Stalk rot of sweet sorghum caused by genetically diverse Fusarium thapsinum strains
Vuyiswa Bushula: University of Pretoria
<div>Sweet sorghum (<em>Sorghum bicolor</em>) is widely used as an alternative feedstock and source for bio-fuel production. Common to all cultivated sorghum, stalk rot diseases affect yield. <em>Fusarium thapsinum</em> is a fungal pathogen causing sorghum stalk rot. Strains of <em>F. thapsinum</em> are genetically diverse and little is understood about their potential for stalk rot on sweet sorghum. The objective of this study was to evaluate stalk rot of sweet sorghum by genetically diverse <em>F. thapsinum</em>. Stalk inoculations of 23 sweet sorghum genotypes including lines of variable sugar content and their hybrids were performed using four <em>F. thapsinum</em> strains (F00915, F00916, F01153, and F01163) in a complete randomized block design with three replications. There was a significant genotype by strain interaction for lesion length. Comparisons of lesion lengths showed significant differences between strains, with strains F01153 and F01163 having the highest lesion length of 14.3 cm each, followed by strain F00915 (13.6 cm) and F00916 (12.4 cm). This result suggests that there is variation in stalk rot pathogenicity between the strains. Comparisons of lesion length amongst genotypes ranged from low to high resistance to stalk rot disease caused by <em>F. thapsinum</em> strains in this panel of sweet sorghums. Our results suggest that genetic variability within <em>F. thapsinum</em> strains plays a role in stalk rot pathogenicity and that breeding efforts in sweet sorghum need to consider genetic diversity in the pathogen.</div>
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