Black point formation in barley: environmental influences and quantitative trait loci

Black point and kernel discoloration of barley both appear to occur under conditions of high humidity at grain fill. Both of these traits are likely to result from the enzymatic oxidation of phenolic compounds to quinones and the transformation of those oxidation products to brown or black pigments during high humidity. However, even though black point symptoms are quite distinct from other types of kernel discoloration, black point of barley has not previously been the sole focus of environmental studies or quantitative trait locus (QTL) analysis. We have evaluated black point tolerance in doubled haploid progeny of Alexis/Sloop and mapped QTLs on chromosomes 2H and 3H. We have also established that the occurrence of low vapour pressure deficit, high humidity, and low temperatures is associated with the formation of black point in susceptible varieties. These environmental conditions probably create a moist environment during grain development so that the developing grain cannot dry out. Stress or wounding to the embryo caused by this environment might then lead to black point formation. The results of this study will enable the use of comprehensive genetic and biochemical approaches to develop a more detailed understanding of this disorder.

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Quantitative trait locus mapping of the transpiration ratio related to preflowering drought tolerance in sorghum (Sorghum bicolor)

Functional Plant Biology ◽

10.1071/fp13363 ◽

2014 ◽

Vol 41 (11) ◽

pp. 1049 ◽

Cited By ~ 15

Author(s):

Mohankumar H. Kapanigowda ◽

William A. Payne ◽

William L. Rooney ◽

John E. Mullet ◽

Maria Balota

Keyword(s):

Sorghum Bicolor ◽

Quantitative Trait ◽

Agronomic Traits ◽

Stomatal Density ◽

Recombinant Inbred Lines ◽

Vapour Pressure Deficit ◽

Field Capacity ◽

Co2 Assimilation ◽

Mean Values ◽

Trait Locus

To meet future food needs, grain production must increase despite reduced water availability, so waterproductivity must rise. One way to do this is to raise the ratio of biomass produced to water transpired, which is controlled by the ratio of CO2 assimilation (A) to transpiration (E) (i.e. the transpiration ratio, A : E divided by vapour pressure deficit) or anything affecting stomatal movement.. We describe the genetic variation and basis of A, E and A : E among 70 recombinant inbred lines (RILs) of sorghum (Sorghum bicolor (L.) Moench), using greenhouse experiments. Experiment 1 used 40% and 80% of field capacity (FC) as water regimes; Experiment 2 used 80% FC. Genotype had a significant effect on A, E and A : E. In Experiment 1, mean values for A : E were 1.2–4.4 mmol CO2 mol–1 H2O kPa–1 and 1.6–3.1 mmol CO2 mol–1 H2O kPa–1 under 40% and 80% FC, respectively. In Experiment 2, values were 5.6–9.8 mmol CO2 mol–1 H2O kPa–1. Pooled data for A : E and A : E VPD–1 from Experiment 1 indicate that A : E fell quickly at temperatures >32.3°C. A : E distributions were skewed. Mean heritabilities for A : E were 0.9 (40% FC) and 0.8 (80% FC). Three significant quantitative trait loci (QTLs) associated with A:E, two on SBI-09 and one on SBI-10, accounted for 17–21% of the phenotypic variation. Subsequent experiments identified 38 QTLs controlling variation in height, flowering, biomass, leaf area, greenness and stomatal density. Colocalisation of A : E QTLs with agronomic traits indicated that these QTLs can be used for improving sorghum performance through marker assisted selection (MAS) under preflowering drought stress.

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