Seed Shattering: A Trait of Evolutionary Importance in Plants

Abstract

Seed shattering refers to the natural shedding of seeds when they ripe, a phenomenon typically observed in wild and weedy plant species. The timing and extent of this phenomenon varies considerably among plant species. Seed shattering is primarily a genetically controlled trait; however, it is significantly influenced by environmental conditions, management practices and their interactions, especially in agro-ecosystems. This trait is undesirable in domesticated crops where consistent efforts have been made to minimize it through conventional and molecular breeding approaches. However, this evolutionary trait serves as an important fitness and survival mechanism for most weeds that utilize it to ensure efficient dispersal of their seeds, paving the way for persistent soil seedbank development and sustained future populations. Weeds have continuously evolved variations in seed shattering as an adaptation under changing management regimes. High seed retention is common in many cropping weeds where weed maturity coincides with crop harvest, facilitating seed dispersal through harvesting operations, though some weeds have notoriously high seed shattering before crop harvest. However, high seed retention in some of the most problematic agricultural weed species such as annual ryegrass (Lolium rigidum), wild radish (Raphanus raphanistrum), and weedy amaranths (Amaranthus spp.) provides an opportunity to implement innovative weed management approaches such as harvest weed seed control, which aims at capturing and destroying weed seeds retained at crop harvest. The integration of such management options with other practices is important to avoid the rapid evolution of high seed shattering in target weed species. Advances in genetics and molecular biology have shown promise for reducing seed shattering in important crops, which could be exploited for manipulating seed shattering in weed species. Future research should focus on developing a better understanding of various seed shattering mechanisms in plants in relation to changing climatic and management regimes.

Harvest weed seed control: impact on weed management in Australian grain production systems and potential role in global cropping systems

“…Now that HWSC techniques are available, there has recently been a concerted research effort to quantify weed seed retention in order to identify the potential for HWSC to target the dominant, and frequently herbicide-resistant, weed species in several of the world's major cropping systems. These studies (see reviews by Walsh et al 2018b;Maity et al 2021) have investigated seed retention at crop maturity of >30 weed species prominent in these grain production systems. Importantly, these studies have identified the opportunity for HWSC to target significant proportions (50-99%) of the seed production of the particularly damaging weeds Palmer amaranth (Amaranthus palmeri), water hemp (Amaranthus tuberculatus), annual ragweed (Ambrosia artemisiifolia L.), Italian ryegrass (Lolium perenne subsp.…”

“…HWSC treatments will most likely continue to be used in Australian grain production systems because of the unique timing of this weed control approach, notwithstanding that there is species-specific, incomplete weed seed retention at crop maturity. With the degree of weed seed retention influenced by genetic and environmental factors (Walsh and Powles 2014;Walsh et al 2018a;Borger et al 2020;Maity et al 2021), HWSC cannot be solely relied on for weed control, but must be viewed as a supplemental weed control practice. Similarly, because HWSC treatments have an end-of-season timing, their use will continue to be supported by earlier, in-crop weed control treatments (usually herbicides) to minimise weed interference during the growing season.…”

Seedbank management through an integration of harvest-time and postharvest tactics for Italian ryegrass (Lolium perenne ssp. multiflorum) in wheat

“…A close examination of the prevailing weather conditions for a 3-wk period before wheat harvest in the two study years revealed that 2018 was relatively warmer and drier (daily average temperature 26 C, relative humidity 73%) with fewer rainfall events (daily average precipitation 0.5 mm), compared to 2019 with 23 C daily average temperature, 83% relative humidity, and 2.5 mm daily average precipitation [weather data was obtained from a nearby weather station located within the Texas A&M research farm (http://afs102.tamu.edu/)]. High seed shattering under warm and dry weather conditions was documented by several studies (e.g., Gan et al 2008;Maity et al 2021c;Shirtliffe et al 2000;Tiwari and Bhatnagar 1989).…”

Formation Mechanism and Occurrence Law of Pod Shattering in Soybean: A Review

“…Studies have shown that the frying rate of French croissant pods at low temperature and high humidity is significantly lower than that at high temperature and low humidity [41]. Subsequently, Cavines et al, successively proposed that relative humidity is an important environmental factor affecting soybean seed shattering [42,43]; in addition, Zhang et al [34], not only verified the above views, but also put forward that there is no obvious correlation between the seed shattering rate and the length of sunshine time and the average daily temperature. Yang researched that seed shattering occurred when the moisture content of beans and seed shattering were lower than 25% and 15%, respectively, indicating that the water content of soybeans is also closely related to seed shattering and also proposed that the spatial distribution of pods in identical soybean does not significantly link [44].…”