ISSN:
1573-5060
Keywords:
Arachis
;
interspecific hybrids
;
peanuts
;
groundnuts
;
Cercospora
;
leafspots
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary Three species of Arachis [A. sp., 10038 GKP, PI 263133 (A), A. chacoense (nomen nudum), 10602 GKP, PI 276235 (B) and A. cardenasii (nomen nudum), 10017 GKP, PI 262141 (C)] and three of their F1 and F2 hybrids (A×B, A×C and B×C) were inoculated with spore suspensions of 10000 conidia/ml concentration of Cercospora arachidicola Hori (pathogen-1) and Cercosporidium personatum (Beck & Curtis) Deighton (pathogen-2). The reactions of the hosts to the pathogens were measured as: number of lesions/cm2 of leaflet, X1; area of leaflet diseased in mm2/cm2, X2; and percentage of defoliation [(fallen leaflets/total leaflets) x 100], X3. The reactions were read on three rooted cuttings of single plants of A, B and C, the three F1 hybrids and on three cuttings each from 70, 85 and 88 F2 plants of A×B, A×C and B×C for pathogen-1 and from 84 and 80 F2 plants of A×B and A×C for pathogen-2, respectively. Pathogen-2 failed to infect B×C. Analyses were made of the F2 data on X1, X2 and X3 individually and jointly on the principal canonical variable, Y1 (disease index), developed from the principal canonical axis projected from Z1=/n X1, Z2 = arcsin (√X2/100), and Z3 = arcsin (√X3/100). All four analyses provided evidence of heritable variation in the parameters measured in the F2 generations. Species A, susceptible to both pathogens -1 and -2, species B, resistant to -1 and mildly susceptible to -2 and species C, susceptible to -1 but resistant to -2 combined into hybrids intermediate in their resistances and susceptibilities. In the five populations studied, F2 plant-to-plant differences were large and significant (P=0.01) in all of the parameters measured but no F2 plants were found to be as resistant as the resistant parents. Heritability estimates for Y1 ranged from 81.7 to 92.9%. The quantitatively continuous distributions of host reaction in the F2 populations were interpreted to indicate that the variation encountered resulted from multifactorial genetic differences in the hosts. Contribution to host variation by genetic differences within the pathogens was thought to be minimal, since the inoculum of each pathogen traced to a single conidial colony of the original isolates. It is concluded that introgression into the genomes of A. hypogaea of genetic factors from each of the two resistant Arachis species should result in increased host resistance to both pathogens. It is also concluded that the variation in multiple measurements of host reaction, compressed by multiple variate canonical analysis into a single canonical variable (disease index), can be utilized as an aid in developing host resistance.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00023710
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