Distribution and pheotypic variability aspects of some quantitative traits among durum wheat accessions

A durum wheat ( Triticum durum Desf.) collection with 111 accessions represents a large part of the collection of Triticeae species in Tunisia were evaluated for six qualitative traits: seed colour, seed size, glume colour, glume pubescence, spike density and beak length. Distribution of traits showed that this germoplasm was dominated by dense spike, white and glabre glume, long beak, brown and large grain. Phenotypic diversity is determined by the index Shannon-Weaver (H'). This index calculated for each parameter revealed that spike density (H' =0.86), glume pubescence (H' =0.80) and glume colour (H' =0.79) showed the best diversity index. Seed size showed the weakest index (H' =0.69) which indicated a low phenotypic variability for this parameter. This durum wheat germoplasm presented an average of diversity index about 0.77, showing a large diversity of this collection. These values showed that the germoplasm has a relatively important diversity, confirming that Tunisia is one of the principal durum wheat secondary centres of diversification. This genetic diversity can be exploited in improvement programmes.Une collection de blé ( Triticum durum Desf.) avec 111 nouvelles acquisitions représentant une grande partie de la collection des espèces Triticeae en Tunisie avaient été évalués pour six traits qualitatifs: couleur de semences, taille de semences, la couleur de glume, pubescence du glume, densité du pointe et longueur de bec. La distribution des traits avait montré que cette germoplasm avait été dominée par une dense pointe, glume blanc et glabre, long bec, grain brun et grande. La diversité phénotypique est déterminée par l'index de Shannon-Weaver (H'). Cet index calculé pour chaque paramètre a révélé que la densité du pointe (H' = 0,86), la pubescence du glume (H' = 0,80) et la couleur du glume (H' = 0,79) avait montré le meilleur indice de diversité. La taille de semences avait montré le plus faible index (H ' = 0,69), ce qui avait indiqué une variabilité phénotypique faible pour ce paramètre. Cette germoplasm de blé dur a présenté une moyenne de l'index de diversité d'environ 0,77; montrant une grande diversité de cette collection. Ces valeurs ont montré que cette germoplasm a une diversité relativement importante, ce qui a confirmé que la Tunisie est l'un de principaux centres secondaire de diversification de blé dur. Cette diversité génétique peut être exploitée dans les programmes d'amélioration

Genotypic variability for salt stress tolerance among wild and cultivated wheat germplasms at an early development stage

This study was conducted to evaluate the variability of salt tolerance potentials among nine wheat genotypes representing wild and cultivated species namely Triticum turgidum subsp. durum, Triticum aestivum and Aegilops geniculata. Ionomic and photosynthetic traits were used for the screening of the studied samples when faced with four salinity levels of NaCl (0, 50, 100 and 150 mM) under green house conditions at the seedling stage. The investigated genotypes exhibited different levels of salt stress tolerance. Ionomic and photosynthetic traits underline the distinctiveness of the common wheat varieties which highlighted particular performances under salt stress conditions and showed higher tolerance potentials among the studied genotypes. Interestingly, the Vaga variety showed more ability to maintain higher K+/Na+ ratios and Pq coefficients compared with the control conditions and stable Fv/F0 and Fv/Fm ratios. Stable behaviour was exhibited by wild Aegilops accessions while durum wheat varieties have been shown to be more sensitive to salt stress. Further investigations were required for the common wheat variety Vaga, which could be useful for successful breeding and biotechnological improvement strategies concerning wheat species

Phenotypic diversity of Tunisian durum wheat landraces

Tunisia is considered as a diversification centre of durum wheat ( Triticum durum Desf.) and barely ( Hordeum vulgare ). It is characterised by large genetic diversity; however, several genotypes are in the process of disappearance. The safeguard and rehabilitatation of this genetic inheritance requires genetic characterisation, evaluation and in-situ and ex-situ conservation. In this context, a local collection of thirty durum wheat accessions was evaluated using agronomical traits. Three other phenological traits: days to maturity, days to heading and filling period were evaluated. The phenotypic diversity was determined by the Shannon-Weaver diversity Index (H') revealing that number of kernel/spike (H'=0.91), yield (H'=0.89), plant height (H'=0.87) and thousand kernel weight (H'=0.86) had the highest diversity index. Flag leaf area (H'=0.32) showed the weakest index. This germplasm presented average diversity (0.77) showing a large genetic variability. Correlations between traits showed a significant positive relation between yield and spikeless tillers/plant (0.90), thousand kernel weight (0.39), plant height (0.35) and flag leaf area (0.36), suggesting the usefulness of these parameter for selecting for improving grain yield. The components analysis explained 59.61% of total variability and led to identification of a group of accessions Jeneh kotifa 1, Jeneh kotifa 2, Jeneh kotifa 3, Sbei glabre, Hamira 1, Hamira 2, Biskri glabre, Mahmoudi, Biskri glabre AP2, Swabaa Elgia, Sbei, and Mahmoudi glabre showing the best agronomical characteristics. These genotypes can, therefore, be used as parents for the improvement of durum wheat.La Tunisie est un centre de diversité génétique du blé dur ( Triticum durum Desf.) et de l'orge ( Hordeum vulgare ). En dépit de la large diversité génétique au niveau du germoplasme local, plusieurs génotypes sont en voie de disparition. La sauvegarde et la réhabilitation de ce patrimoine génétique nécessitent sa caractérisation, son évaluation ainsi que sa conservation in situ et ex situ. Dans ce contexte une collection locale de trente genotypes de blé dur a été évaluée utilisant des paramètres agronomiques. Trois autres paramètres phénologiques à savoir jours de maturation, jours de rétablissement et période de remplissage étaient aussi évaluées. La diversité phénotypique determinée par l'index de diversité de Shannon-Weaver (H') a révélé que le nombre de grains par épi (H'=0.91), rendement (H'=0.89), hauteur des plants (H'=0.87) et le poids de 1000 grains (H'=0.86) avaient un index de diversité le plus élevé. La surface foliare (H'=0.32) a montré un index le plus faible. Ce germplasm presentait un index de diversité moyen de 0.77 montrant ainsi une large variabilité génétique. Les corrélations entre les paramètres a montré une relation positive significative entre le rendement et le nombre de talles d'épillets par plant (0.39), le poids de 1000 grains (0.35) et la surface foliaire (0.36), suggérant ainsi l'utilité de ces paramètres de sélection pour l'amélioration du rendement en grains. L'analyse des composants a expliqué 59.61% de la variabilité totale et a conduit à identifier un groupe de genotypes entre autre kotifa 2, Jeneh kotifa 3, Sbei glabre, Hamira 1, Hamira 2, Biskri glabre, Mahmoudi, Biskri glabre AP2, Swabaa Elgia, Sbei, Mahmoudi glabre montrant les meilleures caractéristiques agronomiques. Ces génotypes peuvent donc être utilisés comme parents pour l'amélioration de blé dur

Allelopathic potential of sunflower against the great brome

Control methods commonly used to suppress the great brome (Bromus diandrus Roth., syn. Bromus rigidus Roth. subsp. gussonii Parl.) in Tunisian cereal crop are essentially chemical, raising both efficacy and safety issues. The introduction of allelopathic species into the crop rotation or utilizing allelopathic plants as living/green mulches has been suggested as a cost-effective way to reduce the weed presence. Among these species, the sunflower (Helianthus annuus L.) has shown an allelopathic potential against some troublesome weed species. In this study, we analyzed the biological activities of water extract of different tissues (root, shoot, leaf and flower) of sunflower on the seedling establishment of the great brome. In a second experiment, the allelopathic influence of sunflower residues (leaf or flower) against this weed was also studied under glasshouse conditions at more advanced stages of growth using different concentrations (0, 6, 12 and 18g tissue dry weight / kg of soil). The first experiment showed an effect depending on the parts of the sunflower. Indeed, the roots seem to be the less allelopathic part (22% of root inhibition growth) as compared to the leaves and flowers (82% and 100%, respectively). This potential seems to simultaneously affect the radicle and the coleoptile growth of the great brome. In the second experiment, weed growth was inhibited in a dose-dependent manner, using increasing amounts of sunflower residues. The allelopathic potential of the leaves or flowers reduced both the root or shoot length and biomass accumulation of the weed. These results suggest that the sunflower can be a good previous crop for cereal cultivation by controlling the presence of some weeds, including the great brome. In this perspective, the inhibitory effects of sunflower residues on cultivated cereals in the field need to be assessed

Evaluation of the allelopathic potential of water-soluble compounds of barley (Hordeum vulgare L. subsp. vulgare) and great brome (Bromus diandrus Roth.) using a modified bioassay

Description of the subject. The present study focuses on the description of the allelopathic interactions between wild and crop species that may occur in a given ecosystem. Objectives. The objective is the evaluation of the allo- and autoinhibition activity of root exudates of barley (Hordeum vulgare L. subsp. vulgare) and great brome (Bromus diandrus Roth.) seedlings by water-soluble allelochemicals. Method. The allelopathic activities of five Tunisian barley genotypes (modern varieties and landraces), one Saudi Arabian barley landrace and great brome were assessed using a modified laboratory bioassay named “seedling-after-seedling agar method”. Results. The barley or the great brome reduced, to a greater extent, the root growth compared to the shoot growth of receiver species. The response of the root system architecture of the great brome towards barley root exudates was studied in detail. All the measured root traits were highly sensitive to the presence of barley. In our conditions, the allelopathic activity of barley root exudates had no apparent relationship with the size of the root and a prominent action of genetic determinants in the allelopathic potential between genotypes is proposed. The alloinhibitory activity of barley or great brome root exudates deferred between the receiver species but was always higher than the autoinhibition potential. The autoinhibition in barley proved to depend on whether the genotypes used as donor and receiver are identical or different, suggesting a specific interaction of allelochemicals with the receiver plant. These molecules seem to be the main actors in the allelopathic barley potential as external factors such variations of pH have no evident relevance in the inhibition process. Conclusions. Barley and great brome exude molecules in their surroundings. This affects the growth of the receiver plants, suggesting that these compounds might contribute to the plant community dynamics

Genetic variation of salt-stressed durum wheat (Triticum turgidum subsp. durum Desf.) genotypes under field conditions and gynogenetic capacity

Agriculture has new challenges against the climate change: the preservation of genetic resources and the rapid creation of new varieties better adapted to abiotic stress, specially salinity. In this context, the agronomic performance of 25 durum wheat (Triticum turgidum subsp. durum Desf.) genotypes (nineteen landraces and six improved varieties), cultivated in two semi-arid regions in the center area of Tunisia, were assessed. These sites (Echbika, 2.2 g l−1; Barrouta, 4.2 g l−1) differ by their degree of salinity of the water irrigation. The results showed that most of the agronomic traits (e.g. spike per meter square, thousand kernels weight and grain yield) were reduced by salinity. Durum wheat landraces, Mahmoudi and Hmira, and improved varieties, Maali and Om Rabia showed the widest adaptability to different quality of irrigation water. Genotypes including Jneh Kotifa and Arbi were estimated as stable genotypes under adverse conditions. Thereafter, salt-tolerant (Hmira and Jneh Khotifa) and the most cultivated high-yielding (Karim, Razzak and Khiar) genotypes were tested for their gynogenetic ability to obtain haploids and doubled haploid lines. Genotypes with good induction capacity had not necessarily a good capacity of regeneration of haploid plantlets. In our conditions, Hmira and Khiar exhibited the best gynogenetic ability (3.1% and 2.9% of haploid plantlets, respectively). Keywords: Durum wheat, Genetic variation, Salinity, In vitro gynogenesi

Review of 100 NVQs and SVQs A report submitted to the Department for Education and Employment

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