Shattering (agriculture)

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Spikelets of Einkorn wheat, Triticum monococcum Usdaeinkorn1 Triticum monococcum.jpg
Spikelets of Einkorn wheat, Triticum monococcum
Shattering in many crops involves dehiscence of the mature fruit, for example, in Brassica napus. Raps2.jpg
Shattering in many crops involves dehiscence of the mature fruit, for example, in Brassica napus .

In agriculture, shattering is the dispersal of a crop's seeds upon their becoming ripe. From an agricultural perspective this is generally an undesirable process, and in the history of crop domestication several important advances have involved a mutation in a crop plant that reduced shattering; thus, instead of the seeds being dispersed as soon as they were ripe, the mutant plants retained the seeds for longer, which made harvesting much more effective. Non-shattering phenotype is one of the prerequisites for plant breeding especially when introgressing valuable traits from wild varieties of domesticated crops. [1]

Contents

A particularly important mutation that was selected very early in the history of agriculture removed the "brittle rachis" problem from wheat. [2] A ripe head ("ear") of wild-type wheat is easily shattered into dispersal units when touched, or blown by the wind, because during ripening a series of abscission layers forms that divides the rachis into short segments, each attached to a single spikelet (which contains 2–3 grains along with chaff).

A different class of shattering mechanisms involves dehiscence of the mature fruit, which releases the seeds.

Rapeseed and the shattering types of sesame are harvested before the seed is fully mature, so that the pods do not split and drop the seeds. [3] [4] [5] Harvesting shattering types of sesame involves wrapping the cut plants before processing. [5]

Genetics

As with all hereditary traits, the genetic basis of shattering is determined through a long process of genetic mapping. Shattering is a quantitative trait, which complicates the process. The result is usually a few genomic regions known as quantitative trait loci; understanding the true molecular nature of this variation will require further analysis of what genes are actually in each locus.

Shattering is heavily studied in the grass family Poaceae, which includes the cereal crops. However, even within this group, there is no single genetic pathway that causes shattering (or the lack thereof): at least the wheat-shattering genes Br1 and Br2 (short for "brittle rachis 1/2") have no obvious ortholog in maize, rice, and sorghum. [6] (Barley has a similar system, however.) [7]

The non-shattering phenotype in sorghum (Sorghum bicolor) is due to loss of function in the YABBY-family Sh1 gene, a change that has independently occurred three times. A similar mutation may play a role in the domestication of maize and rice as the orthologs in the two species are found in shattering-related QTLs. [8]

Shattering is similarly a key domestication trait in many legumes (Fabaceae; Rosid; Eudicot), but still to this day a lot of yield is lost to shattering. Most species have several shattering-resistant mutations, each providing only partial resistance. By breeding plants with different shattering-resistant mutations together one can hope to obtain plants with even lower tendency to shatter. [9]

Shattering genetics is perhaps best understood in the model plant Arabidopsis thaliana , which has its silique shatter like many other plants of the Brassicaceae do. This knowledge is being transferred to crops of the same family such as rapeseed. [10]

Research

Current research priorities to understand the genetics of shattering include the following crops:

References

  1. ↑ Tang, H. (2013). "Seed shattering in a wild sorghum is conferred by a locus unrelated to domestication". PNAS. 110 (39): 15824–15829. Bibcode:2013PNAS..11015824T. doi: 10.1073/pnas.1305213110 . PMC   3785776 . PMID   24019506.
  2. ↑ Dorian Q. Fuller & Robin Allaby (2009). "Seed Dispersal and Crop Domestications: Shattering, Germination and Seasonality in Evolution under Cultivation". Fruit Development and Seed Dispersal. Annual Plant Reviews. Vol. 38. pp. 238–295. doi:10.1002/9781444314557.ch7. ISBN   9781444314557.
  3. ↑ Moazzami, A.; Kamal-Eldin, A. (2006), "Sesame seed is a rich source of dietary lignans", Journal of the American Oil Chemists' Society, 83 (8): 719–723, Bibcode:2006JAOCS..83..719M, doi:10.1007/s11746-006-5029-7, S2CID   85126098
  4. ↑ Duane R. Berglund; Kent McKay & Janet Knodel (2007), Canola Production, NDSU Extension Service, North Dakota State University, retrieved 9 November 2015
  5. 1 2 E. S. Oplinger, D. H. Putnam, A. R. Kaminski, C. V. Hanson, E. A. Oelke, E. E. Schulte, and J. D. Doll, "Sesame", Alternative Field Crops Manual , retrieved 16 June 2024{{citation}}: CS1 maint: multiple names: authors list (link)
  6. ↑ Li, Wanlong; Gill, Bikram S. (October 2006). "Multiple genetic pathways for seed shattering in the grasses". Functional & Integrative Genomics. 6 (4): 300–309. doi:10.1007/s10142-005-0015-y. PMID   16404644.
  7. ↑ Pourkheirandish, Mohammad; Komatsuda, Takao (22 November 2022). "Grain Disarticulation in Wild Wheat and Barley". Plant and Cell Physiology. 63 (11): 1584–1591. doi:10.1093/pcp/pcac091. PMC   9680857 . PMID   35765920.
  8. ↑ Olsen, Kenneth M (June 2012). "One gene's shattering effects". Nature Genetics. 44 (6): 616–617. doi:10.1038/ng.2289. PMID   22641204.
  9. ↑ Parker, Travis A.; Lo, Sassoum; Gepts, Paul (17 April 2021). "Pod shattering in grain legumes: emerging genetic and environment-related patterns". The Plant Cell. 33 (2): 179–199. doi:10.1093/plcell/koaa025. PMC   8136915 . PMID   33793864.
  10. ↑ Nichol, Justin B.; Dutt, Shakshi A.; Samuel, Marcus A. (April 2025). "The Shock of Shatter: Understanding Silique and Silicle Dehiscence for Improving Oilseed Crops in Brassicaceae". Plant Direct. 9 (4) e70058. Bibcode:2025PlanD...9E0058N. doi: 10.1002/pld3.70058 . PMC   11994477 . PMID   40230828.
  11. ↑ Kandemir, N.; Kudrna, D.A.; Ullrich, S.E.; Kleinhofs, A. (2000). "Molecular marker assisted genetic analysis of head shattering in six-rowed barley". Theoretical and Applied Genetics. 101 (1): 203–210. doi:10.1007/s001220051470. S2CID   20181124.
  12. ↑ Fesenko, Ivan N. (2006). "Non-shattering accessions of Fagopyrum tataricum Gaertn. carry recessive alleles at two loci affecting development of functional abscission layer" (PDF). Fagopyrum. 23: 7–10. Archived from the original (PDF) on 22 December 2023. Retrieved 25 July 2023.
  13. ↑ Brenner, D.M. (2002). "Non-shattering grain amaranth populations". In Janick, J.; Whipkey, A. (eds.). Trends in new crops and new uses. Alexandria, VA.: ASHS Press. pp. 104–106.
  14. ↑ Braatz, J.; Harloff, HJ.; Emrani, N.; Elisha, C.; Heepe, L.; Gorb, S. N.; Jung, C. (2018). "The effect of INDEHISCENT point mutations on silique shatter resistance in oilseed rape (Brassica napus)". Theoretical and Applied Genetics. 131 (19): 959–971. doi:10.1007/s00122-018-3051-4. PMID   29340752.
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