Germination ecology of turnip weed (Rapistrum rugosum (L.) All.) in the northern regions of Australia

Abstract

In Australia, turnip weed has been rapidly emerging as one of the major weeds in conservation agricultural systems. Germination and emergence of turnip weed were examined for two populations collected from Gatton and St George regions of Australia; two locations with high and low rainfall, respectively. The seeds of turnip weed germinated at all the tested temperatures, but germination was the lowest at 15/5°C, intermediate at 20/10°C and highest at 25/15°C and 30/20°C. The results indicated a high adaptability of turnip weed to warm environmental conditions, although it is a major problem in the winter season. Germination was higher in dark than light/dark regimes except at 30/20°C. Three was a concomitant reduction in germination as the osmotic potential values decreased from 0 to -1.0 MPa. There was 2 and 4% germination at -0.8 MPa for Gatton and St George populations, respectively, and no germination occurred at an osmotic potential of -1.0 MPa. There was a reduction in germination when the sodium chloride (NaCl) concentration was increased from 0 to 150 mM, and no germination was observed at 200 and 250 mM of NaCl. Turnip weed germinated over a broad range of pH (4 to 10). Seedling emergence was higher at 1 cm depth compared to 0.5 cm or at the soil surface. There was 28 and 33% emergence at the surface for the Gatton and St George populations, respectively, compared to 48 and 56% emergence from 1 cm depth for the Gatton and St George populations, respectively and no emergence was observed from 6 cm depth. The results indicated that tillage leading to shallow burial would promote the emergence of turnip weed; on the contrary, tillage that could bury seeds deep into the soil profile might minimise the emergence. Under ideal conditions and lack of integrated weed management programmes, this weed will emerge, set seeds and enrich the soil seed bank and thereby continue to be a problem in the northern grain region of Australia.

Germination Ecology of Brachiaria eruciformis in Australia and Its Implications for Weed Management

“…For example, the NaCl concentration that inhibited a 50% germination in Rapistrum rugosum (L.) All. was 77 mM [35]. The ability to germinate under high NaCl concentrations has been reported in many weeds, such as Chloris virgata Sw. and Eragrostis pilosa (L.) P. Beauv.…”

Interference of turnipweed (Rapistrum rugosum) and Mexican pricklepoppy (Argemone mexicana) in wheat

“…Turnipweed [Rapistrum rugosum (L.) All.] is a broadleaf weed from the Brassicaceae family with wide distribution in Australia, the United States, Iran, and Russia (Chauhan et al 2006;Hatami et al 2016;Manalil et al 2018;Ohadi et al 2011;Osten et al 2007;Whish et al 2002). Besides being an agricultural weed, it is an invasive species owing to its potential to invade fallow regions, railway tracks, and open forest areas (Cousens et al 1994;Hani et al 2017;Ohadi et al 2011;Pipan et al 2013).…”

Effect of emergence time on growth and fecundity of Rapistrum rugosum and Brassica tournefortii in the northern region of Australia

“…Two populations of R. rugosum and B. tournefortii were collected in 2017 from Gatton (27.56° S 152.28° E) and St. George (37.96° N 113.56° E), located in the northern region of Queensland, Australia with mean long term rainfall of 770 and 500 mm, respectively. As there was physical seed dormancy for R. rugosum, seeds were threshed gently by hand to remove the pod and the recovered naked seeds were used for the study 7 . B. tournefortii seeds germinated over 70% throughout the study.…”

“…(turnip weed) and Brassica tournefortii Gouan. (African mustard) are two troublesome weeds from this family in the northern region of Australia 6,7 . R. rugosum and B. tournefortii, respectively, are ranked 5th and 6th in terms of infestation of crop regions of Australia, and resulted in AU$ 10.6 and 4.9 m revenue loss per annum, respectively 8 .…”

“…In Australia, seed dormancy levels vary greatly (12-90%) in newly dispersed seeds of B. tournefortii biotypes 18 , which contributes to aestivation in hot summer conditions 19 . Likewise, impermeable seed coat results in induced dormancy with lower germination in Australian biotypes of R. rugosum 7,10 . Periodic seed germination due to profuse seed production and seed dormancy, as well as the innate ability of these weeds to germinate in a broad range of environmental conditions all contribute to the invasive success of these plants.…”