Abstract
The formation of aerenchyma in adventitious roots is one of the most crucial adaptive traits for waterlogging tolerance in plants. Pasture grasses, like other crops, can be affected by waterlogging, and there is scope to improve tolerance through breeding. In this study, two summer-active cocksfoot (Dactylis glomerata L.) cultivars, Lazuly and Porto, and two summer-active tall fescue (Lolium arundinaceum Schreb., syn. Festuca arundinacea Schreb.) cultivars, Hummer and Quantum II MaxP, were selected to investigate the effects of waterlogging on root growth and morphological change. Cultivars were subjected to four periods of waterlogging treatments (7, 14, 21 and 28 days), while comparable plants were kept under free drained control conditions. The experiment was arranged as a split–split plot design, with waterlogging treatments (waterlogged, control) considered as main plots, time periods (days of waterlogging) as subplots and cultivars as sub-subplots. Plants began to show signs of waterlogging stress 14–21 days after the onset of waterlogging treatments. There were no significant differences in shoot biomass between the waterlogged and control plants of any cultivar. However, waterlogging significantly reduced root dry matter in all cultivars, with greater reduction in cocksfoot (56%) than in tall fescue (38%). Waterlogging also led to increased adventitious root and aerenchyma formation in both species. Cocksfoot cultivars showed a greater increase in adventitious roots, while tall fescue cultivars had a greater proportion of aerenchyma. Both cultivars within each species showed similar responses to waterlogging treatments. However, an extended screening program is needed to identify whether there are varietal differences within species, which could be used to discover genes related to aerenchyma or adventitious root formation (waterlogging tolerance) for use in breeding programs.
Highlights
Waterlogging is a productivity constraint for many temperate agricultural regions of southern Australia, where it can reduce yields of crops, including maize (Zea mays L.) [1], wheat (Triticum aestivum L.) [2,3,4], barley (Hordeum vulgare L.), field peas (Pisum sativum L.), lupins (Lupinus albus L.) and canola (Brassica napus L.) [2,5]
This study aimed to investigate the root morphological response of two perennial grass species in response to waterlogging
The development of aerenchyma in adventitious roots was a major mechanism involved in the waterlogging tolerance of cocksfoot and tall fescue plants
Summary
Waterlogging is a productivity constraint for many temperate agricultural regions of southern Australia, where it can reduce yields of crops, including maize (Zea mays L.) [1], wheat (Triticum aestivum L.) [2,3,4], barley (Hordeum vulgare L.), field peas (Pisum sativum L.), lupins (Lupinus albus L.) and canola (Brassica napus L.) [2,5]. The losses in crop production invariably result in lower returns and profit [6,7,8]. Waterlogging has been estimated to cause an annual agricultural production loss of more than 71 billion USD worldwide [9]. The energy produced by root respiration is restricted, leading to a substantial decrease in plant growth [12,13]. While the application of management approaches [14,15] has been shown to mitigate waterlogging effects, the development of waterlogging-tolerant varieties is considered as the most economical way to reduce losses [16]. Waterlogging-tolerant plants adapt to waterlogging stresses through changes in anatomical [17,18], metabolic [19] and/or morphological [20] processes and mechanisms. Tolerance is variable among species [9]
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