The authors have declared that no competing interests exist.
We evaluated a set of 37 chilli genotypes collected and maintained at Assam Agricultural University, Jorhat for 27 different traits related to plant habit (5), leaf (6), flower (2), fruit (13) and biotic stress (1). The variation in fruit yield among the genotypes could be attributed to high coefficients of variability for component traits viz., number of fruits per plant (91.7%), plant height (80.8%), leaf breadth (55.9 %), fruit weight (49.7%), leaf length (45.4%) fruit length (35.8%), fruit breadth (35.5%) and number of branches per plant (22.2%). Maximum phenotypic variants were observed for fruit traits followed by leaf characteristics. Phylogenetic analysis revealed Euclidean distances varying from a minimum of 2.065 and a maximum of 13.311 indicating the diverse nature of the genotypes. UPGMA clustering grouped the genotypes into 5 distinct clusters. The largest one, cluster I, had 26 genotypes belonging to
Chilli (
Green fruits of chilli are used as vegetable whereas ripe dried fruits as a spice because of its pungency and pleasant flavour
Plant biodiversity or the plant genetic wealth of an area is the variability between the plant kingdom and the ecosystem complex in which they occur. Capsicum is a highly polymorphic genus with much morphological and genetic diversity at both intra- and inter-specific level. The existence of extensive variability has been reported in local populations but with no such systematic report. In India, a rich diversity in chilli exists due to its diverse geo-climatic regions and the reproductive behaviour of the crop. Moreover, genetic diversity may arise due to the environmental influence and may be determined by the magnitude and nature of their genetic variability in which they are grown
A set of thirty-seven Assam chilli genotypes was considered for morphological characterization which included 30 genotypes of
S No. | Genotype name | Botanical name | Pedigree | Origin | Geographical coordinates |
1-16 | K-L-1, K-L-2, K-L-3, K-L-4, K-L-13, K-L-14, K-L-31, K-L-35, K-S-4, K-S-9, K-S-11, K-S-11, K-S-32, K-S-37, K-S-38, K-S-41, K-S-47 | Purelineselection from Krishna | Assam, India | 26 ̊ 47' Nlatitude94 ̊ 12' E longitude | |
17 | Bireek-1 | Landrace | Assam, India | 25 ̊ 82' N latitude93 ̊ 72' E longitude | |
18 | Bireek-2 | Landrace | Assam, India | Same as above | |
19 | B-1-P Sel | Purelineselection from Bireek 1 | - | 26 ̊ 47 'N latitude94 ̊ 12 ' E longitude | |
20 | B1 x B2 | F1 of Bireek 1/Bireek 2 | - | 26 ̊ 47 'N latitude 94 ̊ 12 ' E longitude | |
21 | Krishna L | Landrace | Assam, India | 26 ̊ 47 'N latitude 94 ̊ 10 ' E longitude | |
22 | Khorika | Landrace | Assam, India | 26 ̊ 47 ' N latitude94 ̊ 10 ' E longitude | |
23 | KA-2 | Unknown | - | - | |
24 | Moni Jolokia |
|
Landrace | Assam, India | - |
25 | Manipuri Bhut |
|
Landrace | Manipur,India | 25 ̊ 12' N latitude93 ̊ 80' E longitude |
26 | Bor Bhut |
|
Landrace | Assam, India | - |
27 | Lota bhut |
|
Land race | Assam, India | - |
28 | Haitha Jolokia |
|
Landrace | Assam, India | 26 ̊ 47 'N latitude94 ̊ 13' E longitude |
29 | Bhekuri Jolokia |
|
Landrace | Assam, India | 26 ̊ 47 'N latitude 94 ̊ 13' E longitude |
30 | Mem Jolokia |
|
Land race | Assam, India | 26 ̊ 47'N latitude94 ̊ 12' E longitude |
31-37 | 2016/CHIVAR-2, 2016/CHIVAR-3, 2016/CHIVAR-4, 2016/CHIVAR-5, 2016/CHIVAR-6, 2016/CHIVAR-7, 2016/CHIVAR-8 | Unknown | - | - |
The experimental area is situated between 26o46/ N latitude and 94o13/ E longitude at an elevation of 86.56 m from the mean sea level. The soil of the experimental area belongs to Inceptisols derived from the alluvial deposits of the river Brahmaputra and its tributary Bhogdoi. The soil is light textured, acidic (pH: 4.8) and medium in organic matter content. Agricultural meteorological data during the experimentation period recorded an average maximum temperature of 27.22oC and a minimum temperature of 16.38oC, an average relative humidity of 94.6 percent and 20.98 mm rainfall.
The fertilizers were applied at 120:60:60 kg N:P2O5:K2O per ha in the form of Urea, Single Super Phosphate and Muriate of Potash at final land preparation. Irrigation was done as and when necessary. Prior to the experimentation, seeds of the genotypes were obtained from previous crops maintained through temporally and spatially isolated plots in poly houses.
Morphological data were obtained from the plants on the all thirty accessions assembled from different places of India. Twenty-seven different traits related to plant habit (5), leaf (6), flower (2), fruit (13) and biotic stress (1) were recorded as per NBPGR Minimal Descriptors for Agri-Horticultural Crops, Part-II: Vegetable Crops
The statistical calculations for mean, range, the coefficient of variation were performed in Microsoft Office Excel 2007. The qualitative and quantitative data were standardized using the mean and standard deviation of the samples and used to work out the Euclidian distances based dissimilarity matrix. An unrooted phylogenetic tree was then produced using Unweighted Paired Group Method using Arithmetic Average (UPGMA) of hierarchical clustering based on dissimilarity matrix as implemented in the DARwin software version 6.0. Principal component analysis (PCA) was performed following the method of
Abundant diversity was observed for all the quantitative traits considered in the study. Plant architecture was studied using plant height, number of branches per plant, leaf length and leaf breadth, plant growth habits, stem colour, leaf size, shape, margin and colour. Plant height ranged from 33 to 315 cm with a maximum height recorded in Manipuri Bhut (
Character | Range | Mean ± SEm | CV (%) |
Plant height (cm) | 33.00 - 315.40 | 80.71 ± 10.87 | 80.77 |
Number of branches/plant | 3.60 - 11.00 | 6.63 ± 0.25 | 22.22 |
Leaf length (cm) | 3.60 - 17.50 | 7.16 ± 0.54 | 45.38 |
Leaf breadth (cm) | 1.42 - 7.60 | 2.97 ± 0.28 | 55.9 |
Fruit length (cm) | 1.32 - 10.20 | 6.14 ± 0.37 | 35.84 |
Fruit breadth (cm) | 0.37 - 2.23 | 1.27 ± 0.07 | 35.48 |
Fruit weight (g) | 1.50 - 10.20 | 4.38 ± 0.36 | 49.74 |
Number of fruits/plant | 28.00 -846.00 | 184.94 ± 31.59 | 91.66 |
Fruit yield/plant (g) | 146.40 -5761.26 | 762.77 ± 172.28 | 138.74 |
Pearson’s correlation coefficient among the quantitative traits revealed a significant positive correlation of plant height (PH), leaf length (LL), leaf breadth (LB) and number of fruits per plant (FN) with fruit yield in the chilli genotypes (
Character | PH | BR | LL | LB | FL | FB | FW | FN |
BR | -0.47 | |||||||
LL |
|
-0.49 | ||||||
LB |
|
-0.43 |
|
|||||
FL | -0.47 |
|
-0.42 | -0.49 | ||||
FB |
|
|
0.47 | 0.38 | -0.14 | |||
FW | -0.01 | -0.02 | 0.12 | -0.01 | 0.46 | 0.36 | ||
FN |
|
-0.20 |
|
|
-0.48 | 0.20 | -0.11 | |
FY |
|
-0.24 |
|
|
-0.20 | 0.41 | 0.29 |
|
PH: Plant height (cm); BR: Branches per plant; LL: Leaf length (cm); LB: Leaf breadth (cm); FL: Fruit length (cm); FB: Fruit breadth (cm); FW: Average fruit weight (g); FN: Fruit number per plant; FY: Fruit yield per plant (g) |
Bold figures indicate significant correlation
The number of phenotypic variants for the 37 genotypes as per NBPGR Minimal Descriptors for Horticultural Crops revealed a lot of variation for the studied traits (
S No. | Trait | Score | Phenotype | No. of genotypes | S No. | Trait | Score | Phenotype | No. of genotypes |
1 | Life cycle | 1 | Annual | 32 | 11 | Ripe fruit colour | 3 | Pale Orange Yellow | - |
2 | Biennial | - | 4 | Orange Yellow | 1 | ||||
3 | Perennial | 5 | 5 | Pale Orange | 2 | ||||
2 | Stem colour | 1 | Green | 17 | 6 | Orange | - | ||
2 | Green with purple stripes | 9 | 7 | Light Red | 4 | ||||
3 | Purple | 11 | 8 | Red | 8 | ||||
3 | Plant growth habit | 3 | Prostrate | 17 | 9 | Dark Red | 19 | ||
5 | Intermediate | 7 | 10 | Brown | 2 | ||||
7 | Erect | 13 | 11 | Purple | - | ||||
4 | Leaf size | 3 | Small | 16 | 12 | Black | - | ||
5 | Medium | 15 | 12 | Fruit shape | 1 | Long | 27 | ||
7 | Large | 6 | 2 | Very short | 2 | ||||
5 | Leaf shape | 1 | Deltoid | - | 3 | Tapering | 1 | ||
2 | Ovate | 13 | 4 | Conical | 3 | ||||
3 | Lanceolate | 24 | 5 | Oval | 4 | ||||
6 | Leaf margin | 1 | Entire | 35 | 13 | Fruit shape at pedicel attachment | 1 | Acute | 10 |
2 | Undulate | 2 | 2 | Obtuse | 18 | ||||
3 | Ciliate | - | 3 | Truncate | 8 | ||||
7 | Leaf colour | 1 | Green | 21 | 4 | Cordate | 1 | ||
2 | Dark Green | 10 | 5 | Lobate | - | ||||
3 | Purple | 6 | 14 | Fruit shape at the blossom end | 1 | Pointed | 24 | ||
8 | Corolla colour | 1 | White | 25 | 2 | Blunt | 9 | ||
2 | Yellow | - | 3 | Shrunken | - | ||||
3 | Purple | 12 | 4 | Shrunken and pointed | 4 | ||||
9 | Anther colour | 1 | White | 1 | 15 | Fruit position | 3 | Pendant | 23 |
2 | Yellow | 1 | 5 | Semi Pendent | 3 | ||||
3 | Pale Blue | 14 | 7 | Erect | 11 | ||||
4 | Blue | 4 | 16 | Adherence of calyx to fruit | 3 | Loose | 11 | ||
5 | Bluish Yellow | 1 | 5 | Semi-hard | 24 | ||||
6 | Purple | 16 | 7 | Hard | 2 | ||||
10 | Mature fruit colour | 1 | White | 1 | 17 | Fruit surface | 1 | Smooth | 19 |
2 | Yellow | - | 2 | Semi wrinkled | 15 | ||||
3 | Green | 15 | 3 | Wrinkled | 3 | ||||
4 | Orange | - | 18 | Biotic stress | 1 | Very low | 26 | ||
5 | Purple | 8 | 3 | Low | 10 | ||||
6 | Deep Purple | 1 | 5 | Intermediate | 1 | ||||
7 | Black | 12 | 7 | High | - | ||||
11 | Ripe fruit colour | 1 | White | - | 9 | Very high | - | ||
2 | Lemon Yellow | 1 |
Among the leaf characteristics, the maximum number of phenotypic variants were found for leaf size (16 small, 15 medium and 6 large) and colour (21 green, 10 dark green and 6 purple). Phenotypic variation for leaf shape gave 24 variants with lanceolate leaves and 13 with ovate leaves and 35 variants had entire leaf margin and 2 had undulating leaf margin. Similarly, for flower characteristics, 25 phenotypic variants were observed with white corolla and 12 variants were with different shades of a purple corolla. A wide variation was observed for anther colour showing phenotypic variants with 1 white, 1 yellow, 14 pale blue, 4 blue, 1 bluish yellow and 16 purple anther.
Among fruit characteristics, fruit colour exhibited enormous variation among genotypes. Phenotypic variants for fruit colour were 1 white, 15 green, 8 purple, 1 deep purple, 12 black matured, 1 lemon yellow, 1 orange-yellow, 2 pale orange, 4 light red, 8 red, 19 dark red and 2 brown ripe. Fruit shape variants among genotypes included 27 long, 2 very short, 1 tapering, 3 conical and 4 oval. The number of genotypes with variation in fruit shape at pedicel attachment were 10 acute, 18 obtuse, 8 truncate and 1 cordate. The blossom end fruit shape was observed to be pointed in 24, blunt in 9 and shrunken-pointed in 4 genotypes. Twenty-three of the phenotypic variants held a pendant position in the stem followed by erect and semi-pendent in 11 and 3 genotypes, respectively. The adherence of calyx to fruits was loose for 11, semi-hard for 24 and hard for 2 genotypes. The fruit surface was found to be smooth, semi-wrinkled and wrinkled for 19, 15 and 3 genotypes, respectively. A very low to intermediate biotic stress was observed in the genotypes with very low to no incidence in 26 variants, low incidence in 10 and intermediate incidence in 1 variant.
Phylogenetic analysis was performed for the 37 genotypes using standardized values for the qualitative and quantitative traits. Dissimilarity matrix of usual Euclidean distances gave a minimum dissimilarity value of 2.065 and a maximum of 13.311 indicating the diverse nature of genotypes under study. The unrooted phylogenetic tree constructed with dissimilarity values using UPGMA method grouped the genotypes into five major clusters (I, II, III, IV and V) clockwise from right to left (
Cluster II at node no. 69 in the unrooted phylogenetic tree (
The plant architecture, leaf, flowers and fruit characteristic distinctly separated the genotypes belonging to the species
PCA explained the proportion of relative contribution of the various characters to the total variance of chilli genotypes under study. The study of many qualitative and quantitative traits is important for the assessment of differences between genotypes and their breeding potential. PCA combines the capacity to provide a synthetic summary of the most relevant traits and assessment of the relative contribution of different characters to the total variability of the population
The highest proportion of total variability exposed by the first component (34.93%) was contributed by a large number of traits with high positive values - plant height, leaf length, leaf breadth, fruit number per plant, fruit yield, fruit shape at blossom end, leaf size, life cycle and traits with low positive values - leaf margin, fruit shape, fruit shape at pedicel attachment and fruit surface (
Trait | Principal component | |||||
C1 | C2 | C3 | C4 | C5 | C6 | |
Plant height (cm) | 0.275 | 0.166 | -0.002 | 0.153 | -0.024 | 0.17 |
No of branches per plant | -0.193 | -0.038 | 0.33 | 0.149 | -0.002 | -0.004 |
Leaf length (cm) | 0.294 | 0.135 | 0.01 | 0.103 | 0.11 | -0.113 |
Leaf breadth (cm) | 0.289 | 0.013 | 0.02 | 0.045 | 0.28 | -0.136 |
Fruit length (cm) | -0.211 | 0.19 | 0.238 | -0.032 | 0.122 | -0.182 |
Fruit breadth (cm) | 0.14 | 0.343 | -0.138 | -0.12 | 0.048 | -0.01 |
Fruit weight (g) | -0.008 | 0.342 | 0.119 | -0.257 | 0.153 | -0.235 |
No of fruits per plant | 0.266 | 0 | 0.108 | 0.205 | 0.035 | 0.125 |
Fruit yield per plant (g) | 0.252 | 0.196 | 0.138 | 0.11 | -0.041 | 0.082 |
Lifecycle | 0.286 | -0.098 | -0.001 | 0.059 | 0.205 | 0.096 |
Stem colour | -0.174 | 0.18 | -0.261 | 0.079 | 0.209 | 0.04 |
Plant growth habit | -0.047 | -0.191 | -0.348 | 0.223 | -0.087 | 0.246 |
Leaf size | 0.258 | -0.072 | -0.103 | 0.053 | 0.13 | -0.257 |
Leaf shape | -0.095 | 0.202 | 0.252 | 0.252 | -0.112 | 0.294 |
Leaf margin | 0.102 | -0.302 | -0.057 | 0.126 | 0.427 | -0.038 |
Leaf colour | -0.036 | 0.192 | -0.209 | 0.368 | 0.181 | 0.091 |
Corolla colour | -0.154 | 0.161 | -0.247 | 0.28 | 0.138 | 0.111 |
Anther colour | -0.176 | 0.227 | -0.266 | 0.006 | 0.24 | -0.06 |
Mature fruit colour | -0.212 | 0.259 | -0.085 | -0.073 | 0.14 | -0.085 |
Ripe fruit colour | -0.17 | 0.181 | -0.21 | -0.182 | -0.067 | 0.123 |
Fruit shape | 0.167 | 0.091 | -0.332 | -0.071 | -0.357 | -0.075 |
Fruit shape at pedicel attachment | 0.161 | 0.123 | -0.092 | -0.419 | 0.114 | 0.292 |
Fruit shape at blossom end | 0.278 | 0.14 | -0.149 | -0.014 | -0.057 | 0.053 |
Fruit position | 0.044 | -0.272 | -0.267 | -0.246 | -0.006 | -0.314 |
Adherence of calyx to fruit | -0.099 | -0.159 | 0.113 | -0.211 | 0.532 | 0.274 |
Fruit surface | 0.155 | 0.262 | 0.206 | 0.059 | 0.013 | -0.274 |
Biotic stress | 0.146 | 0.048 | 0.096 | -0.35 | -0.022 | 0.463 |
Total variance | 9.43 | 4.052 | 3.446 | 2.17 | 1.643 | 1.247 |
Variance explained (%) | 34.926 | 15.008 | 12.763 | 8.039 | 6.085 | 4.619 |
Cumulative (%) | 34.926 | 49.934 | 62.697 | 70.736 | 76.821 | 81.44 |
About 15% of the variability was contributed by the second principal component with high positive values for fruit breadth and fruit weight, and low positive values for plant height, leaf length, fruit length, fruit yield, stem colour, leaf shape, leaf colour, corolla colour, colour of matured fruit/ripe fruits, fruit surface, fruit shape at pedicel attachment and at blossom end, and fruit shape in general (
The PCA biplot diagram of the species drawn on the basis of PC1 and PC2, accounting for a total of 49.9% total variability (
The results presented here demonstrate the utility of cluster analysis and PCA in partitioning the genetic variation among chilli genotypes and in identifying different genotypes of chilli which would serve as potential sources of unique breeding material for future crop improvement. The study also provides guidance for future analysis of genetic diversity using the more reliable molecular markers to facilitate efficient management and utilization of the available germplasm. Genetic fingerprinting of local germplasm would protect the plant genetic resources of the nation in light of the PPVFRA and Convention on Biological Diversity. A core collection could also be created with the morphological diversity for utilization in the future breeding programme.
The first author thankfully acknowledges the help provided by All India Coordinated Research Project on Vegetable Crops (ICAR), IIVR, Varanasi, India for providing some of the materials for the study and also for financial assistance.