, Volume 183, Issue 2, pp 227-241
Date: 21 May 2011

Susceptibility of rice to sheath blight: an assessment of the diversity of rice germplasm according to genetic groups and morphological traits

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Abstract

A sample of 200 accessions was selected from IRRI’s rice (Oryza sativa) germplasm bank, that represents rice diversity in terms of genetic groups (aus, indica, tropical japonica, temperate japonica, and aromatic) and crop duration cycles of the accessions. The sample also captured the diversity of rice germplasm in terms of morphological traits. The accessions were assessed for their level of susceptibility to sheath blight in a field experiment, by inoculating hills at the centre of microfields and measuring disease intensity. Morphological traits of all accessions were also measured. Analyses of variance indicated significant effects of genetic groups and genotypes on sheath blight intensity, measured by different variables (lesion height, relative lesion height, leaf severity, sheath severity, and disease incidence on tillers). Results from multivariate analyses (canonical correlation, hierarchical cluster analyses, correspondence analysis, and discriminant analysis), and logistic regressions indicated that morphological traits were strongly associated with disease intensity, and that their effect was larger than that of genetic groups. In particular, plant height was associated with low sheath blight intensity. Effects of genetic groups could however also be detected, and the combination of results suggested a ranking of genetic groups with increasing level of susceptibility to sheath blight as: aus < indica < japonica.