Cytomorphological analysis of a novel hybrid from Solanum melongena 'Golden' x S. scabrum 'Scabrum' (Solanaceae)

Genotype manipulation through the introduction of novel genes for improved yield, agronomic qualities and a larger gene pool informed an experimental cross between diploid Solanum melongena 'Golden' (2n = 2x = 24) and tetraploid S. scabrum 'Scabrum' (2n = 4x = 48). The F1 fruit contained eight seeds which had a 100% germination and a chromosome number 2n = 6x = 72. Surviving hybrids were closer to the diploid parent in many characters. Leaves were fairly lobed, sparsely hairy and were 13.5 x 8.6 cm in the hybrid compared to the hairy, deeply lobed, 14.8 x 10.6 cm leaves in the diploid and glabrous, entire and 11.4 x 10.6 cm leaves in the tetraploid parent. The inflorescence in the hybrid was a raceme as in the diploid parent but was umbellate in the tetraploid. Pollen viability was 38.2% in the hybrid but was 71% and 97.4% in the diploid and tetraploid parents, respectively. Fruit was seedless in the F2; it was round and red, containing 384 seeds, globose-shaped, yellow seeds in the diploid, and 67, round, purple seeds in the tetraploid parent. Meiosis was regular in the hybrid with few univalents and impaired bivalents due to dissimilar parental genomes. Mitotic chromosomes were asymmetrical with various sizes. Epistasis and negative gene interaction mechanisms were implicated in the hybrids� low quality and breakdown. Backcross to the tetraploid parent may bring about gene recombination and allelic realignment for desirable phenotypes in the F2 and subsequent generations. Endoduplication of the triploid zygote might have produced an autoallohexaploid hybridLa manipulación genotípica permite la introducción de genes nuevos para la mejora de la producción y otras cualidades agronómicas. Se llevó a cabo un cruce experimental entre Solanum melongena 'Golden' (diploide, 2n = 2x = 24) y S. scabrum 'Scabrum' (tetraploide, 2n = 4x = 48). Los frutos de la F1 contenían ocho semillas con un 100% de germinación y un nº de cromosomas 2n = 6x = 72. Los híbridos que sobrevivieron estaban más próximos, en muchos caracteres, al parental diploide. Las hojas del híbrido eran de 13,5 x 8,6 cm, algo lobuladas y tenían escasos pelos, mientras que las del diploide eran de 14,8 x 10,6 cm, con pelos y profundamente lobuladas, y las del parental tetraploide de 11,4 x 10,6 cm, sin pelos y sin lobular. Las inflorescencias del híbrido y del diploide eran en racimo, mientras que en el tetraploide eran umbeladas. La viabilidad del polen fue del 38,2%, 71% y 97,4% en el híbrido, diploide y tetraploide, respectivamente. El fruto de la F2 no tenía semilla, era redondeado y rojizo; mientras que en el parental diploide contenía 384 semillas, era alargado y amarillo, y en el tetraploide tenía 67 semillas, y era redondeado y púrpura. La meiosis en el híbrido fue regular, con algunos cromosomas sin aparear. Los cromosomas mitóticos fueron asimétricos y de varios tamaños. La baja calidad y fallo de los híbridos se explican por la epistasis y los mecanismos de interacción génica negativos. El retrocruzamiento con el parental tetraploide puede dar una recombinación génica y realineamiento de los alelos para los fenotipos deseables en la F2 y generaciones siguientes. La endoduplicación del cigoto del tetraploide podría haber producido un híbrido autoalohexaploid

Effect of X-ray irradiation on growth physiology of Arachis Hypogaea (Var. Kampala)

Small doses of X-ray may stimulate cellular activities and growth while higher doses may cause higher aberrations. Seeds of Arachis hypogaea cv Kampala were exposed singly to X-ray radiations (6 mA-77 mA) X-ray significantly decreased seed germination above 6 mA, reduced root and shoot growth as X-ray exposure increased. X-ray radiation causes chromosomal aberration. Therefore, higher X-ray radiation affects the plant germination negatively by retarding the growth

Métodos de superação de dormência em sementes de Ipomoea e Merremia Dormancy breaking methods in Ipomoea and Merremia seeds

Este trabalho objetivou avaliar os efeitos de métodos de superação de dormência sobre a germinação das sementes de Ipomoea grandifolia, I. hederifolia, I. nil, I. quamoclit, Merremia aegyptia e M. cissoides. Os tratamentos consistiram em ácido sulfúrico concentrado, nitrato de potássio, água quente e calor seco (50 ºC), lixa e fogo. Constatou-se que o ácido sulfúrico promoveu aumento na germinação das sementes de I. grandifolia (58, 37, 22 e 34%), I. hederifolia (76, 49, 82 e 55%), I. quamoclit (43, 33, 66 e 35%), I. nil (69, 79, 72 e 62%), M. cissoides (8, 19, 35 e 57%) e M. aegyptia (24, 64, 56 e 63%) após períodos de imersão de 5, 10, 15 e 20 minutos, respectivamente. A água (20 e 40 minutos), o calor seco (20 e 40 minutos) e o fogo melhoraram a germinação de I. grandifolia (68, 59, 62, 67 e 59%), M. cissoides (50, 52, 18, 25 e 46%) e M. aegyptia (54, 47, 21, 21 e 45%), respectivamente. O calor seco de 20 e 40 minutos melhorou a germinação de I. nil (49 e 36%), e o de 40 minutos, a de I. hederifolia (70%). O uso de nitrato de potássio e lixa não proporcionou melhoria na germinação das sementes.<br>This research aimed to evaluate the effects of dormancy breaking methods on germination of Ipomoea grandifolia, I. hederifolia, I. nil, I. quamoclit, Merremia aegyptia and M. cissoides seeds. The treatments consisted of concentrated sulfuric acid, potassium nitrate, and mechanical and physical scarification for fire, water and dry heat at 50 ºC. The sulfuric acid increased seed germination of I. grandifolia (58, 37, 22 and 34 %), I. hederifolia (76, 49, 82 and 55%), I. quamoclit (43, 33, 66 and 35%), I. nil (69, 79, 72 e 62%), M. cissoides (8, 19, 35 and 57%) and M. aegyptia (24, 64, 56 and 63%) after 5, 10, 15 and 20 min, respectively. Water (20 and 40 min), dry heat (20 and 40 min) and fire increased germination of I. grandifolia (68, 59, 62, 67 and 59%), M. cissoides (50, 52, 18, 25 and 46%) and M. aegyptia (54, 47, 21, 21 and 45%), respectively. Dry heat (20 and 40 min) increased seed germination of I. nil (49 and 36%) and (40min) of I. hederifolia (70%). Potassium nitrate and sandpaper did not increase seed germination

Efeito da luz e da quebra de dormência na germinação de sementes de espécies de plantas daninhas Effect of light and dormancy break on weed species seed germination

Objetivou-se com este trabalho verificar a quebra de dormência, utilizando ácido sulfúrico (H2SO4) e escarificação mecânica, e o efeito da luz na germinação das espécies Euphorbia heterophylla, Ipomoea nil, Sida glaziovii e Brachiaria plantaginea. Para avaliar a germinação, os tratamentos foram realizados no escuro e no claro. Não foram constatadas diferenças entre eles nas condições avaliadas, indicando que as espécies em estudo germinam em ambiente com diferentes luminosidades. Quanto a quebra de dormência, observou-se que o tratamento submetido à quebra de dormência aumentou a porcentagem de germinação em algumas espécies. Desse modo, concluiu-se que a quebra de dormência viabiliza condições para germinação de algumas espécies de plantas daninhas e, sob qualquer condição de luminosidade, há germinação das sementes das espécies estudadas.<br>This research evaluated dormancy break using sulfuric acid (H2SO4), mechanical scarification and the effect of light on the seed germination rate of Euphorbia heterophylla, Ipomoea nil, Sida glaziovii and Brachiaria plantaginea. To evaluate the germination rate, treatments were performed in the dark and light; no differences were observed between both treatments under these conditions, indicating that these species germinate under different light conditions. Dormancy break increases the percentage of germination rate in some species. Thus, dormancy break makes the germination of some species viable. The germination can occur both under light or dark conditions