The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

Maintenance and evaluation of a collection of primitive Gossypium barbadense L. cottons progressed in 1987. Conversion of the non flowering tropical cottons to a flowering, day- neutral habit progressed. So did efforts to incorporate potentially useful biological and environmental stress tolerant traits into agronomic Pima backgrounds. Six cottons of the primitive cotton collection were found to potentially possess bacterial blight resistance. Genetic populations were developed to investigate the inheritance and distribution of two mutant marker traits in cotton. Interspecific Fl hybrid populations were developed for evaluation in 1988.

Five experimental strains, P65, P67, P64 P69, P70, and pima S-6 were grown in 9 regional tests across the pima belt in 1988. Mean yields from the 9 locations showed that P67 averaged highest in yield followed by P69, P70, P65, P68 and pima S-6 respectively. The difference in mean yield between P67, the highest yielding entry, and pima S-6 was 82 pounds of lint per acre. Pima S-6 was the latest maturing and tallest entry in the regional test at Maricopa. The 5 experimental strains had longer, finer, and whiter fiber than pima S-6.

Five experimental strains, P67, P69, P71, P72, P73, and Pima S -6 were grown in Regional tests at eight locations in 1989. P69 averaged highest in mean yield across locations followed by P73, Pima S-6, P71, P67 and P72. The difference in mean yield between P69, the highest yielding entry, and Pima S-6 was 35 pounds of lint per acre. Pima S-6 was the latest maturing and tallest entry in the Regional test at Maricopa. Pima S-6 also showed less tolerance to heat stress than the experimental strains. The experimental strains had longer, stronger, finer, and more whitish fiber than Pima S-6.

In an investigation of the genetic diversity and structure of Gossvpium barbadense L. it was determined that northwestern South America was the species' center of variability and probably the species' center of origin. Cultivars of the species were found to possess as much genetic variability as the center of variability. Cultivar variability was due in large part to introgression with G. hirsutum. Studies of interspecific hybrid performance revealed that development of G. barbadense parents could significantly affect the plant height, earliness, and yield of the resulting hybrids. Environment significantly affected hybrid performance and could enhance or obscure any beneficial effects of hybrid parent selection. A conversion program to convert photoperiodic short-day flowering tropical accessions to day neutrality continues. Preliminary results from inheritance and linkage studies of a male sterility factor and a foliar mutant indicate that both are single gene, recessive traits. No linkages between the male sterility factor and 21 marker traits were found.

Pima experimental strains P67, P69, P71, P73, P74, and Pima S -6 were grown in Regional tests at 11 locations across the Pima belt in 1990. P73 averaged highest in mean yield across locations followed by P74, P69, P67, Pima S-4 and P71. The experimental strains, in comparison with Pima S-6, had longer, stronger, finer, and more whitish fiber. Experimental strains P45, PSI, P53, P62, P66, and EIS were released jointly by the USDA ARS and the Arizona Agricultural Experimental Station, and registered in Crop Science.

An isozyme study of the diversity and structure of Goss_vpium nii revealed levels of genetic variation within the species which were high for an island endemic. Infraspecific diversity of G. darwinii was observed among populations of the various Galapagos Islands. Evidence of introgression of other Gossypium species into darwinii was noted. An investigation into the effects of altered Pima (G. barbadense) fiber genotypes on interspecific hybrid fiber characteristics indicated that parent genotype could significantly affect hybrid fiber length, strength, uniformity, and micronaire. However, hybrid heterosis for fiber length and micronaire greatly exceeded the influence of parent genotype. Hybrid fiber characteristics were unique, fitting within neither the extra -long staple nor long staple classifications. A conversion program to convert photoperiodic short-day accessions of a Gossvpium barbadense germplasm collection to day neutrality continues.

Pima experimental strains P73, P74, P75, P76, P77, and P78 and the varieties Pima S-6 (PS-6) and Pima S-7 (PS-7) were grown in Regional tests at seven locations across the Pima belt in 1991. When yields were averaged across five test locations below 2,500 feet, the strains P73, P74, P75, and P76 ranked higher than PS-6, but lower than PS-7. At two test locations above 2,500 feet the strains P76 and P73 ranked higher in yield than PS-6 and PS-7. There was a trend across all locations for the strains P73, P74, P75 and P76 to be shorter in height than PS-6. The strain P76, which was the highest yielding strain across all locations, was the shortest strain at five of the seven locations. Strains included in all tests tended to have whiter, stronger fiber than PS-6. The above was not the case for P77 and P78, which were present in only two tests.