Responses of Phalaris minor Rezt. and Phalaris brachystachys Link to different levels of soil water availability

C Alcantara,M Saavedra,M J Jimenez-Hidalgo

doi:10.5424/sjar/2010084-1402

Abstract

Phalaris brachystachys and Phalaris minor are common and troublesome weeds in winter cereals in Mediterranean countries. Different distribution and soil preferences have been found for each species in Andalusia (southern Spain). In irrigated fields P. minor is more frequent while P. brachystachys has extended its range to semiarid provinces with low rainfall. This different adaptation to irrigation conditions is difficult to explain considering aspects of their biology, herbicide tolerance, or cultivation practices. The objective of this study was to assess the influence of different soil water availabilities over growth and reproductive aspects to explain the differences found in ecology and distribution of P. brachystachys and P. minor. The experiment was conducted under greenhouse controlled conditions using five levels of water availability: field capacity, light drought, moderate drought, severe drought and extreme drought. Differences between species and among treatments were found in plant height, biomass, tiller number, and reproductive traits. Field capacity and light drought treatments favoured biomass, tiller number, and panicle number in P. minor. In contrast, P. brachystachys had a positive response only in moderate drought and increased the percentage of mature panicle with increasing drought levels. These results could explain the wider distribution of P. brachystachys in fields without supplemental irrigation in semiarid areas, due to its adaptation to moderate drought conditions. It may also clarify the greater frequency of P. minor in irrigated fields and in areas with higher rainfall.

Highlights

The annual Poaceae species Phalaris brachystachys Link (2n = 2x = 12), Phalaris minor Retz (2n = 4x = 28), and Phalaris paradoxa L. (2n = 2x = 14) are common and troublesome weeds in winter cereals in Mediterranean countries (Catizone and Viggiani, 1980; Damanakis, 1983; García-Baudín, 1983), India (Bir and Sidhu, 1979; Chhokar and Sharma, 2008; Vashisht et al, 2008), Pakistan (Waheed et al, 2009) and in California and Arizona (Bell, 1992; Butler et al, 1993)
Several studies have indicated that competition between canary grass species and winter cereals is severe (Cudney and Hill, 1979; Dellow and Milne, 1986; Mehra and Gill, 1988; Walker et al, 2001), sustainable weed management practices are being exploited as control strategies (Franke et al, 2007; Jamil et al, 2009)
The progression of height and aerial biomass shows that there were differences between species and responses to soil water availability (Fig. 1), both species being affected negatively by drought

Summary

Introduction

The annual Poaceae species Phalaris brachystachys Link (2n = 2x = 12) (short-spiked canary grass), Phalaris minor Retz (2n = 4x = 28) (littleseed canary grass), and Phalaris paradoxa L. Due to the high cost and difficulty of control measures (González-Díaz et al, 2009), as well as their high rate of population growth (GonzálezAndújar et al, 2005), farmers consider canary grasses some of the most pernicious weeds of cereal crops. Several studies have indicated that competition between canary grass species and winter cereals is severe (Cudney and Hill, 1979; Dellow and Milne, 1986; Mehra and Gill, 1988; Walker et al, 2001), sustainable weed management practices are being exploited as control strategies (Franke et al, 2007; Jamil et al, 2009)

Objectives

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Conclusion