Identification of Cowpea (Vigna unguiculata. L. (Walp.)) Lines and Polymorphic Genebased. microsatellite Markers for Resistance

Transcription

1 Identification of Cowpea (Vigna unguiculata L. (Walp.)) Lines and Polymorphic Genebased microsatellite Markers for Resistance to Aphids (Aphis Craccivora Koch) Ouedraogo P. Adelaide, Tignegre Jean-Baptiste, Batieno Benoit Joseph, Poda S. Leandre, Traore Fousseni, Ouedraogo Jeremy, Bao-Lam Huynh, Philip Roberts, and Close Timothy Feed the Future Innovation Lab for Collaborative Research on Grain Legumes

2 Presentation outline INTRODUCTION MATERIAL and METHODS RESULTATS CONCLUSION and RECOMMANDATIONS

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4 Figure 1:(left) cowpea plant; (right) Seed characteristics of farmer preferred varieties, Kamboinse 2008 Figure 2: Cowpea based-meals Hay for feeding livestock. Important source of income. Cowpea is grown as a green manure and as a cover crop (United States). Figure 3: (TOP) Vigna unguiculata subsp. Unguiculata cv.-gr. Textilis (BOT) California Blackeye 27 Photo by: Mitchell Lucas

5 Figure 4: Cowpea production by region ( average ), FAOSTAT 2014 Figure 5: Cowpea production ( top 10 producers), FAOSTAT 2014

6 Production constraints: biotic, abiotic and socio-economic (Tignegré, 2010). Yields losses related to insect can be up to 100% in sub- Saharan Africa (Singh and Jackai, 1985). Aphis craccivora is one of the insects responsible for yield losses in cowpea. It causes damage by altering the metabolism, taking nutrients from the plant, and by transmitting plant viruses (Blackman and Eastop 2000)

7 Figure 6: wingless and winged aphids Relatively tiny Adults can be winged or wingless Two reproductive pathways Great adaptability

8 Figure 7:Resurgence of A. craccivora in farmer field 3 weeks after insecticide application

9 MAIN OBJECTIVE: The aim of this study was to contribute to an increase in the yield of cowpea by the identification of aphid resistant lines and polymorphic gene-based markers. SPECIFIC OBJECTIVES: To screen cowpea genotypes for resistance to aphids. To characterize populations of aphids that prevail in cowpea growing areas. To identify polymorphic markers for selection purposes.

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11 MATERIALS Kvx D Figure 8&9:pictures of the 10 varieties of cowpea used for the aphid resistance test Tiligré and Kvx for the polymorphism test.

12 METHODS Source and maintenance of experimental insects Figure 10: Aphids sampling areas located in the three main agro-climatic zones in Burkina. Figure 11: Cages used for aphides maintenance Experimental design: Randomized complete block design with three (3) blocks, five (5) repetitions each. Plants in each block were infested with only one of the three (3) aphid strains.

13 Figure 12: Infestation technique Observations were made every three days and consisted of measuring some parameters: The number of leaves; Plant survival; The dynamics of the aphid populations.

14 No aphid 1 to 5 aphids 5 to 20 aphids 20 to 100 aphids 100 to 500 aphids More than 500 aphids Figure 13: Field layout

15 To look for polymorphic markers, DNA of each parent was extracted, and amplified with each ninety-six (96) pairs of SSR primers. The raw data of 20 DAS, 35DAS, 50 DAS, 65 DAS, one month after infestation and data from the AUDPC were used for several analyzes. XLSTAT 7.1 and SAS 9.4 software were used to analyze the data. The formula used to calculate the AUDPC is: n AUDPC = Σ [(Xi+1 + Xi) / 2] [ti+1 - ti] i=1

16 RESULTS

17 IDENTIFICATION OF RESISTANCE SOURCES THE EVOLUTION OF THE INFESTATION Varieties 20 DAS 35 DAS 50 DAS 65 DAS AUDPC B CB IT97K KN KVX N NS NS-Farako Bâ SARC SARC Varieties 20 DAS 35 DAS 50 DAS 65 DAS AUDPC B CB IT97K KN KVX N NS NS-Farako Bâ SARC SARC Table 1& 2: Means data of degrees of infestation and the AUDPC (Bobo and Kamboinsé)

18 Varieties 20 JAS 35 DAS 50 DAS 65 DAS AUDPC B CB IT97K KN KVX N NS NS-Farako Bâ SARC SARC Table3: Means data of degrees of infestation and the AUDPC (Kamboinsé) Table 4,5 &6 : correlation test between degrees of infestation at 20 DAS ; 35 DAS ;50 DAS ; 65 DAS and the AUDPC (respectively aphids strain of Kamboinsé, Bobo and Pobe) Varia ) bles 20 DAS 35 DAS 50 DAS 65 DAS AUDPC Varia bles 20 DAS 35 DAS 50 DAS 65 DAS AUDPC Varia bles 20 DAS 35 DAS 50 DAS 65 DAS AUDPC 0 DAS 1 5 DAS DAS DAS UDPC DAS 1 35 DAS DAS DAS AUDPC DAS 1 35 DAS DAS DAS AUDPC

19 SIMILARITY AND CORRELATION TEST Table 7:Combined analysis of the AUDPC for the 3 strains of aphids. Fixed term Wald statistic n.d.f. F statistic d.d.f. F pr A.Strains Varieties Strain * Varieties Table 8: Correlations between the 3 variables (number of leaves, survival rate and degree of infestation) N. Lea. 1 N. Lea. D.INF. Surv.R. D.INF SURV.R

20 VARIETIES CLASSIFICATION Dissimilarity IT97K KN-1 B301 KVX SARC CB 27 SARC NS-1 N 2300 NS-Farako Bâ Dissimilarity KVX N 2300 SARC CB 27 IT97K NS-1 SARC NS-Farako Bâ B301 KN-1 Figure 14&15 :Dendrogram representing the three classes of varieties (left:strain of kamboinse; right:strain of Bobo)

21 25 20 Dissimilarity KN-1 KVX IT97K SARC B301 SARC Resistant Moderately Resistant N 2300 NS-1 CB 27 NS-Farako Bâ Susceptible Figure 16 :Dendrogram representing the three classes of varieties (Strain of Pobé) Tableau 9: Characteristics of the 10 varieties studied in the three aphid strains. RESISTANTS MODERELY RESISTANTS SUSCEPTIBLES IT97K B301 N 2300 VARIETIES SARC CB 27 NS-1 KVX SARC NS-Farako Bâ KN-1

22 CHARACTERIZATION OF APHID STRAINS Tableau 9:Fisher's F associated with the square of the Mahalanobis Bobo-Dioulasso Kamboinsé Pobé Mengao Bobo-Dioulasso 0.00 Kamboinsé Pobé Mengao

23 POLYMORPHISM TEST 24 polymorphic markers out 96. Figure 18:Electrophoretic profile

24 CONCLUSION & RECOMMANDATIONS

25 Among the 10 varieties: Four(4) resistant varieties, three (3) moderely resistant. The Pobé strain is similar to that of Kamboinsé and these two strains are different from the Bobo one. Twenty four (24) polymorphic markers found.

26 Validation of polymorphic markers specially codominant ones for selection purposes. Molecular characterization of Bobo, Pobé and Kamboinsé aphid strains in order to give more precise information about the genetics of the different strains of aphids.

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