In this Brassica carinata (Ethiopian mustard) research update, we highlight the symptoms of magnesium deficiency. These images are part of a project by the Southeast Partnership for Advanced Renewables from Carinata (SPARC) to develop a diagnostic series for the identification of nutrient disorders of Carinata. Carinata is an exciting new crop in the Southeast used for a wide variety of primary and secondary agricultural products including cover crops, feedstock, high protein meal, and jet fuel. It is similar in management to canola given both canola and carinata are winter annual Brassica oilseed crops. However, carinata oil is not edible.

Magnesium (Mg) is the central element in the chlorophyll molecule, so initial Mg deficiencies often appear as interveinal chlorosis. Since it can be broken down and translocated, magnesium is a mobile element and will move from the older lower foliage to the newer growth where it is needed. Magnesium deficiency stress manifested early in the course of the experiment. As such, magnesium fertilizer levels should be monitored closely.

Magnesium deficiency first manifests as a slight interveinal chlorosis of the lower foliage (Figure 1). This interveinal chlorosis can be accompanied by necrotic lesions over the leaf surface (Figure 2). These lesions will have necrotic brown centers and may be accompanied with a darker brown margin (Figure 3).

As magnesium deficiency proceeds from beginning to intermediate stages, the interveinal chlorosis becomes more pronounced in color and contrast. This color change can result in certain interveinal regions becoming slightly purple to pink (Figure 4). The underside of the leaf will have a very stark and bright purple to red coloration between the veins (Figure 5).

If allowed to continue, magnesium deficiency will eventually result in the necrosis of lower foliage and eventual abscission. To ensure proper diagnosis the above material should be used in conjunction with a leaf tissue sample and / or field test.

Figure 1. The beginning symptoms of magnesium deficiency will manifest as an interveinal chlorosis of the lower foliage as Mg is translocated to newer tissues where it is needed. Note the interveinal chlorosis is more evident along the base of the leaf.

Forensic Floriculture, 2018

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Figure 1. The beginning symptoms of magnesium deficiency will manifest as an interveinal chlorosis of the lower foliage as Mg is translocated to newer tissues where it is needed. Note the interveinal chlorosis is more evident along the base of the leaf.

Forensic Floriculture, 2018

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Figure 2. Note the progressive symptomology in the form of necrotic regions. These will appear as angular, tan lesions. These will be concentrated along the base of the leaf and will expand outward toward the leaf tip as deficiency becomes more severe.

Forensic Floriculture, 2018

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Figure 2. Note the progressive symptomology in the form of necrotic regions. These will appear as angular, tan lesions. These will be concentrated along the base of the leaf and will expand outward toward the leaf tip as deficiency becomes more severe.

Forensic Floriculture, 2018

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Figure 3. The above photo shows intermediate magnesium deficiency symptoms of the lower foliage. Note that the smaller necrotic regions shown in Figure 2 have expanded and progressed further toward the leaf tip.

Forensic Floriculture, 2018

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Figure 3. The above photo shows intermediate magnesium deficiency symptoms of the lower foliage. Note that the smaller necrotic regions shown in Figure 2 have expanded and progressed further toward the leaf tip.

Forensic Floriculture, 2018

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Figure 4. Magnesium deficiency may also manifest as a reddening or purpling of the leaf surface. This reddening will precede the appearance of the necrotic regions. On top of the leaf, the purple coloration may appear weak, but on the underside stark.

Forensic Floriculture, 2018

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Figure 4. Magnesium deficiency may also manifest as a reddening or purpling of the leaf surface. This reddening will precede the appearance of the necrotic regions. On top of the leaf, the purple coloration may appear weak, but on the underside stark.

Forensic Floriculture, 2018

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Figure 5. In this leaf, advanced stages of magnesium deficiency can be seen. Note the severe purpling or reddening of the interveinal regions of the underside of the leaf. Also note the necrotic tan leaf margin and the darker brown necrotic iris.

Forensic Floriculture, 2018

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Figure 5. In this leaf, advanced stages of magnesium deficiency can be seen. Note the severe purpling or reddening of the interveinal regions of the underside of the leaf. Also note the necrotic tan leaf margin and the darker brown necrotic iris.

Forensic Floriculture, 2018

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We would like to thank the following for grant assistance on this project:

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