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Abstract
Several suggested guidelines for efficient parental choice of cotton parents in cross breeding program for developing superior genotypes were investigated. Therefore, multievaluating (over two environments and generations) of the breeding potentialities, susceptibility index, and stability of mean performance of nine selected cotton genotypes (P1=Eearlipima, P2=Pima S-6, P3=Pima S-7, P4=Dandara, P5=Giza 80, P6=Giza 90, P7=Giza 85, P8=Giza 89, and P9=Giza 83) were crossed in half diallel at two planting dates, 17 March, designated as FSE and 1 May for late planting cropping system designated as SSE were conducted. Several statistical analysis of data for GCA, SCA, gene action, stability of mean performance, susceptibility index, and correlation coefficient between yield and fiber quality revealed the following aspects:
Five crosses in FSE (P1×P4, P2×P5, P3×P9, P4×P8, and P5×P6) and three crosses in SSE (P3×P9, P5×P8, and P7×P8) exhibiting very high percentage of F2HPH as well as significant SCA effect are capable of giving maximum transgressive effects.
The three crosses P3× P4, P5 × P8, and P7 × P8 were classified as tolerant to stress of short season environment based on both seed and lint cotton yield. Therefore, much emphasis will be concentrated on these crosses to be used directly for selecting superior segregants of high yielding ability with stability mean performance and adapted to SSE.
Inbreeding depression was quite very small and in most cases with minus values. These results probably indicate that epistasis and/or dominance effects for F2 heterosis in cotton could be important to a certain extent, but additive and dominance effects are probably important than epistatic effects.
The three cross combinations in FSE, P5×P6, P4×P8, and P2×P4 are unexpected combinations from the cotton breeder point of view because they combine the genes of high yielding ability and earliness.
Eight crosses exhibited stable mean performance for yield potentialities. Out of these crosses three ones P3×P4, P3×P5 and P5×P8 were among the crosses which were rated as late stress tolerant in terms of SSI. Out of the parental genotypes of these three crosses three P3, P4 and P5 are classified as stable mean performance. However P3 and P4 and P8 ) are tolerant for stress of late planting. However, G.90, the highest yielding parent may be used as a source of high yielding genes to enrich the gene poll and must be incorporated in multiple crosses system followed by pedigree selection for obtaining high yielding, stable, and short season cotton lines.
The undesired negative relationship observed in F2 at FSE between cotton yields and each of UHM and UI were changed from antagonistic to favorable in SSE. This indicates that in SSE there is a possibility for selection for high yields with fiber length and fiber uniformity.