ISSN:
1871-4528
Keywords:
PVY
;
régressions linéaires
;
Indices de Résistance
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Description / Table of Contents:
Summary Virus resistance of potato cultivars or hybrids expressed in terms of a 1 to 9 scale can be evaluated objectively. The method is based on the regression of infection on resistance. The regression line goes through the two following points: 1. x=mean of known resistance values of the controls y=mean transformed percentages of diseased control plants (experimental data) 2. x=9 (maximum resistance) y=0 (no infection) The percentage of infected plants is transformed according to equation (2) monocyclic model or (3) polycyclic model. The conversion of resistance of a genotype into values obtained from the resistance index scale is obtained from equation (5) derived from equation (4). PVY resistance trials have been used as an example. Tubers of 41 genotypes and hybrids including 7 controls with known resistance levels were planted in three localities with high vector densities. Tuber samples were taken at harvest time in 1989 to obtain in preculture tests done in glasshouses in Bonin an estimation of the infection level using the biological Solanum demissum “Y” method. Analysis of variance (Table 1) was done on the transformed percentages according to Gregory's (1948) equations (1) and (2). Subsequent computations were carried out using equation (6). (7) and (8) and the results are given in Table 2. The regression line for cv. Ceza as an example is given in Fig. 1. The least significant differences (LSD) were computed from the variance analysis (Table 1). As demonstrated by the example, the aim of the method which is to evaluate the resistance of a genotype on a 1 to 9 scale and to determine the related LSD values has been achieved. The described method facilitates also the comparison of the results of repeated trials done at different times and sites. These comparisons can be done with different controls but it is necessary that the resistance computation method be the same. The effect of cultivar resistance on the rejection percentage during the offical preculture test for six years have been verified.
Notes:
Résumé La résistance aux virus, de cultivars ou d'hybrides, exprimée par une échelle d'indices de résistance de 1 à 9 peut être évaluée de manière objective. Le principe de la méthode consiste à tracer une droite de régression de l'infection sur la résistance. Cette droite passe par le point correspondant à la moyenne des témoins et par le point correspondant aux valeurs remarquables: note=9, infection=0. Grâce à cette droite, on calcule la note de résistance du cultivar ou de l'hybride étudié. La méthode donne aussi la Plus Petite Différence Significative de cette estimation et permet des comparaisons de résultats d'essais répétés dans l'espace et dans le temps.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02357732
Permalink
