Cryo-exposure of Neonotonia wightii Wigth and Am seeds enhances field performance of plants

Key message Exposure of N. wightii seeds to liquid nitrogen allows for dormancy breaking and promotes plant establishment without adverse effects on yield. One of the most widespread legume species in the world is N. wightii, which is used as a cover crop for animal feed and has positive environmental impacts. However, plant establishment is difficult due to the dormancy of seeds. There are several methods available to break dormancy, with exposure to low temperature being the strategy most frequently used. This current study investigated exposure of seeds of N. wightii to liquid nitrogen (LN) and subsequent field evaluation of growth and development of plants until harvest. Exposure of seeds to LN improved plant growth and reproductive development. At 7 days of planting, cryo-exposed seeds showed a 12.5-fold increase in plant emergence compared with controls, but this difference progressively declined reaching only a 2.7-fold difference at 42 days. Plant height and the number of leaves per plant were consistently higher in plants formed from cryo-exposed seeds. They reached 1.5-fold increase of plant height and 1.3-fold increase of leaf number at 42 days. The effect of LN on leaf coverage was substantially higher when evaluated from 60 to 150 days, but declined by 180 days. The highest number of inflorescences was recorded at 104 days of planting with plants derived from cryo-exposed seeds displaying a 1.9-fold increase over the control plants. This also resulted in cryo-exposed plants producing significantly more fruit and pods than control plants (1.8 and 1.7-fold more, respectively). Contrastingly, the pod length, the number of seeds per pod and the weight of 1000 seeds did not show statistically significant differences. The results from this study showed that exposure of N. wightii seeds to LN allows for dormancy breaking and promotes plant establishment without adverse effects on yield.