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Introduction: Wheat grain filling processes under post-anthesis stress scenarios depend mainly on stem traits and remobilization of stem water-soluble carbohydrates (WSC). Methods: A diverse panel of advanced semi-dwarf spring wheat lines, representing a natural variation in stem traits (WSC content, stem diameter, peduncle length, and stem wall width), was used to identify specific traits that reliably reflect the relationship between WSC and grain yield. The panel was phenotyped under various environmental conditions: well-watered, waterlimited, and heat stress in Mexico, and terminal-drought in Israel. Results: Environmental stresses reduced grain yield (from 626 g m-2 under wellwatered to 213 g m-2 under heat), lower internode diameter, and peduncle length. However, stem-WSC generally peaked 3-4 weeks after heading under all environmental conditions except heat (where it peaked earlier) and expressed the highest values under water-limited and terminal-drought environments. Increased investment in internode diameter and peduncle length was associated with a higher accumulation of stem WSC, which showed a positive association with yield and kernel weight. Across all environments, there were no apparent trade-offs between increased crop investment in internode diameter, peduncle length, and grain yield. Discussion: Our results showed that selecting for genotypes with higher resource investment in stem structural biomass, WSC accumulation, and remobilization could be a valuable strategy to ameliorate grain size reduction under stress without compromising grain yield potential. Furthermore, easy-tomeasure proxies for WSC (stem diameter at specific internodes and length of the last internode, i.e., the peduncle) could significantly increase throughput, potentially at the breeding scale. [ABSTRACT FROM AUTHOR]

BACKGROUND: For over a century, genetic diversity of wheat worldwide was eroded by continual selection for high yields and industrial demands. Wheat landraces cultivated in Israel and Palestine demonstrate high genetic diversity and a potentially wide repertoire of adaptive alleles. While most Israeli‐Palestinian wheat landraces were lost in the transition to 'Green Revolution' semi‐dwarf varieties, some germplasm collections made at the beginning of the 20th century survived in gene banks and private collections worldwide. However, fragmentation and poor conservation place this unique genetic resource at a high risk of genetic erosion. Herein, we describe a long‐term initiative to restore, conserve, and characterize a collection of Israeli and Palestinian wheat landraces (IPLR). RESULTS: We report on (i) the IPLR construction (n = 932), (ii) the historical and agronomic context to this collection, (iii) the characterization and assessment of the IPLR's genetic diversity, and (iv) a data comparison from two distinct subcollections within IPLR: a collection made by N. Vavilov in 1926 (IPLR‐VIR) and a later one (1979–1981) made by Y. Mattatia (IPLR‐M). Though conducted in the same eco‐geographic space, these two collections were subjected to considerably different conservation pathways. IPLR‐M, which underwent only one propagation cycle, demonstrated marked genetic and phenotypic variability (within and between accessions) in comparison with IPLR‐VIR, which had been regularly regenerated over ∼90 years. CONCLUSION: We postulate that long‐term ex situ conservation involving human and genotype × environment selection may significantly reduce accession heterogeneity and allelic diversity. Results are further discussed in a broader context of pre‐breeding and conservation. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]