Pathology ABSTRACT INTRODUCTION

Transcription

1 Pathology RESEARCH ON GRASSY SHOOT DISEASE OF SUGARCANE IN MAHARASHTRA STATE G. K. Zende and N. B. Shaikh Sugarcane Research Station Padegaon, Maharashtra, India ABSTRACT Investigations were undertaken to study the various aspects of grassy shoot disease of sugarcane in Maharashtra State. The data collected over 1% decades revealed that the symptoms described as 2 diseases, grassy shoot and albino, are manifestations of one disease. The quality of seed material used for planting purposes is an important factor in determining incidence of the disease. The seed from prematurely sprouted canes and affected canes shows a very high incidence, particularly in the case of ratoon crops. The disease is mainly transmitted through infected seed material and through knives used for cutting the seed cane. The disease is completely arrested when the seed material is given hot water treatment at 50 C for 2 hr. Hot water treatment at temperatures lower than 50 C for up to 3 hr is not so effective in eliminating the disease. Heat treatments at 48 C for 4 hr, at 50 C for 2 hr and at 52 C for 1 hr are very similar in their effectiveness. The use of untreated, affected seed material for planting purposes results in losses in cane yields of 40 to 90%. Cane varieties differ considerably in their degree of susceptibility to grassy shoot and effectiveness of heat treatment in controlling the disease and increasing cane yields. INTRODUCTION A virus disease showing symptoms of stunting of sugarcane with chlorotic leaves was first recorded in Maharashtra State in 1955 (Arakeri and Patel 1955), although it was observed and collected as early as 1949 from the Maharashtra Sugar Mill near Belapur in Ahmednagar district (Chona 1958, Chona et al 1960). The disease has been observed and appears not only on the Co 419 variety but also on other promising varieties, such as Co 678, Co 775, Co 740, Co 1010, and Co 1001 (Albuquerque and Babriwala 1957, Kakde et al 1969). Rane and Dakshindas (1962) presented data to show clearly that the symptoms; of the two diseases, grassy shoot and the albino disease, are manifestations of the same disease. In 'Maharashtra State, the symptoms are not so freely encountered in the plant cane crop as in the affected ratoons. Potentially serious grassy shoot disclftse of the ratoon crop has been recognized as a specific disorder of the sugarcane variety Co 419 since Since then it has assumed epiphytotic form in such districts as Sangali, Satar, Poona, Ahmednagar, Nasik, Dhulai, Jalgaon, Aurangabad, Parbhani, Nanded, Bhir, Osmanabad and Akola and threatens the cultivation of this productive and 1015

2 1016 PATHOLOGY prized variety. At present, the disease is fairly widespread in areas like the Malegaon Sugar Factory near Baramati; Belapur Sugar Factory, Changdeo Sugar. Factory near Puntamba, Ravalgabn Sugar Factory and Walchandnagar Sugar i Factory. In most cases the incidence of the disease in the plant cane (Adsali I crop) is sporadic, but is mainly present in the ratoon crop which is severely,' affected. Neither a fungus nor a bacterium is to be associated with the abnormal- I~ ity. Albuquerque and Babriwala (1957) described the symptomatology and mode of transmission of the grassy shoot disease and summarized the control measures: roguing diseased stools; sterilization of knives in disinfectants; use of healthy, disease-free seed; and hot water treatment at 50 C for 2 hr. Gumaste et al (1955) also concluded that heat treatment at 50 C for 2 hr was effective in eradication of the disease. These authors, however, did not indicate the effect of hot water treatment on the germination nor on the behaviour of the resultant ratoons. In reality, the hot water treatment results in a considerable reduction in germination. Kakde et al (1969) who studied this aspect in great detail reported that the hot water treatment reduced the germination from a normal range of 70-85% to 30-40%. These authors mentioned the probable causes responsible for, the reduction in initial germination. Barve (1955) tried to control the disease by spraying with the trace elements boron, manganese, cobalt, copper and zinc but without success. Seed-borne diseases are responsible for considerable crop.losses and assume serious proportion with crops like sugarcane that are vegetatively propogated. The planting of disease-free seed material under sanitary field conditions therefore becomes an effective method of controlling such diseases (Srinivasan and Thuljaram Rao 1968, Kishan Singh 1967). Since 1955, intensive work has been done in Maharashtra State to control grassy shoot. The data thus collected at different centers, though not voluminous, throw light on the various aspects of the disease. The highlights of the data thus collected are presented in the following pages. MATERIALS AND METHODS Field experiments were laid out to get information on the possible influence of affected seed material on the incidence of the disease and on the germination of setts, the contribution made by knives used in cutting diseased canes in transmission of the disease, the influence of seed quality on incidence of the disease, effect of hot water treatment-of various durations and at different temperatures-on the incidence of the disease and on cane yields, and varietal differences in the degree of disease incidence. The work was carried out at two centers, the Main Sugarcane Research Station, Padegaon, and the Regional Sugarcane Research Station, Kolhapur, with varieties Co 419, Co 740, Co 775 Co 978, Co 853, Co 1098, Co 1284 and Co 678, either grown as an Adsali crop (18 months) or as a plant cane crop (12 months). Investigations were undertaken to' study in detail the symptoms exhibited by sugarcane from the grassy shoot disease and the albino disease and the mode of transmission of the virus.

3 G. K,. ZENDE, N. B. SHAIKH 1017 Data were also recorded on the incidence of the disease III varieties not under general cultivation. RESULTS AND DISCUSSION Influence of Grassy Shoot and Albino Diseased Seed Cane on Disease Incidence Data from studies on 3 varieties of cane are presented in Table 1. Shoots emerging from the affected setts had narrow leaves devoid of chlorophyll and were clustered together in the same clump. Thus the symptoms of grassy shoot and the albino disease occurred in the same affected clump. Neither the variety nor the period ofobservation resulted in much variation in the incidence of the disease after the germination of the buds. Table 1. Influence of grassy shoot and albino affected seed material on the incidence of these diseases after germination. Incidence of grassy shoot and albino after No. 40 weeks 44 weeks 50 weeks buds Grassy Grassy Grassy Seed source Variety germinated shoot Albino shoot Albino shoot Albino Grassy shoot Co affected seed Co II II Albino affected seed Co Based on these observations, Rane and Dakshindas (1962) concluded that the symptoms described for the 2 diseases are manifestations of 1 disease. They also suggested that the disease may be due to a mixture of 2 or more viruses, producing mixed symptoms. Influence of Seed Quality and Infected Cutting Knives on the Degree of Transmission Setts originating from prematurely sprouted plant cane invariably developed typical symptoms of grassy shoot, both in plant cane and ratoon crops. Furthermore, the planting of stalks from diseased clumps resulted in a.high incidence of the disease in plant cane and ratoon crops. On the other hand; planting material taken from a healthy stool in a ratoon crop affected by the disease produced.a low incidence of infection both in plant cane and ratoon crops. When healthy stalks were cut with a knife used previously in cuttingdiseased stalks and planted, 62% of the c;lumps in the resulting ratoon crop were diseased, indicating that grassy shoot dirt be transferred by the cutting knife. Similar observations have been recorded by Hughes and Steindl (1956) in Australia and by Chona et al (1960) in India. Effect of Duration and Temperature in Hot Water Treatment on Disease Incidence and Cane Yield The cost of treatment and the quantity of seed material thatcan be treated.

4 1018 PATHOLOGY with hot water within a stipulated period depends upon the duration of the heat treatment and the temperatures at which the seed is to be treated. For a study of the effects of these factors, field experiments were begun in 1963 and are still in progress. A portion of the data obtained is reported in Table 2. Table 2. Effect of time and temperature during hot water treatment on incidence of grassy shoot disease and yield of cane. Diseased seed, Healthyseed Duration Temperature Infection Yield Infection Yield (min) (C) Year (%) (tons/acre) (%) (tons/acre) Control , , The principal results can be summarized as follows: (a) 'there was drastic reduction in cane yield when diseased seed was planted without any heat treatment; (b) heat treatment at 48 C for 2 to 3 hr did not provide complete control of the disease and did not help much in increasing cane yields; (c) heat treatment at 48 C for 4 hr controlled incidence of infection but did not increase yields to that of healthy seed material; (d) heat treatment at 50 C for 1 hr did not provide adequate control of the disease; (e) heat treatment at 50 C for 2 hr controlled the disease but did not in au instances raise yields to the level obtained from healthy material; (f) heat treatment at 52 C for periods less than 1 hr did not give complete disease control; (g) heat treatment at 52 C for 1 hr eliminated symptoms of the disease and in most experiments resulted in yields comparable to those from healthy seed; (h) except when treated for 30 min or less, the heat treatment of diseased seed material caused marked reduction in germination. Losses in Cane Yield Due to the Disease The data collected at two centers with Co 419 as the test crop are reported in Table 3. It is seen that planting of -diseased material resulted in a high incidence of grassy shoot disease in the subsequent crop and a drastic reduction in yield of cane, the average reduction being about 44% at Kolhapur and 89% at Padegaon. Hot water treatment, therefore, appears to be a must for arresting these ill effects on cane yields. Varietal Differences in Disease Susceptibility' Experiments were conducted with the 3 varieties, Co 419, Co 740 and

5 .-; ~~~-' G. K. ZENDE, N. B~ SHAIKH 1019 Table 3. Losses in yield of cane due to grassy shoot disease at 2 centres with the Co 419 variety. Kolhapur Location Padegaon Quality of Incidence Yield Incidence Yield seed material (%) tons/acre % % tons/acre (%) Healthy Apparently healthy Diseased SE CD (5%) CD (1%) Co 775, using healthy seed without hot water treatment, healthy seed with hot water treatment, diseased seed without hot water treatment and diseased seed with hot water treatment. The results in terms of incidence of grassy shoot and yield in tons of cane/acre are presented in Table 4. Planting of diseased Table 4. Effect of grassy shoot on yields of the 3 varieties Co 419, Co 740 and Co 775. Co 419 Co 740 Co 775 Incidence Yield Incidence Yield Incidence Yield Treatments (%) (tons/acre) (%) (tons/acre) (%) (tons/acre) Healthy seed, untreated Healthy seed, hot water treated* I.l Diseased seed, untreated Diseased seed, hot water treated* * 1 hr at 52 C seed without hot water treatment resulted in severely reduced yields for all 3 varieties. However, Co 775, though not resistant, performed better than the other 2 varieties. Although hot water treatment of diseased seed eliminated all symptoms of the disease from the subsequent crop in Co 419, the yield was still considerably lower than that' from healthy seed given the hot water treatment. However, varieties Co 740 andpoj75 produced as high yields from diseased seed which received the hot water treatment as fromfhealthy seed also given the hot water treatment. Varietal Susceptibility to Grassy Shoot Disease In addition to the varieties included in experiments reported previously, other varieties have also been tested for their degree of susceptibility. Accord-

6 1020 PATHOLOGY ing to Albuquerque and Babriwala (1957), the following varieties are considered to be susceptible to grassy shoot disease: Co 419, Co 678, Co 787, Co 793, Co 800, Co 821, Co 876, Co 909, Co 911, Co 921, Co 949, Co 951, Co 953, Co 961, Co 981, Co 983, Co 987, Co 989, Co 995, Co 1001, Co 1002, Co 1003, Co 1004, Co 1005, Co 1006, Co 1007, Co 1008, Co 1009, and Co However, these varieties differ considerably in their degree of susceptibility. Symptoms of Grassy Shoot Disease The symptoms of grassy shoot disease as observed under field. conditions have been described by Albuquerque and Babriwala (1957) and also by Rane and Dakshindas (1962). According to these authors, the affected ratoon crop exhibits stunted growth and rarely does a normal stalk develop from an affected stool. The shoots resemble a tuft of grass and the leaves often appear as if scalded. Yellow striped leaves are very common. In a plant cane crop, premature sprouting of.the lateral buds and the formation of aerial roots take place when the canes are half grown and more frequently at the lower nodes. On cutting the canes from a diseased stool lengthwise, the nodal region of the lower 5 to 6 mature nodes exhibits an orange-yellow discoloration with minute reddish streaks more intensely marked on the lower portion of the woody tissue. The xylem vessels are clogged and the phloem is disintegrated. There is a proliferation of vegetative buds from the base of the cane giving rise to a crowded bunch of tillers with narrow leaves. In early stages, the leaves are devoid of chlorophyll and later show whitish streaks emerging from the base of the leaf to the tip along the mid rib. In advanced stages, the leaves become chlorotic. The buds of affected canes are usually scaly and abnormally elongated. ' REFERENCES Albuquerque, M. ]., and H. R. Arakeri The problem of diseases of sugarcane in Bombay State-i-Srd Bien. Conf. Sug. Res. and Dev. Workers in India: Albuquerque, M. ]., and G. T. Babriwala Some aspects on the symptomatology, transmission and control of the grassy shoot disease. D.S.T.A., 14th Conf.: Arakeri, H. R., and R. M. Patel Two new diseases of sugarcane in the Bombay State. Farmer, 7: Barve, D. D. 19'55. Ratoon stunting and treatment with trace elements. Proc. D.S.T.A., 12th Conv.: Chona, B. L Some diseases of sugarcane reported from India in recent years. Indian Phytopath., 11:1-9. Chona, B. L., S. P. Kapoor, P. M. Varma, and M. L. Seth.J960. Grassy shoot disease of sugarcane. Indian Phytopath, 13: Gumaste, J. A., B. N. Soman, and B. L. Patil Curative effects of different treatments on sugarcane setts from cane possibly affected by the presence of virus. Proc. D.S.T.A., 12th Conv.: Hughes, C. G., E. V. Abbott, and C. A. Wismer Sugarcane Diseases of the World. Elsevier Publishing Company, N. Y. Hughes, C. G., and D. R. Steindl Some further developments in the study of ratoon stunting disease in Queensland. Proc. ISSCT, 9: Kakde, J. R., N. B. Shaikh, and N. ]. Bendre Chlorotic diseases of sugarcane in Maharashtra. Proc. D.S.T.A., 23rd Conv.: Rane, M. S., and D. G. Dakshindas The sugarcane disease-s-alhino or grassy shoot. India Sugar, 12: Singh, Kishan Heat therapy of sugarcane. India Sugar, May XVII No.2. P. 1-6.

7 G. K,. ZENDE, N. B~ SHAIKH 1021 Singh, Kishan Grassy shoot disease of sugarcane. II. Hot air therapy. Curro Sci., 20: Srinivasan, K. V., and J. Thuljaram Rao, Heat treatment of sugarcane seed material. Indian Sugar, 18:1-5. Vasudeva, R. S Some diseases of sugarcane newly found in India. F.A.O. Plant Prot. Bull., 4: