Aerial transmission of the leaf scald pathogen Xanthomonas albilineans (Ashby) Dowson
Code (CO)MSI99P0100
Author (AU)Autrey, L. J. C.
Saumtally, S.
Dookun, A.
Sullivan, S.
Dhayan, S.
Title - English (ET)Aerial transmission of the leaf scald pathogen Xanthomonas albilineans (Ashby) Dowson
Meeting (MT)3rd ISSCT Sugar Cane Pathology Workshop, MSIRI, Reduit, 22-26 July 1991
Document Type(DT)Conference paper
Date of publication (DP)1991
Language of text (LT)En
Language of summaries (LS)En
Abstract (AB)Leaf stripes ressembling those caused by the gumming disease bacterium were observed in Mauritius in 1989 in several sugar cane varieties including the commercial M695/69, M292/70, M1557/70 and M3035/66 and the promising M1205/70. The stripes, cream yellow in colour, began at the tip or margins of the leaf blade and sometimes reached the leaf sheath. The leaf scald bacterium was isolated from these stripes and in apparently healthy tissue up to 15 cm from the extremities of the stripes. Identification was carried out by serological, biochemical and pathogenicity tests. The leaf scald bacterium was also recovered for the first time in Mauritius from maize, whether growing in sugar cane interrows or in full stand. Symptoms previously undescribed included leaf striping, stunting and death of plants in maize hybrids MSIRI 2, MSIRI 4, EMV 7A and EMV 24. The bacterium was isolated on agar medium from guttation droplets from infected sugar cane leaves. Positive results were obtained when its pathogenicity was tested in young maize seedlings. Diagnosis in guttation droplets was also carried out by immunofluorescence. Because of the presence of viable bacterial cells in guttation droplets, it is concluded that the leaf scald bacterium is, like the gumming organism (Xanthomonas campestris pv vasculorum), airborne and infects sugar cane and maize through foliar wounds, especially through wounds at the leaf tip or along the leaf margin. The severe leaf scald epidemic in 1989, the worst for the last 60 years, is attributable to such aerial dissemination of pathogen. Furthermore, it has become apparent that there are two mechanisms of transmission, hence of re sistance to leaf scald, namely foliar infection and mechanical inoculation. This finding necessitates assessment of varietal r eaction not only by decapitation but also by the exposure method. It may be necessary to avoid cultivation of leaf scald-susceptible varieties in the humid zone where aerial transmission is likely to occur most readily, as happens with gumming disease.
Descriptors - English (DE)SUGARCANE
XANTHOMONAS ALBILINEANS
TRANSMISSION
MAIZE
DISEASES
BACTERIAL DISEASES
LEAF SCALD
Descriptors - Geographic (DG)MAURITIUS
Sort Key 1(K1)Sugarcane: Diseases and disease management
Sort Key 2 (K2)Bacterial diseases: Leaf scald
Date record entered (DA)1992-01-21
Language of analysis (LA)En
Affiliation (AF)Mauritius Sugar Industry Research Institute
Processing status (PS)LIST
MSIRI Staff (MS)PATH