Abstract
Global warming is predicted to impact many agricultural areas, which will suffer from reduced water availability. Due to precipitation changes, mild summer droughts are expected to become more frequent, even in temperate regions. For perennial ryegrass (Lolium perenne L.), an important forage grass of the Poaceae family, leaf growth is a crucial factor determining biomass accumulation and hence forage yield. Although leaf elongation has been shown to be temperature-dependent under normal conditions, the genetic regulation of leaf growth under water deficit in perennial ryegrass is poorly understood. Herein, we evaluated the response to water deprivation in a diverse panel of perennial ryegrass genotypes, employing a high-precision phenotyping platform. The study revealed phenotypic variation for growth-related traits and significant (P < 0.05) differences in leaf growth under normal conditions within the subgroups of turf and forage type cultivars. The phenotypic data was combined with genotypic variants identified using genotyping-by-sequencing to conduct a genome-wide association study (GWAS). Using GWAS, we identified DNA polymorphisms significantly associated with leaf growth reduction under water deprivation. These polymorphisms were adjacent to genes predicted to encode for phytochrome B and a MYB41 transcription factor. The result obtained in the present study will increase our understanding on the complex molecular mechanisms involved in plant growth under water deficit. Moreover, the single nucleotide polymorphism (SNP) markers identified will serve as a valuable resource in future breeding programs to select for enhanced biomass formation under mild summer drought conditions.
Highlights
Abiotic stress has detrimental effects on agriculture worldwide, threatening food security as huge yield losses are already being reported (Daryanto et al, 2016; Fahad et al, 2017)
From a practical point of view, aiming to obtain stable yield under mild drought, a forage grass cultivar continuing slower growth after sensing the water deprivation is preferable to the one that opts for the survival strategy and halts its growth early
For the leaf growth under water deficit experiment, plants were vegetatively propagated into four clonal replicates, each consisting of 20 tillers, and grown in plastic pots (ø15 cm and 12 cm height) filled with 450 g of commercial potting mix substrate (“Spezialmischung 209,” RICOTER Erdaufbereitung AG, Aarberg, Switzerland) under regular irrigation and fertilization in a greenhouse. 4 to 6 weeks after clonal propagation, plants were transferred into a climate chamber (Conviron, 86 Winnipeg, Canada) under controlled conditions with a light/dark photoperiod of 16/8 h and a light intensity of 275 μmol photosynthetically active radiation (PAR) m−2 s−1
Summary
Abiotic stress has detrimental effects on agriculture worldwide, threatening food security as huge yield losses are already being reported (Daryanto et al, 2016; Fahad et al, 2017). Plant breeding for drought tolerant cultivars is considered as an important measures to mitigate the effects of drought on food and feed production, direct selection for yield under water stress resulted in limited genetic gain for drought tolerance (Hu and Xiong, 2014; Kumar et al, 2014; Mwadzingeni et al, 2016; Sandhu and Kumar, 2017). Plants can adapt to water stress in different ways, they might choose between survival, meaning reduced water use and growth halt, or continued slow growth (Claeys and Inzé, 2013). The latter option offers a competitive advantage in biomass accumulation, assuming the stress is temporary but can threaten survival if the stress persists. From a practical point of view, aiming to obtain stable yield under mild drought, a forage grass cultivar continuing slower growth after sensing the water deprivation is preferable to the one that opts for the survival strategy and halts its growth early
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