Afolabi, M.S.

Akoroda, M.O.

Carey, E.E.

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*Afolabi, M. S.1; Carey, E. E. 2 ; Akoroda, M.O.31 Department of Crop and Soil science, Landmark University, Omu Aran, Kwara state, Nigeria. 2 CIP c/o CSIR-CRI, Kumasi Ghana.3 Department of Agronomy, University of Ibadan, Ibadan, Nigeria. *Corresponding author, afolabimike97@yahoo.comDiallel Analysis of Sweetpotato [Ipomoea Batatus (L.) Lam] Genotypes for combined Beta Carotene and Dry Matter Content in southern Guinea Savanna, Nigeria.AbstractRoots of orange fleshed sweetpotato (OFSP) varieties currently available in Nigeria contain high quantities of β-carotene or pro-vitamin A but have high moisture content. These varieties have been found to be a cheap and crucially important remedy for vitamin A deficiency. The cream or white fleshed varieties on the other hand, have a sweet taste but high dry matter content, giving a dry texture, a quality trait preferred by the communities in Kwara State, Southern Guinea Savanna, and Nigeria. Development of sweetpotato genotypes that can combine these two important quality traits is the objective of this breeding work.A diallel experiment using six parental sweetpotato genotypes crossed in all possible combinations were carried out and Thirty progenies were evaluated for beta carotene (β-carotene) and dry matter content in Landmark University, Omu Aran, Kwara State, Nigeria (Southern Guinea savanna). The selected 30 F1 progenies along with their parental lines were planted in the same field trial. The trial was laid out in 6 x 6 triple lattice in two replications. . Highly significant (P≤ 0.01) differences were observed among the genotypes for the traits. The average β-carotene content among the progenies was 2.86 (mg/100g.f.w) while the dry matter content had a mean value of 31.89%. The cross progenies 199024.2 x Excel which had the highest beta carotene(14.37mg/100g.f.w) content with highest dry matter content ( 40. 10%)are therefore recommended for further evaluation.Sweetpotato is one of the most under exploited of the developing world’s major crops (Rees et al., 2003), as evidenced by its breeding initiatives that are at relatively early stages compared to other crops. The need to identify local germplasm with desirable traits has long been recognised by breeders (Rees et al., 2003). It has been long known that many sweetpotato traits are mainly quantitatively inherited (Jones, 1986). To meet the quality needs there is a need to take into account the farmer and consumer preferences when developing and selecting sweetpotato varieties and in most cases this can be addressed through participatory variety selection. Fortunately, the attributes considered most important by farmers and consumers were already identified and ranked by Rees et al. (2003). The present research examined the quantitative inheritance of important traits in sweetpotato by means of a diallel analysis with a view to estimating the GCA and SCA components of genetic variance, and to determine the associated type of gene action controlling β-carotene content and root dry mass.Hand crosses were carried out in a 6 x 6 full diallel, excluding selfs from 2010 to 2011 at Parry Road, University of Ibadan, Nigeria. (3° 45’E and 7° 5730’ N). The parents were from germplasm collection at the Department of Agronomy, University of Ibadan (Table 1).Table 1 Parental genotypes and their traits used in a 6x6 full diallel excluding selfsNo Genotype Root flesh colour Root Dry mass Source1 199024.2 Orange 31.02 CIP Kenya2 440034 Orange 26.92 CIP Kenya3 Excel Orange 28.53 South Africa4 W-151 Yellow 34.29 CIP Kenya5 TIS 87/0087 White 30.67 IITA Ibadan6 440168 White 32.31 CIP KenyaFruits were harvested between 30-50 days after pollination in the early morning to prevent scattering. The fruits were further air dried, shelled, put in a labeled envelope and kept in desiccators. The harvested seeds were soaked in water over night and planted in to polythene bags filled with loamy soil (Figure 1)Statistical analysis of triple latticeData collected on the two traits were subjected to diallel nanalysis using Griffing (1956) Method II (parents and crosses together), Mixed I (fixed effects). Both general and specific combining abilities (gca and sca) were computed using SAS PROC. (1999) for the parent and crosses.Analysis of variance for β-carotene and dry matter contentThe Analysis of variance of the 6x6 triple lattice provides the variances (mean squares) and block corrected means of the parents and their crosses for the β-carotene and dry matter content. There was highly significant (p<0.001) variation among the parents and crosses for the traits (Table 2).Figure 1: pollination and establishment of seeds obtained from crosses.        Results Materials and MethodsTable 2: ANOVA for six sweetpotato parents and their 30 F1 families evaluated in a triple lattice designSource Mean squaresdf β-carotene content (mg 100 g-1) Dry Matter content (%)Rep 1 0.75ns 7.85nsTreatment 35 38.39** 34.28***Block within reps 35 14.1 29.60Intra-block error 70 0.32 5.10Total 141***, ** Significant at P<0.001 (F-probability); NS=not significantThe results of average performances of some of the crosses show that the performances of crosses are significantly higher than the two parents for the traits (Table 5). Cross 1 x 3 and the cross 1 x 4 are the best in term of β-carotene content with means of 14.37 and 12.39 mg 100 g-1, respectively. Cross 2 x 4, 2 x 5, 4 x 5, 4 x 6 and 6 x 3 were the lowest with means of 0.03 mg 100 g-1 each.The cross 1 x 3 has the highest dry matter content with a mean of 40.10%, followed by crosses 2 x 3 and 4 x 6 with means of 38.67 and 38.89%, respectively. Cross 5 x 4 had the lowest means of 24.49% . Table 3: Block corrected means for six sweetpotato parents and their diallel evaluated Parents/Crosses β-carotene content Dry Matter content(mg 100 g-1) (%)1 x 2 1.5 33.001 x 3 14.37 40.101 x 4 12.39 30,51 x 5 1.32 31.881 x 6 3.37 28.432 x 3 5.49 38.672x 4 0.03 31.152 x 5 0.03 27.382x 6 1.74 27.273 x 4 1.5 29.493 x 5 0.12 31.673 x 6 1.38 35.714 x 5 0.02 37.044 x 6 0.03 38.895 x 6 1.38 34.15Reciprocal2 x 1 11.03 33.823 x 1 4.92 31.864 x 1 4.41 29.735 x 1 0.12 34.006 x 1 1.38 34.783 x2 4.92 25.864 x 2 0.13 35.005 x 2 1.66 32.696 x 2 1.50 34.724 x 3 6.12 32.565 x 3 4.92 28.306 x 3 0.03 33.335 x 4 1.38 24.496 x 4 1.5 33.946 x 5 0.03 27.47*Parent 1 1.38 36.25*Parent 2 0.15 32.00*Parent 3 5.49 26.47*Parent 4 0.00 25.86*Parent 5 0.03 29.73*Parent 6 0.12 28.30Mean 2.86 31.89s.e 0.39 5.38CV (%) 15.1 7.01LSD 0.05 0.85 6.04 *Parent 1=199024.2, parent 2=440034, Parent 3=Excel, parent 4= W-151, parent 5= TIS87/0087 and parent 6= 440168General and specific combining ability analysis for β-carotene content and dry matter content ANOVA for GCA and SCA mean squares for β-carotene content and dry matter content were highly significant (p<0.001) (Table 3). The mean squares for reciprocals of β-carotene content is significant whereas mean squares for dry matter for the reciprocal is not significant (p<0.001).Analysis of variance for β-carotene content and dry matter content evaluated in a triple lattice experimental designThe significant (p<0.001) mean square for β-carotene content, and dry matter content shows that there are genetic variation among the parents and their crosses. Crosses outperforming their parents can be attributed to transgressive segregation which is desirable for improving β-carotene content and dry matter content. Progeny from cross 1 x 3 was the best overall.It is therefore recommended that:1. The parent 1 and 3 indentified to be good general and specific combiners of β- carotene and dry matter content should be further intrigressed into other proven cultivatrs in the improvement of β- carotene and dry matter content in sweetpotato.2. The indentified crosses with the highest dry matter and β- carotene content could be incorporate into on-farm trial for proof.This study was made possible through the support of Dr. Ted Carey and supervision by Prof. M.O. Akoroda, the Department of Agronomy Family of the University of Ibadan. I wish to also acknowledge the scholarship funded by CGIAR Research Program on Roots, Tubers, and Bananas (RTB), who sponsor my conference attendance of APA 2013. Thank you very much.Baker, R.J., 1978. Issues in diallel analysis. Crop Science 18: 533-536.Becker, W.A., 1967. Manual of procedures in quantitative genetics (2nd Ed.). Program in Genetics, Washington State University. Washington, USA.Deficiency Information System. Global prevalence of vitamin A deficiency. MDIS Working Paper 2.WHO/NUT/95.3. Geneva, Switzerland.Dickinson, A.G., and J.L. Jinks. 1956. A generalised analysis of diallel crosses. Genetics 41: 65-78.RecommendationDiscussion and conclusionAcknowledgmentsReferences

Diallel analysis of sweetpotato [Ipomoea batatus (L.) Lam] genotypes for combined beta carotene and dry matter content in southern guinea savanna, Nigeria.

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Diallel analysis of sweetpotato [Ipomoea batatus (L.) Lam] genotypes for combined beta carotene and dry matter content in southern guinea savanna, Nigeria.

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