Seed Germination Ecology of Echinochloa glabrescens and Its Implication for Management in Rice (Oryza sativa L.)

Jhoana L Opeña,Aurora M Baltazar,Bhagirath S Chauhan,Jauhar Ali

doi:10.1371/journal.pone.0092261

Jhoana L Opeña, Aurora M Baltazar + Show 2 more

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https://doi.org/10.1371/journal.pone.0092261

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Abstract

Echinochloa glabrescens is a C4 grass weed that is very competitive with rice when left uncontrolled. The competitive ability of weeds is intensified in direct-seeded rice production systems. A better understanding is needed of factors affecting weed seed germination, which can be used as a component of integrated weed management in direct-seeded rice. This study was conducted to determine the effects of temperature, light, salt and osmotic stress, burial depth, crop residue, time and depth of flooding, and herbicide application on the emergence, survival, and growth of two populations [Nueva Ecija (NE) and Los Baños (IR)] of E. glabrescens. Seeds from both populations germinated at all temperatures. The NE population had a higher germination rate (88%) from light stimulation than did the IR population (34%). The salt concentration and osmotic potential required to inhibit 50% of germination were 313 mM and −0.24 MPa, respectively, for the NE population and 254 mM and −0.33 MPa, respectively, for the IR population. Emergence in the NE population was totally inhibited at 4-cm burial depth in the soil, whereas that of the IR population was inhibited at 8 cm. Compared with zero residue, the addition of 5 t ha−1 of rice residue reduced emergence in the NE and IR populations by 38% and 9%, respectively. Early flooding (within 2 days after sowing) at 2-cm depth reduced shoot growth by 50% compared with non-flooded conditions. Pretilachlor applied at 0.075 kg ai ha−1 followed by shallow flooding (2-cm depth) reduced seedling emergence by 94−96% compared with the nontreated flooded treatment. Application of postemergence herbicides at 4-leaf stage provided 85−100% control in both populations. Results suggest that integration of different strategies may enable sustainable management of this weed and of weeds with similar germination responses.

Highlights

The looming water crisis, increasing labor cost, and shortage of labor have led to a shift from transplanted to direct-seeded rice production systems in many Asian countries [1,2]
Effect of temperature and light Germination of E. glabrescens seeds from the IR population was influenced by the interaction between light and temperature (P,0.001) while seeds of the Nueva Ecija (NE) population were stimulated by light but not by the alternating day/night temperatures
In the continuous dark conditions, seed germination in the IR population was lower at 35/25 uC (41.561.7%) than at 25/15 uC (72.565.4%) and 30/20 uC (67.562.7%), whereas in the alternating light/dark conditions, germination was similar at all temperatures (Figure 1)

Summary

Introduction

The looming water crisis, increasing labor cost, and shortage of labor have led to a shift from transplanted to direct-seeded rice production systems in many Asian countries [1,2]. This study was conducted to determine the effects of light, temperature, salt, osmotic stress, burial depth, rice residue, time and depth of flooding, and flooding depth combined with different rates and application timing of PRE and POST herbicides on the emergence and growth of two populations of E. glabrescens. Effect of flooding depth and pretilachlor rates on seedling emergence and biomass Fifty seeds from each of the two populations were sown at 0.5cm depth in small plastic trays (8.0 cm68.0 cm65.5 cm) containing the same soil described in the previous experiments.

Results

Conclusion