<p style="text-align: justify;">Prisustvo plesni i mikotoksina u hrani predstavlja vi&scaron;estruku opasnost, kako sa aspekta bezbednosti hrane, tako i sa aspekta globalne trgovine. Učestalost i intenzitet pojave plesni na uzorcima zrna hlebne p&scaron;enice i spelte prikupljenih u regionu Vojvodine određeni su nakon žetve tokom trogodi&scaron;njeg perioda (2015-2017). Istraživanja su obuhvatila identifikaciju i karakterizaciju 38 izolata A. flavus primenom polifaznog pristupa koji uključuje klasične mikrobiolo&scaron;ke i molekularne metode. Ispitivanjem potencijala biosinteze AFB₁ izolata A. flavus utvrđeno je da su dva izolata poreklom sa zrna hlebne p&scaron;enice pokazala aflatoksigeni potencijal. Ve&scaron;tačka inokulacija različitih Triticum vrsta: hlebne p&scaron;enice, spelte, korasan i hibrida p&scaron;enice toksigenim izolatama izvr&scaron;ena je u fazi cvetanja u cilju poređenja otpornosti ovih vrsta na pojavu A. flavus i produkciju AFB₁. Visok nivo AFB₁ (256 &mu;g/kg) je kvantifikovan samo u zrnu spelte, dok kod drugih Triticum vrstama, zrno nije bilo kontaminirano AFB₁ (&lt;LOD). Određivanjem fizičko-hemijskih karakteristika plevičastih omotača Triticum vrsta potvrđen je njihov potencijalni uticaj na rast i razvoj A. flavus i biosintezu AFB₁. Efekti različitih temperatura (15, 23, 30 i 37&deg;C) i aktivnosti vode (0,85; 0,90; 0,95 i 0,99) na biosintezu AFB₁ ispitani su na ve&scaron;tački inokulisanim uzorcima spelte sa plevičastim omotačima kao i prethodno olju&scaron;tenim zrnima. Optimalni uslovi za biosintezu tj. uslovi pri kojima je ostvaren najveći prinos AFB₁ bili su temperatura 30 &deg;C i aw 0,99 u svim tipovima uzoraka (zrna spelte inkubirana bez plevičastih omotača - ZBPO, plevičasti omotači - PO i zrna nakon lju&scaron;tenja tj. olju&scaron;tena zrna - OZ). Rezultati su pokazali da je prisustvo plevičastih omotača bilo za&scaron;titna barijera za razvoj infekcije i akumulaciju AFB₁ u zrnu. Matematički modeli, razvijeni primenom faktora sa visokom značajno&scaron;ću kao &scaron;to su temperatura skladi&scaron;tenja i aktivnost vode, mogu biti kori&scaron;ćeni u predviđanju akumulacije AFB₁ u zrnu spelte &scaron;to predstavlja ključni korak u proceni rizika. Ispitivanjem uticaja različitih nivoa kontaminacije spelte AFB₁ u poređenju sa kontrolnim nekontaminiranim uzorkom ukazano je na smanjenje određenih parametara tehnolo&scaron;kog kvaliteta i potencijalne gubitke pecivnih svojstava speltinog bra&scaron;na pri sadržaju AFB₁ od&nbsp;&nbsp; 50 &mu;g/kg i 250 &mu;g/kg.</p> / <p>The presence of fungi and mycotoxins in food presents a multiple risk, both from the aspect of food safety and from the aspect of global trade. The frequency and incidence of mycobiota on common wheat and spelt grains samples collected in the region of Vojvodina were determined after harvest during the three-year period (2015-2017). The research covered the identification and characterization of 38 A. flavus isolates using a polyphase approach including classical microbiological and molecular methods. Testing the A. flavus isolates for AFB₁ biosynthesis, it was found that two isolates originating from wheat grains possess the aflatoxigenic potential. Artificial inoculation of different Triticum species: common wheat, spelt, khorasan and hybrid wheat with toxigenic isolates was carried out in the flowering stage in order to compare the resistance of these species to the occurrence of A. flavus and the production of AFB₁. The highest AFB₁ level (256 &mu;g/kg) was determined only in the dehulled spelt grains, in comparison to other species where AFB₁ was not detected in dehulled grains. In order to investigate the impact of wheat hulls on development of A. flavus, including the biosynthesis of toxic fungal metabolites, physico-chemical and structural properties of different Triticum spp. hulls were characterized. The effects of different temperatures (15, 23, 30 and 37 &deg; C) and water activity (0.85; 0.90; 0.95 and 0.99) on AFB₁ biosynthesis were examined on artificially inoculated hull-less as well as hulled spelt grains. The optimal conditions for AFB₁ biosynthesis (the conditions in which the highest AFB₁ yield was achieved) were temperature 30 &deg;C and 0.99 aw in the all tested spelt samples (hull-less grain, dehulled grains and hulls). Accumulation of AFB₁ was significantly higher in hull-less than in dehulled grains that implicate the protective effect of spelt hulls. Mathematical models, developed using high-significance factors such as storage temperature and water activity, can be used to predict the accumulation of AFB₁ in spelt grains, which is a key step in risk assessment. By examining the influence of different levels contamination levels of spelt grain with AFB₁ and comparing to the control (uncontaminated) sample, the reduction in certain technological quality parameters and the potential loss of dough properties of spelt flour with AFB₁ content of 50 &mu;g/kg and 250 &mu;g/kg was pointed out.</p>

The selection of crosses is a fundamental part of a breeding program, and the use of an adequate strategy is crucial. A good strategy should balance the selection of the best individuals and maintenance of genetic diversity throughout cycles of breeding, aiming for long-term genetic gains. Among the methods proposed in the literature, we can highlight the genomic prediction with simulated offsprings, which can be used to estimate the mean and genetic variance of each combination of candidate parents, providing useful information to the breeder. However, as far as we know, there are no reports on how this method performs concerning long-term genetic gain. Thus, the goal of this study was to evaluate how genomic prediction with simulated offsprings performs compared with the traditional phenotypic selection across five cycles of breeding. In silico and data-based simulation was used to investigate these approaches in terms of genetic gain and several other parameters related to the genetic diversity. We simulated an In silico standard wheat breeding program, with a capacity to evaluate 1000 lines per cycle. We considered different scenarios for the heritability, number of populations and the number of offspring per population. A real dataset of 1465 wheat inbred lines was also used to perform simulations. In this case, markers were randomly assigned to be genes. The results indicated that the best method is dependent of the heritability of the trait under consideration, the breeder\'s strategy about how many crosses will be done and also if the breeding goal is to have short or long-term genetic gains. In general, the genomic methods, especially the genomic prediction with simulated progenies, presented the best results under scenarios of low heritability and high number of population, either on short or long-term. However, even though the conversion of genetic variability into genetic gains is faster than any other strategy, the losses of variability are also higher, being interesting to bring new sources of variability with the advance of the cycles of breeding. The adoption of the restriction on the number of times a genotype is a parent in crosses is also of fundamental importance for obtaining long-term genetic gains. / A seleção de cruzamentos é parte importante de um programa de melhoramento e o uso de uma estratégia adequada é crucial. Uma boa estratégia deve balancear a seleção dos melhores indivíduos e a manutenção da diversidade genética ao longo dos ciclos de seleção, visando ganhos a longo prazo. Dentre os métodos propostos na literatura podemos destacar a predição genômica com progênies simuladas, que pode ser utilizada para se estimar a média e a variância genética de cada combinação de parentais candidatos, provendo valiosa informação para o melhorista. No entanto, não há relatos sobre como esse método se comporta em um processo de seleção a longo prazo. Portanto, o objetivo desse trabalho foi avaliar a performance do método de predição genômica com progênies simuladas em relação aos métodos tradicionais de seleção fenotípica, ao longo de dez ciclos de melhoramento. Simulações In silico e utilizando um conjunto de dados foram utilizadas para investigar essas metodologias em relação ao ganho genético e diversos outros parâmetros relacionados a diversidade genética. Simulou-se um programa de melhoramento de trigo com capacidade para avaliar 1000 genótipos a cada ciclo. Diferentes cenários para herdabilidade e a combinação número de populações e número de progênies por população foram avaliados. Um conjunto de dados reais de 1465 linhagens de trigo também foi utilizado com o objetivo de proceder com uma simulação baseada em dados reais. Nesse caso, marcas foram aleatoriamente designadas como genes. Os resultados indicam que o melhor método é dependente da herdabilidade da característica, da estratégia adotada pelo melhorista quanto ao número de cruzamentos realizado e também se o objetivo de melhoramento é a obtenção de ganhos genéticos a curto ou à longo prazo. No geral, os métodos envolvendo seleção genômica, especialmente o que faz uso de progênies simuladas, apresentaram melhores resultados quando a herdabilidade é baixa e o número de populações é alta, tanto a curto como à longo prazo. No entanto, embora a conversão de variabilidade genética em ganhos genéticos seja mais rápida com essa estratégia, a perda de variabilidade é mais acentuada, sendo interessante a reposição de novas fontes de diversidade com o avançar dos ciclos de melhoramento. A adoção de uma restrição no número de vezes que um genótipo atua como genitor é, também, de fundamental importância para a obtenção de ganhos à longo prazo.

Pour soutenir la demande en denrées alimentaires d’une population mondiale croissante, les rendements des productions en céréales, notamment du blé, doivent être améliorés par sélection végétale. À cause du changement climatique et de l’épuisement des ressources fossiles, les systèmes racinaires des futures variétés de blé devront être adaptés aux épisodes de sécheresse et aux sols peu fertiles. Il est donc crucial de développer des outils de mesure de traits racinaires au champ répondant aux exigences de la sélection variétale. Ainsi, la pertinence des minirhizotrons et de l’impédance électrique des plantes a été évaluée en essai agronomique sur des variétés de blé, conçu pour obtenir un panel varié d’enracinement. Nous avons montré que les minirhizotrons fournissent une quantification dynamique et pertinente de la longueur de racines profondes, qui jouent rôle majeur dans les rendements obtenus en conditions pluviales. Malgré une sous-estimation de la partie superficielle des systèmes racinaires, la conversion volumétrique des données issues des minirhizotrons basée sur une profondeur de champ, et à l’aide de prélèvements pour les horizons de surface, a permis une estimation du ratio de masse racinaire sur masse aérienne.À travers une étude méthodologique en laboratoire, nous avons déterminé le montage optimal de mesure d’impédance électrique sur des plants de blé. Son application au champ montre que la qualité de l’estimation diminue au cours de la croissance et dépend de l’humidité du sol.Nous avons montré que l’impédance des plants de blé est décrite par un modèle de condensateur plan, les tissus végétaux formant un diélectrique imparfait. Ainsi, la réactance est un prédicteur de la masse racinaire, uniquement dans les couches superficielles et sèches du sol. / Ensuring the food supply of an increasing world population could be achieved by improvingcrop yields through plant breeding. Due to the climate change and the rarefaction of fossilresources, the root systems of the future wheat cultivars should be adapted to low soilmoisture and low soil fertility. Developing tools for in situ root traits measurements fulfilling the high through put requirement of modern breeding is crucial. For this purpose, anagronomic trial was conducted on wheat cultivars to evaluate the relevance of minirhizotrons and plant electrical impedance on assessing varied rooting architecture.We showed that minirhizotrons provide dynamic and relevant quantifications of deep rootlengths, which was a key factor in crop yield under rainfed conditions. In spite ofunderestimated lengths in the shallow part of the root systems, a volumetric conversion ofminirhizotron data using a depth-of-field criterion, coupled with auger sampling for surfacelayers, allowed fairly estimation root to shoot ratio at different growth stages.We determined the optimal setup of plant impedance measurements by a methodological study performed under laboratory conditions. The application of this optimal set up to an in situ survey showed that the quality of the predictions decreased at later growth stages andunder low soil wetness. The plant impedance was described by an imperfect parallel-platecapacitor mode, where plant tissues acted as the separating medium. Consequently, electrical reactance is a root biomass sensor, but only in surface soil layers at low water content.