Multivariate analysis in sweet potato (Ipomoea batatas (L.) Lam.)

Introduction

Sweet potato is the vital crop which is extremely nutritious plant. It belongs to the family Convolvulaceae [1] . The mode of pollination is cross pollinated and exhibits heterozygosity nature. The ploidy nature of sweet potato is hexaploidy (2n = 6x = 90). China ranks top in the global production contributing 50% of the yield, globally [2] . It is cross-pollinated due to its self-incompatibility [3] . Sweet potato is the sixth most important crop worldwide. The crop has grown across the world around 110 countries. In India, the area under sweet potato cultivation is 0.13 Mha with the production of 1.47 Mtonnes [4] . It is the versatile crop both the tuber and the leaves are highly nutritious. The storage roots are high in protein, dietary fiber, micronutrients, vitamins, and bioactive components such as β-carotene and phenylpropanoids [5] . Domesticated sweet potato varieties vary in certain phenotypic and genotypic characteristics, they are rich in sugars, starch, vitamins, minerals, bioactive proteins and lipids, carotenoids, polyphenols, ascorbic acid, alkaloids, coumarins, and saponins. These phytochemicals, either separately or in combination, aid in the prevention of numerous diseases, such as cardiovascular conditions and some forms of cancer [6] . Sweet potato was first domesticated in Neotropical America, and due to the migration of human, the distribution of sweet potato plant across the world. Sweet potato germplasm has identified mainly by phenotypic characterization. Molecular characterization used to find the genetic diversity of the crop using genetic markers such as SSR, SNP, ISSR, AFLP and RFLP [7] .

Materials and Methods

In this study twenty genotypes were raised in randomized block design with three replications in kharif season 2025. These genotypes were analyzed for nine qualitative such as traits growth habit, ground covering capacity, insect resistance of shoot, vine hairs, predominant vine color, leaf shape, leaf hairs, color of adaxial leaf surface and color of the abaxial leaf surface. The traits were recorded by using IBPGR descriptors. The data of the nine qualitative traits were subjected to a Multiple Correspondence analysis in R version 4.5.3. The list of genotypes utilized in the study are listed in (Table 1).

Results and Discussion

Qualitative analyses

The twenty genotypes were analyzed for nine qualitative traits. Among all seven genotypes showed spreading and two showed very spreading nature. These growth types with spreading require more spacing and that is suited for bed planting due to its thick veins and maximum group coverage. There was no compact habit in any genotypes. Ten of the genotypes had semi compact growth habit. And this is used for pot cultivation. The spreading types could be suitably recommended for mono-cropping or sole cropping. Since these types require wide spacing for spreading their veins and for ground coverage, they need to be raised in wider spacing conditions in field [8] . And the semi-compact genotypes could be recommended suitably for intercropping methods with legumes. Owing to, the compact nature of these genotypes, it prevents the interspecific competitions and allows companion crops sufficient light [9] . Moreover, ten genotypes showed a capability to cover the ground more that 50%, it spreads their lateral vines into nearby areas. Five genotypes were observed with 20% coverage, five genotypes showed a moderate coverage (20% to 50%). These genotypes could also be recommended for multiple and mixed cropping systems [9] . Another trait was resistance to pest attack, only four genotypes were completely resistant pest. And other sixteen showed just mild damage from pest. Thus, the ones with the lowest pest infestations could be suitably recommended to possess a higher marketability and could be further evaluated for quality traits in breeding programs [10] Among all the genotypes, vine hairiness was more common in vine than in leaves. Out of twenty, only two genotypes showed hairy leaves and seven genotypes had hairy veins. Pubescence is a key trait for climate resilience and host plant resistance in sweet potato [11] By analyzing leaf shapes, seven genotype showed lobed leaf, three had cordate leaves, nine had hastate leaf shapes and only one genotype (IB20) exhibited almost divided leaf shape. These leaf shape was suitable for pot culture [12] . The genotype IB 12 showed purple leaf color on both the sides which made that genotype unique. And the genotype IB 13 showed variegated in their leaves which can be used for decorative arrangements. This anthocyanin are free radicle scavengers, reducing oxidative stress and chronic diseases such as diabetes, cancer, and cardiovascular diseases. Also it regulates glucose metabolisms [13] .

Frequency distribution Among all the genotypes, 55% of genotypes exhibited semi compact growth habit, 35% showed spreading type and 10% very spreading growth habit. Semi-compact growth habit is used for container cultivated for tuber production [14] . Spreading and very spreading growth habit has low weed emergence on the field [15] . Then, half of the genotypes were covered almost on the ground, then 25% was moderately covered and 25% showed less than 20% of ground coverage. The complete ground coverage reduces the soil erosion as well performing for weed control [16] . The less ground coverage genotypes are suitable for mono-cropping where it gets high yield [17] . Only four genotypes (20%) were free of insect damage and other 80% of genotypes were affected by pest sparsely. The genotypes which were insect free, they can be used as parental lines to develop pest resistant varieties [18] . Vine hair was the most common traits, 55% of genotypes had vein hairs but 45% of genotypes had no vine hairs. But in leaf 90% of genotypes showed absence of hairs and 10% of genotypes showed presence of hairs. The predominant vines showed diverse colors, 10% of genotypes had green vines, 65% of genotypes showed green with purple spots, 20% of vines had mostly or totally purple and only 5% of genotypes showed totally dark purple. Purple pigmentation act as a defense mechanism in climbing plants. Because, it is associated with higher phenolic compounds which had anti-feeding effects [17] . Followed by leaf shape, only 5% of genotypes showed almost divided shape, 15% of genotypes showed cordate shape of leaves, 45% of genotypes showed hastate shape of leaves, and 35% of genotypes showed lobed type of shape. At last, 55% of total genotypes showed green color in their adaxial leaf surface, 30% of genotypes showed green with purple border, 5% of green with veins and 10% of the genotypes showed purple surfaces. Meanwhile, 35% of genotypes showed green color in abaxial leaf surface, 30% of genotypes showed purple at the vein base, 20% of genotypes were main vein partially or totally purple, 5% of genotypes showed all veins partially or totally purple and 10% of genotypes ad purple surfaces and veins. The anthocyanin pigment in leaves protect tissue under stress and improve survival in exposed climbing habitats [18] .

Cluster Analysis

In this clustering by MCA (Multiple Correspondence Analysis), a high variability among twenty genotypes were observed. These genotypes were divided into three clusters. Among the three, cluster 3 was the largest cluster with sixteen genotypes. And other two clusters had two genotypes respectively. Cluster 3 was grouped with the genotypes according to their moderately ground covering capacity, leaf shape and predominant vine color. It had hastate, cordate and lobed leaf shape. These genotypes also had green with purple spots veins. These kinds of leaves are common in improving light absorbing capacity in verticals systems. Also it has better light penetration in canopy coverage [19] . Cluster 1 had two genotypes, G12 and G13. They had hairiness traits with purple pigmentation. Trichomes act as the mechanical and chemical barriers against pest from feeding the plants [20] . And the cluster 2 also had two genotypes, G1 and G20. The genotypes G20 showed almost divided shape of leaf which is unique and it was also affected by pest but G1 was free of insect damages. It can be used as a parental line for resistant line development [21] .

The divided leaf shape could be a major reason for its exposure to pest damage and useful for studying host-pest interaction in future [22] .

Tables and figures

References

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