Internal browning

Internal browning of Brussels sprout buds was seen mainly as a problem for quick-freeze crops where even a small percentage of blemished buds would cause rejection since affected buds could not be identified and extracted from

Table 8.4. Nutrient composition of field-grown cauliflower leaves showing normal and tipburn growth.

Nutrient composition (percent dry weight)

Table 8.4. Nutrient composition of field-grown cauliflower leaves showing normal and tipburn growth.

Nutrient composition (percent dry weight)

Nutrient

Normal

Tipburn

Probability based on t-test

Nitrogen

4.70

4.80 (102%)

0.40

Phosphorus

0.64

0.52 (81%)

0.50

Potassium

1.31

1.58 (121%)

0.20

Calcium

0.50

0.18 (36%)

0.05

Magnesium

0.33

0.26 (79%)

0.30

From Maynard et al. (1981).

From Maynard et al. (1981).

Table 8.5. Calcium efficiency ratio for collards (Brassica oleracea var. acephala) grown in controlled conditions.

Calcium efficiency ratio1 Leaves2

Cultivai

Tipburn reaction

Young

Old

Total plant

Vates

Suceptible

107b

44a

69a

Blue Max

Tolerant

206a

43a

64a

Heavi Crop

Tolerant

183a

42a

66a

1 Mean separation among cultivars within a calcium level by least significant difference at P = 0.05.

2 Young leaves (blade and midrib) = terminal five leaves that were 2-6 cm long; old leaves (blade and midrib) = all leaves older than the fifth leaf from the terminal.

After Johnson (1991).

the processing line. Consequently, they would end up in the packs sold by supermarkets and found by the consumer. The latter would react badly to having purchased damaged goods to the disadvantage of the supermarket, processor and, ultimately, the grower.

Factors that have been implicated in the development of internal browning include: bud size (larger sprouts more prone to the syndrome); the density of leaf packing in the bud (the greater the density then the greater the likelihood of internal browning); seasonality (the incidence is most common in early maturing rapid, growing, and mid-season types (October to December)); and genotype (some cultivars are more susceptible than others). Symptoms are characterized by the death and subsequent brown discoloration of leaf tissue in the apical third of the sprout bud; symptoms are not seen frequently on either the older, outer or the youngest internal leaves. In severe cases, the browning can spread downwards along the petiole to the base of the sprout bud. It has been suggested that water condenses within the sprout bud, which may then restrict calcium transport and lead to marginal leaf necrosis in the bud.

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