Evaluation of Resistance in Introduced Sugarcane Genotypes to Smut (Ustilago scitaminea Sydow) Disease

Abstract

Fourteen sugarcane (Saccharum spp.) genotypes were
evaluated for resistance to the smut fungus (Ustilago scitaminea H.
Sydow) disease of sugarcane in a field trial for two consecutive seasons
(2006/07 and 2007/08) at Guneid, Sudan. The commercial cultivars CO
527, CO 997 and CO 6806 were used as checks. The setts were inoculated
artificially by two methods: (a) the Taiwanese pin-prick method (TPPM)
and (b) dipping method (DM). Data were analyzed by the weighed
complete linkage cluster algorithm (CLINK). The results showed that the
17 genotypes tested could be grouped into 4 clusters in DM and 5 clusters
in TPPM. In both categories, resistance was weakest in cluster I and
strongest in cluster IV in DM and cluster V in TPPM. The resistance
characters also gradually increased from cluster I to IV and cluster I to V
in DM and TPPM, respectively. Meanwhile, on the conventional scale, 10
genotypes were rated as highly resistant or having resistant reactions
similar to those of the resistant checks CO 6806 and CO 997. They can,
thus, be propagated in commercial fields. Two genotypes; namely, D
9227 and FR 9973, had smut grades of S5 corresponding to medium
susceptible reaction type and are considered unstable and consequently
not suitable for further propagation. Another two genotypes, FR 99204
and FR99314, were rated between highly resistant and resistant and the
cluster discrimination identified these genotypes as suitable, due to a
strong bud resistance, and can thus be used. Also, all the 10 resistant
genotypes were classified as resistant by the clustering method and were
grouped in clusters III and IV in DM and clusters III, IV and V in TPPM.