Natural occurrence and diagnosis of yellow leaf disease affecting sugarcane genotypes under tropical and sub-tropical conditions in India

Abstract

Aim: To diagnose the cause of yellow leaf disease (YLD) and to record its incidence in the 189 sugarcane genotypes planted under tropical (n= 47) and sub-tropical (n= 142) conditions in India during 2016–17 and 2017–18 crop growing seasons. Methodology: The symptomatology, disease incidence and diagnosis of YLD was carried out in all 189 genotypes comprising of 47 tropical and 142 sub-tropical genotypes during 2016–17 and 2017–18 crop growing seasons. Further, all the YLD symptomatic samples were subjected to nested PCR assay for detection of the associated phytoplasma, and to study its distribution in different YLD affected plant parts using universal primers. Results: YLD affected genotypes were characterized by the mild to prominent yellowing of the midribs, extending the yellowing toward leaf lamina followed by leaf-tip drying from top towards the leaf base, bunching at the crown region and subsequently complete drying of the leaves and stunted growth. Of the total 189 genotypes, disease incidence in 142 sub-tropical genotypes during 2016 – 17 and 2017 – 18 crop growing seasons ranged from 1.17% to 65.38% and 7.95% to 67.44%, respectively. Similarly, of the total 47 tropical genotypes, disease incidence was found in 39 genotypes and ranged from 3.89% to 55.58% and 2.38% to 62.96% in 2016-17 and 2017 – 18 crop growing season. All the 95 symptomatic samples from sub-tropical and tropical genotypes were tested by nested PCR assay of which 94 samples showed ~1.2 Kb size amplicons. Interpretation: From the present study, it was concluded, that among the total 189 genotypes, 94 genotypes were found affected due to YLD and presence of phytoplasma in these genotypes were diagnosed. Remaining 95 genotypes which were found apparently healthy would be a good source of resistance and can be further involved for the development of YLD resistant sugarcane progenies in India.