Genetic Diversity Assessment of Brinjal Germplasm for Varietal Improvement

Forty-one (41) brinjal ( Solanum melongena L.) germplasm of were evaluated at the field of Plant Genetic Resources Centre, BARI, Gazipur to identify the salient features and to assess genetic divergence of germplasm in the time of rabi season 2021-22. Distinct variation was observed in qualitative characters among the germplasm except two characters i.e. fruit cross section and fruit position. For the characters length breath ratio and calyx prickles of fruit, the topmost variation was found. In case of quantitative characters, variation was noticed maximum in the length of fruit (CV-43.79%), afterwards individual weight of fruit (CV-32.91%) and yield plant -1 (CV-30.12%). The highest number of germplasm was dispersed into cluster I. Among the clusters, cluster II and cluster III were occupied by ten germplasm, respectively. Cluster mean value was noted maximum in cluster II for the characters days required for 50% flowering (67.90%), plant height (97.97 cm), individual fruit weight (107.35 g), and yield plant -1 (2.51%). Among the principal components, 27.28% of the total variation interpreted by the first PC and the second PC clarified 22.36% of the variation. In the biplot, germplasm NF-15, NF-20, NF-13, NF-7, NF-4, NF-25, NF-16, and NF-2 etc. were independently far away from the studied germplasm by keeping a distance from the centroid. These results displayed distinctiveness and divergence of germplasm as regards of the studied traits. Populations with high values for the first eigen vectors are individual fruit weight (0.642), yield plant -1 (0.564), and width of fruit (0.313), these characters were the utmost significant contributors towards the diversity of germplasm in PC1. The germplasm NF-4 (3.45 kg), NF-30 (3.38 kg), and NF-25 (3.08 kg) were higher yielders among the tested germplasm and may be used for future varietal improvement of brinjal.


Introduction
Brinjal (Solanum melongena L., 2n = 24), is the most important year-round vegetable crop, and is regarded as one of the members of Solanaceae family.Brinjal is being cultivated from the subtropics to the Mediterranean region.By covering 87% growing area more than 90% of global brinjal is produced in Asia (Bhagirath and Kadambini 2009).In Bangladesh brinjal got the second position after potatoes considering production.It is also noted poor man"s vegetables for its high production capacity and availability (Kumar et al., 2014).In 2019, brinjal is a significant fruit vegetable that exceed world production by about 55.20 million tones (FAO, 2020).Brinjal"s total production in Bangladesh was 585,000 tons during 2019-20 (BBS, 2020)).Huge indigenous biodiversity persists in brinjal with plant type, leaf size, midrib colour, stem colour, leaf tip; size, shape, colour of fruit and yield; fruit and cooking quality, and pests and diseases tolerance (Ullah et al., 2014).
*Corresponding author e-mail: nasrin.jahan83@gmail.comDuring the development of variety by a hybridization program, germplasm characterization is surely substantial to figure out genetic information.In plant breeding programs, characterization of germplasm is an essential task to deliver required information (Lin, 1991).Collected germplasm"s characterization is necessitated to determine lines suitable for development of new varieties (Adeniji and Aloyce, 2012).Plant breeders are focused on study of genetic divergence on the basis of qualitative and quantitative characters since these traits could be scored shortly and simply through low-cost methods (Uddin et al., 2021).Forty-one germplasm of brinjal were collected under a project entitled "Collection and Characterization of Brinjal Genotypes for Varietal Improvement" from special research allocation funded by Science and Technology Ministry.Hence, this research was executed to characterize the germplasm of brinjal morphologically and to estimate genetic divergence for future crop improvement.

Materials and Methods
The experiment was executed at Plant Genetic Resources Centre"s research field of Bangladesh Agricultural Research Institute (BARI), Gazipur, at rabi season 2021-22.Forty-one (41) brinjal germplasm were used that were collected from different upazilas of Narsingdi, Bogura district and PGRC, BARI, Gazipur.Seeding was done in seed beds on 1 st December 2021 and thirty days aged seedlings were transplanted.The size of plot was 3 X 1.4 m 2 .Each germplasm were planted in two rows plots having four pits.Distance between row to row and plant to plant was maintained in 70 cm X 70 cm.Fertilizer doses were 10 ton/ha Cow dung, 300 kg/ha Urea, 250 kg/ha TSP, 200 kg/ha MP, 100 kg/ha gypsum, and 10 kg/ha Boric acid (Azad et al., 2019).The entire amounts of cowdung, TSP, gypsum and boron were applied at the time of land preparation prior to one week of transplanting.Urea and MP were put on in application in the three equivalent splits at 15 after transplanting, before flowering and before fruiting.Weeding and mulching were executed according to need.Bagging was done in individual fruit to avoid crosspollination.The data were recorded according to the descriptor developed by IBPGR, 1990.Qualitative data was illustrated in the method of frequency distribution.Quantitative data were analyzed over simple descriptive statistics incorporating mean, variance, standard deviation, and coefficient of variation.Cluster analysis and Principle component analysis were carried out by computerized software Statistical Tool for Agricultural Research (STAR 2.0.1, 2014).

Results and Discussion
Forty-one (41) germplasm of brinjal were studied for characterization and divergence.These germplasms were characterized by twenty-six (26) different characters including 18 qualitative and 8 quantitative characters.

Qualitative characters
A total of 18 qualitative characters were assessed to find out the variation of germplasm (Table 01 and  02).The studied characters displayed well defined variation except cross section and position of fruit.The topmost variation was noticed in overall length breath ratio and calyx prickles of fruit.

Variability in growth and foliage
Entirely the studied traits appertaining to plant growth habits and foliage displayed distinct variations among the germplasm (Table 01).Plant growth habits were observed in three types i.e. upright (34.14%), intermediate (60.98%), and prostrate (4.88%).(Shekar et al., 2013) grouped the brinjal germplasm into upright and intermediate.(Islam et al., 2018) clustered 48% intermediate, 45% upright, and 7% prostrate growth habit amongst the 40 germplasm at the vegetative stage.They advocated that the recording of plant growth habit is needed for the identification of brinjal varieties.In case of leaf blade lobing 12 germplasm had weak type (29.27%), 12 germplasm had intermediate type (88%), 13 germplasm had strong type (31.71%) and very strong type leaf blade lobing was found in only 4 germplasm (9.76%).(Sunseri et al., 2010) stated 60% weak type, 37% intermediate, and 3% strong type lobbing of leaf blade in brinjal.Very acute (2.44%), acute (51.22%), intermediate (31.71%), and obtuse (14.63%) categories of leaf blade tip angle were observed among the studied germplasm.(Dash et al., 2019) noted acute type leaf blade tip angle in many brinjal genotypes.In case of leaf blade length, variation was exhibited in three types i.e. 14.63% germplasm of short leaf length and 58.54% germplasm had an intermediate leaf length which was the maximum, and 26.83% germplasm had longer leaf length.For the character leaf prickles, variation was exhibited in three types i.e. 95.12% germplasm had no leaf prickles and the rest had very few (2.44%) and intermediate (2.44%).Considerable variation was observed in leaf prickle by (Uddin et al., 2021) where maximum genotypes (72 genotypes) had intermediate leaf prickle.

Variability in characters of fruit
Characters pertaining to the brinjal fruit displayed prominent variation among the germplasm excluding cross section and position of fruit (Table 02).In the case of fruit length/breadth ratio, 12.21% germplasm had "broader than long" type.7.32% and 9.76% germplasm had "as long as broad as "and "slightly longer than broad" type, respectively."Twice as long as broad" type was observed in 7.32% germplasm and "three times as long as broad" in 29.74%.The rest (17.85%) had "several times as long as broad" type fruit.No fruits were found curved in 90.20% of the germplasm.7.32% germplasm showed slightly curved and 2.44% showed curved.(Parida et al., 2020) noticed that 68 genotypes had no curvature on fruit; 37 genotypes showed slightly curved fruit and 25 genotypes had curved fruit.Fruit apex was exhibited as three categories such as, protruded (17.07%), rounded (39.03%) and depressed (43.90%).(Sunseri et al., 2010) reported that 38, 34, and 28% of eggplant genotypes had depressed, rounded, and protruded types of fruit apex shape, respectively.Four categories of fruit color at ripening such as green (75.61%) which was maximum and lilac grey (9.76%), purple (7.32%), and black purple (7.32%) were observed (Fig. 03).Fruit color distribution was exhibited as uniform (14.63%), mottled (21.95%), netted (36.59%) and striped (26.83%).

Cluster means
Characterizations of individual germplasm were made with respect of their mean value for different characters to get an idea of whether the germplasm has similar characteristics that could be disseminated.In cluster means the genetic differences between clusters were reflected.Enormous variations were observed in cluster mean for all characters (Table 06).The maximum cluster mean value was observed in Cluster II for the characters days to 50% flowering (67.90%), plant height (97.97 cm), Individual fruit weight (107.35g), and yield per plant (2.51%).Larger fruit length and fruit width were observed in cluster III and cluster I, respectively.Grouping of the germplasm to different clusters allows selecting germplasm to develop high-yielding and good-quality varieties.02).The first PC displayed 27.28% of the total variability and the second PC explained 22.36% of the variation among 41 brinjal germplasm.Thus, the present study revealed that the first PC was more important than the second PC for explaining the variability among the germplasm based on studied traits.Begum et al. (2013) observed that the first axes totally accounted for 20.07%variation among the genotype.The brinjal germplasm NF-15, NF-20, NF-13, NF-7, NF-4, NF-25, NF-16, and NF-2 were independently far away from the others and they were at a distance from the centroid.These results displayed their distinctiveness and divergence of the germplasm.

Eigenvalues and Eigen vectors
The eigenvalues and vectors of eight characters for a PCA of important traits for the first fifth principal components in 41 brinjal germplasm are shown in Table 07.Populations with high scores for the first eigenvectors are individual fruit weight (0.642), yield per plant (0.5643), and fruit width (0.3138), these traits were the most important contributors to the diversity of the germplasm in PC1.The second eigenvector was mostly connected with scores of fruit length (0.5837) and number of fruits per plant (0.4893), these traits were the second most important contributors among the eight characters for 41 germplasm.Quamruzzaman et al., 2009 found three characters for contribution towards divergence.

Conclusions
The genetic variability of forty-one germplasm of brinjal was estimated through morphological characterization and the assessment of genetic divergence through biometrical approaches assisted in choosing genetically diverged parents for a fruitful hybridization program.The study indicated that the brinjal germplasm NF-20, NF-13, NF0-7, NF-4, NF-25, NF-16, and NF-2, etc. were separately isolated from the others in respect of different characters.Therefore, the promising germplasm identified in the present study might be used in future breeding programs for crop improvement.

Fig. 1 .
Fig. 1.Cluster tree of forty-one germplasm of brinjal based on quantitative characters Germplasm Distribution and Dendrogram Forty-one brinjal germplasm were grouped into three clusters based on 8 quantitative traits.The dendrogram showed that the cluster I included 21 germplasm.Cluster II and Cluster III included ten

Fig. 2 .
Fig. 2. The plot of the first two PC1 and PC2 for forty-one brinjal germplasm showing relationship between germplasm and characters

Table 1 .
Variability in growth and foliage characters in brinjal germplasm

Table 2 .
Variability in fruit characters in brinjal germplasm

Table 3 .
Quantitative variation of different characters in brinjal

Table 4 .
Listing of quantitative traits descriptors of forty-one brinjal germplasm

Table 5 .
Distribution of forty-one germplasm in three different clusters

Table 6 .
Cluster means for eight characters of forty-one brinjal germplasm Principal component analysis was carried out by calculating the first two principal components that are accounted for 49.64 % of the total divergence (Figure

Table 7 .
Principal Components for eight traits of brinjal germplasm