3.4.67
STUDIES ON THE INHERITANCE OF RESISTANCE TO SOFT ROT IN DIPLOID POTATO FAMILIES
STUDIES ON THE INHERITANCE OF RESISTANCE TO SOFT ROT IN DIPLOID POTATO FAMILIES
R LEBECKA, L DOMANSKI, E ZIMNOCH-GUZOWSKA
Plant Breeding and Acclimatization Institute (IHAR), Radzikow, Mlochow Center, 05-832-Rozalin, Poland
Background and objectives Soft rot of potato tubers is caused by bacteria of the genus Erwinia: (E. carotovora subsp. atroseptica (Eca), E. carotovora subsp. carotovora E. chrysanthemi). They cause severe damage of potato crop during storage. The low effectiveness of chemical control against soft rot disease and insufficient level of resistance to this genus stimulated interest in breeding of resistant cultivars. The purpose of this study was to estimate effects of GCA and SCA, heritability and maternal effects, based on the evaluation of tuber resistance to soft rot in diploid unselected populations of potato. Diploid interspecific hybrids of potato, used in our experiment showed outstanding level of resistance to tuber soft rot. These hybrids contain in their pedigree wild species of potato: (Solanum chacoense; S. phureja), with sources of resistance to erwinias . Ten populations were chosen for evaluation of breeding values of parents and heritability, and four in order to define the maternal effect on tuber resistance.
Materials and methods
The selected families were propagated in the field. Tuber resistance to soft rot were evaluated on 40 genotypes per family. Tubers of parental forms and six standards were evaluated together with tubers of tested families. Each tuber was point inoculated with two polypropylene tips containing 50 ml of Eca suspension and left in place for 72 hours, in a dark mist chamber at temperature 27 C and about 95 % relative humidity. After incubation the width of decayed tissue was measured in vertically sliced tubers. Three tuber's per genotype in 1995/1996 and five tubers per genotype in 1995/1996 and 1996/1997 were tested twice a year.
Results and conclusions
Analysis of variance revealed that both components of genotypic variation GCA and SCA as well as interactions GCA x Years and SCA x Years were important in the inheritance of potato tuber resistance to the soft-rotting bacteria. The heritability for potato tuber resistance to soft rot was rather low. The significance of the SCA variance and interactions implies that considerable part of heritable variation must have been due to non-additive effects and tuber resistance to soft rot of a progeny cannot be adequately predicted from its parents GCA'S. In such a case it is suggested making preliminary progeny testing. Maternal effect studied on two sets of diploid families derived from reciprocal crosses was not significant, enabling the potential use of resistant diploid lines as poilinators in crosses with tetraptoid females. The moderately high estimate of broad sense heritability for resistance to soft rot suggests the possibility of transferring this resistance to tetraploid potato. Unreduced pollen (FDR type) transfers both non-additive and additive genetic effects from parents to the offspring . In 1997 the interploid (4x - -2x) crossing program was realized. True potato seeds were obtained in factorial crosses of 8 tetraploid potato females with 3 diploid potato males and 24 populations have been sown and replanted to the field in 1998. The evaluation of tuber resistance to soft rot will be done after harvest and will be repeated in the following two years
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