BackgroundWater availability is a major limiting factor for wheat (Triticum aestivum L.) production in rain-fed agricultural systems worldwide. Root system architecture has important functional implications for the timing and extent of soil water extraction, yet selection for root architectural traits in breeding programs has been limited by a lack of suitable phenotyping methods. The aim of this research was to develop low-cost high-throughput phenotyping methods to facilitate selection for desirable root architectural traits. Here, we report two methods, one using clear pots and the other using growth pouches, to assess the angle and the number of seminal roots in wheat seedlings– two proxy traits associated with the root architecture of mature wheat plants.ResultsBoth methods revealed genetic variation for seminal root angle and number in the panel of 24 wheat cultivars. The clear pot method provided higher heritability and higher genetic correlations across experiments compared to the growth pouch method. In addition, the clear pot method was more efficient – requiring less time, space, and labour compared to the growth pouch method. Therefore the clear pot method was considered the most suitable for large-scale and high-throughput screening of seedling root characteristics in crop improvement programs.ConclusionsThe clear-pot method could be easily integrated in breeding programs targeting drought tolerance to rapidly enrich breeding populations with desirable alleles. For instance, selection for narrow root angle and high number of seminal roots could lead to deeper root systems with higher branching at depth. Such root characteristics are highly desirable in wheat to cope with anticipated future climate conditions, particularly where crops rely heavily on stored soil moisture at depth, including some Australian, Indian, South American, and African cropping regions.

The Ligurian Sea (NW Mediterranean) experienced warm summers in 1998, 1999 and from 2003 to 2005. The temperature was 1-3°C higher than the mean summer value (24°C) and remained high over a long period. During these summers, mass-mortality events, affecting several sessile benthic species, were reported. In the present study, we tested the long-term (3-7 weeks) effect of different temperatures (20°C measured in spring and autumn, 24°C observed in summer, and 26°C and 28°C abnormal summer values) on two Mediterranean corals, Cladocora caespitosa and Oculina patagonica. Growth rate, photosynthetic efficiency (F v /F m ), relative electron transport rate (ETR), zooxanthellae and chlorophyll (chl) contents were measured during 48 days incubation. At 20°C, all parameters remained constant during the whole experiment for both species. At higher temperatures, most physiological parameters were affected by only 2-5 weeks at 24°C, and were severely depressed at higher temperatures. Small replicate samples (nubbins) of O. patagonica significantly decreased their zooxanthellae and chl concentrations at all temperatures, after 2 weeks of incubation. Their F v /F m values, as well as their growth rates, were also gradually reduced during the incubation at all temperatures. However, only a few nubbins maintained at 28°C showed signs of tissue necrosis after 34 days, and these gradually recovered tissue when temperature was returned to normal. In nubbins of C. caespitosa, chl and zooxanthellae concentrations decreased only after 34 days of incubation at 26°C and 28°C. At the same time, tissue necrosis was observed, explaining the loss of the symbionts. F v /F m was reduced only after 34 days of incubation at the different temperatures, and growth rate was first enhanced, before collapsing by 30% at 24°C and by 90-100% at 26°C and 28°C. All samples maintained at 26°C and 28°C had died, due to tissue necrosis, by the end of the experiment. Results obtained suggest that O. patagonica is more able than C. caespitosa to resist high temperature conditions because of its rapid bleaching capacity. In contrast, it seems that C. caespitosa is living close to its thermal limit during the summer period; therefore, a long-term increase at 24°C or above could be lethal for this coral, just as was observed in situ during the recent warm summers.

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Roots play a key role in plant growth regulation. It is well described that the below-ground plant architecture has a significant impact on plant performance under abiotic constraints and maintains stability under increased grain load (Lynch, 2013). Although loci influencing root traits have been shown to affect grain yield and agronomic performance (e.g., Canè et al., 2014), knowledge about the genetic control of root growth in major grain crops is limited. Here, we demonstrate that VERNALIZATION1 (VRN1), a key regulator of flowering behavior in cereals (Deng et al., 2015), also modulates root architecture in wheat and barley. Our discoveries provide unexpected insight into underground functions of a major player in the flowering pathway.