Spatial Dependence in Anthracnose Development in Mixtures of Stylosanthes scabra

• Published in: Journal of phytopathology Vol. 143; no. 11-12; pp. 693 - 699
• Main Authors: Chakraborty, S., Pettitt, A. N., Choy, S. Low, Boland, R. M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.1995; Blackwell
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; Australia; Oceania; Queensland; Plant pathogen; Phytopathogen resistance; Tropical crop; Host agent relation; Epidemiology; Field experiment; Fungi; Leguminosae; Dicotyledones; Dissemination; Angiospermae; Spermatophyta; Fungi Imperfecti; Fodder crop; Colletotrichum gloeosporioides; Thallophyta; Cultivar
• ISSN: 0931-1785; 1439-0434
• DOI: 10.1111/j.1439-0434.1995.tb00225.x

Development of anthracnose caused by Cotletotrichum gloeosporioides in mixtures of the tropical pasture legume Stylosanthes was studied in 3 successive years. The performance of three accessions of Stylosanthes sp., 36260, QiaO42 and 55860 and cv. Seca were evaluated by growing these in three different mixtures with other susceptible or resistant components. Small test plots of these mixtures were established within large grazed background paddocks which were sown to a pure stand of S. scabra cv. Seca or a mixture of six S. scabra genotypes, including ‘Seca’, This simulated the widely used practice of oversowing existing pastures with improved cultivars. In all 3 years, 36260, Q10042, 55860 and ‘Seca’ developed more disease when grown in a mixture with the susceptible ‘Fitzroy’. A hexagonal lattice design was used in the test plots to study the influence of nearest neighbours on the partially resistant 55860. At a plant level, the area under the disease‐progress curve, averaged over the six neighbours, NADPC, was used as a covariate to approximate the influence of inoculitm pressure in th e neighbourhood. The partial regression coefficient for this covariate wa s significant (P < 0.05) for mixture with ‘Fitzroy’ in 1989 and 1990, for mixture with the highly resistant 93116 in 1989, and for mixture with the moderately resistant ‘Verano’ in 1990. The NADPC was further subdivided into three components to separate inoculum pressure due to the component unique to a mixture, the resistant component ‘Seca’ and th e three moderately resistant components 36260, 55860 and Q10042. This showed that the NADPC effect was largely due to inoculum pressure from the moderately resistant components. The study demonstrates the lack of any significant protection of susceptible components from resistant components in the immediate neighbourhood. The practical implication of this finding is that only resistant components should be used when oversowing Stylosanthes pastures.