Transcript Document

Selection of potato breeding clones resistant to potato nematode Globodera
rostochiensis Ro1 using artificial inoculation and adaption of molecular markers
assisted selection in State Priekuļi Plant Breeding Institute.
G. Ūsele1, I. Mežaka 1, I. Skrabule 1 and N. Rostoks2
1
State Priekuļi Plant Breeding Institute
2Faculty of Biology, University of Latvia, 4 Kronvalda Blvd., Riga, Latvia
E-mail: [email protected]
Introduction/Problem
Potato cyst nematodes (PCN) are the major problem in worldwide potato production
especially in cool-temperate areas.
Potato cyst nematodes are sedentary endo-parasites, requiring the roots of potato to
complete their lifecycle. During PCN invasion, occupation and subsequent emergence into
the rhizosphere, the roots are irreparably damaged, reducing their ability to take up water
and minerals.
In infested fields, mature females and cysts may be found on potato roots within eight to
eleven weeks after crop emergence. Cysts are visible to the naked eye and can be seen as
minute white or yellow globes on the root surface (Fig.1. and 2. ) G. rostochiensis females
progress from white to a golden yellow colour before darkening into the cyst, the golden
yellow phase lasting 4-6 weeks.
Breeding of resistant cultivars is the most desirable and effective method of control of pest.
Potato breeding material has been screened using artificial inoculation in State Priekuli Plant
Breeding Institute since year 2000. Adaption of molecular markers for detection of nematode
resistance genes has been initiated since 2010. Marker assisted selection (MAS) could
fasten breeding work and save material and labor expenses.
Methodology
Fig.1. Potato roots infected with
Globodera rostochiensis cysts ten
weeks after inoculation
Inoculation
Third year generation tubers have been planted in pots with soil infected with nematode.
Inoculation were done in three replications for each breeding line. The pathotype Ro1 of
Globodera rostochiensis was used for inoculation, as it is the only confirmed patotype
presented in Latvia. Inoculation was carried out in May and after 8-11weeks infection
degree was determined and susceptible to nematode clones was discarded. Genotypes
were designated resistant when no cysts were, and susceptible when the test of resistance
showed more than three cysts in every replication. If one or two of replications from one til
three cycts were found, cultivar was counted as partialy resistant. Resistant standarts were
the cutivars Brasla and Lenora, susceptible standart were the cultivar Mutagenagrie.
First steps of implementation of MAS
Marker assisted selection (MAS) has been initiated at 2010 to test nematode pathotype Ro1
resistance. The first steps of MAS implementation is to verify results of molecular markers
by comparing them with results obtained by artificial inoculations. If MAS proves to be
reliable, application of MAS could help fasten selection towards nematode resistance
testing and to save costs and labor because hybrids with no resistance would be discarded
at early generations.
Markers Ro1 (indicator of gene H1 that confers resistance to G. rostochiensis pathotypes
Ro1, Ro4 from S. tuberosum spp. andigena) and Gro1 (indicator of the presence of
resistance to G. rostochiensis pathotypes Ro1, Ro2, Ro3, Ro4 and Ro5 from S. spegazzinii),
published by Biryukova (2008), are being used to detect resistance genes in breeding
clones and simultaneously the same clones were artificially inoculated with nematode
pathotype Ro1 to verify the results obtained with molecular markers.
Table 1. Potao breeding sheme 2010, Priekuli, Latvia
Year
Breeding material
Number of
genotypes
1.
Hybridization -crosses
2.
Seedlings
22000
3.
1st year field clonal genetarion
18000
4.
2nd year field clonal generation
1640
5.
3rd year field clonal generation (inoculation
and paralel testing with markers)
240
6.
Primary assesment of yield, quality and diseases
and pest resistance
150
Assesment of yield, quality and diseases and
pest resistance
130
7. – 9.
10. – 12.
Results:
Amount of resistant breeding clones in tested material varied from 68% to 74% depending
on parents (Fig.3.- Fig.5.).
Molecular markers usually are developed in biparental mapping populations and often are
applicable only to test resistance in hybrids of the certain cross. To test whether markers
would be applicable in wider set of germplasm, data on variety resistance to PCN
pathotype Ro1 was acquired from public database www.europotato.org and compared to
resistance status acquired by molecular markers.
Two known genes are known for resistance to PCN pathotype Ro1 – Gro1 and H1.
Therefore testing results were considered consistent if 1)presence of resistance allele of
either gene or both genes was detected by molecular markers and inoculations tests
revealed that variety is resistant or 2)succeptible allele of both genes was detected and
inoculation tests revealed that variety is resistant.
In 92% of samples data obtained from databases was consistent with data obtained by
molecular markers. In 7% of cases susceptible allele was detected by molecular markers in
varieties in which resistance was reported in databases. In 1% of cases resistant allele was
detected by molecular marker in varieties in which were reported as susceptible.
Inconsistency of results could be explained by several reasons: 1) resistance could be
maintained by other gene than tested one; 2) there has been a crossover between marker
and resistance gene; 3) there could be phenotyping of genotyping errors.
Fig.2. Potato plant ten
weeks after inoculation
150
Official DUS and VSU tests for including in Plant
Variety Cataloque
1
Results of inoculation from year 2005 til year 2010, depending on resistance status
of parents
resistant
9%
17%
susceptible
partialy
resistant
74%
Fig.3. One of parents resistant
7%
25%
12%
20%
68%
68%
Fig.5. Both parents resistant
Fig.4. Both of parents susceptible
Conclusions
Even if both of parents were resistant to nematode, no more than 74% of
progenies were resistant therefore testing is especially significant because
even choice of resistant parents does not guarantee resistant progenies.
To test on variety resistance to PCN In 92% of samples data obtained from
databases was consistent with data obtained by molecular markers. High level
of compatibility of data assures that markers Ro1 and Gro1 published by
Biryukova (2008), can be applied to wide set of germplasm.
References
Biryukova V.A., Zhuravlev A.A., Abrosimova S.B., Kostina L.I., Khromova L.M., Shmyglya
I.V., Morozova N.N., Kirsanova S.N., 2008, Use of molecular markers of potato Golden
nematode resistance genes H1 and GRO1. Russian Agricultural Sciences 34: 365-368
Acknowledgements
Implementation of molecular markers has been funded by EU Structural Funds (project:
“Development, improvement and implementation of environmentally friendly and sustainable
crop breeding technologies”, 2009/0218/1DP/1.1.1.2.0/09/APIA/VIAA/099 ),.