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Not AvailableSugarcane production is affected by different diseases caused by fungal, bacterial, viral and phytoplasmal pathogens in the country. Major fungal diseases such as red rot and smut are managed through deploying disease resistant varieties. Due to vegetative propagation the viral pathogens along with other non-fungal pathogens causing RSD and GSD gradually increase in their load in the canes over the generations. Such a high population of different pathogens leading to ‘varietal degeneration’ i.e. loss in vigour of sugarcane varieties. Due to this, longevity of many elite sugarcane varieties was reduced in the past. Since most of the pathogens are transmitted through seed in sugarcane, greater emphasis are given to seed health to manage the diseases. Hence disease-free nursery programmes form the basis of healthy crop in the field. Otherwise, the disease severity aggravates in the ratoons, scope of multi-ratooning and mechanization depends on the use of healthy planting material. In the past, impact of these diseases was ignored in the past due to lack of precise diagnostic techniques and clarity in symptoms caused by different viral diseases in sugarcane. Ever since yellow leaf disease (YLD) became a serious threat to sugarcane cultivation, ICAR-SBI has given more emphasis on healthy seed programme to address varietal degeneration by elimination of systemic virus infections through tissue culture combined with molecular diagnosis. At ICAR-SBI sensitive diagnostic techniques such as RT-PCR and PCR techniques were developed for the specific detection of the RNA viruses and phytoplasmas infecting sugarcane, respectively. These techniques have been applied to detect the pathogens in the tissue culture derived in vitro clones. Although the pathogen titre is expected to be very low, these techniques are highly sensitive to detect such a low titre in young plantlets. When tissue culture derived seedlings are utilized for commercial planting without diagnosis for the designated pathogens, the process also facilitates spread of the diseases far and wide and this will have a catastrophic effect in the field on crop health. Hence production of disease-free seedlings through tissue culture should be indexed for the designated viruses and phytoplasmas. Such virus-free seedlings are to be used as breeder seed in the three-tier seed nursery programme as they cannot be directly planted for commercial cultivation. Canes from this nursery can be used to raise single bud settlings in protrays under shade-net and such healthy settlings are used for planting in the field either for commercial cultivation or subsequent multiplication. Large scale adoption of such nurseries in Erode and Namakkal Districts in Tamil Nadu resulted in significant jump in cane yield as compared to the conventional planting. Critical monitoring of YLD-free fields revealed that the disease-free fields always maintained a vigorous crop stand and the farmers realized an average increase of 37.5-50 tonnes/ ha in cane yield in the region. In addition, rapid multiplication of healthy planting materials is achieved through settlings in the nurseries. Ultimately this approach would increase land productivity, increase farmer’s income and sustain sugarcane productivity. Our interventions in producing virus-free seedlings have opened new vistas towards effective management of diseases and supply of healthy planting materials in sugarcane.Not Availabl

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Not AvailableSugarcane production is affected by different diseases in the country and among them red rot, smut, wilt and pineapple disease (sett rot) are the important fungal diseases. Leaf scald (LSD) and ratoon stunting (RSD) are the important bacterial and mosaic and yellow leaf disease (YLD) are the major viral diseases prevalent in almost all parts of the country. Besides these, a phytoplasma disease, grassy shoot (GSD) is also a serious disease, which affects sugarcane productivity. Further, foliar diseases such as pokkah boeng, rust, brown spot, ring spot, brown stripe, eye spot, etc may cause loss to sugarcane depending on the prevailing environmental conditions. Slow buildup of many non-fungal pathogens in sugarcane causes decline in varietal performance and this affects crop vigour and overall productivity of the ruling varieties under field conditions. Hence we are unable to harness the potential yield of the elite varieties for many years in a sustained way. Since most of these pathogens are transmitted through seed in sugarcane, greater emphasis are given to seed health to manage the diseases. Ever since YLD became a serious threat to sugarcane cultivation, ICAR-SBI has given more emphasis on healthy seed programme to address varietal degeneration by elimination of systemic virus infections through tissue culture combined with molecular diagnosis. This report gives a brief information on the impact of meristem culture combined with molecular diagnosis to produce healthy planting materials and effective management of YLD and other non-fungal disease especially GSD in the popular sugarcane variety of tropical states ‘Co 86032’. This approach resulted in achieving about 250 tonnes of cane yield per ha in the popular variety.Not Availabl

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Not AvailableYellow leaf (YL) of sugarcane caused by Sugarcane yellow leaf virus (ScYLV, a Polerovirus of the Luteoviridae family) is a serious disease affecting the crop production and productivity in India. Although impact of the disease on cane growth is observed, no systematic study has been done so far for the tropical Asian region to establish its impact on various physiological parameters, cane yield and juice quality. We have assessed physiological parameters in symptomatic and asymptomatic plants of 10 different cultivars and a genotype. In addition, similar comparisons were made between virus infected and virus free plants derived through meristem culture. Our studies established that among several physiological parameters, photosynthetic rate (A), stomatal conductance (gs) and SPAD meter values were significantly reduced in cultivars severely infected with ScYLV. Virus-infected cultivars exhibited significant reduction in growth/yield parameters, viz. stalk height, stalk thickness and number of internodes. Plant growth reductions were found to be 42.9, 42.3 and 38.9% in susceptible cultivars CoPant 84211, Co 86032 and CoC 671, respectively. In addition to reduction in stalk weight, height and girth, YL disease also reduced juice yield in the affected canes up to 34.15%. Similarly, comparison of diseased (virus-infected) and virus-free plants derived through meristem culture also revealed a drastic reduction in cane growth/physiological parameters and juice yield due to virus infection. The present study is the first comprehensive report demonstrating that YL disease caused by ScYLV seriously affects cane and juice yield in major sugarcane varieties under tropical climatic conditions (India). Consequently, this situation warrants a massive programme to provide healthy seed material and initiate breeding for YL resistance in sugarcane.Not Availabl

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Not AvailableYellow leaf (YL) caused by Sugarcane yellow leaf virus (SCYLV) is a serious viral disease affecting production and productivity in many ruling sugarcane varieties in India. Usually the characteristic disease symptoms appear during maturity phases of the crop; also many of the infected varieties don’t exhibit disease symptoms and disease expression is influenced by virus titre and other factors including prevailing climate. The present study was taken up to quantify and compare SCYLV in meristem derived tissue culture raised in vitro plantlets and asymptomatic sugarcane plants in RT-qPCR by relative standard curve method. The standard curve was prepared with serial dilutions of plasmid standards from 3x107 to 3x103 copy numbers of virus target gene. In this assay, copy number of virus population in in vitro plantlets and asymptomatic plants was estimated from 20,314.58 to 4,330.87 and from 8.96 to 0.27 million copy of viruses, respectively. Relative expression level of the virus between in vitro plantlets and asymptomatic plants was in the ratio of 73.7:243393.1 based on 2^ (-(ΔΔCt)). The results clearly established that meristem derived tissue culture significantly reduced SCYLV population and it is concluded that the relative standard curve method efficiently detect the copy numbers of target virus in different sugarcane samples.Not Availabl