη της Τρίπολης. Tο βιοκλίμα στο μεγαλύτερο τμήμα της περιοχής μελέτης έχει ασθενή μέσο-μεσογειακό χαρακτήρα εκτός από το νοτιοανατολικό τμήμα της περιοχής που εμφανίζει έντονο μέσο-μεσογειακό χαρακτήρα. Σύμφωνα με την έρευνά μας, η χλωρίδα του όρους Σαϊτά αποτελείται συνολικά από 800 taxa από τα οποία 774 αναφέρονται για πρώτη φορά από την περιοχή. Από αυτά η Iris hellenica αποτελεί νέο είδος για την επιστήμη, το υποείδος Bromus hordeaceus subsp. hordeaceus είναι νέα αναφορά για την Πελοπόννησο, ενώ η Viola oligyrtia ήταν γνωστή ως τώρα μόνο από το όρος Ολίγυρτος. Από τον προσδιορισμό των βιομορφών προκύπτει πως επικρατούν τα ημικρυπτόφυτα και τα θερόφυτα. Στο όρος επικρατούν τα μεσογειακά γεωστοιχεία. Τα ελληνικά ενδημικά taxa της περιοχής ανέρχονται σε 67. Με βάση τον δείκτη Sørensen για το σύνολο της χλωρίδας ο Σαϊτάς εμφανίζει τη μεγαλύτερη χλωριδική ομοιότητα με τα όρη της Βόρειας Πελοποννήσου, Ερύμανθο, Κυλλήνη και Παναχαϊκό. Αντιστοίχως, με βάση τον υπολογισμό του δείκτη Sørensen για τα ελληνικά ενδημικά, ο Σαϊτάς παρουσιάζει τη μεγαλύτερη χλωριδική ομοιότητα με τα όρη Ερύμανθο, Κυλλήνη και Χελμό. Από το σύνολο της χλωρίδας του Σαϊτά, 53 taxa περιλαμβάνονται σε εθνικούς και διεθνείς καταλόγους και βιβλία σπάνιων και απειλούμενων φυτών. Για τη μελέτη της βλάστησης του όρους Σαϊτά εφαρμόσαμε τη φυτοκοινωνιολογική μέθοδο του Braun-Blanquet. Κατά την αναλυτική φάση μελέτης της βλάστησης πραγματοποιήθηκαν 231 φυτοληψίες. Περιγράφονται 5 φυτοκοινωνίες, 16 κοινότητες και 2 όψεις που ανήκουν σε 10 συνενώσεις, 9 τάξεις και 7 κλάσεις.

Evaluation of New Harvesting Methods to Reduce Weeds on Arable Fields and Collect a New Feedstock

During harvesting, grain, straw, and chaff with weed seeds are separated. The chaff is returned to the fields, resulting in weed problems in the subsequent crops. We estimated the fraction of weed seeds a combine harvester could potentially harvest and used various methods to collect the chaff and treat it with heat to kill weed seeds or reduce weed seed germination. Chaff with weed seeds was placed on top of the straw and afterwards baled with the straw as a method to remove weed seeds from the field. We exposed chaff with weed seeds to exhaust gas with various temperatures and durations to study whether this heating method could be used to reduce the input of viable weed seeds to the soil during harvesting. By collecting the shed weed seeds during the growing season, we estimated that a combine harvester could potentially harvest 41%, 11%, and 100% of the seeds produced in the growing season by Bromus hordeaceus, Cirsium arvense, and Galium aparine, respectively. When the chaff was placed on top of the straw, 45% of the weed seeds stayed in the chaff fraction on top of the straw swath after one day, 35% got into the straw swath, and 20% past through the swath to the ground. Therefore, baling straw with chaff placed on the top only had a limited effect on reducing weed seed infestation. The study showed that thermal weed seed control during harvesting could potentially be applicable and incorporated in an integrated weed management approach.

Phosphorus-utilisation efficiency and leaf-morphology traits of Rytidosperma species (wallaby grasses) that differ in their growth response to phosphorus fertilisation

Rytidosperma species are perennial grasses found in cool temperate grasslands of Australia. The species differ in their intrinsic growth rates, response to phosphorus (P) fertiliser application and critical external P requirements (P required for 90% maximum growth). The present study examined whether internal P-utilisation efficiency (PUE) by Rytidosperma species influenced these differences. The PUE of nine Rytidosperma species and two grasses of Mediterranean origin, Bromus hordeaceus L. and Lolium perenne L., was assessed using alternative measures of shoot P concentration or its reciprocal. No measure of PUE was correlated with the critical external P requirements of the species. One measure of PUE, shoot dry matter per unit P, when assessed at a common shoot P content was correlated with potential growth rate (P < 0.001; r = 0.93; 4 mg shoot P). However, other measures of PUE were not correlated with potential growth rates. All of the fast-growing species (B. hordeaceus, L. perenne, Rytidosperma duttonianum (Cashmore) Connor & Edgar and Rytidosperma richardsonii (Cashmore) Connor & Edgar) exhibited high PUE, whereas PUE varied substantially among the slower-growing species. The fast-growing Rytidosperma species differed in the contribution that area-based P concentration of leaves and specific leaf area (SLA) made to the achievement of high PUE, and they retained shoot-morphology traits normally associated with slow-growing species such as smaller leaf area, smaller SLA and higher leaf dry matter content.

Wpływ nawadniania pól uprawnych ściekami wytwarzanymi podczas produkcji drożdży na skład flory segetalnej

W doświadczeniu przeprowadzonym na polach produkcyjnych należących do firmy Leasaffre Polska z siedzibą w Wołczynie (51˚4’N, 17˚57’E) oceniano wpływ nawadniania ściekami uzyskanymi z przemysłu spożywczego (po produkcji drożdży) na występowanie oraz skład gatunkowy chwastów w łanie mozgi trzcinowatej, pszenicy jarej, pszenicy ozimej oraz kukurydzy. Niezależnie od rośliny uprawnej oraz zastosowanej dawki polewowej ścieku główny składnik flory segetalnej nawadnianych plantacji stanowiły gatunki higrofilne, tj. Phragmites australis, Equisetum arvense, higro-, i nitrofilne, tj. Polygonum hydropiper, Symphytum officinale, Echinochloa crus-galli, Poa trivialis, Apera spica-venti, Matricaria maritima ssp. Indora, oraz nitrofilne, tj. Galium aparine, Solanum nigrum, Urtica dioica i Galinsoga parviflora. Natomiast na plantacjach, na których nie stosowano nawadniania ściekiem, najczęściej występowały gatunki siedlisk suchych lub okresowo wysychających, tj. Setaria viridis, Conyza canadensis, Bromus hordeaceus czy Plantago lanceolata. Ponadto dość liczną grupę stanowiły gatunki, które występowały zarówno na polach nawadnianych, jak i nienawadnianych, a które można określić mianem neutralnych, tj. Elymus repens, Capsella bursa-pastoris, Fallopia convolvulus, Geranium pusillum, Polygonum aviculare i Cirsium arvense.

Herbicides and Mowing to Control Barb Goatgrass (Aegilops triuncialis) and Restore Native Plants in Serpentine Grasslands

Serpentine grasslands are relatively free of the invasive species that typify other California grasslands, but recently are threatened by the spread of barb goatgrass, a Eurasian annual that is unique in its tolerance of serpentine soils. We evaluated two graminicides (clethodim and fluazifop), one broad-spectrum herbicide (glyphosate), mowing, and hand pulling for their effectiveness in controlling barb goatgrass and for restoring native species cover and diversity. We also evaluated application timing for the graminicides: before goatgrass flowering (early season), at flower initiation (midseason), and at early seed development (late season). Glyphosate was applied at early seed development. The 10 treatment combinations were applied to 10 blocks of 4-m2 (43-ft2) experimental plots in an inner Coast Range serpentine grassland with high cover of barb goatgrass but few other nonnative species. After 2 yr of treatment, all treatments except glyphosate reduced goatgrass frequency. Hand pulling, fluazifop, and mowing were most effective at controlling goatgrass, reducing frequency by 60, 51, and 48%, respectively (compared to a 30% increase on control plots). Midseason applications of clethodim and fluazifop were more effective than those applied early or late. Hand pulling, fluazifop, and clethodim increased native forb frequency by 31, 46, and 74%, respectively, with the benefit of the graminicides decreasing with later applications. Native grasses were at least partially resistant to the graminicides. Cover of one sided blue grass (Poa secunda), the most widespread native grass, might have been reduced slightly by early-season applications but was increased by late-season applications. Cover of soft brome (Bromus hordeaceus), the only other widespread nonnative species in the study, was reduced by early-season applications of the graminicides. Clethodim and fluazifop show great potential to selectively remove barb goatgrass and other nonnative annual grasses in grasslands that are otherwise dominated by native grasses and forbs. Mowing is a less selective, but viable alternative.

Growth and Yield of Cultivated Grape with Native Perennial Grasses Nodding Needlegrass or California Barley as Cover Crops

Two California native perennial grasses, nodding needlegrass [Nassella cernua (Stebbins & R.M. Love) Barkworth] and California barley [Hordeum brachyantherum Nevski ssp. californicum (Covas & Stebbins) Bothmer, N. Jacobsen & Seberg], were compared with a conventional grass cover crop, ‘Blando’ brome (Bromus hordeaceus L.), as well as resident (weedy) vegetation and a clean cultivated control for effects on growth and yield of cultivated grape (Vitis vinifera L. cv. Barbera). Statistical analyses did not reveal yield differences between treatments with floor vegetation (the native grasses, ‘Blando’ brome, and resident vegetation) and clean cultivation, the cover crop treatments (the native grasses and ‘Blando brome’) and clean cultivation, nor the native grass treatments versus treatments with non-native floor vegetation (‘Blando’ brome and resident vegetation). However, there was a significant difference between the two native grasses with the average yield of nodding needlegrass 26.2% higher than that of California barley. Treatments did not differ in °Brix, berry weight, or pruning weight. At the end of the study, vine trunk diameter was 7.1% higher under the cover crop treatments than resident vegetation. Given these results, in vineyards where a neutral effect on growth or yield is desired, nodding needlegrass would be suitable as a permanent cover crop, whereas California barley would not.

Suppression of vulpia and goose grass in dryland pastures through the choice of sown pasture species

Vulpia (Vulpia myuros) and goose grass (Bromus hordeaceus) are common annual grass weeds throughout New Zealand in dryland pastures. They compete with sown species, suppressing pasture production and livestock performance.