Indicator kriging modeling epidemiology of common bean anthracnose

New cultivars of the common bean (Phaseolus vulgaris) with durable resistance to anthracnose can be developed by pyramiding major resistance genes using marker-assisted selection. To this end, it is necessary to identify sources of resistance and molecular markers tightly linked to the resistance genes. The objectives of this work were to study the inheritance of resistance to anthracnose in the cultivar TO (carrying the Co-4 gene), to identify random amplified polymorphic DNA (RAPD) markers linked to Co-4, and to introgress this gene in the cultivar Rudá. Populations F1, F2, F2:3, BC1s, and BC1r from the cross Rudá × TO were inoculated with race 65 of Colletotrichum lindemuthianum, causal agent of bean anthracnose. The phenotypic ratios (resistant/susceptible) were 3:1 in the F2 population, 1:1 in the BC1s, and 1:0 in the BC1r, confirming that resistance to anthracnose in the cultivar TO was monogenic and dominant. Six RAPD markers linked to the Co-4 gene were identified, four in the coupling phase: OPY20830C (0.0 centimorgan [cM]), OPC08900C (9.7 cM), OPI16850C (14.3 cM), and OPJ011,380C (18.1 cM); and two in the repulsion phase: OPB031,800T (3.7 cM) and OPA18830T (17.4 cM). OPY20830C and OPB031,800T, used in association as a codominant pair, allowed the identification of the three genotypic classes with a high degree of confidence. Marker OPY20830C, which is tightly linked to Co-4, is being used to assist in breeding for resistance to anthracnose.

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Investigating Phenotypic Variability in Colletotrichum lindemuthianum Populations

Phytopathology ◽

10.1094/phyto-06-11-0179 ◽

2012 ◽

Vol 102 (5) ◽

pp. 490-497 ◽

Cited By ~ 14

Author(s):

J. M. A. Pinto ◽

R. Pereira ◽

S. F. Mota ◽

F. H. Ishikawa ◽

E. A. Souza

Keyword(s):

Genetic Variability ◽

Common Bean ◽

Asexual Reproduction ◽

Phenotypic Variability ◽

Colletotrichum Lindemuthianum ◽

Basic Knowledge ◽

Sexual And Asexual Reproduction ◽

Mycelia Growth ◽

Bean Anthracnose

Colletotrichum lindemuthianum, causal agent of anthracnose in the common bean, has wide genetic variability. Differential bean cultivars and morphological and physiological characteristics were used to analyze 74 isolates of C. lindemuthianum collected in two counties in the state of Minas Gerais, Brazil. Six different races were found, with a predominance of race 65 at both locations. Isolates were classified according to their sensitivities to the fungicide thiophanate-methyl, normally used in the control of common bean anthracnose. In all, ≈10% of isolates were resistant to the fungicide in vitro. Characteristics such as indexes of mycelia growth rate, colony diameter, sporulation capacity, and percentage of germination demonstrated the high genetic variability of C. lindemuthianum. We also observed variation in conidial cytology. The conidia of most isolates showed septa formation after germination, in contrast to septa absence, previously reported in the literature. Sexual and asexual reproduction were evaluated for mechanisms that may contribute in the generation of variability in C. lindemuthianum. Conidial anastomosis tubes were commonly found, indicating that asexual reproduction can help increase variability in this species. Information from this study confirmed high variability in C. lindemuthianum and will guide future studies in basic knowledge and applied technologies.

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