Identification of Four Gossypium sturtianum Monosomic Alien Addition Derivatives from a Backcrossing Program with G. hirsutum

Alien chromosome addition lines provide means to distinguish effects of specific alien chromosomes, to detect homoeologies between chromosomes of different species, and to conduct chromosome‐specific introgression. Over the last few years, numerous monosomic addition (MA) stocks were derived from interspecific backcrosses of Gossypium sturtianum J.H. Willis (2n = 2x = 26, C1 genome) with G. hirsutum L. [2n = 4x = 52, (AD), genome] as recurrent parent. Using 10 MA plants of varied pedigrees from this project, our objectives were to (i) identify and characterize different MA stocks, (ii) determine the phenol) pic effect of each addition chromosome, and (iii) estimate the frequency of (AD)1‐C1 recombination. We identified 4 distinct G. sturtianum MA types among the 10 analyzed, and have temporarily designated these as C1‐A, C1‐B, C1‐C, and C1‐D. The C1‐A, C1‐B, and C1‐D MA stocks differed phenotypically from the recurrent parent, while the C1‐C MA stock was phenotypically indistinguishable from the recurrent parent. None of the MA chromosomes was pollen transmissible, but all were ovule transmissible in vivo. Frequencies of ovule transmission from the MA chromosomes ranged 13.7% for C1‐B to 77% for C1‐A. Cytogenetic analyses of the parental stocks and their backcross progenies revealed low but nonetheless increased frequencies of abnormal meiotic chromosomal configurations, possibly due to previous intergenomic recombination, the meiotic disturbances, or both. Genetic data to substantiate recombination have not yet been obtained, but chiasmata were observed at a frequency of 1.7% per meiotic C1 chromosome in the MA stocks, indicating that recombination with chromosomes of G. hirsutum is occurring, albeit infrequently. The establishment and characterization of these four MA stocks will facilitate development of dispersed repetitive genomic probes for the C1 genome, analysis of interspecific C1‐to‐(AD)1 genomic introgression, and the derivation of additional C1 MA stocks.