On leaves of Erucasativa forming circular, zonate, light brown to grayish or dark brown spots up to 12 mm. diam. then coalescing; on the mid ribs of the leaves the spots are oblong or linear and sunken (Figure 2(A)). Conidiophores arising in groups of 2 - 10 or more from the hyphae, emerging through stomata, usually simple, erect or ascending, straight or flexuous, frequently geniculate, more or less cylindrical but often slightly swollen at the base, septate, mid-pale grayish olive, smooth, up to 170 µ long, 6 - 11 µ thick, bearing one to several small but distinct conidial scars (Figure 2(B)). Conidia solitary or occasionally in chains of up to 4, acropleurogenous arising through small pores in the conidiophores wall, straight or slightly curved, obclavate, rostrate, with 6 - 19 (usually 11 - 15) transverse and 0 - 8 longitudinal or oblique septa, pale or very pale olive or grayish olive, smooth or, infrequently, very inconspicuously warted, 75 - 350 µ long and usually 20 - 30 µ (sometimes up to 40 µ) thick in the broadest part, the beak about 1/3 to 1/2 the length of the conidium and 5 - 9 µ thick (Figure 2(B)).

The first symptoms of brown spot disease are small, circular, dark-brown lesions on the lower leaves. The lesions enlarge as the leaves mature and are surrounded by an irregular, yellow halo. The halo is caused by the secretion of toxins. Often there are numerous lesions, about 25 mm in diameter, which may coalesce and affect more than 80% of the leaf area. Large infected leaves senesce prematurely and the affected part of a leaf may be yellow when the rest is dark green. A uniform infection, covering up to about 10% of leaf area (Figure 3(A)).

Conidiophores arising singly or in groups, erect or ascending, simple or loosely branched, straight or flexuous, cylindrical, septate, rather pale olivaceous brown, up to 80 µ long, 3 - 5 µ thick, with 1 or several conidial scars (Figure 3(B)). Conidia sometimes solitary but usually in chains, boclavate, rostrate, pale to mid pale brown, smooth or verruculose, overall length 35 - 110 (69) µ, body of conidium 11 - 21 (14) µ thick in the broadest part, tapering gradually into the pale brown beak which is usually 1/3 to 1/2 the total length, 2 - 5 µ thick and often slightly swollen at the tip; there are 3 - 7, usually 5 - 6 transverse septa and 1 to several longitudinal or oblique septa (Figure 3(B)).

The symptoms recorded on Ficus carica leaves were small, circular, brown necrotic spots all over the foliage. The spots gradually enlarged in size and later became irregular in shape or remained circular with concentric rings or zones. In the later stage of infection, these spots coalesce causing blighting of leaves resulting in withering, extensive drying and shedding of leaves. The spots were initially light brown and later turned dark brown (Figure 4(A)).

Conidiophres solitary or in groups, simple or branched, straight or flexuous, more or less cylindrical, septate, pale or mid pale brown, smooth, with 1 or several conidial scars, up to 115 µ long, 4 - 6 µ thick (Figure 4(B)). Conidia solitary or in short chains, straight or curved, obclavate or with the body of the conidium ellipsoidal tapering gradually to the beak which is up to half the length of the conidium, usually shorter, sometimes tapered to a point but more frequently swollen at the apex where there may be several scars, pale to mid clear golden brown, usually smooth, sometimes minutely verruculose, generally with 4-7 transverse and several longitudinal or oblique septa, slightly or not constricted at the septa, overall length 22 - 95 (54) µ, 8 - 19 (13.8) µ thick in the broadest part; beak 2 - 4 µ thick, swollen apex 4 - 5 µ wide (Figure 4(B)).

In natural field infections it was observed that elongated necrotic lesions with dark brown margins develop progressively from lower to upper leaves. A yellow halo was sometimes seen around the lesions. Sometimes the margin of top leaves became brittle when dried and the tissue tore (Figure 5(A)).

Conidiophores often emerging through stomata in fascicles, simple or branched, straw colored, up to 100 µ long, 5 - 9 µ thick (Figure 5(B)). Conidia solitary or in chains of 2 - 3, broadly fusiform to obclavate, rostrate, pale to mid pale golden brown, smooth or occasionally minutely verruculose, 50 - 170 µ long, 12 - 35 µ thick; body with 3 - 10 transverse and several longitudinal or oblique septa; beak much shorter than the body, 4 - 6 µ thick along of its length but often swollen to 7 - 8 µ at the apex (Figure 5(B)).

Infection is first evident as small, oval, discoloured lesions irregularly scattered on the leaves. As the lesions enlarge they become dark brown to grey and irregular in shape. Some are surrounded by a bright-yellow marginal zone. As the disease progresses, several lesions coalesce to cover large areas, resulting in the death of the entire leaf (Figure 6(A)).

Conidiophores arising singly or in small groups, simple or branched, straight or flexuous, sometimes geniculate, pale to mid golden brown, smooth, up to 80 µ long, 3 - 6 µ thick, with 1 or several conidial scars (Figure 6(B)). Conidia formed in long, often branched chains, conical, obpyriform or obclavate, tapering gradually to a beak which is up to half the total length of the conidium and often swollen at its tip, pale to mid golden brown, distinctly verrucose and rather thick-walled, with up to 8 transverse septa usually close together and several longitudinal or oblique septa, overall length 20 - 70 (50) µ, 9 - 18 (14) µ thick in the broadest part; 3 - 5 µ wide (Figure 6(B)).

Conidial and conidiophores measurements in (Table 1) showed clear differences either in conidial or conidiophores measurements among tested species. Conidiophores of A. brassicae showed greater length and thickness (150 µ, 8 µ) compared to other species, while A. Pleospora infectoria showed the least length and thickness (71 µ, 4 µ). This trend changed in conidial measurements in which A. triticicola takes the first place in conidial length and thickness, and septal features, while A. Pleospora infectoria takes the last place. A. brassicae showed greater beak length and thickness followed by Alternaria longipes, while Alternaria triticicola had the least beak

length. All these measurements were close to a large extent with that recorded by [14] [15] , which refer to the belief that the diversity of spatial and climatic conditions do not play a significant role in the difference among conidial patterns.

There are more than 300 species of Alternaria that can be found in most situations in the environment. Some species are plant pathogens that, collectively, cause a range of diseases with economic impact on a large variety of important agronomic host plants including, ornamentals, fruit, vegetable and other crops. Leaf spots caused by Alternaria rarely kill plants but they can reduce their aesthetic quality and commercial value. The necrotrophic nature of the Alternaria species leads to extensive damage of the plant and harvest product [20] [21] .

The main economic impacts result from the effect on germination and the subsequent seedling blight. Seed with reduced germination due to infection may not be saleable as certified [22] . Ref. [23] noted that Alternaria species can pose a threat to the production of food items such as young seedlings of Chinese radish (Raphanus sativus var. hortensis) which is a popular food garnish in Japan. Likewise, in the USA, Alternaria spot on the edible leaves, heads and other parts of vegetables can make them unsaleable [24] . The metabolites from plant pathogenic Alternaria usually toxic to plants and are called phytotoxins. They were further divided into host- specific and host non-specific toxins [25] . The Alternaria specific toxins cause necrosis on leaves of susceptible cultivars at concentrations as low as 10⁻⁸ to 10⁻⁹ M and no necrosis on leaves of resistant cultivars even at higher concentrations [26] .

Alternaria species also produce types of toxins that are non-host specific. In addition to AB-toxin, other toxic substances including desipeptides and fucicoccin-like compounds are also being produced by different pathotypes of Alternaria [27] [28] .