Differential germination characteristics of glyphosate-resistant and glyphosate-susceptible Chloris virgata populations under different temperature and moisture stress regimes

Abstract

Thorough knowledge of the germination behavior of weed species could aid in the development of effective weed control practices, especially when glyphosate resistance is involved. A study was conducted using two glyphosate-resistant (GR) (SGW2 and CP2) and two glyphosate-susceptible (GS) (Ch and SGM2) populations of Chloris virgata, an emerging and troublesome weed species of Australian farming systems, to evaluate their germination response to different alternating temperature (15/5, 25/15 and 35/25°C with 12 h/12 h light/dark photoperiod) and moisture stress regimes (0, -0.1, -0.2, -0.4, -0.8 and -1.6 MPa). These temperature regimes represent temperatures occurring throughout the year in the eastern grain region of Australia. Seeds germinated in all the temperature regimes with no clear indication of optimum thermal conditions for the GR and GS populations. All populations exhibited considerable germination at the lowest alternating temperature regime 15/5°C (61%, 87%, 49%, and 47% for Ch, SGM2, SGW2, and CP2, respectively), demonstrating the ability of C. virgata to germinate in winter months despite being a summer annual. Seed germination of all populations was inhibited at -0.8 and -1.6 MPa osmotic potential at two alternating temperature regimes (15/5 and 35/25°C); however, some seeds germinated at 25/15°C at -0.8 MPa osmotic potential, indicating the ability of C. virgata to germinate in arid regions and drought conditions. Three biological parameters (T10: incubation period required to reach 10% germination; T50: incubation period required to reach 50% germination; and T90: incubation period required to reach 90% germination) suggested late water imbibition with increasing moisture stress levels. The GR population SGW2 exhibited a distinctive pattern in T10, T50, and T90, possessing delayed germination behaviour and thus demonstrating an escape mechanism against pre-plating weed management practices. Knowledge gained from this study will help in developing site-specific and multi-tactic weed control protocols.

Germination biology of liverseedgrass (Urochloa panicoides) and its response to postemergence herbicides in Australian conditions

“…Br. ]), for which seeds germinated at temperatures ranging from 15/5 to 35/25 C (Chauhan et al 2018;Desai and Chauhan 2021). In junglerice [Echinochloa colona (L.) Link], another problematic summer grass species in eastern Australia, seeds germinated at temperature regimes ranging from 20/10 to 35/25 C but did not germinate at 15/5 C (Mutti et al 2019).…”

Effect of temperature on the growth, reproduction, and germination pattern of two populations of Chloris virgata

“…The present study was conducted to understand the effect of alternating temperature regimes on the vegetative growth, seed production, and germination pattern of two agroecologically distinct populations of C. virgata. In our previous experiment, C. virgata populations exhibited differential germination patterns in response to different alternating temperature regimes 3,10 . However, currently, no holistic knowledge of the germination, growth, and reproduction of C. virgata in different thermal conditions is available.…”

Distinctive germination attributes of feather fingergrass (Chloris virgata) biotypes in response to different thermal conditions

“…All biotypes are from different agroecosystems or climatic conditions. Seed collection was performed as described by Desai and Chauhan (2021a). The entire seed lot was then transported to the Queensland Alliance for Agriculture and Food and Innovation (QAAFI) weed science laboratory in Gatton, Australia (27.555°S, 152.334°E), where seeds were manually separated from panicles and kept in airtight containers to prevent contamination.…”