Abstract
The investigation was carried out to study genetic diversity and induced mutation of mango at
Bangladesh Agricultural University, Mymensingh during 2007-2009. Evaluation and
morphological characterization of 60 mango genotypes were performed using different
qualitative and quantitative characters. Wide range of variation among the genotypes in
respect of plant, leaf, inflorescence, fruit and stone characters were observed. In all the traits,
genotypic coefficient of variation (GCV) was always smaller than phenotypic coefficient of
variation (PCV). Narrow difference between GCV and PCV and high heritability coupled with
high genetic advance confirmed least environmental effect on % flowering shoot, number of
fruits per plants and yield per plant, which offered better scope for selection. Genetic diversity
was assessed using 15 morphological characters. Based on multivariate (D2) analysis, 60
mango genotypes were grouped into 8 clusters. Principal component analysis revealed that
first nine axes accounted for 88.30% of total variation and the rest 6 characters accounted for
11.70% variation. From principal coordinate analysis, the highest inter cluster distancе
(151.82) was between cluster II and cluster VIII and the lowest (55.47) was between cluster
VII and cluster VIII. Considering univariate and multivariate study ten promising genotypes
viz., MI01, MI04, MI09, MI23, MI24, MI25, MI26, MI28, MI94 and MI95 were selected for
further breeding programme. Three enzymes viz., gulutamate oxaloacetate transminase
(GOT), malate dehydrogenase (MDH) and peroxidase (PER) were used to investigate genetic
diversity of 60 mango genotypes at protein level. Eight zymotypes with GOT, 10 with MDH
and 7 with PER were formed by 22, 39, 12 bands, respectively at different Rf values. Again
based on three isozymes banding patterns, the 60 genotypes were grouped into 8 clusters.
Compared with three studied DNA extraction protocols of mango such as SDS, CTAB and
water saturated ether (WSE) method with NaCl, it was found that WSE method with NaCl had
highest value of average percentage (85.44%) in DNA content of the mango genotypes. RAPD
analysis of 60 mango genotypes was done to detect genetic diversity at DNA level. Of 40
primers, 11 decamer primers amplified 104 bands of which 101 (97.12%) were polymorphic.
Nei's (1973) highest genetic distance (0.883) was observed between MI01 and MI18. The
mean genetic diversity among all the accessions was 0.323 and Shannon's information index
was 0.489 across all loci. The UPGMA dendogram. based on Nei's (1972) genetic distances
revealed that 60 mango genotypes were grouped into 7 clusters. Clustering of accessions
based on morphological characters did not match with the clustering obtained from isozyme
and RAPD analysis. It was evident from morphological, isozyme and RAPD analysis that
there was no relationship between genetic divergence and geographical distribution of
genotypes. From correlation study between yield and yield contributing characters, plant
height, % flowering shoot, % perfect flower and number of fruits per plant were found
positive and significantly correlated with yield. Genotypic correlation coefficient was higher
than phenotypic ones for most of the cases indicating strong inherent relation among the
characters. Path coefficient analysis showed that plant height, panicle per shoot and % perfect
flower had maximum direct effect on yield per plant followed by fruit weight both at
genotypic and phenotypic level. Induction of mutation on 8 selected genotypes derived from
morph-molecular diversity study was performed by applying three doses of radiation such as
20 Gy, 30 Gy and 40 Gy. Sixteen mutants of mango derived from 20 Gy and 30 Gy radiation
were characterized with RAPD analysis. With primer OPA-10, the amplified bands OPA-10-
675bp, OPA-10-850bp, ОРА-10-875bp and OPA-10-925bp; with primer OPB-18, the
amplified bands OPB-18-458bp, OPB-18-500bp, OPB-18-825bp and OPB-18-950bp; with
primer OPC-12, the amplified bands OPC-12-1100bp and with primer OPC-13, the amplified
bands OPC-13-350bp, ОРС-13-600bp and OPC-13-1500bp, were found in mutants but were
not formed that of their parents. None of five primers alone was able to detect all 24 mutants.
These findings suggest, these bands may reflect the existence of inter-allelic interactions in
RAPD markers. For distinguishing mango genotypes at intra-species level more RAPD
primers may be included in future studies.