Chromosome identities were assigned to 15 linkage groups of the RFLP joinmap developed from four intraspecific cotton (Gossypium hirsutum L.) populations with different genetic backgrounds (Acala, Delta, and Texas Plains). The linkage groups were assigned to chromosomes by deficiency analysis of probes in the previously published joinmap, based on genomic DNA from hypoaneuploid chromosome substitution lines. These findings were integrated with QTL identification for multiple fiber and yield traits. Overall results revealed the presence of 63 QTLs on five different chromosomes of the A subgenome (chromosomes-03, -07, -09, -10, and -12) and 29 QTLs on the three different D subgenome (chromosomes-14 Lo, -20, and the long arm of -26). Linkage group-1 (chromosome-03) harbored 26 QTLs, covering 117 cM with 54 RFLP loci. Linkage group-2, (the long arm of chromosome-26) harbored 19 QTLs, covering 77.6 cM with 27 RFLP loci. Approximately 49% of the putative 92 QTLs for agronomic and fiber quality traits were placed on the above two major joinmap linkage groups, which correspond to just two different chromosomes, indicating that cotton chromosomes may have islands of high and low meiotic recombination like some other eukaryotic organisms. In addition, it reveals highly recombined and putative gene abundant regions in the cotton genome. QTLs for fiber quality traits in certain regions are located between two RFLP markers with an average of less than one cM (approximately 0.4-0.6 Mb) and possibly represent targets for map-based cloning. Identification of chromosomal location of RFLP markers common to different intra- and interspecific-populations will facilitate development of portable framework markers, as well as genetic and physical mapping of the cotton genome.

gressed into 97 primitive G. hirsutum race stock accessions by a large backcross breeding program (McCarty Effective use of converted day-neutral Gossypium hirsutum L. et al., 1979;McCarty and Jenkins, 1993). The converted race stocks in cotton genetic improvement programs depends on the extent of genetic variation for desirable alleles and the accurate char-primitive accessions are reservoirs of various genes for acterization of the variability within and among germplasm accessions resistance to pests such as boll weevil (Anthonomus in the collection. This study was conducted to survey the molecular grandis grandis Boheman) (McCarty et al., 1986), fuvariation in the converted race stock collection by using simple sesarium wilt [Fusarium oxysporum Schlechtend.:Fr. f. sp. quence repeat (SSR) DNA markers and to determine the genetic vasinfectum (Atk.) W.C. Snyder & H.N. Hans.], and distance of each race stock from a typical G. hirsutum cultigen. The tarnished plant bug (Lygus lineolaris Palisot de Beaumolecular marker data will also provide a measure of the degree to vois) (Jenkins et al., 1979). Introgression can be which the recurrent photoperiodic parent has been recovered during achieved without serious losses in agronomic perforbackcross conversion to day-neutral stocks. Fifty-six flourescently lamance (McCarty et al., 1996). beled SSR primer pairs arranged in multiplex bins were used to geno-Photoperiodic collections of other tetraploid Gossyptype 97 day-neutral BC 4 F 4 race stock accessions. The majority of the accessions had genetic distances Ͻ0.25 from the G. hirsutum standard ium species exist. DeJoodie and Wendel (1992) charac-TM1. There was strong evidence that the accessions were heterozy-terized the diversity of G. tomentosum Nutt. ex Seem, gous or heterogeneous, so 10 plants were genotyped within the most G. mustelinum Miers ex Watt, and G. darwinii Watt diverse nine accessions, those with genetic distance from TM1 Ͼ0.25.relative to G. barbadense L. and G. hirsutum. Unfortu-In some families, the primitive photoperiodic parent was recovered, nately, day-neutral versions of these tetraploid species and in others there was extensive linkage drag from the day-neutral

The fruiting sites at which cotton, Gossypium hirsutum L., plants set bolls that are harvested influence how well the plants tolerate insects. The objective of this research was to determine the fruiting patterns of eight cultivars of cotton in terms of fruiting sites of harvestable bolls when planted in a conventional pattern of rows spaced 1‐m apart with a plant population of approximately 95 000 plants ha−1 for 2 yr in Mississippi. Descriptive terms are defined as follows: (i) sympodium—a fruiting branch; (ii) monopodium—a vegetative branch; (iii) node—the place on the main stem where sympodia monopodiarise, we numbered the nodes beginning with the cotyledeonary node as number one; (iv) position—refers to the order which buds (potential bolls) are produced on a sympodinm branch; and (v) fruiting site—any specific node‐position combination. Cultivars compared and their release dates were: Stoneville 213, 1962; Stoneville 506, 1980; Stoneville 825, 1979; Tamcot CAMD‐E, 1979; Deltapine 50, 1984; McNair 235, 1975; DES 119, 1986; and Deltapine 20, 1985. Bolls at position one on sympodial branches produced 66 to 75% of total yield; those at position two produced 18 to 21%; all other positions on sympodial branches produced from 2 to 4% of total yield. Monopodial branches produced from 3 to 9% of the total yield. Sympodial branches from Nodes 9 through 14 produced the bulk of the lint in all cultivars. Distribution of lint over sympodia among cultivars was significantly different for positions one and two, with the newer, early maturing cultivars producing significantly more lint from sympodial branches at Nodes 6 through 8 than the older cultivar Stoneville 213. Tamcot CAMD‐E, McNair 235, and Deltapine 20 also produced less lint on monopodial branches than Stoneville 213. This research provides valuable information needed to more effectively manage the production of the newer, early maturing cuitivars of cotton presently being grown in the mid‐South.