Characterization of resistance of cassava genotypes to bacterial blight by evaluation of leaf and systemic symptoms in relation to yield in different ecozones

Abstract

Twenty-two improved and local cassava genotypes were evaluated for their bacterial blight symptom types in reaction to infection by Xanthomonas axonopodis pv. manihotis under field conditions in the forest, forest savanna transition and wet savanna zones of Togo. High genotype · environment interactions in development of each symptom type were observed. Combining data on environments and genotypes, spot, blight and wilt symptoms were positively correlated. Analysing genotype reactions across environments, indications for independent mechanisms of resistance on leaf and stem level, varying by genotype, were found. Genotypes Main27 with resistance to spot and blight symptoms and TMS4(2)1425 with resistance to wilt symptoms are recommended to breeders to introgress their resistance characteristics. Significant negative correlations were generally observed between blight and wilt symptom development and root yield across ecozones, with blight being more important under lower, and wilt under higher inoculum pressure. Genotypes TMS30572, CVTM4, TMS92/0429 and TMS91/ 02316 showed low spot, blight and wilt symptoms combined with high root yield across ecozones.

Leaf Surface Colonization of Sugarcane byXanthomonas albilineansand Subsequent Disease Progress Vary According to the Host Cultivar

“…Therefore, resistance to X. albilineans may vary between leaves and stalks, and different resistance mechanisms may be involved. A similar phenomenon was observed with cassava genotypes tested for resistance to cassava blight (31). Leaf blight due to colonization of the leaf by X. axonopodis pv.…”

Heat shock transcription factor 3 regulates plant immune response through modulation of salicylic acid accumulation and signalling in cassava

“…It is particularly tolerant to drought and low-fertility soils, and is highly efficient in photosynthesis and starch production; however, it is susceptible to bacterial blight, such as Xanthomonas axonopodis pv. manihotis (Xam) (Boher et al, 1995;Wydra et al, 2007). Moreover, the molecular mechanism of the immune response of cassava and the functional identification of pathogenrelated protein in cassava are very limited.…”

Distribution of Cassava Bacterial Blight and Reaction of Selected Cassava Genotypes to the Disease in Kenya

“…Resistance to CBB is considered to be polygenic and additively inherited (Hahn et al, 1979) and is introgressed in cassava from its wild relative Manihot glaziovii (Wydra et al 2007). The quantitative resistance of cassava to CBB includes several mechanisms such as formation of suberin and tyloses in the xylem vessels limiting disease extension in stems (Kpe´moua et al 1996), production of latex with high contents of PR-proteins (Cooper et al 2001), and deposition of phenolic compounds and lignin (Pereira et al 2000).…”

“…Symptoms and severity were evaluated from 7 days post inoculation and then every seven days up to 35 days, using a scale of 1 to 5 as described by Wydra et al (2007) where 1 = no symptoms, 2 = angular leaf spotting only, 3 = wilting, angular leaf spotting, leaf blight, defoliation, gum exudates on stems or petioles, 4 = wilting, blighting, defoliation, gum exudation, shoot tip die back, 5 = wilting and blighting, defoliation and gum exudation, abortive lateral shoot formation, stunting, complete die back. The area under the disease progress curve (AUDPC) was calculated on a single plant basis by the trapezoidal integration over the whole observation period as using the formula below (Jorge et al 2000).…”