Morphological and molecular analysis for assessing intraspecific variation in sweet potato (Ipomea batatas (L.) Lam.) and interspecific divergence in Ipomoea spp.
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Date
2020
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Department of Plant Biotechnology, College of Agriculture, Vellayani
Abstract
The study entitled “Morphological and molecular analysis for assessing
intraspecific variation in sweet potato (Ipomoea batatas (L.) Lam.) and interspecific
divergence in Ipomoea spp.” was carried out in the Division of Crop Improvement,
ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram
during 2019-2020 with an objective to analyse the intraspecific variation in sweet
potato and interspecific divergence in Ipomoea spp. based on morphological and
molecular markers.
Forty one Ipomoea batatas accessions from the National Active sweet potato
germplasm site at ICAR-CTCRI and 6 wild species collected from ICAR-CTCRI
campus and KAU, Vellayani (Ipomoea aquatica, Ipomoea palmata, Ipomoea obscura,
Ipomoea vitifolia, Ipomoea nil and Ipomoea triloba) were used for the study.
Morphological analysis was performed by using eighteen sweet potato
descriptors as provided by IPGRI (CIP et al., 1991). The recorded data were analyzed
statistically by various tools such as PCA and cluster dendrogram using Multivariate
statistical package (MVSP 3.22). The dendrogram separated the accessions into two
principal clusters at a Euclidean distance of 1.7. The PCA analysis revealed
predominant vine colour, leaf lobes type, shape of central leaf lobe, immature leaf
colour and petiole pigmentation as the major variables that contributed to the
clustering of the sweet potato accessions.
. Molecular characterisation was performed using ISSR markers. The genomic
DNA was isolated from young leaves using Dellaporta et al. (1983) method. 11 ISSR
primers were used for screening of forty seven accessions. PCR amplicons obtained
using selected primers were resolved on 2% agarose and polymorphic bands were
scored. The selected primers showed 100% polymorphism and the number of bands
ranged from 12 to 23 with a mean value of 19.2 polymorphic bands per primer. A total
of 211 polymorphic bands were obtained. The data analysed using NTSYS PC 2.02
program generated a dendrogram, which grouped the forty seven accessions into two
principal clusters bas, ed on Jaccard‟s similarity coefficient. All the sweet potato
accessions were included in the first principal cluster which was subdivided into seven
sub-clusters and there was a lot of intra-cluster variation. The second principal cluster
consisted of all the 6 wild species with Ipomoea palmata as an outlier. The clustering
was also found similar in morphological characterization. The similarity between the
different accessions ranged between 50-85%. The accessions S623 and S632 (Iba 3
and Iba 5) were 85% similar. The least similar accessions were AR-2017-2 (Iba 19)
and I.vitifolia (35%). Three Ipomoea batatas [S 823 (Iba 38), S 663(Iba 24) and SD-
11 (Iba 31)] showed maximum similarity (72%) with the wild Ipomoea spp. Ipomoea
triloba and Ipomoea aquatica were the most similar ones among all the wild species
by 72%. The least similar accessions among wild species were Ipomoea palmata, I.
aquatica and Ipomea vitifolia (59%). Among all the wild species I.triloba showed
maximum similarity (72%) with sweet potato (Iba 31). Mantel‟s test also showed a
significant correlation (r = 0.4365; p = 0.0001) between the molecular and
morphological distance matrices indicating that the morphological characters that were
used in this study are genetically controlled and not affected by the environment. The
hexaploid nature of the crop, self-incompatibility, along with the outcrossing nature
together might have contributed to the high variation observed among the accessions.
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