Unraveling Molecular and Genetic Studies of Wheat (Triticum aestivum L.) Resistance against Factors Causing Pre-Harvest Sprouting

Abstract

Pre-harvest sprouting (PHS) is one of the most important factors having adverse effects on yield and grain quality all over the world, particularly in wet harvest conditions. PHS is controlled by both genetic and environmental factors and the interaction of these factors. Breeding varieties with high PHS resistance have important implications for reducing yield loss and improving grain quality. The rapid advancements in the wheat genomic database along with transcriptomic and proteomic technologies have broadened our knowledge for understanding the regulatory mechanism of PHS resistance at transcriptomic and post-transcriptomic levels. In this review, we have described in detail the recent advancements on factors influencing PHS resistance, including grain color, seed dormancy, α-amylase activity, plant hormones (especially abscisic acid and gibberellin), and QTL/genes, which are useful for mining new PHS-resistant genes and developing new molecular markers for multi-gene pyramiding breeding of wheat PHS resistance, and understanding the complicated regulatory mechanism of PHS resistance.

Impact of Cultivar and Growing Conditions on Alpha‐Amylase Properties in Wheat

“…[ 40 ] In addition, it stimulates the production of the plant hormones associated with the germination (i.e., gibberellic acid), [ 45 ] which then promotes the activity of α‐amylase. [ 4 ] However, the data presented showed that the increase in enzyme activity of grain exposed to rain was not accompanied by any visible sprouting symptoms in both cultivars. A similar finding was made by previous researchers, who found that wheat cultivars could induce α‐amylase activity per se before germination, although no visible germination symptoms are present.…”

“…However, an excess of natural -amylase activity in wheat grains leads to a faster starch degradation in flour, resulting in breadmaking process in sticky dough, reduced loaf volume, compact, and dark crust. [3] Wheat grains had increased -amylase activity caused by preharvest sprouting as a result of untimely rainfall during the harvest period [4] or by late-maturing amylase due to daily temperature fluctuations during grain filling. [5] Such wheat quality defects DOI: 10.1002/star.202000032 have a strong impact on the alteration and/or degradation of the chemical grain components, resulting in significant financial losses in the wheat industry.…”

“…[6,17] Considerable studies on the variation of -amylase activity were limited to red-grained wheat compared to whitegrained one. [4,9,18] This is due to the fact that grain color is associated with seed dormancy, [19] which consequently has an effect on -amylase activity. [18] Although there are relatively few reports about the -amylase activity in cultivars that differ in their growth habit (winter vs spring wheat).…”

Transcriptomic profiling of wheat near-isogenic lines reveals candidate genes on chromosome 3A for pre-harvest sprouting resistance

“…Resistance to PHS is controlled by quantitative trait loci (QTL) [ 13 – 15 ] that are located on all 21 chromosomes in bread wheat; of which, QTL on chromosome groups 3 and 4 consistently explain large phenotypic variation [ 16 – 19 ]. Several candidate genes have been identified for a major 4AL locus responsible for PHS resistance, including two seed dormancy genes PM19-A1 and A2 by transcriptomic analyses [ 20 ], and a causal seed dormancy gene MKK3 located next to PM19 by a comparative genomics method [ 21 ].…”

Molecular Genetics, Genomics, and Biotechnology in Crop Plant Breeding

“…Germination of mature seeds before harvest, based on weather conditions, results in poor baking quality and is referred to as pre-harvest sprouting (PHS). Resistance to PHS is controlled by many genes and their interaction with the environment is revealed in a comprehensive review of 236 papers [2]. Seed dormancy is the major genetic factor controlling PHS resistance and is controlled by QTLs located on all 21 chromosomes of hexaploid wheat.…”