Fruit morphological attributes to assess genetic diversity in jujube (Ziziphus mauritiana L.) germplasm of Bahawalpur

Genetic diversity plays a major role in varietal improvement of crops. The genus Ziziphus (jujube or ber) is an important fruit crop of arid zones consisting of above 100 species of deciduous or evergreen plants and shrubs widely scattered in the desert, tropical and subtropical areas. In Pakistan, several local and exotic accessions are being cultivated for fruit production. Jujube is neglected fruit crop in Pakistan with diminutive assessment of fruit morphological characters. In this study, 22 selected accessions were characterized based on various physico-morphological traits. The results proved broad genetic base in all 22 genotypes for various commercial traits. Fruits from the selected genotypes were assessed based on fruit weight, fruit length, seed weight, seed length, seed diameter, fruit pulp weight and total soluble solids (TSS). Highest variation (7.22%) was recorded in fruit weight which ranged from 6.08 to 37.64 g among the tested genotypes; however, least variation was recorded in seed weight. Strongest correlation of r = 0.99 was measured between fruit and pulp weight with all 22 genotypes were clustered into three main classes with maximum variation of 163% within class c followed by classes a and b with variation of 73.35 and 64.18% within the classes, respectively. Studied genotypes had broad genetic base with a high flow of characters among them, could be used in advanced breeding for varietal improvement programs.


Introduction
The genus Ziziphus (jujube, also known as Ber) is an important member in the family Rhamnaceae.This genus consists of more than 100 species of trees and shrubs Ber is among the neglected fruit crops in Pakistan.Recently, demand for its nutritive fruit is steadily increasing.This demand for Ber attracted scientists to understand basic characteristics of fruit morphology of different available accessions in the country.Therefore, the present study offers the needed information for consumers.The main objective of this study was to evaluate the morphological characters of fruit to assess the diversity of Ber in Pakistan and identify suitable promising accessions for trait improvement and breeding programs.

Statistical analysis
The study was conducted as a completely randomized single factor design.The main factor is the variety at 22 levels (22 varieties) with 5 replications (5 plants).
Different fruit morphological observations were recorded and subjected to statistical analysis using EXLSTAT (2015) software.

Summary of statistic and correlation of traits in PCA analysis
Multivariate analysis of collected data showed highest variation (7.22%) in fruit weight ranged from 6.08 to 37.64 g among the tested jujube genotypes.This was followed by pulp weight, seed length and fruit length as shown in Table 1.The least variation was recorded in seed weight in all 22 genotypes.Correlation matrix values of studied traits in all 22 genotypes showed strongest correlation of 0.99 between fruit weight and pulp weight.This was followed in fruit diameter and pulp weight (0.964) and fruit weight and fruit diameter (0.962).There is negligible correlation for TSS with all other traits, however, Fruit and seed length had high negative correlation with TSS (Table 2).The results proved broad genetic base of all 22 genotypes for various commercial traits like fruit weight, pulp weight and seed length, moreover, strong correlation was also recorded among these traits.Results proved broad genetic base in all 22 genotypes that could be utilized in breeding and variety improvement progam of jujube germplasm of desert zones of Bahawalpur to address its salinity and drought stresses for high quality fruit production.These results are in line with the finding of Saran et al.
[14], who studied the broad genetic base in Indian jujube for various morphological traits.

Conclusion
The present study has shown that the quantitative and qualitative traits of fruits are helpful to assess the diversity among the varieties of jujube.The results proved that the studied genotypes have a broad genetic base with a high flow of characters among them.Information in this manuscript could be used in selection breeding in varietal improvement programs.
tropics and subtropics [1].It is believed that Z. mauritiana found in almost every continent of the world.This hardy species is easy to grow and can survive on a wide range of soils even in desert conditions.It is a prominent vegetation of India & Pakistan deserts [2].Present jujube varieties are the result of wide selection process in India and China and they created thrust for improvement and research [3].In Pakistan, total area of jujube orchards is over 5425 ha with an annual production of about 28 thousand tones [4].Nonetheless, only limited research work is available on fruit morphology [1].There is no serious attempt made on the classification of Ber varieties on the basis of fruit setting habit, fruit morphology and blooming time even though many varieties are being grown in Pakistan [5].Ber varieties were identified on basis of fruit characters including the following fruit traits: fruit with a distinctly pointed apex, fruit with a slightly pointed apex, fruit with a round apex, and fruit apex round with a depression [6].The size of fruit varies from chary to plum size depending on cultivar [7].There is physio-chemical difference among the Ber verities [8].Jujube germplasm characterization, evaluation and improvement are fundamentally based on morpho-physiological traits.The lack of breakthrough is a consequence of underutilization of genetic variability for superior quality and high yield potential [9].
Fig. 1.The genotypes in plan B and C are more diverse for their spread away from center of planes.The least spread genotypes were present in plan D, showing less narrow genetic base.Genotypes in plan A could successfully crossed with genotypes in plan D to get diverse lines in breeding and variety improvement program.Similarly, accessions in plan B and C had potential to be crossed to get diverse lines and screen out elite lines for cultivation.

Table 2 . Correlation of studied traits among 22 jujube genotypes (Values in bold are significant at P < 0.05)
Abbreviations: FW: fruit weight, FL: fruit length, FD: fruit diameter, SW: seed weight, SL: seed length, SD: seed diameter, PW: pulp weight, TSS: total soluble solidsPCA plot analysis of genotypesScattering pattern of all genotypes on principal component plot showed high level of diversity for studied morphological traits.Cumulative diversity in genotypes was 75.42% covered in first two principal components as shown