#Alternaria_black_spot_in_cabbage
Brassicas, Alternaria black leaf spot:
It is considered one of the common fungal diseases in cabbage fields and represents an increasing threat to cabbage crops all over the world. It can infect all parts of the plant at all stages of growth (seedlings, leaves, petioles, stems, heads, flower discs, and seeds). The disease is caused by several types of Alternaria fungi and has a large number of plants. The host weakens the infected plants without causing their death.
# The pathogen and the conditions suitable for the development of the disease:
There are several types of fungi:
Alternaria brassicae
Alternaria brassicicola
They affect: broccoli, Brussels sprouts, cabbage, cauliflower, Chinese cabbage, cabbage, and kale. And cruciferous wild plants.
Its ideal temperature is 18-24°C.
Alternaria raphani
It infects radishes and can infect other cruciferous plants.
Its ideal temperature is 20-30°C.
Relative humidity of 100-95% for 12-20 hours.
Free moisture on the plant is not less than 5 hours.
The fungus produces large quantities of spores, and the spores are spread throughout the fields by the wind, where they can be transmitted up to 1760 m by the wind. They are also transmitted to healthy plants through spraying water, agricultural equipment, workers, animals, and flea beetle insects when they feed on infected plants.
# Symptoms:
It affects seedlings in the form of spots on the leaves and can cause their stunting and death.
The leaves appear in the form of dark brown to black spots at any stage of growth and vary in size from a point to a diameter of 5 cm. They are clearer on the lower leaves of the plant. When the disease develops, the spots expand in diameter and take the shape of a bull’s eye. Concentric circles with a black center in the middle separate easily.
It may cause yellowing of the affected leaves, and the infected spots may gather in large areas and fall
Papers.
Infection with the heads of cauliflower causes deterioration and damage to the entire head and loss of the marketing ability of the tablets. The injury appears in the form of black spots on the heads. These spots range from small pinpoints to larger circular spots with a diameter of up to several millimeters.
As for cabbage, damage to the heads makes it impossible to store them.
Infected heads and discs also become susceptible to soft rot, which we talked about in a previous article.
Severe infestation may result in reduced photosynthesis, reduced plant activity, and decreased productivity.
#Source of infection:
1- Seeds, where the fungus can be present on the seed coat and remain viable for two years, or inside it in the form of mycelium and then remain viable for 12 years.
2- In the soil and infected plant waste.
The fungus was found to exist in two forms, microsclerotia and chlamydospores.
#Injury prevention and treatment:
1- Purchase certified seeds that are disease-free and can be treated with hot water.
2- The agricultural cycle for a period of not less than two years.
3- Deep cultivation of the soil.
4- Adherence to the specified planting distances and directing the planting rows with the direction of the wind in order for the plants to receive good air and sunlight with the specified planting density.
5- Getting rid of weeds.
6- Watering early in the morning and avoiding using overhead spraying.
7- Spraying with copper fungicides (copper chlorine oxide) 3 grams per liter of water. Spraying with mancozeb 3 grams per liter of water can be done when the disease appears and with an interval of 10-15 days between sprays, while getting rid of the affected leaves to improve air movement around the plants and reduce the number of spores present in the plant. big.
8- After harvesting, plant waste must be disposed of and the soil cultivated.
the reviewer:
Bart PH, Thomma J. 2003. Alternaria spp.: from general saprophyte to specific parasite. Molecular Plant Pathology 4(4): 225-236. [DOI:
10.1046/j.1364-3703.2003.00173.x]
Bassey EO, Gabrielson RL 1983. The effects of humidity, seed infection level, temperature and nutrient stress on cabbage seedling disease caused by Alternaria brassicicola. Seed Science and Technology 11:
403-410.
Brun H., Plessis J., Renard M. 1987. Re- sistance of some crucifers to Alter- naria brassicae (Berk.) Sacc. Proc. Seventh Int. Rapeseed Congr. Poz-nan, Poland: 1222-1227.
Buchwaldt L., Green H. 1992. Phytotoxicity of destruxin B and its possible role in the pathogenesis of Alternaria brassicae. Plant Pathology 41: 55-63. [DOI: 10.1111/j.1365-
3059.1992.tb02316.x]
Chevre AM, Eber F., Brun H., Plessis J., Primard C., Renard M. 1991. Cyto- genetic studies of Brassica napus – Sinapsis alba hybrids from ovary culture and protoplast fusion. At-tempts to introduce Alternaria re-sistance into rapeseed. Proceedings of International Rapeseed Confer-ence 8: 346-351.
Chirco EM, Harman GE 1979. The effects of Alternaria brassicicola in-fection on Brassica seed vigor and viability. Journal of Seed Techno-gy 3: 12-22.
Conn KL, Tewari JP 1986. Hypersensi- tive reaction induced by Alternaria brassicae in Eruca sativa, an oil-yielding crucifer. Canadian Journal of Plant Pathology 8: 348.
Conn KL, Tewari JP, Dahiya JS 1988. Resistance to Alternaria brassicae and phytoalexins-elicitation in rape-
seed and other crucifers. Plant Sci- ence 56: 21-25. [DOI:
10.1016/0168-9452(88)90180-X] Degenhardt KJ, Petrie GA, Morrall
RAA 1982. Effects of temperature on spore germination and infection of rapeseed by Alternaria brassicae,
A. brassicicola, and A. raphani. Ca- nadian Journal of Plant Pathology 4:
115-118.
Doullah MAU, Meah MB, Okazaki K. 2006. Development of an effective screening method for partial re- sistance to Alternaria brassicicola (dark leaf spot) in Brassica rapa. European Journal of Plant Pathology 116: 33-43. [DOI: 10.1007/s10658-
006-9035-2]
Fahleson J., Rahlen L., Glimelius K. 1988. Analysis of plants regenerated from protoplast fusions between Brassica napus and Eruca sativa. Theoretical and Applied Genetics
76(4): 507-512.
[DOI: 10.1007/BF00260900]
Hansen LH 1998. Intertribal somatic hybridization between rapid cycling Brassica oleracea (L.) and Came- lina sativa (L) Cranz. Euphytica
104: 173
Hansen LH, Earle ED 1995. Transfer of resistance to Xanthomonas cam-pestris pv. campestris (L.) by proto-plast fusion. Theoretical and Applied Genetics 91: 1293-1300. [DOI: 10.1007/BF00220944]
Hansen LH, Earle ED 1997. Somatic hybrids between Brassica oleracea (L.) and Sinapis alba (L.) with re-sistance to Alternaria brassicae (Berk.) Sacc. Theoretical and Applied Genetics 94: 1078-1085. [DOI: 10.1007/s001220050518]
Ho WC, Wu TY, Su HJ, Ko WH 2007. Effect of oriental medicinal plant extracts on spore germination
of Alternaria brassicicola and na- ture of inhibitory substances from
English 
Arabic