Original Articles

Resistance of sorghum hybrids to ergot caused by Claviceps africana

Published in: South African Journal of Plant and Soil
Volume 17, issue 1, 2000 , pages: 1–5
DOI: 10.1080/02571862.2000.10634857
Author(s): N.W. McLaren, Republic of South Africa

Abstract

Thirty-one sorghum hybrids were evaluated for ergot ‘escape’ resistance at Bethlehem and Potcherstroom during the 1996/97 and 1997/98 seasons. Trials were designed so that flowering and artificial inoculation occurred over a range of flowering dates and thus, ergot potentials Non-linear regression analysis was applied to determine the relationship between ergot potential of a flowering date and observed ergot severity in a hybrid. Ergot potential of a flowering date was calculated from weather data and is defined as the expected ergot severity in a genetically broad-based sorghum population. Ergot resistance was quantified using the Ergot Breakdown Point which is the ergot potential required to induce disease, arbitrarily taken as 5% observed ergot severity (5% EBP), Sixteen hybrids showed various degrees of resistance with 5% E BP'S which ranged from 5.2–34.6%, Most 5% EBP's tended towards the lower end of the scale. Similarly hybrids differed in the rate of resistance breakdown. The relationship between pollen viability and ergot potential was quantified in five hybrids and in all cases the relationship between weather induced reductions in pollen viability and increased ergot susceptibility was highly significant, Results suggest that hybrid resistance to ergot is relatively low and can be significantly improved.

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