BUSCADOR RECOLECTA

Digital.CSIC. Repositorio Institucional del CSIC

oai:digital.csic.es:10261/192019

Trabajo presentado en la 53º Reunião Anual da Sociedade Brasileira de Zootecnia, celebrada en Gramado (Brasil), del 1 al 4 de agosto de 2016, Alfalfa (Medicago sativa L.) is a high quality persistent legume, which can be used as forage, silage or hay. Alfalfa cultivar Crioula is the most frequently grown and the bestadapted cultivar to Brazil, and it is considered as a hay-type because of its upright habit and limited tolerance to severe defoliation. Nevertheless, experiments conducted at Federal University of Rio Grande do Sul (UFRGS) observed variability in characters of this cultivar such as the morphology of seedlings. Therefore, the objective of this work was to evaluate new grazing tolerant genotypes of alfalfa by selecting genotypes with resistance and susceptibility to disease caused by the pathogen Alternaria alternata at UFRGS and with a short 1 st internode length. The growth habit and length of the first internode of six alfalfa genotypes were evaluated, with this character considered as a complementary morphological marker to select alfalfa populations more adapted to grazing. Decumbent habit and shorter internode lengths were considered positive because are indicative of adaptation to grazing. Several alfalfa genotypes were selected: Crioula resistant (CR) and susceptible (CR) to Alternaria alternata, original seeds (CO), E1C4 (Crioula 1st internode short; 4th cycle of selection, realized by UFRGS) resistant (ECR) and susceptible (ECS) to Alternaria alternata, and E1C4 original seeds (ECO). The plants and treatments were arranged at random (n= 20), and every seedling was considered as one replicate of each genotype. The selection for plant resistance to grazing tolerance was carried out from March 2015 to April 2015 in a growth chamber at the Institute of Agrobiotechnology (IdAB) in Spain. To evaluate the length of the 1st internode, the seeds were sterilized, mechanically scarified with sand paper to break dormancy and then placed on water-agar plates in a growth chamber at 25 °C until the radicles of the seedlings were about 10 mm long. Then, seedlings were transferred into a glass jars containing nutritive solution with nitrate as nitrogen source. On seventh day, the growth habit of the seedlings were evaluated for erect or decumbent growth habit and after that, the seedlings were transferred to plates and pictures were taken daily during 7 days to measure the size of the internodes with the software Image J. Data were analyzed using Tukey's test (SAS Inst. Inc., Cary, NC). The CR and ECO alfalfa genotypes showed the best results (P<0.005) for both variables evaluated demonstrating habit tending to decumbent and length of the 1st internode 0.429 and 0.463 cm respectively, at the last day of evaluation (day 15). These genotypes will be used for subsequent research and selection cycles in the UFRGS Experimental Station., This work was supported by the AGL2014-52396-P grants from the Spanish Ministry of Science and Innovation., Peer reviewed