Exploring Thinopyrum spp. Group 7 Chromosome Introgressions to Improve Durum Wheat Performance under Intense Daytime and Night-Time Heat Stress at Anthesis

Abstract

Durum wheat (DW) is one of the major crops grown in the Mediterranean area, a climate-vulnerable region where the increase in day/night (d/n) temperature is severely threatening DW yield stability. In order to improve DW heat tolerance, the introgression of chromosomal segments derived from the wild gene pool is a promising strategy. Here, four DW-Thinopyrum spp. near-isogenic recombinant lines (NIRLs) were assessed for their physiological response and productive performance after intense heat stress (IH, 37/27 °C d/n) had been applied for 3 days at anthesis. The NIRLs included two primary types (R5, R112), carriers (+) of a differently sized Th. ponticum 7el1L segment on the DW 7AL arm, and two corresponding secondary types (R69-9/R5, R69-9/R112), possessing a Th. elongatum 7EL segment distally inserted into the 7el1L ones. Their response to the IH stress was compared to that of corresponding non-carrier sib lines (-) and the heat-tolerant cv. Margherita. Overall, the R112+, R69-9/R5+ and R69-9/R112+ NIRLs exhibited a tolerant behaviour towards the applied stress, standing out for the maintenance of leaf relative water content but also for the accumulation of proline and soluble sugars in the flag leaf and the preservation of photosynthetic efficiency. As a result, all the above three NIRLs (R112+ > R69-9/R5+ > R69-9/R112+) displayed good yield stability under the IH, also in comparison with cv. Margherita. R112+ particularly relied on the strength of spike fertility/grain number traits, while R69-9/R5+ benefited from efficient compensation by the grain weight increase. This work largely confirmed and further substantiated the value of exploiting the wild germplasm of Thinopyrum species as a useful source for the improvement of DW tolerance to even extreme abiotic stress conditions, such as the severe heat treatment throughout day- and night-time applied here.

Keywords: grain number; grain weight; heat stress; proline; stress physiology; water-soluble carbohydrates; wild wheat relatives; yield stability.

Figure 1

Durum wheat Thinopyrum spp. near-isogenic recombinant lines (NIRLs) tested under intense heat conditions. 7el₁L: chromosome segment derived from the long (L) arm of the Th. ponticum 7el₁ chromosome; 7E: donor chromosome of Th. elongatum “nested” segments into 7el₁L; 7A: durum wheat recipient chromosome, present in NIRLs lacking any alien introgression (HOM−).

Figure 2

Experimental setting, modalities of stress application and data recording.

Figure 3

Mean values of stomatal conductance (SC), maximal photochemical efficiency of PSII (F_v/F_m) and Performance Index (PI) of unstressed (C) and intense-heat-stressed (IH) plants of NIRLs (+), their sib lines lacking the alien segment (−) and cv. Margherita at anthesis. For Tukey test values, see Table S1.

Figure 4

Proline (Pro) and water-soluble carbohydrate (WSC) content in control (C) and intense-heat-stressed (IH) flag leaves (FL) and spikes (SP) at anthesis. For Tukey test values, see Table S1A,B.

Figure 5

Relative water content (RWC) values in control (C) and intense-heat-stressed (IH) plants at anthesis. For Tukey test values, see Table S1A,B.

Figure 6

Effects of intense heat (IH) stress vs. control conditions on main yield-related traits: comparison between alien segment carrier (+) and non-carrier (−) NIRLs (A) and between NIRLs+ and cv. Margherita (B). Error bars represent standard errors of the means, and letters above histograms correspond to the ranking of Tukey test at p < 0.05 significance level. Reported traits showed significant G × T interaction, except for TGW (see Table 2). For trait acronyms, see Table 1.