Traits Relationship in Sainfoin (Onobrychis viciifolia) under Normal and Water Stress Conditions

Sainfoin (Onobrychis viciifolia Scop.) is widely grown as forage and pasture legume in Iran and is tolerant to a range of environmental stress. This experiment was conducted to investigate relationship between morphological, physiological and agronomic traits and to identify components affecting forage yield using several multivariate statistical methods on 10 local sainfoin varieties under normal and water stress condition. Drought stress significantly affected most of the measured traits. Results indicated that under normal condition, the correlation coefficients of dry matter yield with fresh matter yield, stem percent, relative water content, number of stem per plant, number of stem per square meter and number of node per stem were significantly positive. However, its correlation with leaf percent and leaf to stem ratio were significantly negative. Under stress condition, the correlation coefficients of dry matter yield with fresh forage yield, stem percent, number of node per stem and relative water content were significantly positive, while those of leaf percent and leaf to stem ratio were significantly negative. Results of stepwise regression for non-stress condition showed that stem percentage, percentage of dry matter and number of stem per square meter explained the highest variation of forage yield, while under stress the majority of variation was explained by stem percentage, percentage of dry matter and plant height. Factor analysis revealed five factors which justified more than 90 and 87 percent of total variation under normal and drought stress conditions, respectively. In non-stress condition, the factors classified as forage production, forage yield components, reproductive factor, photosynthesis and phenological factors while under drought stress condition were classified as forage yield components, photosynthesis factor, reproductive factor, proline content and percentage of dry matter respectively. Results indicated that drought stress changed the relationships of measured traits, therefore, identifying separate selection index for normal and moisture stress conditions could better lead to improve forage yield in sainfoin breeding programs.