Genetic diversity and DNA content of three South American and three Eurasiatic Trifolium species

Six species of Trifolium (T. polymorphum Poir., T. riograndense Burkart, T. argentinense Speg., T. medium L., T. pratense L. and T. repens L.) were analyzed using inter-simple sequence repeats (ISSR) markers. Six selected primers generated 186 polymerase chain reaction (PCR) products exploring 112 loci in 34 genotypes analyzed with molecular sizes ranging from 200 to 1300 bp. These primers were able to discriminate among and within species, with the PCR products being on average 41.6 percent species-specific and 59.9 percent polymorphic at the within species level. Nuclear DNA content was determined by flow cytometry and revealed variation among species. The 1Cx genome size values were calculated and were found to range from 0.46 pg (T. pratense) to 0.96 pg (T. polymorphum). Genome size values of South American species were higher than those of Eurasiatic origin. The analyses of the molecular data grouped the six species in agreement with their geographical origin and clearly differentiate T. polymorphum from T. argentinense. The Eurasiatic group showed the highest average of species-specific bands (45.3 percent) and the South American group exhibited the highest amount of total bands (59.7). The highest level of intra-species polymorphisms was detected in T. argentinense (92.9 percent), followed by T. medium (89.5 percent).

Post Weaning Feeding Management And Performance Of Merino Ewes Grazing On Natural And Improved Pastures At Mating Season

In the uruguayan Basalt region, the reproductive performance of 300 Merino ewes and the effect of 3 post-weaning feeding managements (PWFM: I: 1.2 cm height of available forage and 16 ewes/ha; II: 2.03 cm height of available forage and 5 ewes/ha; III: 2.5cm height of available forage and 1 ewe/ha) as well as 2 feeding levels before and during the breeding season (FLM: native pastures: green DM/ha: 883kg, CP: 114g/kg DM, NDF: 781g/kg DM and improved pastures: DM /ha: 1270kg, CP: 194g/kg DM, NDF: 598g/kg DM) were studied with a factorial arrangement of treatments. The PWFM extended for 70 days, ewes were mated in the period from 13/4/96 to 13/5/96 and FLM were applied for 30 days, starting 15 days before beginning of breeding. There were not differences on the ovulation rate (P>0.05); however, the P values might indicate some effect of the treatments. The number of born lambs/ewe served increased with the ovulation rate because the higher number of ovulations balanced their less viability, individually considered. Actually, the number of born lambs/ewe served was higher with animals coming from PWFM III (1.18, 1.11 and 0.96, PWFM III, II and I, respectively; P = 0.02) and with the animals grazing on improved pastures at mating period (1.13 and 1.03, improved pastures and natural pastures, respectively; P = 0.10), were those which showed slight higher ovulation rate.

Na região de solos de Basalto (Salto, Uruguai: 32.5° de latitude sul e 58° de longitude oeste), estudou-se, em um delineamento em blocos casualizados com arranjo fatorial, o efeito de 3 manejos alimentares pos-desmame (MAPD: I : 1,2cm de altura da forragem disponível e 16 ovelhas/ha; II: 2,03cm de altura da forragem disponível e 5 ovelhas/ha; III: 2,5cm de altura da forragem disponível e 1 ovelha/ha) e 2 níveis de alimentacão no período de encarneiramento (NAE: campo natural: 883kg MS verde/ha, PB: 114g/kg MS e FDN: 781g/kg MS; pastagem artificial: 1270kg MS/ha, PB: 194g/kg MS e FDN: 598g/kg MS), no desempenho reprodutivo de 300 ovelhas Merino. O MAPD estendeu-se por 70 dias. O período de encarneiramento foi de 13/4-13/5/96 e os NAE foram aplicados por 30 dias, iniciando-se 15 dias antes do início do período de cobertura. O número de cordeiros nascidos/ovelha cobertas incrementou-se ao aumentar a taxa ovulatória devido ao fato de o maior número de óvulos liberados compensar a menor viabilidade destes. O número de cordeiros nascidos/ovelha coberta foi maior nas ovelhas provenientes do MAPD III (1,18, 1,11 e 0,96, MAPD III, II e I, respectivamente, P = 0,02) e naquelas que foram submetidas às pastagens artificiais durante o período de encarneiramento (1,13 e 1,03, pastagem artificial e natural, respectivamente, P = 0,10). Essas foram as que apresentaram uma tendência de valores superiores em taxa ovulatória.