Ischaemum Rugosum) Population of Indo-Gangetic Plain Region
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Indian Journal of Weed Science 49(4): 385–390, 2017 DOI: 10.5958/0974-8164.2017.00099.5 Germination ecology of wrinkle grass (Ischaemum rugosum) population of Indo-Gangetic plain region Navjyot Kaur*, Renu Sethi and Makhan S. Bhullar Department of Agronomy, Punjab Agricultural University, Ludhiana, Punjab 141 004 Received: 27 September 2017; Revised: 8 November 2017 ABSTRACT Wrinkle grass (Ischaemum rugosum Salisb.) is a highly competitive weed in rice production that can cause huge yield reductions. Information on germination ecology of this weed is essential for the development of effective integrated weed management systems. No information is available on germination ecology for populations of this weed from Indo-Gangetic plain region of India. This study was conducted to generate information on effects of major environmental factors, viz. light, temperature, burial depth, moisture, salinity and pH on germination/emergence of this weed. Seed germination was independent of light and more than 50% germination was recorded under a wide temperature range of 20/ 10 to 35/25 °C day/night (12/12 h). Maximum emergence was observed when seeds were placed on surface or buried up to 1 cm; but considerable emergence was also observed from deeper soil layers (up to 6 cm depth). Germination was above 75% at 160 mM but completely inhibited at 320 mM of NaCl. Germination was sensitive to moisture stress and was completely inhibited at water potential of -0.8 MPa. Seeds were able to germinate under wide pH range of 3-10. Key words: Burial depth, Germination, Ischaemum rugosum, Light, pH, Salinity, Temperature Weed infestations are the major biotic et al. 1977). At its vegetative stage, this weed constraints in the rice production. Globally, weeds are resembles the rice plant, making it difficult to estimated to account for 32% potential and 9% actual distinguish (Ampong-Nyarko and De Datta 1991). It yield losses in rice (Oerke and Dehne 2004). is a highly competitive weed in rice production and Depending on ecological and climatic conditions, can cause up to 48% yield reductions (Lim et al. weeds can reduce rice yields by 45-95% (Manandhar 2015). Limited herbicide options like anilophos as et al. 2007). Yield reductions due to weed competition pre- and fenoxaprop and cyhalofop as post- vary under different rice establishment systems. emergence are available for its control in rice (Duary Singh et al. (2005) estimated 76, 71 and 63% rice et al. 2015). Many of the commonly used herbicides yield reduction due to weeds in dry-seeded, wet- in rice like butachlor, pendimethalin, pretilachlor, seeded and transplanted rice, respectively. Herbicides pyrazosulfuron and oxadiargyl provide poor control have been the major tool for weed control in rice in of this weed (Anonymous 2015). Due to labour and Indo-Gangetic plains region (IGPR) particularly in water scarcity, IGPR farmers are shifting from north western India. Even after herbicide puddled transplanted rice (PTR) to dry-direct seeded applications, weeds can decrease rice yield by 10- rice (DSR). In PTR, ponding of water serves as an 30% (Hossain et al. 2016). Escaped weed plants need effective weed control measure against emergence of to be removed by manual labour, which is impractical wrinkle grass, but this weed control tool is missing in owing to labour scarcity and rising labour wages in DSR resulting in more weed competitiveness (Lim et the region. Continuous use of herbicides with similar al. 2015). Continuous depletion of ground water in mode of action has resulted in the evolution of IGPR is further complicating the weed problem in herbicide resistance in barnyard grass (Echinochloa PTR, as it becomes difficult to obtain enough water crus-galli) and wrinkle grass (Iwakami et al. 2015, resulting in aerobic weeds like wrinkle grass Plaza and Hernandez 2014). To counter these appearing in PTR fields (Bhatt et al. 2016). problems, it is necessary to develop sustainable weed Information on germination ecology may management systems that may reduce both herbicide identify the weakest link in the life-history of a weed dependency and the burden of manual weeding. which is essential for the identification and Wrinkle grass (Ischaemum rugosum Salisb.) is development of effective integrated weed an annual grass weed that is native to tropical Asia but management systems for better weed control has invaded rice fields in South Asia and Africa (Holm (Bhowmik 1997). Seed germination is the first stage *Corresponding author: [email protected] at which the weed can compete for an ecological 385 Germination ecology of wrinkle grass (Ischaemum rugosum) population of Indo-Gangetic plain region niche and is mediated by various environmental in an environmental chamber (Model MAC MSW- variables such as temperature, light, pH, soil salinity 127, Delhi, India). For control treatment, seeds were and moisture (Chachalis and Reddy 2000). germinated using distilled water. Competitiveness of any weed species in an agro- Light and temperature experiment: The ecosystem depends on the ability of seeds to germination of seeds was tested under fluctuating germinate in response to different environmental day/night temperatures (12/12 h), viz. 15/5, 20/10, factors. The requirement for light is the principal 25/15, 30/20, 35/25 and 40/30 °C and two light means by which germination may be restricted to an regimes – light/dark for day/night environments (12/ area close to the soil surface and species requiring 12 h) and continuous dark (24 h). For continuous light for germination are likely to be more prevalent in dark treatment, Petri dishes were immediately no-till cropping systems (Cousens et al. 1993). wrapped in double layers of aluminum foil after Temperature is an important factor for successful adding water to prevent light penetration; and seed germination; some weeds may germinate over germination count was taken on 15th day only. wide range of temperature while others require narrow temperature range for germination (Shoab et Burial depth experiment: This experiment was al. 2012, Derakhshan and Gherekhloo 2013). Soil pH, conducted using 25-cm plastic pots placed under salinity and moisture stress are other environmental field conditions during months of June to August. Soil factors affecting seed germination and thus used in pots was collected from fields which had no distribution of various weeds. Information on previous incidence of wrinkle grass. Fifty seeds were germination ecology has been available for wrinkle sown on the soil surface in pots and covered to a grass populations belonging to Malaysia (Bakar and depth of 0, 1, 2, 4, 6, 8 and 10 cm. The pot surface Nabi 2003) and Philippines (Lim et al. 2015), but no was kept moist throughout the study period. such information is available for weed populations Emergence of wrinkle grass was recorded daily for from Indian IGPR. Knowledge of the response of one month. One set of 3 pots was not seeded to test wrinkle grass to environmental factors will help to for presence of wrinkle grass in the field soil. This bring a broader perspective for its effective experiment was repeated thrice using four management and in predicting its potential to spread. replications each time. This study was conducted to enhance our Moisture and salinity experiment: The germination understanding of the role of temperature, light, moisture, response of seeds under different levels of simulated salinity, pH and soil depth in germination ecology of moisture stress (0, -0.1, -0.2, -0.4, -0.6, -0.8 and - wrinkle grass population from Indian IGPR. 1.0 MPa) was tested using solutions of PEG 8000 prepared according to equations of Michel and MATERIALS AND METHODS Kaufmann (1973). The germination ability of seeds Wrinkle grass seeds were collected from several under different levels of salt stress was examined rice fields of Punjab Agricultural University, using NaCl solutions of 1, 10, 20, 40, 80, 160, 240, Ludhiana, India (30°56' N and 75°52' E). Cleaned 320, 400, 450 and 500 mM concentrations. seeds were stored at room temperature in air tight pH experiment: The effect of pH on seed plastic containers. The 1000-seed weight was 3.70 ± germination was investigated using buffered solutions 0.28 g. with pH ranging from 3 to 10 (Chachalis and Reddy Germination protocol: Before initiating laboratory 2000). A 2 mM potassium hydrogen phthalate buffer and field experiments, wrinkle grass seeds were solution was adjusted to pH 3 and 4 with 1 N HCl. tested for viability using 1% tetrazolium chloride Buffer solutions of pH 5 and 6 were prepared using 2- solution (Steadman 2004) and seeds possessed more mM solution of MES [2-(N-morpholino) ethane than 95% viability. Uniform-sized seeds were surface sulfonic acid] adjusted with 1 N HCl or NaOH. A 2- sterilized using 0.1% mercuric chloride for 2 min, mM HEPES [N-(2-hydroxymethyl) piperazine-N’-(2- followed by thorough washing with distilled water to ethane sulfonic acid)] solution was adjusted to pH 7 protect against any fungal infection (ISTA 2010). or 8 and 2-mM tricine [N-tris-(hydroxymethyl) Seed germination was tested in 3 replicates with 30 methylglycine] buffer solution was adjusted to pH 9 seeds placed evenly on Whatman No.1 filter paper in or 10 with 1 N NaOH. Unbuffered distilled water (pH 9-cm petri dishes. For studying the effect of light, 6.6) was used as control. moisture stress, salinity and pH, petri dishes were Except for continuous dark treatment, moistened with 5 ml of treatment solution and germination counts were recorded at 24-h intervals incubated at 30/20 oC day/night (optimal temperature) for 15 days after start of the experiment, with the 386 Navjyot Kaur, Renu Sethi and Makhan S. Bhullar criterion for germination being visible protrusion of Effect of temperature the radicle.