Predicting the Severity of Alfalfa Root rot Disease Under Salinity Conditions

Alfalfa roots are infected with several fungal pathogens under salinity conditions. The effect of two salts of NaCl and CaCO 3 at three concentrations was studied in vitro. Mycelial growth and disease severity (DS%) were estimated to determine the relationship between (DS%) and water salinity. The highest effect on mycelial growth was detected at the electrical conductivity (EC W value) of 18.75 ds/m 2 which ranged from 8.80 and 9.44% with NaCl and CaCO 3 , respectively. Furthermore, Exserohilum sp. was the most affected by water salinity. With the different levels of water salinity, the DS% of alfalfa root rot increased gradually with the increased water salinity level. The highest level of water salinity with NaCl and CaCO 3 EC W value at 18.75 ds/m 2 ranged (42.76 and 43.53% severity for NaCl) and (44.04 and 44.42% severity for CaCO 3 , respectively). Moreover, with water salinity NaCl and CaCO 3, Fusarium sp. was the highest (DS%) with NaCl. Alfalfa root rot prediction model based on information gathered from the interaction of pathogen, water salinity, disease severity, and root and shoot length. It was found the relation between DS% with fungi, salt type, salt concentration, root and shoot length in the multiple regression model (r 2 =88.83%).