Genotypic differences for heat tolerance traits in bread wheat using five parameters genetic model

Abstract EN

The present work was carried out during 2008/ 2009 to 2011/ 2012 to study five populations (P1, P2, F1, F2 and bulk of F3) for the three crosses i.e., Giza 168 × Pastor, Kanchan × Pastor and Debira × Kanchan under optimum and late sowing date in two experiments.

The first experiment was planted in optimum sowing date (15 November) and the second was planted in late sowing (15 December) in Shandaweel Station, Sohag Governorate, Agriculture Research Center.

The three crosses were significantly differed for almost the studied traits.

Under optimum sowing date, highly significant and positive heterotic effects, compared to better parent, were found for maturity date in the second cross, number of kernels/ spike in the first cross, and 100-kernel weight and grain yield/ plant in the third cross.

Under late sowing date, significant and positive heterotic effects were found for maturity and grain yield/ plant in the first and second crosses, and number of spikes/ plant in the second cross.

Overdominance towards the higher parents, was detected under optimum sowing date for number of spikes/ plant in the second cross, grain yield/ plant in the first cross and 100-kernel weight and grain yield/ plant in the third cross.

Under optimum and late sowing dates, inbreeding depression estimates were found to be significant and positive for heading date and 100-kernel weight.

Additive gene effects under the optimum sowing date were positive and significant for maturity date in the second and third crosses, number of kernels/ spike in the second cross, 100-kernel weight and grain yield/ plant in the first cross.

However, the additive gene effects under late sowing date were found to be significant and positive for maturity date in the second cross, number of kernels/ spike in the first and third crosses and grain yield/ plant in the first cross.

Dominance gene effects were significant and positive for grain yield/ plant in the first and second crosses under optimum sowing date and maturity date in the first cross and number of kernels/ plant and grain yield/ plant in the third cross under late sowing date.

Narrow sense heritability estimates ranged from 0% for number of spikes/ plant in the third cross, to 71.11% for 100- kernel weight in the first cross under optimum sowing date, and from 31.14% for number of spikes/ plant in the second cross to 78.21% for maturity date in the first cross under late sowing date.

The parent off-spring regression heritability, under optimum sowing date, were found to be high to moderate and ranged from 31.99% for number of spikes/ plant in the third cross to 77.19% for grain yield/ plant in the first cross, and from 49.11% for 100-kernel weight in the second cross to 77.85% for number of kernels/ spike in the first cross under late sowing date.

The expected genetic gain, under optimum sowing date ranged from 0.16% for number of spikes/ plant in the third cross to 17.95% for grain yield/ plant in the second cross, and from 0.42% for 100-kernel weight in the third cross to 18.42% for grain yield/ plant in the first cross under late sowing date.

Actual genetic gain, under optimum sowing date ranged from 0.59% for 100-kernel weight in the third cross to 18.58% for grain yield/ plant in the second cross, while, under late sowing date it ranged from 0.58% for 100-kernel weight in the third cross to 20.69% for grain yield/ plant in the first cross.