Leaf blight of sunflower caused by Alternaria tenuissima and A. alternata in Beijing, China

Figures & data

Table 1. Geographic origins and number of Alternaria isolates obtained from infected sunflower leaves collected in Beijing, China.

Geographic origins of Beijing	Number of fields	Number of Alternaria isolates
		A. tenuissima	A. alternata
Yanqing District	36	119	19
Shunyi District	20	62	21 (1)
Tongzhou District	12	27	0
Daxing District	18	44	4 (1)
Mentougou District	5	14	3 (1)
Fangshan District	5	12 (2) ^a	1
Changping District	5	14	0
Pinggu District	21	41 (1)	6
Miyun District	25	32 (1)	6 (1)
Huairou District	11	26	1 (1)
Haidian District	6	18	4 (1)
Fengtai District	2	5	0
Chaoyang District	1	3	0
Total	170	417 (4)	65 (6)

^a Numbers in parentheses represent the numbers of corresponding Alternaria isolates used in pathogenicity and phylogenetic analyses.

Fig. 1 (Colour online) Symptoms of sunflower leaf blight and morphologies of the causal fungi, Alternaria tenuissima and A. alternata. (a), Necrotic flecks and chlorotic lesions on diseased sunflower leaves. (b, d, f), Colonies, sporulation patterns and conidia of the representative isolates of Alternaria tenuissima. (c, e, g), Colonies, sporulation patterns and conidia of the representative isolates of A. alternata. (h–j), Pathogenicity of the representative isolates of A. tenuissima on detached sunflower leaves. (k–m), Pathogenicity of the representative isolates of A. alternata on detached sunflower leaves.

Table 2. Disease incidence and disease index of four isolates of Alternaria tenuissima and six isolates of A. alternata on detached sunflower leaves.

Alternaria species	Disease incidence (%)	Disease index
A. tenuissima	100.0 (100.0 ± 0.0) ^a	33.3 (33.3 ± 0.0)
A. alternata	50.0–86.7 (67.4 ± 0.2)	16.7–28.9 (22.5 ± 5.2)

^a Values in parentheses are the mean value and standard deviation based on the data of each tested Alternaria isolate of the corresponding species. No significant differences were observed between A. tenuissima and A. alternata for disease incidence and disease index according to the least significant difference test (P < 0.05).

Fig. 2 Phylogenetic tree based on the partial coding sequences of histone 3 genes of four A. tenuissima isolates, six A. alternata isolates and three reference sequences retrieved from GenBank. The tree was constructed by neighbour-joining using the Kimura two-parameter distance method. Bootstrap values (in percentage) above 70 from 1000 pseudo-replicates are shown for major lineages within the tree. The marker denotes a measurement of relative phylogenetic distance. Alternaria infectoria was used as an outgroup.

Fig. 3 Phylogenetic tree based on the sequences of the ITS region of rDNA of four A. tenuissima isolates, six A. alternata isolates, and three reference sequences retrieved from GenBank. The tree was constructed by neighbour-joining using the Kimura two-parameter distance method. Bootstrap values (in percentage) above 70 from 1000 pseudo-replicates are shown for major lineages within the tree. The marker denotes a measurement of relative phylogenetic distance. Alternaria infectoria was used as an outgroup.