Directional selection for flowering time leads to adaptive evolution in Raphanus raphanistrum (Wild radish)

Area of Science:

• Agricultural Science
• Evolutionary Biology
• Plant Science

Background:

• Herbicides are crucial for weed control in agriculture but have led to widespread herbicide resistance.
• Nonherbicidal weed seed control methods intercept seeds at harvest, preventing entry into the soil seed bank.
• These methods exert strong selection pressure, favoring weed traits that allow evasion of collection, such as early seed shedding.

Purpose of the Study:

• To investigate the adaptive evolutionary potential of wild radish (Raphanus raphanistrum) to selection imposed by harvest seed collection techniques.
• To determine if selection for early or late maturity influences phenology and growth traits in wild radish populations.

Main Methods:

• A field-collected wild radish population was subjected to recurrent selection for five generations for early maturity and three generations for late maturity.
• Phenological traits (flowering time) and growth traits (height, biomass) were measured in selected generations.
• Adaptive capacity was assessed by comparing trait evolution between early- and late-flowering selection lines.

Main Results:

• Five generations of selection for early flowering halved the time to flowering in wild radish.
• Early-maturing phenotypes exhibited reduced height and biomass, developing less competitive, prostrate growth forms.
• Three generations of selection for late flowering doubled the time to flowering, increasing biomass and plant height at maturity.

Conclusions:

• Wild radish demonstrates significant adaptive capacity to rapid evolutionary change in response to harvest seed collection.
• Selection for altered flowering time can quickly modify growth traits, impacting weed competitiveness and evasion of control methods.
• These findings highlight the potential for rapid evolution in weed populations within agro-ecosystems under intense selection pressure from modern weed management strategies.