How can field selection for Striga resistance and tolerance in sorghum be improved?

Rodenburg, J and Bastiaans, L and Weltzien, E and Hess, D E (2005) How can field selection for Striga resistance and tolerance in sorghum be improved? Field Crops Research, 93 (1). pp. 34-50. ISSN 0378-4290

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Abstract

Breeding for high yielding Sorghum bicolor varieties with effective resistance and tolerance against the hemi-parasitic weed Striga hermonthica requires suitable selection measures for both characteristics. The objective of this research was to develop a set of practical selection measures that contains independent, reliable and discriminative criteria for resistance and tolerance. Ten sorghum genotypes (CK60-B, CMDT39, E36-1, Framida, IS9830, N13, Seredo, Serena, SRN39 and Tiémarifing) were grown in the field with and without Striga infestation in a split-plot design in 3 successive years (2001-2003) using different Striga infestation levels (low, high and intermediate). Resistance against Striga in the below-ground stages was determined separately in an agar-gel assay and a pot trial. The addition of Striga-free control plots facilitated the calculation of the relative yield loss, which represents the result of resistance and tolerance combined. Correlation analysis indirectly demonstrated that both resistance and tolerance are important yield determining traits under Striga infestation. Tolerance was relatively more important under low Striga infestation levels, whereas resistance was relatively more important at high infestation levels. With respect to resistance, both the area under the Striga number progress curve (ASNPC) and maximum above-ground Striga number (NSmax) turned out to be discriminative and consistent selection measures. Both measures also corresponded well with the expression of resistance during below-ground stages of the parasite. It proved more difficult to arrive at a satisfactory measure for tolerance. Inclusion of Striga-free plots is an essential step for the determination of tolerance, but in itself not sufficient. It provides a basis for the determination of the relative yield loss, which then needs to be corrected for differences in infection level resulting from genotypic differences in resistance. A linear correction for infection level disregards the density dependency of the relative yield loss function. It is expected that clarification of the relation between Striga infection level and yield loss, provides a solid basis for the development of unambiguous tolerance measures in the field. This will enable the breeder to select for resistance and tolerance separately, which is likely to result in the optimum combination of both defence mechanisms

Item Type:	Article
Divisions:	UNSPECIFIED
CRP:	UNSPECIFIED
Uncontrolled Keywords:	Sorghum bicolor; Striga hermonthica; Parasitic weeds; Screening methodologies
Subjects:	Mandate crops > Sorghum
Depositing User:	Ms K Syamalamba
Date Deposited:	03 Nov 2011 10:29
Last Modified:	03 Jan 2012 05:46
URI:	http://oar.icrisat.org/id/eprint/3601
Official URL:	http://dx.doi.org/10.1016/j.fcr.2004.09.004
Projects:	UNSPECIFIED
Funders:	Financial assistance for this study was made possible through the beneficence of the Netherlands Foundation for the Advancement of Tropical Research (WOTRO)
Acknowledgement:	Financial assistance for this study was made possible through the beneficence of the Netherlands Foundation for the Advancement of Tropical Research (WOTRO). We are grateful for contributions and support of WUR and ICRISAT-Mali. We especially thank Ana Amosse Dolo, Ibrahima Sissoko, the late Idrissa Sangare and Badara Diallo of ICRISAT. Professor Dr. Martin Kropff and Aad van Ast of Wageningen University are gratefully acknowledged for their input and advice. We would like to thank Jacques Withagen and Dr. Niels Dingemanse for advice on statistics and quantitative genetics. This article is dedicated to the memory of the late Idrissa Sangare
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