Phenotypic, Cytological and Molecular (AFLP) Analyses of the Cotton Synthetic Allohexaploid Hybrid (<i>G. hirsutum</i>×<i>G. longicalyx</i>)^²

The wild cotton diploid species (2n = 2x = 26) are important sources of useful traits such as high fiber quality, resistance to biotic and abiotic stresses etc., which can be introgressed into the cultivated tetraploid cotton Gossypium hirsutum L (2n = 4x = 52), for its genetic improvement. The African wild diploid species G. longicalyx Hutchinson and Lee could be used as donor of the desirable traits of fiber fineness and resistance to reniform nematode. However, hybridization of wild diploid species and cultivated tetraploid cotton encounters a sterility problem of the triploid (2n = 3x = 59), mainly due to ploidy. The restoration of the fertility can be done by creating an allohexaploid (2n = 6x = 78) through the doubling with colchicine of the sterile triploid chromosomes. With this method, a synthetic allohexaploid hybrid (G. hirsutum × G. longicalyx)2 has been obtained. This genotype was studied using phenotypic, cytological and molecular (AFLP) analyses in order to confirm its hybridity and its caryotype, and also to verify the expression of the desirable traits coming from G. longicalyx. The studied genotype showed a quite good level of pollen fertility (83%), and apart from larger seeds and some minor seedling anomalies, most of its morphological characteristics were intermediate between the two parental species. It had 78 chromosomes, proving its hexaploid status. Molecular analysis revealed 136 AFLP loci in this hexaploid, all from G. hirsutum and G. longicalyx, demonstrating its hybrid status. In addition, the hexaploid exhibited the useful traits of G. longicalyx with regard to its remarkable fiber fineness and its high resistance to the reniform nematode. This allohexaploid hybrid constitutes an interesting agronomic material, which can be used as a bridge for the transfer of useful agronomic traits from wild species to varieties of G. hirsutum.

Medium effects on micropropagation and genetic stability of Citrullus lanatus oleaginous type

To regenerate adventitious shoots from the cotyledon proximal parts of Citrullus lanatus (Thunb.) Matsum. and Nakai ssp. mucosospermus (Fursa) oleaginous type, different concentrations of MS mineral elements, sucrose, 6-benzylaminopurine (BAP) and agar were tested. Shoot induction proved to depend on the interaction between levels of sucrose, BAP and MS mineral elements in the medium. The medium containing 3/2 strength of MS mineral elements, 35 g/l sucrose and 1 mg/l BAP solidified with 6 g/l agar allowed the production of numerous shoots without a callus phase. After 3 weeks of culture, 76.7% of the cotyledon proximal parts induced shoots with an average of 12.26 shoots per explant and a mean shoot length of 17.13 mm. The induced shoots were directly rooted and thus complete plants ready for acclimatization were obtained using a two steps procedure. Depending on the genotype, the shoot induction from cotyledon proximal parts ranged from 54% to 96%. Rooted plantlets were acclimatized and transferred to field, where they grew well, developed flowers and fruits like seeded plants. The assessment of the genetic stability of the in-vitro-regenerated plantlets by means of an Amplified Fragment Length Polymorphism (AFLP) analysis with the combination of 5 primers revealed no differences between regenerated plantlets and mother plants.

Determination of the Genetic Structure of the Oleaginous <i>Lagenaria siceraria</i>of the Nangui Abrogoua University Germplasm Collection

Thirty accessions of Lagenaria siceraria from the Nangui Abrogoua University germplasm collection were analyzed using three microsatellite markers. The average Polymorphism Information Content (PIC) value was 0.61. The average observed heterozygosity value (H0 = 0.631) compared to the average expected heterozygosity value (He = 0.645) did not show significant differences in the selected accessions, which suggested random mating in the set of accessions. Within accession inbreeding estimate (FIS), was 40% and was not significantly different from zero. The reduction of heterozygotes was likely the result of presence of null alleles. Analysis of Molecular Variance (AMOVA) within and among 30 accessions of L. siceraria revealed that 39% of the total variation resides among accessions and 61% within accessions. Accession structuring pattern derived from Bayesian clustering analysis revealed two clusters. Based on the genetic structure of the accessions analyzed, a sampling strategy to collect and conserve genetic resources of L. siceraria was suggested.