Morphological and pathogenic variability among isolates of Bipolaris maydis causing Maydis leaf blight of maize.

摘要

The maydis leaf blight of maize caused by Bipolaris maydis was observed in six districts of southern Rajasthan Udaipur, Dungarpur, Banswara, Bhilwara, Chittorgarh and Kota. The disease was moderate to severe with severity score of 3.5 to 4.5 (on a 1-5 scale?) on maize hybrid HKI-141, inbred EI-586-X-38 and even on the local land races of maize grown in the farmers' fields. Eight isolates recovered from diseased samples exhibited variations in symptoms, lesion size and morphological characters. Isolate Bm-04 (Udaipur) produced maximum number of conidia 23.2x104 conidia/mm2 on PDA with maximum mean length of conidia 68.0 (45.1-75.4) urn and mean number of septa 8.5 per conidium. Pathogenic variability among the isolates studied by inoculating pot-grown plants of 18 maize germplasm lines showed significant variations in the latent period and disease severity. Udaipur isolate (Bm-04) was found most virulent with shortest latent period of 32.7 h with maximum mean disease score (3.83) across the maize germplasm lines. The differences in the latent period and mean disease score were statistically significant (P<=0.05) for the host lines, isolates and also for the host line x isolates interactions.