Effects of ten years organic and conventional farming on early seedling traits of evolving winter wheat composite cross populations

Early vigour traits of wheat composite cross populations (CCPs) based on high yielding (Y) or high quality (Q) orY*Q varietal intercross evolving under organic or conventional conditions in parallel populations were studied hydroponically. To eliminate storage and year effects, frozen F-6, F-10, F-11 and F-15 seeds were multiplied in one field, resulting in the respective F x 1 generations. This eliminated generation and growing system effects on seed size for the F-6(.1) F-10.1 and F-15(.1). Due to a severe winter kill affecting the F-11, the generation effect persisted, leading to larger seeds and markedly different seedling traits in the F-11(.1) compared to the F-10.1 and F-15.1. Seedling traits were similar among parallel populations. Shoot length and weight increased in both systems until the F-11(.1) across farming systems and remained constant thereafter. Overtime seminal root length and root weight of organic CCPs increased and total- and specific- root length decreased significantly compared to the conventional CCPs. Rooting patterns under organic conditions suggests better ability to reach deeper soil nutrients. In both systems, Q and YQ CCPs were more vigorous than Y CCPs, confirming genetic differences among populations. Overall, heterogeneous populations appear very plastic and selection pressure was stronger in organic systems.