Evaluation of an Italian germplasm collection of Festuca arundinacea Schreb. through a multivariate analysis

Summary Forty-eight accessions of tall fescue (Festuca arundinacea Schreb.), collected from Northern to Southern Italy, were analyzed using both univariate and multivariate analysis applied to a set of 12 quantitative traits. Four principal components were found to explain 77% of the total variation in the dependence structure. Productivity characters together with heading time and dimensions of flag leaf appeared to be the major sources of diversity among tall fescue populations. On the basis of the 4 principal components similar populations were clustered according to minimal distance analysis. Seven clusters were identified. The results of cluster analysis confirmed the presence of a remarkable diversity within the germplasm collection and explained why results of a univariate analysis of variance did not reveal significant differences among groups of accessions collected in Northern, Central and Southern Italy. The multivariate approach seemed to point out a problem of genetic erosion of the local germplasm in the Po Valley (Northern Italy) and, on the whole, appeared to be a valid system for tall fescue germplasm evaluation.Research supported by C.N.R., Italy, special grant I.P.R.A., Subject 1.5.1., paper n. 1146.     

Pattern analysis and genotypic x environment interactions in faba bean (Vicia faba L.) populations

Summary Twenty-nine populations of faba bean (Vicia faba L. subsp. major, equina and minor) of mediterranean origin were evaluated for the genetic variability of 12 biomorphological characters at four locations in Apulia and Basîli cata regions (Italy) in 1983–84.A pattern analysis appoach, based on classification and ordination procedures is presented for to characterize differences among population in mean performance and response across environments. Informations about G × E interaction were obtained.Research work supported by CNR, Italy. Special grant I.P.R.A. Sub-project 1. Paper N. 1099.     

Variation in durum wheat populations from three geographical origins. I. Material and spike characteristics

Summary Sixteen durum wheat landraces. i.e. 6 from Algeria, 5 from Ethiopia and 5 from Italy were analysed in order to ascertain the amount of variation for all 11 spike characters. For each population the differences among spike progenies were significant for all the observed characters. Principal component analysis showed that 4 factors accounted for 80% of the total variation. Component 1 accounted for 32% of the total variation and was associated with spike width, spike density, number of kernels per spikelet and kernel weight. Component 2 accounted for 24% of the total variation and was associated with number of fertile spikelets, total number of spikelets and spike length. In a scatter diagram of all 1127 spike progenies for the first two principal components, the material from Ethiopia and Italy clustered at two opposite sides, while the material from Algeria had the largest swarm and overlapped the other two groups of material. Differences among populations from the same origin were found. The ecological and anthropological causes that may have played a role in the creation of the observed variation in the examined populations, are discussed.     

Genetic structure of putative heterotic populations of alfalfa

Semi‐hybrids between genetically distant alfalfa (Medicago sativa subsp. sativa) populations may display heterosis whose extent is affected by the structure of genetic diversity across populations. This study aimed to assess the genetic diversity across three putative heterotic populations, one Italian, one Egyptian and one of semi‐erect germplasm from Eastern Europe, Canada and Spanish Mielga (EECM population). Each population was bred from ten parents after various selection cycles. Fifteen genotypes per population were characterized by 20 polymorphic SSR markers. The among‐population variance was over eightfold smaller than the average within‐population variance (2.05 vs. 17.24) and accounted for 10.6% of the total variation. G’_ST = .090 across markers indicated modest population differentiation. Various diversity measures, multidimensional scaling, and cluster analysis of the genetic structure indicated that the Italian population was more distant from the EECM population than the Egyptian one. The EECM and Egyptian populations were the most distant geographically and genetically. EECM displayed widest intrapopulation variation, accordingly to its constitutive geographical diversity. In conclusion, this study indicates modest genetic differentiation between alfalfa populations even for geographically distant germplasm.     

Effect of generation of inbreeding, cutting treatment and year on agronomic traits in berseem populations

The selfing effect in berseem clover (Trifolium alexandrinum L.) was analysed by comparing generation means for nine agronomic traits (dry matter yield, plant height, leaf-stem ratio, harvest index, seed yield and its components). Parents, S₁, S₂, S₃, and S₄ generations of six populations of different geographical origin (3 from Egypt and 3 from southern Italy) were investigated to estimate the relative changes with increasing homozygosity and to prove the effectiveness of selfing in a breeding program. The experiment was carried out at Foggia (Italy) under field conditions for two years (1995 and 1996) adopting two cutting treatments: at fifth internode elongation (A) and flowering (B). The mean values decreased with the advancement in selfing generations in both years and cutting treatments for the most of the traits. Treatment B yielded more biomass and seed yield than treatment A in both years. Cutting treatments did not affect the adaptability of the selfed progenies of populations with different geographical origin, in fact, the Italian populations were more productive for dry matter under both cutting treatments (856.6 g m^-2 on average), whereas Egyptian populations proved superior for seed yield particularly under treatment B (62.5 g m^-2 on average). Inbreeding depression was greater for forage dry matter and seed yield (−62and −79% on average, respectively), whereas the plant height and 1000-seed weight were the least susceptible traits (−26 and −19% on average, respectively). Estimates of the parameters of the stability analysis showed that not all populations responded to inbreeding level and environment variations to the same degree. Differences were evident under treatment A, only. Development of self-fertile, relatively vigorous inbred lines of berseem clover with different degrees of homozygosity appears possible. Genotypes tolerant to selfing from Egyptian and Italian groups have been obtained by inbreeding and selection for self-fertility; they could be utilised as basis for producing new breeding activities. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phenotypic Variability for Bio-Agronomical Traits in Berseem (Trifolium alexandrinum L.) Populations of the Meskawi Botanical Group

The phenotypic variability and adaptability for bio-agronomic traits in berseem populations (Trifolium alexandrinum L.), was evaluated. The number of genotypes was 32 (26 of southern Italy origin and 6 Egyptian). They were evaluated under field conditions for two years (1989–90) in Foggia (Italy) adopting different cutting regimes: at 7–8th inter-nodes stem length, beginning of flowering, and no cutting. The genotypes of the Italian origin appeared to be better adapted when the cut was applied in the early stage of development, and more productive in seed yield. The Egyptian populations were most productive in forage in the later cuts and had a higher seed weight. The range of variation among the bio-agronomical traits was higher when the cut was applied at early flowering. The traits with wider range of variation were: dry matter, plant height at cut, regrowth at the fourteenth day after cut, tiller density and seed yield. Considering a multiplicative selection index, 6 populations were well adapted and could be used as parents in breeding programs and in extended farm cultivation.     

Partial resistance to a Fusarium root disease in Egyptian white lupin landraces

A Fusarium sp. root pathogen of lupin is the causal agent of the most important disease that affects the cultivation of white lupin (Lupinus albus L.) in Egypt. The aim of our research was to investigate whether host resistance to Fusariumroot disease was available in Egyptian landraces ofLupinus albus. Five Fusarium isolates collected from white lupin samples in Egypt were tested with an Egyptian landrace and a French cultivar. The most aggressive isolate was used to screen an additional 15 Egyptian landraces, two cultivars released in Egypt after selection among landraces, one Polish cultivar, and two French cultivars. The assessment of host response to Fusarium was performed in a field, and under controlled conditions in a greenhouse pot experiment. Most landraces and the two Egyptian cultivars showed better resistance with good accordance between field and pot experiment. This experiment showed that Egyptian genetic resources of white lupin possess partial resistance to Fusarium root rot. Egyptian germplasm may be an alternative genetic source for incorporating partial resistance to Fusarium root rot into the breeding pools. This revised version was published online in July 2006 with corrections to the Cover Date.     

A diversity analysis of genetic resources in rice

Summary A total of 1407 japonica and 488 indica accessions representing nine countries were randomly drawn from the International Rice Research Institute catalog of germ plasm resources for an analysis of diversity. The qualitative gene frequencies as well as means and coefficients of variation for quantitative traits for each race and country in general confirmed the widely recognized pattern of indica-japonica differentiation but suggested more overlap than often realized. Use of a diversity index showed indica to be more variable than japonica, but with different countries having similar levels of diversity. A multivariate analysis based on 39 characters showed divergence among countries within each race but with a great amount of overlap in the scatter of individual entries. This study was carried out simply to illustrate some genetic resource analyses and it is therefore discussed in relation to the documentation aspects.     

Multivariate analysis of morphological characters in Setaria leiantha Hackel

Summary Continuous characters related to plant morphology and seed production were measured in eight populations of Setaria leiantha. Phenotypic variation for 12 traits was analyzed by multivariate methods. A canonical variate analysis provided a preliminary criteria for distinguishing the populations. The first three canonical components account for 93% of the total variance. Seed weight per ear was the most important character to discriminate among populations. The preliminari groups formed will serve as centers of diversity for future collections.     

Genetic variation in a Norwegian germplasm collection of white clover (Trifolium repens L.)

Phenotypic (r_p), genotypic (r_g), genotype × location (r_gl) and error (r_e)correlations for important agronomic characters were estimated for eleven Norwegian populations of white clover (Trifolium repens L.), originating from between 58^°52′N and 69^°30′N latitude, and from altitudes of 10 to 450 m a.s.l. The populations were evaluated in monoculture clonal field plots for two years at two locations in Norway. All pairwise correlations between foliage height, leaflet length, dry matter yield (DMY) and general performance were positive and significant. Winter survival was positively correlated with general performance, spring growth and DMY, but negatively associated with internode length, while seed yield showed a small positive genotypic correlation with foliage height. Considerable differences were, however, revealed among populations with regard to sign and magnitude of the estimated correlations. Within-population estimates of r_g were consistently positive between DMY, general performance and most other characters; between foliage height on the one hand and leaflet length, winter survival and seed yield on the other hand, and between internode length and leaflet length, indicating pleiotropy. Correlations involving other character-combinations varied substantially among populations, and imply presence of linkage and/or coadaptation. Path coefficient analysis was used to partition the genotypic correlations between some of the characters into direct and indirect effects. Path coefficients revealed that foliage height had the highest positive direct effect on DMY, followed by winter survival and internode length. Leaflet length, which showed a positive, significant simple correlation with DMY, exhibited a negligible direct influence, counterbalanced nearly completely by the positive indirect effect on DMY via foliage height. Positive indirect effects on DMY via foliage height were also found for winter survival and internode length. The coastal populations from North and Middle Norway, and a southern highland population showed the largest expected responses to phenotypic selection for most of the characters. The results demonstrate that there is enough genetic variation in adapted local populations to develop new improved cultivars adapted to high-latitude environments that combine upright growth habit with sufficient winter-hardiness and persistency. This revised version was published online in July 2006 with corrections to the Cover Date.     

Use of RAPD and microsatellite (SSR) variation to assess genetic relationships among populations of tetraploid alfalfa, Medicago sativa

The level of random amplified polymorphic DNA (RAPD) and microsatellite variation present in four ecotypes and two varieties of alfalfa (lucerne) from Italian and Egyptian germplasm sources was evaluated. A sample of 100 plants from 10 populations was analysed by means of 41 RAPD markers and 37 simple sequence repeat (SSR) markers. Both molecular approaches revealed a high degree of genetic diversity within each of the cultivated populations and enabled each of the plants considered to be uniquely fingerprinted. The genetic relationships among plants and populations were analysed by computing AMOVA (analysis of molecular variance) and F_ST analyses. RAPDs were able to separate the Italian populations from the Egyptian variety. SSRs allowed strong separation of the four Italian alfalfa ecotypes. It was concluded that RAPD and microsatellites could be useful and powerful tools for assessing genetic variation and genetic relationships in tetraploid alfalfa.     

Chloroplast microsatellite variations in tetraploid alfalfa

Four chloroplast simple sequence repeat (cpSSR) loci were identified in alfalfa (lucerne), Medicago sativa L. The occurrence of allelic variation at these loci was evaluated in 100 plants from 10 populations of tetra‐ploid alfalfa, belonging to four Italian ecotypes and to an Italian (‘Lodi’) and an Egyptian (‘Iside’) variety. Twenty‐four different alleles were identified, four of which were exclusive to the ‘Iside’ variety. The genetic relationship among plants and among populations was analysed by computing an analysis of molecular variance and an unweighted pair group means analysis clustering. This analysis allowed clear separation of the ‘Iside’ variety from Italian germplasm and the recognition of close relationships within the Italian populations. The data presented suggest that cpSSR analysis of tetraploid alfalfa could be used for germplasm polymorphism analysis.     

Structure and variation of subterranean clover populations from Sicily,Italy

Summary A collection of subterranean clover lines singled out from populations of the species Trifolium brachycalycinum and T. subterraneum collected in Sicily, Italy, was examined at two localities for flowering time and at one locality for oestrogen content and seed yield. The structure and variation of the populations of the two species were compared. The relationship between flowering time of the populations and some environmental features of their collection sites was examined to assess whether the maturity requirements of the two species were similar and to frame selection models focused on developing varieties of appropriate maturity. Populations of T. subterraneum were, on average, more complex than those of T. brachycalycinum, being characterized by higher number of lines per population and greater intra-population variation for flowering time, oestrogen content and seed yield. Furthermore, populations of T. subterraneum were, on average, about 15 days earlier than sympatric populations of T. brachycalycinum. Both the greater variation and the relative earliness of T. subterraneum occurred irrespective of the environments of origin of the populations. Inferences are drawn on the adaptive advantages that such features confer to T. subterraneum. Mean flowering time of the populations increased on increasing annual rainfall and altitude of the collection sites. However, the changes in maturity appeared almost exclusively related to variations in rainfall in T. subterraneum, while in T. brachycalycinum the effect of altitude was greater and that of rainfall less marked than in the former species.     

Genetic evaluation of cultivated garlic germplasm (Allium sativum L. and A. ampeloprasum L.)

Garlic cultivated in rural farms of South Italy is often a heterogeneous clone population, which can comprise different cytotypes. A collection of cultivated garlic from the University of Basilicata gene-bank, was evaluated for ploidy level, and 16 different morphological traits. Out of50 accessions, 7 were hexaploids (Allium ampeloprasum L.) and43 diploids (Allium sativum L.). Significant differences in yield were observed within and between ploidy levels. The heritable traits most correlated with yield were plant height (h² = 0.62) within diploid types and neck diameter (h² = 0.75) within hexaploids. Discriminant analysis did show that four characters (leaf basal width, total n^° of leaves, clove diameter and neck height) were able to correctly discriminate all germ plasm accessions between the two species. This revised version was published online in August 2006 with corrections to the Cover Date.     

RAPD genetic diversity of Albanian olive germplasm and its relationships with other Mediterranean countries

RAPD markers were used for the study of 19Albanian olive cultivars and two wild olives (oleasters). A total of 76polymorphic bands (4.8 polymorphic markers per primer) out of 107 reproducible were obtained using 16 primers. The number of bands per primer ranged from 4 to 10,whereas the number of polymorphic bands ranged from 1 to 9, corresponding to 71%of the total amplification products. All the accessions could be identified by the combination of four primers: OPA-19;OPA-02; OPK-16 and OPP-19. The dendrogram,based on Jaccard's index, included three major groups according to their origin: 1)most of the cultivars from the area of Berat (South of Albania) 2) cultivars from the Centre and Centre-North of Albania and3) cultivars from the Centre and North-West of Albania along with the oleaster from Elbasan. In order to evaluate the origin of Albanian cultivars they were compared to those diffused in other countries like Greece, Italy and Turkey, due to geographical and historical affinity among these countries, by using a one way AMOVA. Although most of the genetic diversity was attributable to differences among cultivars within each country (91.47%) significantφ-values among countries(φ_st = 0.085; p < 0.001)suggested the existence of RAPD phenotypic differentiation. Significant φ-values in all pairs formed by Albania with the other countries were observed. These results are consistent with the autochthonous origin of Albanian cultivars. This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis of an incomplete diallel cross among three ssp. tuberosum varieties and seven long-day adapted ssp. andigena clones of the potato (Solanum tuberosum L.)

Summary The main aim of the experiment was to study the behaviour of seven long-day adapted clones of Solanum tuberosum ssp. andigena (A) and three varieties of S. tuberosum ssp. tuberosum (T) in an incomplete diallel cross. The four groups of crosses, TxT, TxA, AxT and AxA, held 2, 12, 20 and 21 populations, respectively. Eleven of the intersubspecific crosses were exact reciprocals. Thirty random clones per population were grown as second clonal generation in an incomplete block design with four replications in plots of two plants per clone in 1980, the parents included in many plots. Data were recorded on ten characters.The results showed that group TxA gave the highest tuber yield and AxT the second highest. The F-values indicated highly significant genotypic effects for all characters in all populations. The mean genotypic coefficients of variation (GCV), were the highest for group AxA for all characters. The ANOVA, based on population means showed significant mean squares for general combining abilities (GCA) and for differences of reciprocalls for all characters; the specific combining ability (SCA) mean squares were significant only for date of emergence, plant height and haulm type. Almost all GCA effects of the parents were significant positive or negative. Several populations showed also significant SCA effects. The correlations between the GCA effects and the parental values were of about the same magnitude as the heritabilities; those between the population means and the midparental values were slightly lower.Compared to the midparental values, most populations showed significant positive heterosis for date of emergence, haulm type, number of tubers and under water weight; all populations had significant negative heterosis for mean tuber weight and nearly all for plant height and general impression. All populations from groups TxT and AxA had significant negative heterosis for tuber yield and so had 13 out of the 20 populations from group AxT, while seven of the 12 from group TxA showed significant positive and four significant negative heterosis. The average heterosis for tuber yield of group TxT was –11%, of TxA 3.4%, of AxT–9% and of AxA–18%. The highest mean tuber yields were obtained from crosses with a very high yielding A-parent as female, while the heterosis was negative. Though significant differences between the 11 reciprocals occurred for all characters, consistent differences occurred only for tuber yield. Averaged over the 11 crosses the TxA populations outyielded their exact reciprocals by 10.7%. For the highest tuber yields in A-T crosses, therefore, the tuberosum cytoplasm seems to be preferable. By contrast for a high male fertility the andigena cytoplasm is preferable.     

Regional phenotypic diversity of Puccinia triticina and wheat host resistance in western Europe, 1995

Pathogenicity data from surveys of Puccinia triticina (formerly P. recondita f. sp. tritici) conducted in western Europe in 1995 were analysed to compare the structure of regional populations of the pathogen. Many of the populations differed in phenotypic diversity and pathotypic composition, even though they occurred within a single epidemiological unit, suggesting that local factors may influence the establishment and propagation of individual pathotypes in the regional populations. Neighbouring regions were more similar than distant regions, and all regions shared at least one pathotype, except populations in northern Italy and Scotland. A high degree of similarity was found between populations in northern France and Great Britain, providing strong evidence of free movement of inoculum between these regions. Resistance genes were postulated for a selection of 91 wheat cultivars, representing those most commonly grown in western Europe in 1995. Thirteen cultivars lacked detectable seedling resistance genes and the remaining 78 possessed from one to three resistance genes; those detected were Lr1, Lr3a, Lr10, Lr13, Lr14a, Lr17b, Lr20, Lr26 and Lr37. The most commonly detected resistance gene was Lr13, which was present singly or in combination with other resistance genes in 48 cultivars (53%). The gene Lr14a was detected in 18 cultivars, Lr26 was present in 16 cultivars. The role of host selection in the composition of the regional populations of P. triticina in western Europe in 1995 was difficult to assess on the basis of the results obtained, since virulence data were not available for Lr13 and Lr14a. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic variability of Striga asiatica (L.) Kuntz based on AFLP analysis and host-parasite interaction

AFLP analysis was used to estimate genetic variability within and among 14 populations of Striga asiaticaL. Kuntze collected from different locations within the Republic of Benin. The mean within-population genetic distances ranged from 0.028 to 0.038, while the mean among-population genetic distances ranged from 0.019to 0.088, with an assumed minimum genetic distance of0.01 in each case. Intra- and inter-population variation was reflected by a highly significant R² of 0.61for the regression of geographic distance versus genetic distance. Interactions of the different Strigapopulations with susceptible host genotypes, 8338-1 (Zea mays) and CK60B (Sorghum bicolor),indicated a high degree of host-specialization, with CK60B failing to support growth of the parasite from any of the populations. The various Striga populations also exhibited different degrees of virulence on susceptible host plants. Our results support the hypothesis that different populations of this parasite may well be considered and treated as ecotypes in plant breeding programs developing resistance to S. asiatica. This revised version was published online in August 2006 with corrections to the Cover Date.     

The inheritance of seed colour and vernalization requirement in Brassica napus using doubled haploid populations

Summary In the Mediterranean coastal region, spring barley cultivars are sown in the autumn, corresponding with the rainy season. Thirty eight cultivars out of 44 spring which were collected from North African countries including Morocco, Algeria, Tunisia, Libya and Egypt were of a single dominant spring gene type (+Sh ₂+). Almost the same situation was found in Spain, Italy and Greece, with exceptions for France and Turkey. Kernel row of North African cultivars was characterized by six-rowed type, though there was one exception in Egypt. In the South European countries of Spain, Italy and Greece, six-rowed type varieties were also prevalent. As to non-brittle rachis, in North African countries oriental type cultivars (Btbt ₂) were much higher in frequency than occidental type cultivars (btBt ₂), while in European countries, occidental type cultivars were rather dominant, except for Italian cultivars. In Turkey, located in the joint area between Europe and Asia, cultivars tested were mostly occupied by spring genotype other than +Sh ₂+, and also characterized by tworowed head and occidental type for non-brittle rachis. In the Mediterranean coastal region, especially in North Africa, restricted genotypes, +Sh ₂+ for spring growth habit and v for six-row may indicate adaptability favorable to the growth conditions in these areas. Furthermore, North African cultivars were characterized by the oriental type of non-brittle rachis. This may give us information about the migratory routes of the original landrace to North Africa.     

Morphological characterization of Mediterranean populations of Biserrula pelecinus L.

A collection of 24 populations of Biserrula pelecinus L. (biserrula)from Italy (Sardinia), Spain. France (Corsica). Morocco and Greece was evaluated in nursery rows at Perth, Western Australia. Fifteen morphological traits were recorded and chromosome numbers of representative populations were counted: The quantitative characters were analysed using principal component analysis and k-means clustering. The chromosome number of all accessions was 2n= 2x= 16. In other respects there was substantial variation in biserrula collected from the Mediterranean basin, the Moroccan populations in particular being distinct, some with strongly curved pods and others with long linear pods. All Greek populations had while flowers and large seeds. Populations from Italy. France and Spain were similar, with linear pods, blue flowers and smaller seeds. Most populations from Morocco were early flowering, had larger leaves, longer pods and produced more seeds per plant than other populations. All populations were extremely hard seeded (>98% hard-seeded after a one-summer exposure on the soil surface). It wits concluded that there is sufficient variation in Mediterranean populations of biserrula lo initiate a selection programme for southern Australia, and other areas with Mediterranean-type climates, especially for areas where serradella ((Ornithopus compressus L.) is adapted. Seed production is far easier than for serradella, and this advantage alone offers potential for its use in duplex soils where the deep rooting habit of serradella gives it an ecological advantage over conventional pasture legumes.