Exploring the link between more negative osmotic potential and ryegrass summer performance

Abstract

This paper outlines recent research studying within-population variation in selected New Zealand perennial ryegrass cultivars, for traits related to tolerance of summer moisture deficit. Two clonal replicates of 220 genotypes from ‘Grasslands Nui’ (Nui, n=50), ‘Grasslands Samson’ (Samson, n=80), and ‘Trojan’ (n=90) were exposed to 1 month of moisture deficit challenge, with plant water relations measurements performed to evaluate putative drought-response mechanisms. Water use of individual genotypes ranged from <100 to >1000 g water/g DM indicating large within-population variation for this trait. Mean water use efficiency (WUE) was for Nui, Samson, and Trojan, respectively, 424±16, 412±10, and 319±9 g water/g DW (P<0.001), suggesting that commercial plant breeding may have indirectly reduced water use in modern cultivars without specific focus on water relations. Principal component analysis indicated more negative osmotic potential may contribute to reduced water use while maintaining yield under water deficit, giving a potential focus for future breeding selection targeting summer water deficit tolerance.

A comparative analysis of agronomic water‐use efficiency and its proxy measures as derived from key morpho‐physiological and supportive quantitative genetics attributes of perennial ryegrass under imposed drought

“…Supporting this, our study that laid the foundation for the present work (see Weerarathne et al, 2021) revealed that conventional pasture breeding has indirectly resulted in high WUE A and drought tolerance in modern PRG cultivars. This was further confirmed in other related studies (Chapter 3 of Weerarathne, 2021;Weerarathne et al, 2018). As expected, calculated ΔG c or the estimate of prediction of the expected response to selection was high for WUE A and ranged from moderate to high for related traits including WUE i at MS2 and MS3 (see Table 9).…”

“…This planting system allowed root development similar to that in field swards. The soil used was from the A horizon of an "Egmont Black Loam" (a Typic Distrandept under USDA nomenclature; Perrott & Sarathchandra, 1987;Weerarathne et al, 2018Weerarathne et al, , 2021. Pots were packed to a standard weight of 3.7-3.9 kg air-dried soil per pot.…”

Screening of tall fescue genotypes for relative water content and osmotic potential under drought stress

“…Higher harvest indices and translocation of dry matter in sorghum were also related to osmotic adjustment (Santamaria et al, 1990). Weeratathne et al (2018) observed a linkage between low leaf OP to reduced water use and high yield in ryegrass under water deficit in a glasshouse pot experiment.…”

A Comparative Analysis of Agronomic Water-Use Efficiency and its Proxy Measures as derived from Key Morpho-Physiological and Supportive Quantitative Genetics Attributes of Perennial Ryegrass under Imposed Drought

“…This planting system allowed root development similar to that in field swards. The soil used was from the A horizon of an 'Egmont Black Loam' (a Typic Distrandept under USDA nomenclature; Perrott & Sarathchandra, 1987;Weerarathne et al . 2018;2021).…”