Botrytis fabae
Encyclopedia
Botrytis fabae is a plant pathogen, a fungus that causes chocolate spot disease of broad or fava bean plants, Vicia faba
.
, stems
and flowers
of broad bean plants. These enlarge and develop a grey, dead centre with a reddish-brown margin. Spore
s form on the dead tissue and spread the infection to other plants. In severe infections leaves and flowers may fall and badly affected stems may keel over.
in the soil or on crop stubble and residues. It can also be introduced by the use of infected seed. The sclerotia germinate and condiophores are formed, the conidia (asexual spores) are dispersed by air currents and deposited by rain on susceptible young plants. When the conidia germinate
, small lesion
s are formed on previously healthy leaves. As the crop grows and within four or five days of infection, conidiophores are produced and secondary inoculum is produced. The conidia are liberated from dead or dying leaves and flowers, usually those that have fallen to the ground, and are spread to other plants in the vicinity by wind and splashes of water. This secondary spread of infection proceeds most rapidly under cool, humid conditions, the optimum conditions being a temperature between 15°C and 22°C and a relative humidity of at least 90%. Under dry conditions the pathogen remains within the limits of the chocolate-coloured spots but under wet conditions the lesions expands aggressively. Alternating wet and dry conditions may lead to spots with a series of concentric growth rings, however during longer periods of wet weather the fungus thrives and the leaf is killed. After harvest the fungus remains in a semi-dormant state in plant debris until the next growing season. Infected seed may be stored with healthy seed and infect a new crop.
Vicia faba
This article refers to the Broad Bean plant. For Broadbean the company, see Broadbean, Inc.Vicia faba, the Broad Bean, Fava Bean, Field Bean, Bell Bean or Tic Bean, is a species of bean native to north Africa and southwest Asia, and extensively cultivated elsewhere. A variety is provisionally...
.
Symptoms
Chocolate spot disease caused by Botrytis fabae manifests itself as small red-brown spots on leavesLeaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
, stems
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
and flowers
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
of broad bean plants. These enlarge and develop a grey, dead centre with a reddish-brown margin. Spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s form on the dead tissue and spread the infection to other plants. In severe infections leaves and flowers may fall and badly affected stems may keel over.
Life cycle
The pathogen survives as sclerotiaSclerotium
A sclerotium is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot, sclerotia become detached and remain dormant until a favorable opportunity for growth. Other fungi that produce...
in the soil or on crop stubble and residues. It can also be introduced by the use of infected seed. The sclerotia germinate and condiophores are formed, the conidia (asexual spores) are dispersed by air currents and deposited by rain on susceptible young plants. When the conidia germinate
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
, small lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s are formed on previously healthy leaves. As the crop grows and within four or five days of infection, conidiophores are produced and secondary inoculum is produced. The conidia are liberated from dead or dying leaves and flowers, usually those that have fallen to the ground, and are spread to other plants in the vicinity by wind and splashes of water. This secondary spread of infection proceeds most rapidly under cool, humid conditions, the optimum conditions being a temperature between 15°C and 22°C and a relative humidity of at least 90%. Under dry conditions the pathogen remains within the limits of the chocolate-coloured spots but under wet conditions the lesions expands aggressively. Alternating wet and dry conditions may lead to spots with a series of concentric growth rings, however during longer periods of wet weather the fungus thrives and the leaf is killed. After harvest the fungus remains in a semi-dormant state in plant debris until the next growing season. Infected seed may be stored with healthy seed and infect a new crop.