Mapping Of Genes Resistant To Late Blight (Phytophthora Infestans) And Gray Mold (Botrytis Cinerea) And Multiple Gene Selection Assisted By Molecular Markers For Breeding In Tomato (Lycopersicon Esculentum)

Tomato (L. esculentum) late blight (Phytophthorainfestans) and gray mold (Botrytis cinerea) can be a yearly devastating disease around the world to tomato production especially under the protected facilities. They usually caused the production loss and low quality. Until now, no varieties have been released to give the resistance to one of them in China. Furmore, the related works have been left behind comparing to other groups. Meanwhile, most of cultivars used at present are mostly susceptive to both of them. Although wild species of tomato encompassed many of useful genes as a resistant resource, the exploration of the germplasms with the resistance to gray mold is still ongoing. Hence, screening of resistant germplasms and the combination of traditional breeding and the molecular technology would possibly facilitate the exploration of tomato germplasms with the resistance to late blight or gray mold or both. In this paper, the identified germplasms in our project have been used to map the genes with the resistance to both of them based on tomato database using molecular biology technology so that to meet the urgent requirement for tomato production in the practice in China. The main results obtained in this paper were concluded as the following:1. 22 wild germplasms of tomato from 8 different species have been screened by the artificial inoculation with gray mold during the seedling. The results showed that L. hirsutum PI134417, PI247087, PI126445, LA1392, LA 1341, L. lycopersicodie LA2951, LA2408 presented more resistant than others. The percentage of disease lesion was less than 5% of leaf area. According to the reported results from other research groups, we concluded that some germplasms of L. hirsutum and L. lycopersicode could provide the resistance to gray mold for tomato breeding.2. The germplasms including L. hirstum LA 1033, LA1777 and LA2099with the resistance to 8 different races of late blight in China have been identified through the artificial inoculation. The interspecies hybrid crossing these wild species as a male parent with L. esculentum as a female parent was obtained using embryo culture. The results from NILs (near isogene lines) containing Ph-2 and Ph-3 genes have proved that all of them gave a age-related resistance during the seedling stage. The resistance of most lines was increased significantly along with the development of the plant age.3. A linkage map including 13 linkage groups was constructed by AFLP and SSR makers based on 200 individuals of BC₁ population derived from crossing the line 99165-30 with L. hirsutum PI134417 was constructed. The total distance of this map was 801cM. Mapping of QTLs with the resistance to gray mold in tomato leaves and fruits were also conducted. The results indicated that two QTLs were involved. Among them, one QTL with resistance to gray mold in the leaves was located on tomato chromosome 2 and tightly linked with E40/M59-9 marker and accounted for 9.0% of phenotype variation with LOD 3.83. The interval was 14.3 cM flanked by E40/M61-11 and SSR32. The second QTL was mapped on the end of chromosome 3 and accounted for 8.8% of the phenotypic variation in disease severity of the leaves tightly linked with SSR11. The LOD was 2.90 with the effective factor 0.068. The last resistance QTL for the fruit was mapped on tomato chromosome 2 and accounted for 16.5% of phenotype variation with LOD 3.11 with the effective factor-38.08. The interval was 7.0 cM flanked by E32/M59-6 and SSR57.4. In order to identify QTLs involved in the resistance to gray mold on other tomato species, 38 and 93 introgression lines respectively from L. hirsutum LA 1777 and L. lycopersicode LA2951 together with their parent lines L. esculentum E6203 and VF36 have been screened. The results indicated that the resistance QTLs from LA 1777 were distributed on chromosome 1, 2, 3, 4, 6, 7, 8, 10, 12. Among them, the locus named hirgm4-2 flanked by TG22 and TG464 on the end of chromosome 4 gave a good contribution for the phenotype variation. The area of disease lesion was reduced 78.53% comparing to E6203. However, QTLs from LA2951 were located on chromosomel, 2, 4, 5, 6, 7, 8, 9, 11, 12. Among them, one QTL named Iygm7-1 located on chromosome 7 flanked by TG499 and TG438 gave more resistance and the area of the disease lesion was reduced 82.8% comparing to VF36 after the inoculation. Comparative analysis of different QTLs from two species suggested that some QTLs were co-localized on chromosome 1,2,4,8. Co-localization of QTLs derived from PI 134417, LA 1777 and LA2951 was also found and linked with TGI91. The identified QTLs especially hirgm4-2 and Iygm7-1 in this paper would pave a way for tomato breeding with resistance to gray mold.5. 93 introgression lines derived from LA 1777 together with LA 1777 and E6203 also have been used to identify QTLs with resistance to races Tl, Tl,2 and T 1,2,4 of late blight. The results proved that one locus named LB12R3 linked with TG301 on chromosome 1 gave the resistance to race Tl,2. The second loci named LB12R2 flanked by TG254 and CT47 on chromosome 9 presented the resistance to race Tl,2. The last loci named LB1R1 or LB12R2 flanked with TG557 and CT102 on chromosome 11 gave the resistance to both of race Tl and Tl,2. Meanwhile, 6 loci on chromosome2, 3, 4, 5, 8, 3 loci on chromosome 4, 8 and 12 loci on 12 chromosomes all gave the susceptive to one or more races of Tl, Tl,2 and T 1,2,4 of late blight.6. 3 lines including LA3937, LA3946 and LA3999 identified showed the resistance not only to late blight but also to gray mold. Among them, LA3999 gave the significant difference comparing to L. esculentum E6203. The LB1R1 loci resistant to late blight and hirgyl-2 resistant to gray mold on chromosome 1 showed the co-localization. Hence, this line could be a very useful resource for the resistance to both of the diseases in tomato.7. Based on the major diseases including gray mold, root knot nematode, tomato mosaic virus(ToMV) , tomato spotted wilt virus (TWSV ) in China for tomato production, a CAPs maker tightly linked with lygml-1 loci identified in this paper from LA2951 introgression lines was developed. Then a multiple PCR system which could be used to simultaneously identify both of genes including Iygm7-1 with the resistance to gray mold, Mi gene with resistance to root knot nematode, Tm22 gene with the resistance to ToMV and Sw-5 gene with the resistance to TSWV was established. The multi-PCR could be used as an efficient tool for the selection assisted by molecular makers at the early stage for tomato breeding.