Abstract
The main objective of the current investigation was to introduce a rapid genetic assay for testing cotton (G. barbadense) genotypes to endure the late planting conditions. A set of properly selected nine divergent lines was crossed in a 5X4 Factorial-mating design II fashion. Parental lines and their 20 F 2 crosses were evaluated for growth-based and yield-based earliness traits in two divergent planting dates (Middle march, D 1, and Middle May, D 2 ) at Cairo University Experimental Station in the summer seasons of 2010 through 2012. The parental genotypes G90 (cultivar; =39.70g/plant, =0.49), PS6( andG75 ( were identified as late planting (LP) stress tolerant. They showed a high yield potential in late planting and possessed a low to moderate LP susceptibility index "S". Genotypes G90, EC2, PS6 and PS7 were identified as high earliness index stress tolerant. The "S" values based on seed cotton (SC/P) revealed that the cross combinations G86 x G75 (4), G90x G75 (12), G80 x PS7 (18), and G80 x G83 (19) were moderate LP stress tolerance. These crosses showed the highest yield potential at D2. Cross combinations EC1 x PS6, G90 x PS7, EC2 x PS6, EC2 x G83 and G80 x PS6 were earlier, hence, required less number of days to first boll and recorded the highest earliness index. Significant additive and non-additive variation exhibited in the traits expression. The variances due to general combining ability (GCA) were large in magnitude than those due to specific combining ability (SCA), only for first fruiting node, days to first flower (LP), and days to first boll (LP); the remained traits showed greater variances of SCA. These results were supported by the ratios obtained for the relative importance of additive to non-additive variances. The average degrees of dominance over all loci indicated partial dominance of various degrees for all studied traits. The broad sense heritability was greater than narrow sense for all traits. This was associated with high narrow sense heretabilities with some traits. The study concluded to the following recommendations: 1) the lines EC1, EC2, PS6 and their descendents can be utilized as a breeding nucleus to develop barbadense genotypes that can be planted up to early May, 2) LP tolerant genotypes should have low "s" index, shorter than current genotypes, having low node of first sympodial, early for days to first boll and have high yielding capacity reflected in high earliness index, 3) breeding by backcrossing with the selected genotypes followed by repeated selfing is a successful breeding strategy for improving tolerance to late planting and enhance shortening the growing season.
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Claims 15
Claim · model-written summary
Parental genotype G90 was identified as late-planting stress tolerant.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e2“The parental genotypes G90 (cultivar; =39.70g/plant, =0.49), PS6( andG75 ( were identified as late planting (LP) stress tolerant”
Claim · model-written summary
Genotypes G90, EC2, PS6 and PS7 were identified as high earliness index stress tolerant.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e3“Genotypes G90, EC2, PS6 and PS7 were identified as high earliness index stress tolerant”
Claim · model-written summary
Crosses G86 x G75 and G90x G75 showed moderate late-planting stress tolerance.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e4“the cross combinations G86 x G75 (4), G90x G75 (12), G80 x PS7 (18), and G80 x G83 (19) were moderate LP stress tolerance”
Claim · model-written summary
Crosses G80 x PS7 and G80 x G83 showed moderate late-planting stress tolerance.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e4“the cross combinations G86 x G75 (4), G90x G75 (12), G80 x PS7 (18), and G80 x G83 (19) were moderate LP stress tolerance”
Claim · model-written summary
The moderately tolerant crosses showed the highest yield potential at the later planting date.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e5“These crosses showed the highest yield potential at D2”
Claim · model-written summary
Crosses EC1 x PS6, G90 x PS7 and EC2 x PS6 were earlier, with the highest earliness index.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e6“Cross combinations EC1 x PS6, G90 x PS7, EC2 x PS6, EC2 x G83 and G80 x PS6 were earlier, hence, required less number of days to first boll and recorded the highest earliness index”
Claim · model-written summary
Crosses EC2 x G83 and G80 x PS6 were earlier, with the highest earliness index.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e6“Cross combinations EC1 x PS6, G90 x PS7, EC2 x PS6, EC2 x G83 and G80 x PS6 were earlier, hence, required less number of days to first boll and recorded the highest earliness index”
Claim · model-written summary
General combining ability variance was larger than specific combining ability variance only for first fruiting node and days to first flower and first boll under late planting.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e7“The variances due to general combining ability (GCA) were large in magnitude than those due to specific combining ability (SCA), only for first fruiting node, days to first flower (LP), and days to first boll (LP)”
Claim · model-written summary
For the remaining traits, specific combining ability variance was greater than general combining ability variance.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e1“the remained traits showed greater variances of SCA”
Claim · model-written summary
Additive and non-additive variation was significant for the traits expressed.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e1“Significant additive and non-additive variation exhibited in the traits expression”
Claim · model-written summary
Degrees of dominance indicated partial dominance for all studied traits.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e1“The average degrees of dominance over all loci indicated partial dominance of various degrees for all studied traits”
Claim · model-written summary
Broad-sense heritability was greater than narrow-sense heritability for all traits.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e1“The broad sense heritability was greater than narrow sense for all traits”
Claim · model-written summary
Lines EC1, EC2 and PS6 and their descendants can be used as a breeding nucleus for genotypes planted up to early May.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e1“the lines EC1, EC2, PS6 and their descendents can be utilized as a breeding nucleus to develop barbadense genotypes that can be planted up to early May”
Claim · model-written summary
LP-tolerant genotypes should have a low "s" index and be shorter than current genotypes, with low first sympodial node, early boll set and high earliness index.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e1“LP tolerant genotypes should have low "s" index, shorter than current genotypes”
e2“having low node of first sympodial, early for days to first boll and have high yielding capacity reflected in high earliness index”
Claim · model-written summary
Backcrossing with selected genotypes followed by repeated selfing is a successful breeding strategy for late-planting tolerance.
Verbatim
e0“testing cotton (G. barbadense) genotypes to endure the late planting conditions”
e1“breeding by backcrossing with the selected genotypes followed by repeated selfing is a successful breeding strategy for improving tolerance to late planting”