EFFECT OF PURPLE LETTUCE AQUEOUS EXTRACT IN CYTOGENETICS ACTIVITY OF LETTUCE ROOT UNDER SALT STRESS

Salinity can affect cell division and cause chromosomal abnormalities such as the formation of micronuclei, chromosome stickiness, c-mitosis and multipolar anaphases. Plants react to salt stress with morphological, biochemical, physiological, cellular and molecular adjustments. The aim of this study was to evaluate the effect of different leaf extract concentrations of purple lettuce on the cytogenetic activity of lettuce roots, cv. Regina, from seeds subjected to salt stress. Four extract concentrations of purple lettuce (0, 50, 100 and 150 g lettuce leaves L-1 water)and five concentrations of sodium chloride (0, 30, 60, 90 and 120 mM) were tested, constituting 20 treatments, with distilled water for a negative control. The analyses were of mitotic index (MI), phase index of mitosis (prophase, metaphase, anaphase and telophase) and the presence of chromosomal aberrations. Salt reduces the mitotic index and all index phases of the lettuce roots. The purple lettuce extract does not affect the mitotic index, reduces the cell index in prophase and increases the cells in telophase of lettuce roots. The purple lettuce extract and salt cause chromosomal abnormalities in lettuce root cells; however, a smaller number of mutations is found by applying 100 g L-1 extract.

Meiotic Studies in Some Species of Tribe Cichorieae (Asteraceae) from Western Himalayas

The present paper deals with meiotic studies in 15 species belonging to 6 genera of the tribe Cichorieae from various localities of Western Himalayas. The chromosome number has been reported for the first time inHieracium crocatum(2n=10) andLactuca lessertiana(2n=2x=16). Further, intraspecific variability has been reported for the first time inH. umbellatum(2n=2x=10and2n=6x=54),Tragopogon dubius(2n=2x=14and2n=4x=28), andT. gracilis(2n=2x=14). The chromosome report of2n=2x=10inYoungia tenuifoliais made for the first time in India. Maximum numbers of the populations show laggards, chromosome stickiness, and cytomixis from early prophase to telophase-II, leading to the formation of aneuploid cells or meiocytes with double chromosome number. Such meiotic abnormalities produce unreduced pollen grains and the reduced pollen viability.

Cytogenotoxic effects of ethanolic extracts of Annona crassiflora (Annonaceae)

Infusions of the leaves and seeds of Annona crassiflora Mart. are commonly employed in the treatment of diarrhoea, snakebites, tumours and disorders of the hair and scalp. The aim of the present study was to investigate the cytotoxic and genotoxic properties of ethanolic extracts of A. crassiflora by evaluating their effects on germination, root elongation, chromosome structure and the cell division of Lactuca sativa (lettuce). The experiment followed a randomized design involving the treatment of L. sativa seeds with ethanolic extracts from leaves and seeds of A. crassiflora applied at ten concentrations (0.0125, 0.025, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 mg/L) and with five repetitions per treatment. Seeds of L. sativa exposed for 48 h to A. crassiflora leaf extract at concentrations ≥ 0.1 mg/L, or to seed extracts at concentrations ≥ 0.2 mg/L, showed germination percentages that were significantly (p < 0.05) lower than those of seeds exposed to aqueous ethanol control. Exposure of L. sativa seedlings to leaf (but not seed) extracts of A. crassiflora produced significant (p < 0.05) reductions in the mitotic indices of root meristem cells of lettuce and induced chromosome and nuclear abnormalities in the root cells. The presence of chromosome stickiness, bridges, fragments, laggard chromosomes and nuclear condensation were also observed. The cytogenetic effects observed suggest that folkloric medicines prepared with extracts of the leaves or seeds of A. crassiflora should be employed with caution.

Chromosome stickiness during meiotic behavior analysis of Passiflora serrato-digitata L. (PassifloraCEAE)

Almost 90% of species of the genus Passiflora are native to the American continent, with high commercial value due to the fact that some species are used for human food while others have ornamental and medical qualities. Passiflora serrato-digitata is one of the species that integrates the Paraná Agronomic Institute germoplasm bank at its experimental base in Londrina, PR, Brazil. Collected flower buds were fixed in ethanol/acetic acid (3:1 v/v) for 24h, transferred to 70% alcohol and stored under refrigeration. Slides were prepared by the squashing technique and stained with 1.0% propionic carmine; they were analyzed under an optic microscope. Irregularities in the chromosome segregation process of P. serrato-digitata have been verified by meiotic behavior analysis. These comprised precocious migration to poles in metaphase I and II, non-oriented chromosomes in metaphase plate in metaphase I and II, laggard chromosomes in anaphase I and II towards the formation of micronucleus in telophase I and II, and microspores in tetrads. Chromosome stickiness was another irregularity reported in the Passiflora genus for the first time. These irregularities which also contributed to the formation of monads, dyads and triads, resulted in normal imbalanced 2n and 4n microspores. According to the observed Meiotic Index of 71.83%, this species is not meiotically stable.

Microsporogenesis in Brachiaria bovonei (Chiov.) Robyns and B. subulifolia (Mez) Clayton (Poaceae)

Some African species of Brachiaria have been introduced into the Americas and became the most important forage for pastures in the tropics. New cultivars can be obtained either from direct selections from the natural existing variability in the germplasm collections or from interspecific hybridizations. Polyploidy is predominant in the genus Brachiaria and correlated with apomixis which complicates hybridization. The objective of cytological studies underway on the Brachiaria germplasm collection at Embrapa Beef Cattle is to determine the chromosome number and meiotic behavior of accessions. For the breeding of Brachiaria species, compatible sexual and apomictic accessions need to be identified. Microsporogenesis was evaluated in two accessions of Brachiaria bovonei (BO01 and BO05) and one accession of B. subulifolia (SU01). BO01 is pentaploid (2n = 5x = 45), BO05 is tetraploid (2n = 4x = 36), and SU01 is hexaploid (2n = 6x = 54), derived from x = 9. Meiotic abnormalities typical of polyploids, characterized by precocious chromosome migration to the poles in metaphases, laggard chromosomes in anaphases, and micronuclei in telophases and tetrads, were recorded in high frequency in all the accessions generating unbalanced gametes. Both accessions of B. bovonei presented chromosome stickiness. The results are discussed in the view of the Brachiaria breeding program objectives.