In this Brassica carinata (Ethiopian mustard) research update, we highlight the symptoms of boron 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.

Boron (B), while a micronutrient, is still needed by the plant even if in smaller quantities. Boron is necessary for cell elongation, so growth and expansion of new tissue at the growing tips of plants is affected. Boron is also essential for reproductive growth. Boron deficiency manifested quickly in carinata. Symptomatology first manifested on the new growth or upper foliage given that boron is an immobile element in carinata and other plants that use sucrose as the primary photosynthetic metabolite.

The first symptoms of boron scarcity in carinata manifested as a general stunting and distortion of newly expanding leaves and upper foliage (Figure 1). The upper foliage of the plant folded inward and downward creating a wilted leaf look, while new growth was distorted, creating a crinkled and wrinkled leaf. Petioles and midribs of upper foliage as well as new growth also developed signs of cracking (Figure 2).

In advanced B deficiency conditions, the leaf will distort severely at the margin resulting in an inward cupping of the leaf (Figure 3). If allowed to continue, B deficiency will result in the death of the growing tip (Figure 4). This will result in the growth of the axillary shoots and in carinata will cause excessive side shoot formation (Figure 5). If B continues to be limited, the axillary shoots will also become necrotic, and the plant will eventually die. To ensure proper diagnosis the above material should be used in conjunction with a leaf tissue sample and/or field test.

Figure 1. Boron deficiency first manifested as a general distortion of the upper leaves. Note that the distortion resulted in a folding of the leaves rather than as a curling, cupping, or withering of the leaf surface.

Forensic Floriculture, 2018

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Figure 1. Boron deficiency first manifested as a general distortion of the upper leaves. Note that the distortion resulted in a folding of the leaves rather than as a curling, cupping, or withering of the leaf surface.

Forensic Floriculture, 2018

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Figure 2. As boron deficiency symptomology progressed, the folding became more severe, especially on new foliage. The newest foliage appeared rolled in on itself like a tube of paper.

Forensic Floriculture, 2018

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Figure 2. As boron deficiency symptomology progressed, the folding became more severe, especially on new foliage. The newest foliage appeared rolled in on itself like a tube of paper.

Forensic Floriculture, 2018

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Figure 3. As symptoms progressed, the new leaves showed signs of cracking along the midrib and petiole. This leaf curling along with the cracking are classical boron deficiency symptoms.

Forensic Floriculture, 2018

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Figure 3. As symptoms progressed, the new leaves showed signs of cracking along the midrib and petiole. This leaf curling along with the cracking are classical boron deficiency symptoms.

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Figure 4. In the advanced stages of boron deficiency, the growing tip will eventually die. You can see the necrotic center of the plant where the growing tip should be. This results in the proliferation of axillary shoots as the plant continues to grow.

Forensic Floriculture, 2018

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Figure 4. In the advanced stages of boron deficiency, the growing tip will eventually die. You can see the necrotic center of the plant where the growing tip should be. This results in the proliferation of axillary shoots as the plant continues to grow.

Forensic Floriculture, 2018

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Figure 5. Boron deficiency will eventually result in the death of the growing tip. This sudden loss of apical dominance will result in the axillary shoots to begin growing in earnest, resulting in many side shoots. Note the dense cluster of side shoots.

Forensic Floriculture, 2018

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Figure 5. Boron deficiency will eventually result in the death of the growing tip. This sudden loss of apical dominance will result in the axillary shoots to begin growing in earnest, resulting in many side shoots. Note the dense cluster of side shoots.

Forensic Floriculture, 2018

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

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