Growth, Development, and Seed Biology of Feather Fingergrass (Chloris virgata) in Southern Australia

Abstract

Feather fingergrass is a major weed in agricultural systems in northern Australia and has now spread to southern Australia. To better understand the biology of this emerging weed species, its growth, development, and seed biology were examined. Under field conditions in South Australia, seedlings that emerged after summer rainfall events required 1,200 growing degree days from emergence to mature seed production and produced 700 g m−2shoot biomass. Plants produced up to 1,000 seeds panicle−1and more than 40,000 seeds plant−1, with seed weight ranging from 0.36 to 0.46 mg. Harvested seeds were dormant for a period of about 2 mo and required 5 mo of after-ripening to reach 50% germination. Freshly harvested seed could be released from dormancy by pretreatment with 564 mM sodium hypochlorite for 30 min. Light significantly increased germination. Seed could germinate over a wide temperature range (10 to 40 C), with maximum germination at 15 to 25 C. At 20 to 25 C, 50% germination was reached within 2.7 to 3.3 d, and the predicted base temperature to germinate was 2.1 to 3.0 C. The osmotic potential and NaCl concentration required to inhibit germination by 50% were −0.16 to −0.20 MPa and 90 to 124 mM, respectively. Seedling emergence was highest (76%) for seeds present on soil surface and was significantly reduced by burial at 1 (57%), 2 (49%), and 5 cm (9%). Under field conditions, seeds buried in the soil persisted longer than those left on the soil surface, and low spring–summer rainfall increased seed persistence. This study provides important information on growth, development, and seed biology of feather fingergrass that will contribute to the development of a more effective management program for this weed species in Australia.

Germination of Chloris barbata, Cynodon dactylon, and Cyperus rotundus from Angola at Constant and Alternate Temperatures

“…C. barbata seeds probably had a low primary dormancy and high germinability and were able to quickly germinate at all incubation temperatures, apart from 10 °C and 15-5 °C, so its base temperature for germination should be in the 15-10 °C range. This behaviour is similar with what was reported for other Chloris species from Australia, namely C. truncata and C. virgata, even if those two species were able to germinate at 10 °C [42][43][44]. Given that temperatures in the Sumbe area are normally above the base temperature for C. barbata, germination can therefore occur all year around, soon after soil moisture allows seed imbibition (i.e., after rainfall or irrigation).…”

Germination Ecology of Two Australian Populations of African turnipweed (Sisymbrium thellungii)

“…Water stress is a limiting factor for germination of many weed seeds, because water absorption and tissue hydration are essential in the sequence of metabolic events that lead to embryo development and seedling growth (Marcos-Filho 2005). Osmotic stress negatively affecting germination has been reported for many weeds (e.g., Ngo et al 2017; Reddy and Singh 1992). However, water stress tolerance during germination has also been reported for some closely related weed species.…”

Glyphosate Resistance of Chloris virgata Weed in Australia and Glyphosate Mobility Are Connected Problems

“…Chloris virgata is tolerant to drought stress [63]. Many studies on Chloris virgata seed biology have been completed in China, India, Qatar, and Honduras [63], while very few studies have been conducted in Australia [64,65].…”

“…In a study related to growth, development, and seed biology of Chloris virgata in South Australia, Chloris virgata seedlings emerging after summer rainfall events under field conditions needed 1200 growing degree days from emergence to mature seed production [65]. Harvested seeds of Chloris virgata were dormant for a period of about 2 months and took 5 months of after-ripening to reach 50% germination [75].…”