genotypes collected in Kamataka viz., Bidar local, Chitapur local, Kandkur local, Karmoli local, Muddebihal local, Houuntagi local etc., were also reported to be ...
Agric. Rev., 28 (3) : 197-206, 2007
PRESENT STATUS AND FUTURE RESEARCH NEEDS ON THE MANAGEMENT OF CHARCOAL ROT OF SORGHUM Shamarao Jahagirdar All India Co-ordinated Sorghum Improvement, Regional Agricultural Research Station, Bijapur-586101, India
ABSTRACT Charcoal rot of sorghum is most catastrophic disease in rabi. In this paper the aspects on economic importance, epidemiology, variability of the pathogen, disease management as holistic approach and future thrust areas in the management of charcoal rot of rabi sorghum in a total approach are covered.
The chief cereals grown for both grain and fodder in India are sorghum, wheat, rice and maize. These are grown in rainy and winter seasons and also under rain fed condition. They are subjected to different ecological conditions as well as various group of soil borne plant pathogens and their pressures. Among these root and stalk diseases are economically important in dry land ecosystem. Although, these groups of diseases are not new in the present juncture, but their intensity is very high as compared to late 1950. The possible reasons attributed to the present state of affairs is the more exertion of plants to give more sink i.e., grain yield, due to excessive fertilizers particularly N fertilizers without much FYM added, high management and use of susceptible genotypes. In addition to this, harsh environment (both temperature and soil moisture) might have aggravated the situation by pre-disposing the plants to pathogens through root senescence or pith senescence. Dodd (1978) opined that sugars would be reduced due to photosynthetic stress and translocation at grain filling stage ultimately leading to root and stalk tissues senescence and finally succumbing to pathogens present in the soil.
effective control measures except host plant resistance are available at present, there is a good scope of IDM of these stalk rots using tolerant/ resistant varieties + Bioagent + organic matter either FYM or plant debris. Sorghum is the most staple food crop of several countries in tropical, subtropical and semi tropical parts of the world. In India, the major states growing sorghum are Maharastra, Kamataka, Andra Pradesh, Madhya Pradesh, Tamil Nadu and Rajasthan. Although, the area under Rabi sorghum is almost stable during last several years, the yield levels fluctuate substantially due to biotic and abiotic stresses. Among the biotic stress, diseases viz., Downy mildew and grain molds in kharif and stalk rots in Rabi take heavy toll. The pathogen and Economic importance:
Root and stalk diseases of sorghum are caused by several soil borne pathogens appearing both in kharif and rabi seasons. The major pathogens in their predominance of association in India are Macrophomina phaseolina, Fusarium moniliforme, Fusarium spp” Colletotrichum graminicola and Erwinia carotovora. The diseases caused by these organisms are usually referred as charcoal rot, Among cereals, stalk rot of sorghum stalk rot, root rot, red rot, etc., depending upon and maize has attained serious status and the pathogen involved and symptoms presently cultivated genotypes are quite produced. susceptible resulting in reduced grain yield and Among these, Macrophomina also fodder quality and quantity. Although no phaseolin a causing charcoal rot is predominant
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TABLE 1: Lodging and grain yield of charcoal rot infected CSH 6 sorghum under four stress treatments at four locations. Moisture stress treatment Irri2:ation to Grain maturity 50% anthesis Boot swollen Ligulevisible
ICRlSAT Lodg % Yield
DHARWAD Lodg% Yield
NANDIYAL Lodg% Yield
SUDAN Lodg% Yield
8 42 46 55
7 86 100 100
1 2 36 47
3 5 56 73
2.2 2.2 1.8 1.6
3.3 2.5 2.1 1.7
3.0 2.0 1.7 1.1
2.1 1.9 1.9 1.6
Yd=kg/m
in rabi season and is most widely distributed causing major losses in grain yield and therefore has caught the attention of several Pathologists both in India and abroad. Almost all the hybrids/ varieties cultivated in different parts of India, are susceptible to the disease. Loss in grain yield is mostly due to reduction in size of grain. It has been estimated to reduce the yield by 15 to 55% (Anahosur and Patil, 1983), The loss in yield in kharif ranges from 11.8 to 48.7%, whereas in rabi it ranges from 18.5 to 63.2%. Similarly, Mughogho and Pande (1983) also reported loss ranging from 23-64%, There was close correlation between lodging percent and yield loss in most of the genotypes tested. Path coefficient analysis revealed that percent lodging of plants had strong and positive association with loss in seed weight (Anahosur et.al, 1983).
Considerable information has been generated on the possibility of existence of pathogenic strains within M phaseolin a infecting different crops. This pathogen has been reported to cause diseases in more than 400 plant species. Most of the researchers have isolated from different hosts and by cross inoculation studies have established that there is considerable variation in the pathogenicity of isolates from different crops. The recent studies by Subramaniam and Anahosur (1995) revealed that an isolate from oil palm was most virulent as compared to other isolates. Jahagirdar et al., (2000) reported existence of physiologic races in M.phaseolina and reported that Solapur isolate is more virulent than Bijapur and Dharwad isolates.
The disease becomes severe under moisture stress situation associated with high temperature and senescence. It has been shown that there is a definite relation between sink source and charcoal rot severity. The plants become susceptible to diseases at post flowering to grain filling stage when the food reserves are translocated from stem to ears and food supply to roots is reduced.
Several workers have studied relation of the disease with fertilizer application. Anahosur et.al., (1983) and Mote and Ramesh (1980) reported that higher application of N predisposes the plants and disease severity will be more. It is reported that the lesion length in the stem increases with increase in the nitrogen fertilization. Other agronomic practices like delayed sowing in kharif(rainy season) (Anahosur and Patil, 1983), higher plant density (Patil et.al., 1982; Mughogho and Pande, 1983) favored this disease. Stress caused by severe leaf diseases also has been observed to favour the disease.
Under experimental conditions 100 % lodging and grain losses of 23-64 % in CSH 6 hybrids at 3 locations in India and 1 in Sudan were observed (Mughogho and Pande, 1983) (Table,1).
Pre-disposing factors influencing the disease.
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TABLE 2: Correlation coefficients among parameters of charcoal rot disease scores under depleting soil moisture condition at four locations (Pattancheru, Dharwad, Nandyal and Madhira). Disease parameter inflorescence. Lodging % Soft Stalk Mean no. of nodes crossed Mean score for root infection
Lodging %
Soft Stalk %
0.96
Mean no. of nodes
0.88 0.88
Although it may be possible to manage the diseases by eliminating the moisture stress at post flowering stage by providing irrigation and also by improving the moisture holding capacity of soils by application of high levels of organic matter, it is not practical as the crop is cultivated mainly under rainfed situation where there are no irrigation facilities and cost of inputs can not be increased since it works out uneconomical. Therefore the only way to combat the disease is by using resistant genotypes. Charcoal rot of sorghum caused by the fungus M.phase is a stalk rot of great destructive potential in most sorghum growing areas. Drought stress is the primary factor that predisposes sorghum to charcoal rot. A most reliable, efficient and epidemiologically sound resistance screening technique for charcoal rot is yet to be developed. Several anatomical and physiological plant characters have been associated with resistance to charcoal rot and suggested as selection criteria in resistance to screening programs. The most promising plant character that is positively correlated with charcoal rot resistance, which is used as a selection criterion, is non-senescence. In India also, it was found that positive and significant correlation between charcoal rot resistance and plant nonsenescence has existed. However, multilocation testing for stability of non- senescence character showed that lines non senescent at one location were not necessarily non-senescent at another
Mean score for root
0.57 0.52 0.47
Leaf and plant death
0.65 0.60 0.52 0.92
location this would be expected from variations in pathogen inoculum density and in levels of drought stress to which plants are subjected duringevaluationatdifferentlocations.Stability of non- senescence would most probably depend on the level of drought stress. Up to a specific level of stress, a genotype would show stability in non -senescence at several locations, but beyond that it may not. Further research is needed to evaluate this. Breeding approach: Three steps are required to develop a disease resistant hybrid include i) finding a source of resistance with a usable level of heredity. ii) Combining this resistance with other required crop traits and iii) Isolating parental lines that in hybrid combinations maintain an acceptable level of resistance without sacrificing yield. The disproportionate number of resistance genes to yield, latter sometimes estimated at nearly 5000,suggests an applied breeding approach to isolate a genetic source ofresistance. Plant characters associated with resistance: The plant characters, most promising to be positively correlated with charcoal rot resistance is non-senescence, which is increasingly being used as selection criterion. Rosenow (1980) reported significant correlations betwe.en nonsenescence, lodging resistance and charcoal rot resistance in Texas, USA. Pande and Karunakar (1992) have tested a set of 47 lines at four
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locations in India (Pattancheru, Dharwad, Nandyal and Bijapur). Four lines from Australia (Q101, Q 102, Q 103, and Q 104) retained 963 % green leaf area and were tree from root and stalk rot. Rosenow, (1980) identified 13 nonsenescence lines as good sources of resistance to charcoal rot. But, these lines were not stable in different countries where charcoal rot is a problem.
associated with senescence of plant tissues and lack of non-structural carbohydrates in the senescing tissue. Further more, this type of tissue in maize has shown to produce less DIMBOA, one of the metabolites involved in resistance to microorganisms, apparently accounting for the ability of weak pathogens to invade the complex inheritance patterns linked to environmental and physiological interactions in plants. These interactions are explained by photosynthetic-stress translocation balance concept of predisposition to root and stalk rots (Dodd, 1977). i)Water deficits: Charcoal rot of sorghum most commonly associated with water deficits water stresses occurring after flowering increase charcoal rot up to 90% (Edmunds, 1964). Odvody and Dunkle (1979) showed that Mphaseotina only penetrated host cells application of stress. Predisposition of plants by effect of water deficit on photosynthesis’s probably leads to any of the maturity related stalk rots. ii) Leaf destruction: Any reduction in actively photosynthesizing leaf tissue reduces the amount of carbohydrates available to the plant for cell maintenance and storage in grains. Artificial removal of distal halves of leaves increases the rate of cell death in sorghum (Papellis and Katsanos, 1966) and it was also shown in maize (Papellis, 1963). Reduction in productive leaf area by foliar pathogens and insects predispose the plants for root and stalk rot diseases. iii) Light Reduction: A prolonged period of cloud cover creates photosynthetic stress, pre disposing sorghum to root rot. Light reduction also occurs through plant competition from narrow rows, or crowded adjacent plants within a row.
Genetics of charcoal rot resistance: Though resistance to this disease has been indicated to be of qualitative nature (Rosenow and Frederiksen, 1982), majority of the workers have reported poly genic nature of resistance. The genetics of charcoal rot resistance in sorghum as indicated by non-lodging of inoculated plants was investigated through combining ability analysis ( Gururaja Rao et at., 1993). Both general and specific combining ability variances were highly significant suggesting the importance of additive and nonadditive gene action in the genetic control of this trait. Dominant genes were most frequent than recessive genes as indicated by the predominance of additive gene action and moderate heritability. The results of the study indicated that charcoal rot inherited as recessive character and is controlled by a set of five pairs of gene exhibiting trigenic ratio depending on the parents involved in the cross. Patil et at (1982) have studied the role of sugars and phenols in charcoal rot resistance of sorghum. High level of sugar and phenols in stalk of the sorghum genotypes may be attributed to the resistance mechanism against charcoal rot and may be taken up as supporting criteria in identifying sources of resistance in addition to IV ) Mineral deficiencies : Addition of other character. potassium-to-potassium deficient soils has Physiological basis of disease resistance in decreased stalk rot and lodging in sorghum sorghum: (Murphy, 1975). Potassium is known to l.Photosynthetic stresses influencing stalk involved with senescence and apparently acts rots : The occurrence of stalk rots is generally on carbohydrates production.
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are well known ant fungal, antibacterial and antiviral compounds. They inhibit fungal spore germination, mycelial growth, fungal enzymes and toxin produced by pathogens. Some of the phenolics will detoxify toxins produced by pathogen. Host enzymes like poly phenol oxidase and peroxidase oxidize phenolics to quinines and the quinines are more fungi toxic than phenolics. Hence, sometimes the increased activity of these enzymes may be responsible for disease resistance. Anahosur et.al.,(1983) reported that high level of sugar and phenols in sorghum root and stalk have close relationship with resistance mechanism. ii) Phytoalexins: Phytoalexins are low molecular weight, antimicrobial compounds that are synthesized by and accumulated in plants after exposure to microorganisms. Phytoalexins are mostly isoflavonoids, terpenoids and poly acetylene compounds and synthesized de novo on infection by the pathogens. Phenylalanine and acetic acid may be involved in the biosynthesis of Phytoalexins and Phenylalanine ammonialyse (PAL) has been considered to be the key enzyme. iii) Lignin: Lignins are mostly synthesized through shikimic acids pathway. Phenylalanine and cinnamic acid are the important precursors. Lignin may act as physical barrier to the pathogens. Lignification occurs at the site of fungal penetration and this is resistant to callulase and macerating enzymes of the pathogen.iv) Callose: It is the substance found in the sieve tubes and may prevent the leakage of sieve tube sap or water in the cell walls. Penetration of incompatible pathogens into the host tissues results in the production of papillae and the papillae may mostly contain callose. v) Sugars: Sugars are precursors of synthesis of phenolics, Phytoalexins, lignin and callose. Hence, they may play an important role in the defense mechanisms of plants and have been i) Phenols: Several kinds of phenolics classified the diseases into high sugar diseases compounds occur naturally in plants. Phenolics and low sugar diseases. Sugar concentration
Translocation balance and predisposition to stalk rots: It is reported that cloudy weather during this time could have great effect on establishing kernel number and size of the grain sink. Filling of the grain head is involved with predisposition to root and stalk rot development, and the factors influencing the grain size needs to be considered. The predisposition of sorghum plants to root and stalk rots is influenced by pre flowering and post flowering environments. Genotypes will respond to these environments in different ways. Some varieties will react to excellent pre flowering environment by establishing an exceptional grain sink that can be supplied only by excellent post flowering conditions. Producing adequate carbohydrate to maintain the roots and still meets the demand of grain sink such a variety will exhibit outstanding yields in this situation. Genotypes vary in their ability to cope with low soil water potential with differences in root size, leaf structure and cellular physiology. We need to identify these differences and find practical means of screening for genotypes that are less affected by drought stress. The combination of high yielding potential and resistance to root and stalk rots of sorghum will come from genotypes that are most energy efficient. Theses genotypes will combine higher leaf area per plant, complete leaf canopy, efficient use of maintenance energy, large grain sinks, and efficient root systems. This obviously multi genically inherited system will be difficult to select, but probably will be constructed over many years through cooperative contributions from many disciplines. Defence mechanisms influencing stalk and root rots: In addition to photosynthesis and translocation balance several other defense mechanisms are operating in plant system are discussed below.
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may affect the toxins producing ability of the pathogen. vi) Aminoacids: Amino acids are the comer stones for synthesis of proteins and some of them are essential for the synthesis of phenolics, Phytoalexins and lignin. Phenylalanine, tyrosine and tryptophan are important precursors of defense chemicals. Research work on these biochemical factors governing disease resistance would definitely help in selection breeding programme. Management of charcoal rot of sorghum. Research on identifying and developing resistant genotypes is in progress in many parts of the world. Inheritance of resistance to this disease has been worked in Rabi genotypes ( Gururaj Rao et.al., 1993). The study indicated dominance of susceptibility which is controlled by a set of 5 pairs of genes with 2 pairs of genes common to the parents of the two crosses thus exhibiting separate trigenic ratios depending on the parents involved in the cross (Guraraja Rao et.al., 1993). For developing resistant genotypes two important pre requisites are source of resistance and proper screening method. Although tooth pick method (Hsi, 1961) and stem tape inoculative method can be used successfully, the most practical and highly dependable method is sick plot method using susceptible check variety Spy -86 or hybrid like CSH-6. However, of late it was found that use of sick plot method has not served the purpose of uniform distribution(inoculum density) of the inoculum over entire sick plot. Hence, now along with sick plot technique for advanced screening material f resistant nursery material tooth pick technique was also followed, not to lose data generation on this valued material in coordinated programme. The results of screening have shown several resistant genotypes among which E-361 has been found to be stable. Several local genotypes collected in Kamataka viz., Bidar local, Chitapur local, Kandkur local, Karmoli
local, Muddebihal local, Houuntagi local etc., were also reported to be resistant for charcoal rot ( Jahagirdar et aI., 2002). Jahagirdar et al (2000) reported IUS line promising for charcoal rot resistnce in sorghum. Breeding for resistance to charcoal rot has been in progress m Maharastra and Karnataka. From UAS Dharwad center DSV 4 and DSV 5 were released as charcoal rot resistant cultivars during 1995-96. In breeding fot resistance programme at Bijapur center four crosses were made I) 9-13X RSLG 262 II) BRJ 356X E 36-1 III) GRS 1XE 36-1 IV) 9-13X E 36-1. The material generated is now in F2 stage. The major emphasis in selection of above said crosses was to breed for charcoal rot resistance along with development of genotypes for resistance to terminal stress. Another set of material was developed back crossing with M 35-1 with Fl of above said crosses. A few workers have attempted biological control of this disease. Although the bioagents viz., T. viride and other fungal species have been found effective in laboratory and pot conditions, their success rate was limited under field conditions with susceptible genotype. However, under background of moderately resistant genotypes like 9-13 and GRS 1, seed treatment with Trichoderma was found effective in bringing down incidence level further with application of recommended dosage of FYM at the time of sowing. (J ahagirdar et at., 2001). However. there is a need for estimation of population dynamics of both pathogen and introduced bioagent. It was also suggested to use native bioagent than commercial bioagents. Priority Research Problems: l. Determine the inheritance and heritability of resistance. 2.Identify the immune genera and new sources of resistance.3.Understand host, parasite, and environment interactions for various geographical locations. 4.Identify plant traits conferring the resistance.
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i) Sorghum stalk rot: Application of yielding susceptible lines assembling biotechnology combinations of these desirable genes. MIGHT BIOTECHNOLOGY SPEED UP Although much progress has been made for SORGHUM IMPROVEMENT FOR STALK charcoal rot resistance by using the nonsenesence trait (Rosenow, 1984;Pande ROT RESISTANCE? and Kamukar,1992; Kamukar et al.,1993). In stalk rot research little is known New information indicates that additional about the host pathogen interaction. criteria for resistance to charcoal rot should However, developing cultivars screened for be used (Tenkouano et al., 1992). other characters than resistance to pathogen Mechanisms of resistance to M.phase are still per se made much progress. Three main known. Although research on those traits is characters have been mentioned in literature being conducted (Frederiksen, 1993). The w.r.t. Stalk rot resistance are lodging resistance, non-senescence, and green bug relationship of nonstructural carbohydrate resistance (Mughogho and Pande, 1984; (NSC) partitioning and charcoal rot Rosenow, 1984; Giorda et at., 1994). The resistance in sorghum was investigated by first two may considered as phenotypic Tenkouano et.al., (1992). These authors expressions of pots flowering drought suggested that high yielding cultivars tolerance. Drought tolerance is a complex resistant to M phaseolina could be developed trait influenced by the interactive effect of since the developing grain could not be many genes. Ejeta (1993) has reported that identified as the cause or the beneficiary of several” QUANTITATIVE TRAIT LOCI” stem NSC exhaustion. So far, most of the (QTL) associated with pre and post flowering unaffected hybrids tolerant to charcoal rot stress tolerance. Since complex traits are yield nearly as well as the unaffected involved, it might be possible to discern the susceptible ones. These observations are genetic basis of the resistance quickly and encouraging for improving sorghum for more precisely with RFLPS, RAPD etc. thistrait. Tolerance to moisture stress under post Different biotechnological flowering drought conditions is manifested approaches are currently being used to detect by a stay green (non- senescence) variability among M. phaseolina isolates. phenotype. Most of the genotypes with Knowledge of pathogen variability would be enhanced drought tolerance often show useful in breeding programmes. Hence, there limited yield potential. is need for clustering of physiologic races Several reports have summarized of M. phaseolina isolated from different the application of different molecular geographical area and thus helping in markers to tag useful genes and to determine cultivar selection for divergent agro climatic the gene action ( Jones and Canada, 1994). areas of Rabi sorghum. Plant response to Based on these observations ,efforts should concentrate on identifying the QTL loci disease by induction; of a large array of host associated with specific stalk rot responses response genes and modification of the under uniform conditions for disease expression of these genes could lead to development. In this way, once traits (Post enhanced disease resistance. This approach flowering drought and macrophomina stalk has recently been investigated and might also rot resistance) are tagged, it might be constitute a strategy to improve resistance possible to use RFLP/RAPD to improve high to charcoal rot.
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TABLE 3: Reaction of different genotypes to isolates of Macrophomina phaseolina Isolate No. CSV 8R CSV 14R SWATHI M 35-1 CSH 15R CSH 13R RS29 E 36-1 9-13 GRS1 C.D. (0.05) CV%
MLS
SOLAPUR MNC
BIJAPUR MLS(C MNC
DHARWAD MLS (CM) MNC
37.00 15.15 23.15 25.15 21.60 22.05 25.45 11.30 15.95 19.05 6.53 13.47
2.70 2.35 1.75 2.45 1.95 1.75 1.95 1.15 1.10 1.10 0.47 11.58
33.85 14.35 16.85 23.05 21.60 26.10 27.15 13.10 13.60 14.85 8.78 18.50
26.40 20.80 14.20 18.40 12.85 17.95 19.80 11.10 11.10 6.35 4.05 11.05
2.60 1.5 1.85 1.70 1.75 1.65 2.15 0.75 0.75 1.05 0.57 15.76
2.40 1.75 1.70 1.65 2.40 2.60 1.70 0.80 0.80 1.25 0.61 15.93
TABLE 4: Evaluation of bio control agents in the management of charcoal rot of sorghum. Treatment
Charcoal rot % 1998
1999
Lodging % due to CR Mean
1998
1999
Mean
21.1(27.3) 44.3(41.7)
20.4(26.8) 39.7(39.1)
20.7(27.1) 42.0(40.4)
8.1(16.5) 19.8(26.4)
9.1(17.5) 17.5(24.7)
8.6(17.0) 18.7(25.6)
5.3(13.3) 18.7(25.6)
4.8(12.6) 19.8(26.4)
5.1(13.0) 19.2(25.9)
Variety M 35-1 BCA CONTROL
20.6(26.9)* 39.7(39.1)
16.9(25.7) 36.8(37.4)
18.7(26.5) 38.2(38.2) Variety GRS 1
BCA CONTROL
11.1(21.1)* 21.5(27.6)
10.8(19.2) 20.2(26.7)
11.8(20.1) 20.8(27.1) Variety 9-13
BCA CONTROL
10.4(18.8)* 20.3(26.7)
9.8(18.2) 21.1(27.5)
10.1(18.5) 20.8(27.1)
BCA: Trichoderma viride @ 4g/kg of seed.
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SUMMARY: Charcoal rot of sorghum is the number one disease in Rabi. The disease causes significant economic loss in yield both in terms of grain quality and quantity. Though, resistance sources available so far, have shown variable reaction pathogens. This suggests the existence of physiologic races in M phaseolina. Attempts should be made to tag the different
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genes associated with the resistance to sorghum stalk rot diseases and to use linked RFLP/ RAPD for instance, to pyramid these genes into a single line. Resistant gene combinations may contribute to the durability of resistance. Hence, there is need for understanding of these races and possible grouping them in to clusters. This will further help in development ofIDM package forthisdisease.
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Rosenow, D.T. (1980). Sorghum diseases world Review: Proc International Workshop on sorghum diseases, Sponsored Jointly By Texas A&M University (USA) and ICRISAT, Patancheru, AP.502 324,India, ICRISAT. Rosenow, D.T and Frederiksen.RA,(1982).Sorghum in eighties (ICRISAT Ed.), ICRISAT, Pattancheru, AP, India. Shamarao Jahagirdar. et al (2000). Plant Disease Res 15(2): 237-239. Shamarao Jahagirdar. et al (2001). Agic.Sci. Digest, 21(4): 235-237. Shamarao Jahagirdar. et al (2001). Agric Sci. Digest, 21(4): 238-240,0 Shamarao Jahagirdar. et al (2003). National Symposium on Plant Pathogens diversity in relation to plant health, held on Jan., 16-18,2003 at Osmania University, Hyderbad.135pp. Tenkouano,A,et al(1992). Sorghum Newsl 33:33
