Eight bread wheat genotypes were screened by the six ISSR primers and
scored a total of 54 amplified DNA bands. The number of bands varied from
40 to 69 bands form primers ISSR 2 (6 fragments) to ISSR 5 (13 fragment).
Number of polymorphic fragments varied from 1 for ISSR 4 to 8 for ISSR 1
and ISSR 5. The six ISSR primers generated 314 scorable bands across 8
studied genotypes. These primers produced a total of 54 reproducible
fragments, from which 30 (55.55%) were polymorphic. The lowest genetic
similarity (0.63) was obtained between P3 and P7, while, the highest genetic
similarity (0.89) was scored between P7 and P8. The parents were crossed in
a 8x8 half diallel scheme in 2015/2016. Parents and their 28 F1 crosses were
evaluated under normal and stress conditions during 2016/2017 in two
irrigation levels experiments. The mean squares were significant for all
studied traits. The highest mean values were detected by parents P2, P2, P8,
P2, P6 and p2 for plant height, spike length, no of spike/ plant, 1000-kernel
weight, biological yield/ plant and grain yield/ plant in the combined
analysis, respectively. While, the highest mean values were recorded under
combined analysis with crosses P1xP6 for biological yield/ plant and the
cross P2xP4 for grain yield / plant. Mean squares for combining ability
estimates were highly significant for all studied traits. The ratios GCA /SCA
exceeded the unity for all studied traits, revealing that additive and additive
x additive types of gene action are more important than non-additive gene
action in controlling these traits. The parental P6 exhibited positive and
significant ĝi effects for grain yield/ plant and its attribute. The highest
desirable SCA effects were obtained with the crosses P1xP6, P1xP7, P2xP4,
P3xP7, P3xP8, P4xP8, P5xP8 and P6xP7 for grain yield/ plant which
exhibited significant and positive ŝij effects. Positive correlation coefficients
were found between genetic diversity and each of mean performance and
SCA for grain yield/plant. Hence, ISSR marker can be used as a tool for
determining the extent of genetic diversity among wheat genotypes and can
be used to precisely predict the yield performance value for F1 hybrids. |
