Abstract
Black root rot (BRR) is an economically important disease of cotton and other crops, especially in cooler regions with short growing seasons. Symptoms include black discoloration of the roots, reduced number of lateral roots and stunted or slow plant growth. The cultivated tetraploid Gossypium species are susceptible to BRR. Resistance to BRR was identified in G. arboreum accession BM13H and is associated with reduced and restricted hyphal growth and less sporulation. Transcriptome analysis indicates that BM13H responds to infection at early time points 2- and 3-days post-inoculation, but by day 5, few differentially expressed genes are observed between infected and uninfected roots. Inheritance of BM13H resistance to BRR was evaluated in an F6 recombinant inbred population and shows a single semi-dominant locus conferring resistance that was fine mapped to a region on chromosome 1, containing ten genes including five putative resistance-like genes.
Highlights
Black root rot (BRR) is a seedling disease of cotton caused by a soil-borne filamentous, hemibiotrophic fungus previously known as Thielaviopsis basicola, but recently reclassified into two species, Berkleyomyces basicola and B. rouxiae [1]
A molecular phylogenetic analysis by Nel et al [1] of geographically isolated fungal isolates that cause BRR disease in a number of countries, showed that what was previously classified as T. basicola is two species that were renamed; B. basicola and B. rouxiae
To determine which species is associated with BRR of cotton in Australia, DNA was isolated from a single spore culture of the fungal isolate WTB-001 used throughout this study
Summary
Black root rot (BRR) is a seedling disease of cotton caused by a soil-borne filamentous, hemibiotrophic fungus previously known as Thielaviopsis basicola, but recently reclassified into two species, Berkleyomyces basicola and B. rouxiae [1]. The seedling disease characterized by dark brown or black discoloration of the roots as a result of the rotting of the cortex [4]. Diseased cotton plants show stunted or slow growth early in the season compared to uninfected plants, causing delayed flowering or maturity that can result in up to a 46% decrease in seed cotton yield [5]. In addition to the direct effect of BRR infection, lesions caused by the fungus may facilitate infection by other cotton seedling pathogens such as Rhizoctonia, Pythium, and Fusarium [6] and in North America significant interactions have been observed between T. basicola and the root-knot nematode
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