Barley breeding for quality improvement in Tunisia

This study was initiated to assess the effectiveness of three selection procedures applied in the early  segregating generations of barley crosses for quality traits. The selection procedures were pedigree selection (PS), bulk selection (BS) and single seed descent selection (SSD). Selection was operated in F2’s crosses. Field trials were conducted with 19 F3 crosses of barley in two different environments, a sub-humid  environment at Beja and a semi-arid one at Kef. Heading date (HD), thousand kernel weight (TKW), protein  content (PC), â-glucan content (BG) and husk percentage (HP) were evaluated. Data were subjected to an  additive main effects and multiplicative interaction (AMMI) model to determine the efficiency of each method of selection for the proper environment. The results show that the AMMI model generated predictive  optimizing selection method. The pedigree selection was more efficient in high input environment, while the bulk method was very effective for the selection of kernel weight in target environment.Key words: Additive main effect and multiplicative interaction (AMMI) model, Barley, breeding methods, efficiency of selection, quality traits

In vitro screening of soil bacteria for inhibiting phytopathogenic fungi

At present, the greatest interest resides with the development and application of specific biocontrol agent for the control of diseases on plant and this form the focus of this work. Several soil bacteria were evaluated in vitro for their effectiveness on the basis of their ability to suppress fungi in plate inhibition assays. 51 strains of 12 bacterial species were performed against 12 strains of 10 phytopathogenic mould species. Almost all soil bacteria species; but about 50% of the bacteria strains, showed an antagonistic activity against at least one phytopathogenic fungus. Sphingomonans spp was the only specie that did not show any antagonistic effect to all fungi. Bradyrhizobium japonicum could highly inhibit the mycelial growth of five moulds (Botrytis cinerea, Phoma medicaginis, Fusarium verticilloides, Rhizoctonia solani and Phytophtora infestans) with a growth inhibition varying between 12.38 and 37.61%. 12 Bacillus strains and five Pseudomonas strains were antagonistic to the major phytopathogenic moulds used in this trial. Bacillus subtilis exhibited strong antagonism against fungi both from cultural medium and from sterile filtrate. Results show that bacterial suspension and bacterial supernatant did not operate in the same way. Supernatant from bacterial strains seemed to be efficient against phytopathogenic moulds. The mycelial growth of R. solani, P. medicaginis and F. verticilloides was inhibited by 12-fold dilution of the supernatant from B. japonicum. The latter draws a conclusion that bacteria isolated from soil are promising natural biocontrol agents and should be further studied and tested for the control of numerous plant diseases. Additional studies are required to definitively determine their mode of antifungal action, safety and biocompatibility.Keywords: Bacteria, phytopathogenic fungi, antagonis

GENETIC DIVERSITY OF FABA BEAN (VICIA FABA L.) POPULATIONS ESTIMATED BY ISOZYMIC AND MOLECULAR MARKERS: RELATIONSHIP BETWEEN THE TWO METHODS

In our previous studies, the genetic diversity among nine Tunisian faba bean (Vicia faba) populations was analysed using isozymes and sequence-specific amplification polymorphism (SSAP) markers. The objectives of this study were to compare the application and utility of isozymes and sequence-specific amplification polymorphism (SSAP) techniques for analysis of genetic diversity among nine Tunisian faba bean (Vicia faba) populations. A high genetic diversity within populations was detected by both isozymes (SOD, 6-PGD, ME, EST, SKDH, FDH and GDH) and (SSAP) markers (PDR1, Tps19 and Tvf4). For all populations, the genetic diversity revealed by SSAP was more pronounced than that detected with isozyme, based on polymorphic profiles. The analyses of correspondance between the tow methodes based in Mantel test revealed a low correlation ( r=0.177). The low correspondance indicated the absence of correlation and therfore the complimentarit

Relationship between epistasis and aggressiveness in resistance of pepper (Capsicum annuum L.) to Phytophthora nicotianae

This study evaluated the types of gene action governing the inheritance of resistance to Phytophthora nicotianae necrosis in populations derived from two crosses involving two susceptible (Beldi and Nabeul II) and one resistant (CM334) cultivars of pepper (Capsicum annuum L.). Populations, composed of Pr, Ps, F1 , F 2 , BC 1 Pr, and BC 1 Ps generations, were inoculated with six P. nicotianae isolates. Generation means analysis indicated that an additive-dominance model was appropriate for P. nicotianae isolates Pn Ko1 , Pn Ko2 and Pn Kr1 , which showed low aggressiveness in the two crosses. For the more aggressive isolates Pn Bz1 , Pn Bz2 and Pn Kr2 , epistasis was an integral component of resistance in the two crosses. The presence of epistasis in the resistance of pepper to P. nicotianae was dependent on the level of aggressiveness of the isolates. Selection in pepper with less aggressive isolates was efficient, but not with more aggressive isolates; on the other hand, selection with more aggressive isolates was more stable. The minimum number of genes controlling resistance was estimated at up to 2.71. In the majority of cases, the additive variance was significant and greater than the environmental and dominance variance

Epistasis and genotype-by-environment interaction of grain protein content in durum wheat

Parental, F1 , F 2 , BC 1 and BC 2 generations of four crosses involving four cultivars of durum wheat (Triticum durum Desf.) were evaluated at two sites in Tunisia. A three-parameter model was found inadequate for all cases except crosses Chili x Cocorit 71 at site Sidi Thabet and Inrat 69 x Karim at both sites. In most cases a digenic epistatic model was sufficient to explain variation in generation means. Dominance effects (h) and additive x additive epistasis (i) (when significant) were more important than additive (d) effects and other epistatic components. Considering the genotype-by-environment interaction, the non-interactive model (m, d, h, e) was found adequate. Additive variance was higher than environmental variance in three crosses at both sites. The estimated values of narrow-sense heritability were dependent upon the cross and the sites and were 0%-85%. The results indicate that appropriate choice of environment and selection in later generations would increase grain protein content in durum wheat

Epistasis and genotype-by-environment interaction of grain yield related traits in durum wheat

Genetic control of the number of heads per plant, spikelets per spike and grains per spike was studied in two durum wheat (Triticum durum Desf.) crosses, Inrat 69/Cocorit71 and Karim/Ben Bechir, respectively. Separate analyses of gene effects were done using means of four generations (parents P 1 and P 2 , F 1 , F 2 , and the two reciprocal BC 1 ) at two sites. A three-parameter model was inadequate to explain all traits except number of heads per plant in Inrat 69/Cocorit 71 at one site. In most cases a digenic epistatic model explained variation in generation means. Dominance effects and dominance × × × × dominance epistasis (l) were more important than additive effects and other epistatic components. Considering the genotype-by-environment interaction, the interactive model was applied and found adequate in all majority of cases except spiklets per spike and grains per spike in Inrat 69/Cocorit71. The results of this study indicate that maintenance of heterozygosity is useful for exploitation of epistatic effects and adaptability to varied environmental conditions for spiklets per spike and grain per spike in the cross Karim/Ben Bechir. Estimates of narrow-sense heritability indicated that the genetic effect was larger than the environmental effect. The additive effect was the largest component of genetic effects

Estimation of dominance components in noninbred populations by using additive animal model residuals

Abstract. In the case of noninbred and unselected populations with linkage equilibrium, the additive and dominance genetic effects are uncorrelated and the variance-covariance matrix of the second component is simply a product of its variance by a matrix that can be computed from the numerator relationship matrix A. The aim of this study is to present a new approach to estimate the dominance part with a reduced set of equations and hence a lower computing cost. The method proposed is based on the processing of the residual terms resulting from the BLUP methodology applied to an additive animal model. Best linear unbiased prediction of the dominance component $ d is almost identical to the one given by the full mixed model equations. Based on this approach, an algorithm for restricted maximum likelihood (REML) estimation of the variance components is also presented. By way of illustration, two numerical examples are given and a comparison between the parameters estimated with the expectation maximization (EM) algorithm and those obtained by the proposed algorithm is made. The proposed algorithm is iterative and yields estimates that are close to those obtained by EM, which is also iterative

Karyological and genome size insights into cardoon (Cynara cardunculus L., Asteraceae) in Tunisia

6 pág., gráf., tablas -- Post-print del artículo publicado Caryologia. Versión revisada y corregida.This study contributes the first genome size data for wild populations of Cynara cardunculus, the presumed progenitor of artichoke and cultivated cardoon. C-values estimated by flow cytometry are 2C = 1.98–2.14(3.03) pg for wild cardoon (10 populations), 2C = 2.10–2.11 pg for cultivated cardoon (two accessions) and 2C = 2.05 pg for artichoke (one accession). Chromosome counting (carried out for all material except the artichoke) establishes diploidy in all accessions. In order to provide a phylogenetic framework for Tunisian populations, internal transcribed spacer (ITS) region was sequenced and analysed together with previously published Cynara sequences. The wild and crop cardoons present similar karyological features and genome sizes despite strong morphological differentiation, with the single exception of a Tunisian population (from Tajerouine), which exhibits a 42–53% higher genome size. Along with Sicilian individuals, Tunisian wild C. cardunculus appear genetically closer to artichoke and cardoon than to studied wild relatives from the remaining distribution. This highlights the crucial importance of taking into consideration the North African territory in deciphering the history of C. cardunculus crop domestication.This work was subsidised by the Ministerio de Educación y Ciencia, Spain (Project CGL2010-22234-C02-01 and 02/BOS) and Generalitat de Catalunya (“Ajuts a Grups de Recerca Consolidats”2009/SGR/00439). SK benefited from a grant from the Tunisian government and OH from a Juan de la Cierva postdoctoral contract from the Ministerio de Ciencia e Innovación, Spain.Peer reviewe

Natural population of oat crown rust in Tunisia

Oat crown rust, caused by Puccinia coronata f. sp. avenae, is considered the most widespread and damaging disease of oat (Avena sativa) in Tunisia. The virulence structure of the natural oat rust population in Tunisia was studied in four areas from 2002 to 2007 using Puccinia coronata resistance genes (Pc-genes). The areas are located in northern Tunisia: Afareg, Bourbia, Sedjnen and Ariana. In this survey, Pc38, Pc39 and Pc68 showed a high level of resistance to natural oat crown rust. But the most important finding in 2004 in Ariana was that the rust was virulent on Pc68 (IT ‘4’). Moreover, in 2002 Sedjnen survey, there was a high degree of virulence to Pc39 (IT ‘3’). In the other areas and other years, Pc68 and Pc39 were highly resistant to natural oat crown rust. Only Pc38 showed a stable high level of resistance to natural oat crown rust in all four areas and during the six years of the study. Areas showing a high degree of similarity were Sedjnen and Afereg (SI=4.5). Ariana and Bourbia showed little similarity to the other areas, and had the greatest dissimilarity to each other (SI=11.30). The virulence phenotypes of the P. coronata natural population in Tunisia are certainly influenced by the alternate host, Rhamnus lycioïdes which is abundant in the mountains of northwestern Tunisia. A combination of the Pc38, Pc39 and Pc68 genes will provide a high level of durable protection from crown rust in Tunisia