RAPD and SCAR markers linked to resistance to frogeye leaf spot in soybean

Sebastião Martins Filho,Everaldo Gonçalves De Barros,Maurilio Alves Moreira,Carlos Sigueyuki Sediyama

doi:10.1590/s1415-47572002000300012

Sebastião Martins Filho, Everaldo Gonçalves De Barros + Show 2 more

Open Access

https://doi.org/10.1590/s1415-47572002000300012

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Abstract

The soybean (Glycine max (L.) Merrill) frogeye leaf spot is caused by the fungus Cercospora sojina Hara and is a widespread disease in Brazil and other countries, causing severe losses in grain yield and also affecting seed quality. The availability of DNA markers linked to genes for resistance to this disease would accelerate breeding programs, particularly when other traits are also being evaluated. Bulked segregant analysis was applied to 3 F2 populations derived from crosses between the resistant cultivars Parana, Cristalina and Uberaba, and the susceptible cultivar Bossier. In the cross 'Parana' x 'Bossier', 2 RAPD markers were identified, CSOPA1(800C) and CSOPA2(1,250C), located at 4.4 ± 1.8 centiMorgans (cM) and 3.4 ± 1.7 cM respectively from the resistance locus. DNA fragments of similar molecular weight were observed in the population derived from the cross 'Cristalina' x 'Bossier' at 2.3 ± 1.2 and 4.7 ± 1.5 cM from the resistance locus, respectively. In the offspring of the cross 'Uberaba' x 'Bossier', a DNA fragment corresponding to marker CSOPA1(800C) was detected at 5.6 ± 2.1 cM from the resistance locus. Although marker CSOPA2(1,250C) was not observed in this population, an additional marker was detected (CSOUB1(1,100C)) at 6.7 ± 2.2 cM from the resistance locus. The 1,250 bp fragment of CSOPA2(1,250C) was cloned and converted into a SCAR marker, which amplified a single fragment whose size corresponded to the cloned segment of the crosses involving cultivars Cristalina and Parana. Markers CSOPA1(800C), CSOPA2(1,250C) and CSOUB1(1,100C) were mapped to soybean linkage group J with the aid of known SSRs linked to the Rcs3 locus, indicating that the RAPD and SCAR markers identified in our research also tag this resistance gene.

Highlights

Frogeye leaf spot, caused by the fungus Cercospora sojina Hara, is a worldwide important soybean disease, causing both yield losses and seed deterioration
We report on the identification of DNA markers linked to soybean loci responsible for resistance to C. sojina in soybean cultivars Cristalina, Parana and Uberaba, and on the confirmation of the resistance locus identity
These bands were present in all resistant individuals of the bulks and absent in all susceptible individuals. These markers were designated CSOPA1800C and CSOPA21,250C, because they are linked to a locus which controls resistance to C. sojina (CSO) originally detected in cultivar Parana (PA), contain approximately 800 and 1,250 bp, respectively, and are in the coupling-phase (C) with regard to the resistance gene

Summary

Introduction

Frogeye leaf spot, caused by the fungus Cercospora sojina Hara, is a worldwide important soybean disease, causing both yield losses and seed deterioration. The use of resistant cultivars is the most efficient and costeffective means of controlling this disease, but the existence of several C. sojina races (Yorinori, 1989b) demands the permanent search for new sources of resistance and their incorporation into resistance breeding programs. Another factor to be considered is that the evaluation of soybean crops with regard to this disease is a timeconsuming process, which requires expertise for the precise distinction between susceptible and resistant plants. These problems can be better managed in breeding programs by identifying and using DNA markers linked to resistance genes. We report on the identification of DNA markers linked to soybean loci responsible for resistance to C. sojina in soybean cultivars Cristalina, Parana and Uberaba, and on the confirmation of the resistance locus identity

Material and Methods

Evaluation of symptoms

Results and Discussion