ABSTRACT

Karyotype, phytochemical, palynological, molecular, morphological, anatomical analysis and growth studies were carried out on three species ofAnnona (A. muricata L. (soursop), A. squamosa L. (sweetsop) and A. senegalensis Pers (wildsop) obtained from the Utuiu and Umuahia in Abia State to assess phylogenetic relationship among them. Karyotype analysis was earned out using the conventional squashing protocol in aceto—orcein ofthe root tissues after heating was adopted. Photomicrograph ofthe tissues were taken. All the species studied were diploid with somatic chromosome number of 2n — 2X — 14. The total length ofshort arm ranged from 1.234 pm in sweetsop to 1.344 pm in soursop. The total length of long arm varied from 1.789 pm in the soursop to 1.834 pm in sweetsop. Centrometric index of the species varied from 1.906 pm in sweetsop to 2.095 pm in soursop. The highest arm ratio of 1.486 pm was obtained in sweetsop while soursop had the shortest arm ratio of 1.331 pm. Phytochemical studies of ethanol leaf extacts revealed the presence of alkaloid, tannins, flavoniod, phenol, saponin and steroid/triterpenes. Gaschromatography-mass spectrometry (GC-MS) analysis revealed fifty-six compounds with their fragmentation pattern, molecular formular and molecular weight. Compounds identified includes Aminopyrrolidial, longifolenaldehyde, Ntegerrimine, Dodecannoic acid, Neophytadiene, etc. Palynological study was carried out using acetolysis treatment. Soursop had the highest pollen diameter of 229 pm and the monad diameter of 111 pm followed by wildsop with the diameter of 130 pm and the monad diameter of 72 pm while sweetsop pollen had the diameter of 99 pm and the monad diameter of 50 pm. In all the species, the pollen were tetrads and inaperturate, tetragonal, acalyme except for soursop which was rhomboidal tetrahedral. The exine sculpture of sweetsop and wildsop was rugulate while forsoursop it was recticulate. The differences and similarities in pollen morphology ofthe three investigated species showed significant evidences which are of diagnostic importance to complement plant identification. Cross-species amplification of all the SSR markers used, successfully amplified in soursop and sweetsop but did not in wildsop. RAPD markers showed cross species-amplification. Polymorphic information content (PIC) value ranged from 0.3457 (OPT05) to 0.5926 (OPPI04) for RAPD markers with an average of 0.5103 indicating existence of sufficient genetic diversity among the three species genotypes studied. The PIC for SSR markers were uniform (0.6250). Phylogenetic tree showed genetic relatedness of the three species studied. SSR markers indicated that soursop and sweetsop are monophyletic and are more closely related than they aie to wildsop, while RAPD markers indicated that wildsop and soursop are more i elated than they are to sweetsop. Growth parameters were taken at interval oftwo weeks and measurements were made with a meter rule. Plant materials were sectioned and stained foi anatomical studies. The intrageneric characters they share in common includes 2n 2x—14 chromosome number, tetrad and inaperturate pollen grains, uniseriate collenchymatous stem epidermal cells, hypostomatic stomatai occurrence, 6 yellow petals, entile leafmargin, alternate leaf arrangement, syncarpous fruit, eucamptodromous venation etc. All these characters are useful in their identification and classification. Observations made in the similarities of characters studied, supports the present-day classification ofthese species in the same genus.