Journal of Horticultural Sciences

B. Padmakar ¹, C. Kanupriya ², P. Madhavi Latha ², C. Vasugi ², M. R. Dinesh ², D. Sailaja ³, C. Aswath ²

Affiliations
1 Center for Biotechnology, JNTU, Hyderabad, Telangana, IN
2 ICAR-Indian Institute of Horticultural Research, Hesaraghatta Lake Post, Bengaluru - 560089, Karnataka, IN
3 Department of Biotechnology, GRIET, Hyderabad, Telangana, IN

Abstract

The present research focuses mainly on molecular mining and morphological evaluation of guava genome within a full-sib population and, thereby, mapping of quantitative trait loci related to fruit quality traits, viz., seed strength (hardness/softness) and average fruit weight. Linkage maps were enriched for both parental lines, 'Kamsari' and 'Purple Local' using a set of 60 RAPD markers following the pseudo-testcross strategy on a panel of 94 progeny. A total of 480 scorable markers were identified, of which 131 were specific to 'kamsari' and 28 to 'Purple Local', segregating as test cross markers, and, 321 showing intercross pattern common to both. 'Kamsari' spanned a total length of 1959.1cM with average marker interval distance of 3.93cM, while 'Purple Local' spanned a length of 1537.9cM with average marker interval distance of 3.29cM, by forming 11 linkage groups. Estimated genome length observed was 93.02% and 92.77% in 'Kamsari' and 'Purple Local', respectively. Composite Interval Mapping (CIM) was computed at significance of 0.05 and LOD threshold greater than 3.0, which led to detection of one major QTL for the trait of average fruit weight, and, four QTLs for the trait of seed strength (hardness/softness). Of these, two were major and two minor QTLs. Our study provides molecular mapping information on marker-assisted selection for improvement of guava in a breeding program.

Keywords

Composite Interval Mapping, Guava, Linkage Map, Pseudo-Testcross, Quantitative Trait Loci (QTL).

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B. Padmakar ¹, D. Sailaja ², C. Aswath ³

Affiliations
1 Centre for Biotechnology, Jawaharlal Nehru Technological University, Hyderabad, Telangana, IN
2 Department of Biotechnology, Gokaraju Rangaraju Institute of Engineering and Technology, Hyderabad, Telangana, IN
3 Division of Ornamental Crops, ICAR-Indian Institute of Horticultural Research, Bangalore, Karnataka, IN

Abstract

In the present study, molecular evaluation of two guava mapping populations (MP), MPI comprising 94 F1 progenies and MPII comprising 46 F1 progenies, was carried out using simple sequence repeat (SSR) and random amplified polymorphic DNA (RAPD) markers. A pseudo-test cross strategy was implemented where 'Kamsari' X 'Purple Local' and 'Purple Local' X 'Allahabad Safeda' were crossed, and, these showed variation in fruit quality traits such as seedstrength (hardness/softness), fruit weight, TSS and pulp color. A set of 30 RAPD markers was used for genotyping MPI while a set of 55 SSR markers was used for genotyping MPII. In case of MPI, 30 RAPD markers generated 214 scorable markers, of which 80 markers were specific to 'Kamsari', 14 markers to 'Purple Local' and the remaining 120 were intercross markers. As for MPII, 55 polymorphic SSR markers resulted in generation of 207 alleles (with a maximum of 4 alleles and a minimum of 3 alleles per locus), of which 108 alleles were specific to 'Purple Local' while 99 were specific to 'Allahabad Safeda'. Genotypic data thus generated can be further exploited for constructing genetic linkage maps and mapping complex QTLs governing fruit quality traits in guava..

Keywords

Guava, Genotyping, M13-Tailed PCR, SSR, RAPD.

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M. V. Naga Chaithanya ¹, M. R. Dinesh ², C. Vasugi ², D. C. Lakshmana Reddy ¹, D. Sailaja ³, C. Aswath ¹

Affiliations
1 Division of Biotechnology, ICAR- Indian Institute of Horticultural Research, Hesaraghatta Lake Post, Bengaluru-560 089, IN
2 Division of Fruit Crops, ICAR- Indian Institute of Horticultural Research, Hesaraghatta Lake Post, Bengaluru-560 089, IN
3 Department of Biotechnology, Gokaraju Rangaraju Institute of Engineering and Technology, Hyderabad-500090, IN

Abstract

Although the varietal diversity is fairly rich in guava, most varieties lack one or more desirable characters. Hence, attempts were made for improving specific traits, viz., attractive pink pulp colour, soft seeds, medium fruit size, high TSS and high ascorbic acid. Genetic diversity analysis is a prerequisite for identifying potential parents in breeding programs and germplasm conservation. Molecular characterization helps discriminate closely-related genotypes, as, this technique is unaffected by environment, rendering it more reliable. In this study, 48 polymorphic SSRs screened from a total of 115 SSR markers were used for analyzing marker segregation in 72 guava accessions. Statistical analysis was done using IDENTITY1.0 and CERVUS 3.0 software. Cluster analysis was done with DARwin 5.0 software, using Wards Minimum Variance method, and weighted group neighbour joining method, to check reliability of grouping among clusters. The trend in grouping was found to be similar in both methods. Dendrograms generated showed that the hybrids clustered with their parents; exotic collections fell into two different sub-groups based on productivity; the wild species formed one group; and Navalar cultivars from Dharwad clustered together, reflecting similar origin.

Keywords

Guava, Genetic Diversity, Dendrogram, Simple Sequence Repeats.

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