Abstract
Xanthomonas phaseoli pv. manihotis (Xpm) is the causal agent of Cassava Bacterial Blight (CBB), one of the most important cassava diseases. The aim of this study was to evaluate the susceptibility of sweet cassava genotypes to strains of Xpm from three different geographic regions of Brazil in greenhouse conditions. The inoculation of 14 genotypes of cassava was made by cutting leaflets using scissors previously soaked in a bacterial suspension with 1 × 108 UFC ml-1 and also by inserting a soaked toothpick into the bud of the oldest leaf. The results showed significant differences when the cassava genotypes were individually evaluated in relation to the Xpm strains used; however, the relationship between cassava genotypes and Xpm strains was significant for wilt symptom. The UnB 1111 strain was more aggressive than the UnB 1386 strain based on the average value of the reaction grade, showing the variation that exists between the bacterial isolates from different regions. Considering the reaction of cassava germplasm’s resistance to the three strains used in the study, the BGMC 434 genotype was the only one classified as resistant based on the average reaction grade. The genotypes BGMC 753, BGMC 1289, BGMC 982 and the elite clones BRS 396, BRS 397, BRS 398, 259/08 and BRS 399 were classified as moderately resistant, which indicates the possibility of recommending them for disease favorable regions.
Highlights
Cassava, Manihot esculenta Crantz (Euphorbiaceae), is a perennial shrub grown mainly in tropical countries
One of the main diseases that affect the crop in cultivation areas in the Center South region of Brazil is the bacteriosis known as Cassava Bacterial Blight (CBB) (Fukuda et al, 2002) caused by Xanthomonas phaseoli pv. manihotis (Xpm) (Constantin et al, 2016)
The results of the joint analysis of variance revealed the existence of significant differences at 5% probability of error, in relation to the average scores of the individual symptoms of S, W, complex of symptoms of systemic nature (CSSN) and degree of reaction (DR), between the genotypes evaluated for the three strains of Xpm used in the study (Table 3)
Summary
Manihot esculenta Crantz (Euphorbiaceae), is a perennial shrub grown mainly in tropical countries. It is important in the food security of these populations due to its robustness, which is reflected in the capacity to store high amounts of starch in its roots under conditions in which other species would not even survive (Filgueiras & Homma, 2016). One of the main diseases that affect the crop in cultivation areas in the Center South region of Brazil is the bacteriosis known as Cassava Bacterial Blight (CBB) (Fukuda et al, 2002) caused by Xanthomonas phaseoli pv. In conditions favorable to the development of the disease, with sudden temperature fluctuations between day and night above 10 °C and annual precipitation above 1200 mm, root yield losses can vary from 30 to 100% (Anjos et al, 2013)
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