Selection of alfalfa genotypes for resistance to the foliar pathogen Curvularia geniculata

Abstract

Foliar diseases impose severe restrictions on the persistence and productivity of Medicago sativa, both of which may be increased by developing disease resistant and more competitive genotypes that can improve pasture quality. We found Curvularia geniculata as the principal alfalfa foliar pathogen in the Brazilian state of Rio Grande do Sul (RS). Growth chamber experiments evaluated the resistance of alfalfa genotypes 'E 1 C 4 ', 'CPPSul', 'ABT 805' and 'CUF-101' to C. geniculata as compared the control 'Crioula' genotype. These genotypes were also evaluated in field trials at a sea level site in Eldorado do Sul in central RS and at two sites £200 m above sea level, one in Bagé municipality in south west RS and the other at a farm near the town of Alto Feliz in north east RS. Plants were spray-inoculated with 1.6 x 10 6 ml -1 of C. geniculata spores and visually evaluated for leaf damage 14 days later. The C. geniculata infection rates varied from zero to 100%. Alfalfa persistence and forage mean dry mass (DM) production at the Eldorado site were measured during different seasons from November 2013 to January 2015 by calculating the incidence of invasive plants and morphologically separating leaves from stems and calculating both leaf and stem DM. Data were analysed using mixed statistical models. The best results for persistence and forage DM were shown by the 'CPPSul' genotypes (DM = 16,600 kg ha -1 ) and 'Crioula' (DM = 15,750 kg ha -1 ). These two genotypes will be used for subsequent investigations and selection cycles.

Physiological traits involved in grazing tolerance of alfalfa genotypes

“…The plants and treatments from experiment ' A' were arranged at random (n= 20), with five plates and four plants on each plate, and every seedling was considered as one replicate of each genotype. To investigate the grazing tolerance, seedlings alfalfa were grown and evaluated in the greenhouse (Experiment 'B'), and the variables measured were: 1) Growth habit and variables were measured: 1) Growth habit and 2) Fungal foliar diseases (Curvularia geniculata and Alternaria alternata), in order to monitor the pre-selected susceptibility or resistance [26]. Three repetitions for each genotype (total 8) were evaluated (n = 24) using the same type of substrate (organic waste, vermiculite, NPK and Limestone in the composition), temperature (maximum temperature 25 degrees) and irrigation.…”

“…Besides, the gains of alfalfa yield appear to be primarily due to improved disease resistance [25]. Therefore, some of the genotypes used in this study are the results of a selection of two types of leaf diseases, which were performed by Ávila et al [26] in field and greenhouse. The objective of this paper was to evaluate and select grazing-tolerant germplasm by evaluating genotypes (preselected in previous studies) by physiological measurement and methyl jasmonate application.…”

Precrop Effect of Red Clover (Trifolium pratense L.) and Alfalfa (Medicago sativa L.) on the Population Development of the Northern Root-Knot Nematode Meloidogyne hapla Chitwood, 1949 and on Succeeding Crops—A Pot Study

“…Due to the high forage quality and the multiple effects of both alfalfa and red clover cultivation on soil condition, there is a substantial body of research into their cultivar development as well as the improvement in their cultivar yield [16][17][18][19][20].…”