ASSESSMENT OF THE HYBRID VIGOR AND THE COMBINING ABILITY FOR SOME GROWTH CHARACTERISTICS OF THE OKRA DIALLEL CROSSES AND RECIPROCALS HYBRID

Two experiments were conducted. One in the open field during the spring season 2021, in which crosses- and Reciprocal-Crosses (full diallel crossing) were conducted between five selected okra varieties and the other was a comparative experiment in the heated plastic green-house of the Department of Horticulture and Gardening Engineering, College of Agriculture, University of Tikrit, Iraq for the winter season 2022. The results showed that the differences between the parental genotypes and their reciprocal and Reciprocal-Crosses led to the emergence of hybrid vigour and in the desired direction in the results of a number of crosses, where the special values for the hybrid's strength were calculated based on the average of the best (shortest) father H (BP), as the hybrid's strength was characterised as in the plastic greenhouse, the hybrid (P5xP4) had a significant negative value, while 19 hybrids had undesirable positive values. In the open field, 11 hybrids had negative and significant hybrid strength, 2 had non-significant negative values and 7 had undesirable positive values. The results also showed that the effects of the general ability of compatibility for the first generation in the plastic green-house were high for the genotype P4, where the effects of GCA were significant and negative, as well as the parental styles recorded high and negative values, respectively, P3 and P2, while the effects of the P5 models and P1 were highly significant and positive, and the effects of the genera were positive. The results also showed that the effects of the specific combining ability varied in terms of genetic values of hybrids between the plastic green-house and the open field. The hybrids P3xP1, P4xP5, P4xP2, P1xP2, P3xP2 and P5xP3 had the highest negatively significant values for the effects of the special ability of compatibility in the greenhouse, while the hybrids P1xP2, P5xP3, P4xP3 and P1xP5 had the highest negative significant values in the open field. Percentage exceeded the average vigour of the hybrids for the characteristic of the number of okra branches in the open field compared to the plastic green-house, where 9 hybrids recorded negative and significant hybrid strength, with (P1xP5) having the highest value -40.994 and (P3x P2) the lowest. It had 12 leaf models. A negative and significant hybrid, where (P2xP5) had the highest value and (P5xP4) the lowest, 3 hybrids had non-significant negative values and 5 had undesirable positive values. In the plastic greenhouse, 10 hybrids had high and negative significant values, including P2xP45.