Importance of Morphogenetic Assessment of Variability to Enhance Resistance to Banded Leaf and Sheal Blight of Maize
The unstable and ephemeral nature of resistance to banded leaf and sheath blight (BLSB) has led to considerable difficulty in the identification of stable resistant genotypes for resistance breeding. An understanding of variability in pathogen vis-a-vis its reaction to different genotypes, thus is imperative. Ten isolates of Rhizoctonia solanif, sp. sasakii from different locations in India were studied for morphological and sclerotial characters on PDA, and for their molecular diversity. Isolates from different locations could be grouped into two color classes namely butter yellow and brownish. The colony texture also formed two groups; one with profuse fluffy, cottony mycelial growth and the other possessed a compact and dense growth. Ultra-structure of sclerotia indicated surface pits in some isolates. All isolates were of multi-nucleate nature. Likewise, all the isolates belonged to AG-11A anastomosis group. Remarkable differences in reactions of 10 inbred lines to BLSB isolates were noticed. RAPD analysis using 60 primers resulted in 626 bands out of which 528 were highly polymorphic. Based on Jaccards similarity coefficient of polymorphic DNA of isolates, two distinct groups, one with Jorhat, Pusa, Murorissa, BBSROrissa and the other having Kamal, Delhi, Almora, Dhaulakuan, Ludhiana and Pantnagar were established. Phylogeny of the isolates based on rDNA and ITS 2 region sequence homology using partial sequencing of 350bp indicated almost total homology among isolates. Isolates exhibited high level sequence variation in the DNA ITS 2 region, but not in 5.8s rDNA coding sequence. The present study revealed a high degree of instability of disease manifestation of R. solani f. sp. sasakiiin different environmental regions. This gives us a pointer that for achieving practical levels of resistance, a protocol of screening germplasm using isolates with identical similarity indices, developing location-specific cultivars, and identifying across-group resistant genotypes for use in cyclical breeding procedures to develop broad- spectrum durable resistance, needs to be followed.
Maize Variabilit Banded leaf and sheath blight
P. Srinivas R. C. Sharma
Division of Plant Pathology, Rubber Research Institute of India, Kottayam-686009, Kerala, India Division of Plant Pathology, India Agricultural Research Institute, New Delhi-110012, India
国际会议
第九届亚洲玉米大会(the Ninth Asian Regional Maize Workshop)
北京
英文
120-124
2005-09-05（万方平台首次上网日期，不代表论文的发表时间）