Seed germination ecology of Conyza stricta Willd. and implications for management

Abstract

Numerous cropping systems of the world are experiencing the emergence of new weed species in response to conservation agriculture. Conyza stricta Willd. is being a newly emerging weed of barley-based cropping systems in response to conservational tillage practices. Seed germination ecology of four populations (irrigated, rainfed, abandoned and ruderal habitats) was studied in laboratory and greenhouse experiments. The presence/absence of seed dormancy was inferred first, which indicated seeds were non-dormant. Seed germination was then recorded under various photoperiods, constant and alternating day/night temperatures, and pH, salinity and osmotic potential levels. Seedling emergence was observed from various seed burial depths. Seeds of all populations proved photoblastic and required 12-hour light/dark period for germination. Seeds of all populations germinated under 5–30°C constant temperature; however, peak germination was recorded under 17.22–18.11°C. Nonetheless, the highest germination was noted under 20/15°C alternating day/night temperature. Ruderal and irrigated populations better tolerated salinity and germinated under 0–500 mM salinity. Similarly, rainfed population proved more tolerant to osmotic potential than other populations. Seeds of all populations required neutral pH for the highest germination, whereas decline was noted in germination under basic and alkaline pH. Seedling emergence was retarded for seeds buried >2 cm depth and no emergence was recorded from >4 cm depth. These results add valuable information towards our understanding of seed germination ecology of C. stricta. Seed germination ability of different populations under diverse environmental conditions suspects that the species can present severe challenges in future if not managed. Deep seed burial along with effective management of the emerging seedlings seems a pragmatic option to manage the species in cultivated fields. However, immediate management strategies are needed for rest of the habitats.

Seed germination ecology of Conyza sumatrensis populations stemming from different habitats and implications for management

“…The differences in populations are direct effect of the environmental cues faced by the maternal plants. Plenty of literature is available that supports our results pertaining to differences among seed germination biology of different populations due to maternal environments [ 14 , 15 , 17 , 18 , 44 ]. However, genetic factors also mediate the germination traits of different populations.…”

“…Our second hypothesis pertaining to the impacts of environmental cues on seed germination biology of the studied populations also stood valid and there are plenty of evidences to support our hypothesis [ 13 – 15 , 17 , 18 , 45 ]. Seeds of Conyza species require a definite light period for their successful seed germination.…”

“…The authors reported significant differences among the populations and warned that herbicide resistant population could invade more area due to its higher germination ability under a broad range of temperatures. Similarly, Ali et al [ 18 ] studied seed germination biology of C . stricta and reported that the species had the potential to extend its range; thus, immediate management strategies are needed for different habitats to halt the further spread of the species.…”

“…These environmental cues include temperature, light/dark period, abiotic stresses, soil pH and seed burial depth [ 13 – 16 ]. Light has a positive impact on the seed germination of almost all Conyza species which require a definite light period for their successful seed germination [ 18 , 23 , 24 ]. Moreover, seeds of these species buried deep in the soil are unable to emerge due to unavailability of sufficient light for completing germination phase [ 13 , 15 , 25 – 27 ].…”

Seed germination ecology of Sumatran fleabane (Conyza sumatrensis) in relations to various environmental parameters

“…A recent study revealed that populations of erect horseweed [ Conyza stricta (Willd.)] can tolerate salinity and germinate under 0 to 500 mM NaCl levels of salinity (Ali et al 2020). In another study, it was found that C. bonariensis populations could germinate at an NaCl concentration of 200 mM, and germination was zero at 250 mM NaCl (Loura et al 2020).…”