Evaluation of Reaction Thirty Dwarf Mahaleb Genotypes to Root and Crown Rot Phytophthora Disease using Laboratory Methods

Iran is one of the biggest sweet cherry producers in the world. Turkey, the U.S.A and Iran are among the major producers of cherry in the world. Mahaleb(Prunus mahaleb L.) is used as a principal rootstocks for sweet and sour cherries in Iran. Mahaleb is a good rootstock on light, calcareous soils and arid climates in Iran. Since pathogenic species, P.citricola, P.cryptogea, P.dreschleri, P.cactorum, P. syringae, P.cinnammomi, P.megasperma, P.cambivora on mahaleb been reported by different researchers (Sajadinejad et al., 2011) According to the pathogenesis of four species of P. nicotianae, P.citricola, P.cactorum and P.citrophthora on stone fruit trees in Iran and other countries, based on the hypothesis that the relative resistance to Phytophthora species in selected dwarf Mahaleb genotypes adapted to environmental conditions exist and can be introduced as resistant rootstocks to crown rot disease, this study was conducted to evaluate the susceptibility of 30 selected dwarf Mahaleb genotypes to P.nicotianae, P.citricola, P.cactorum and P. citrophthora. Sofar, the selection of resistant or tolerant to Phytophthora cherry rootstock, studies have not been done. Therefore, it is appropriate to introduce the cherry trees for planting in various parts of the country, the need to evaluate several species of Phytophthora resistance or tolerance to the grades mentioned above. Considering the history of the pathogenesis off our species of P. nicotianae, P.citricola, P.cactorum and P.citrophthora the stone fruits this study aimed to evaluate the reaction of 30 cultivars of dwarf Mahaleb to P.nicotianae, P.citricola, P.cactorum, P.citrophthora was carried out.
In this study, the reaction of 30 dwarf Mahaleb genotypes were investigated to disease caused by four species of the fungus Phytophthora root and crown rot. Excised twig, annual and perennial shoots to measuring resistance using laboratory methods. Excised twig, excised annual and perennial shoots assessment based on Jeffers et al., (1981) and Matheron and Mircetich(1985) respectively.
In evaluating the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes to four species of Phytophthora, rot and discoloration symptoms were observed, All control shoots of Mahaleb genotypes were evaluated in this trial did not show any symptoms of discoloration and Phytophthora rot but shoots treated with four species of Phytophthora showed that different degrees of light brown to dark discoloration and decay. The results of the analysis of variance showed that the genotypes of disease progression on the tissues of all three types of excised shoots inoculated with four species of Phytophthora were difference statistically significant. Also, the results of comparing the length average of progression of symptoms (necrosis) on this experiment were as follows which are outlined below.
P.cactorum
On the test assessment the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes, least amount of sensitivity to species belongs to genotype199 with an average contamination of 12.44%, 162 with an average contamination of 1.42% and 162 with an average contamination 0.01 %, respectively.
P.citrophthora
On the test assessment the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes, least amount of sensitivity to species belongs to genotype 265 with an average contamination of 15.67%, 155 and 162 with an average contamination of 0.01% and 262, 228, 224 and 188 with an average contamination 0.01 %, respectively.
P.citricola
On the test assessment the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes, least amount of sensitivity to species belong to genotype 124 with an average contamination of 11.80%, 100 with an average contamination of 0.60% and 266 with an average contamination 3.13 %, respectively.
P.nicotianea
On the test assessment the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes, least amount of sensitivity to species belong to genotype 120 with an average contamination of 16.15%, 100 and 95 with an average contamination of 0.01% and 188 with an average contamination 0.87%, respectively.
There were significant differences between the genotypes of disease progression in the tissues of all three types of excised shoots inoculated with four Phytophthora species.
The results showed that, some mahaleb genotypes (100, 124, 155, 162, 188, 195, 199, 224, 266 and 265) have potential resistance to species P.nicotianae, P.citricola, P.cactorum and P.citrophthora, that can be considered in breeding programs.