Seed Health Management for Better Productivity - Govind Ballabh ...

(Seed Health Management for Better Productivity)due to combination of its competitive saprophytic ability and high pathogenic potential that makesH. sasakii a persistent and destructive plant pathogen.(Saxena, 1997).Economic lossesThe disease was earlier reported as a minor disease on maize (Payak and Renfro 1966).The importance of the disease was only realized in early 1970s when an epidemic occurred inwarm and humid foot hill areas, in the Mandi district of Himachal Pradesh. The disease results inthe direct loss exhibiting premature death, stalk breakage and ear rot. Losses to the extent of 11-40 per cent were reported while evaluating 10 different varieties of maize.Losses in grain yield showed a high positive correlation with premature death of plants anddisease index that caused drastic reduction in grain yield to the tune of 97 per cent. A directcorrelation with other yield parameters exibited.in a yield loss of 5 to 97.4 per cent at diseasescore levels ranging from 3.0 to 5.0.Host RangeThe pathogen has wide host range and infects plant belonging to over 32 families in 188genera. H. sasakii infects by artificial inoculations a number of crop plants belonging to familiesGraminae, Papilionacae and Solanaceae : Paspalum scrobiculatum, Pannisetum purpureem,Setaria italica, Panicum miliaceum, Coix lachryma –jobi, Echnochola fromentacea, Pennisetumamericanum, Zea maxicana Zea mays, Oryza sativa, Saccharum officinarum Sorghum bicolor,Arachis hypogea, Glycine max, Pisum sativum, Vigna radiata and Lycopersicum esculentum. Riceand maize isolates are, however, indistinguishable on the basis of cross inoculation tests, hostrange, virulence, number of nuclei per hyphal cell, and other morphological characters includingpathogenicity. Comparison studies of rice maize, sugarcane and sorghum isolates revealed thatmaize and rice are similar than those isolates of sugarcane and sorghum.SymptomsThe symptoms of the Banded leaf & sheath blight are observed on all aerial parts of themaize plant except tassel. The disease manifests itself on leaf, leaf sheaths, stalks and ears asleaf & sheath blight, stalk lesions or rind spotting and stalk breakage, clumping and cracking ofstyles (silk fibre), horse-shoe shaped lesions with banding of caryopses, ear rots, etc. Undernatural conditions, disease appears at pre- flowering stage on 30 to 40 day-old plants but infectioncan also occur on young plants which may subsequently result in severe blighting and death ofapical region of growing plants.On LeavesUnder natural conditions, dropping blades especially the distal halves of leaves proximateto soil surface are affected. Infection spreads from leaf shealths to the basal portion of leaves.Lesions appear as in irregular patches, similar in colour but larger in size and spread more rapidlythan on leaf sheath, covering greater areas with alternating dark bands.On Leaf SheathsThe symptoms are more common on sheaths than on leaves. The disease appears onbasal leaf sheaths as water soaked, straw colored, irregular to roundish spots on both the- 129 -