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Average cotton yield per hectare in China has been increased at a rate of 16.14 kg · ha-1year-1 since 1950, to which cotton breeding has made tremendous contributions. The objectives of the present study were to compare the performance of selected cotton cultivars released since the 1950s in order to estimate the genetic gain for lint yield, fiber quality, and other major agronomic traits. The results indicated that the yield gain due to cultivar improvement was 8.75 kg·ha-1year-1 for springsow cultivars grown in the Yellow River Valley, 8.16 kg·ha-1year-1 for spring-sow cultivars grown in the Yangtze River Valley, and 7.92 kg·ha-1year-1 for short season cultivars, which accounted for 46-54% of annual yield increase. The increase in yield potential in later released cultivars was attributed to the increase in number of bolls per plant and lint percentage. Furthermore, modern cultivars had improved fiber strength, earliness, and resistance to Fusarium wilt and Verticillium wilt diseases. However, they were significantly taller with slightly smaller boll, smaller seed, and coarse fiber. No significant improvement in fiber length was detected. [ABSTRACT FROM AUTHOR]

Five short season cultivars (SSC) with no premature senescence were selected to cross with 5 SSC cultivars with premature senescence. The parents, F1, and F2 from the reciprocal crosses were field tested in replicated trials in 2001 and 2002. The results indicated that the activities of protecting enzymes of the antioxidant system such as CAT, SOD, and POD were higher in the early maturing SSC with no premature senescence than these in the SSC parental cultivars that showed premature senescence, while the MDA content in the former was lower than that in the latter. Various genetic variances and heritabilities for these biochemical traits and IAA, ABA, and chlorophyll contents were also estimated. There existed significant additive variance for CAT, POD, ABA and IAA, while CAT specific activity and SOD activity were largely controlled by dominant effects. Both maternal and dominant variances played equally predominant roles in POD and SOD specific activity, MDA and soluble protein contents. The relative contributions of the various genetic components to the phenotypic variation varied in boll-setting period. [ABSTRACT FROM AUTHOR]

An abstract of the article "Study on Inheritance of Earliness and It's Relative Traits of Short-Season Cotton and QTLS Mapping," by Shuli Fan, Shuxun Yu and Meizhen Song is presented.

Genetic effect and its environment interaction were studied for short season cotton of Upland cotton (Gossypium hirsutum L.) by Mixed linear model approaches using a 9×9 incomplete dialelle crosses in three ecological environments. The results reviewed that the hereditability in narrow sense(h²N) for earliness traits were low, only 16.1%,and it's environment interaction was significant, about 17.5%, especially first fruiting branch node and squaring with the lowest hereditability and the highest environment interaction, but growth date, plant height and flowering with higher hereditability and lower environment interaction when same experiment materials planted in different test places were affected. The h²N for yield traits were 20.1%, and it's environment interaction was low, about 7.4%, Lint percent, boll weight and seed index are three most important traits in short season cotton yield breeding because of their relative higher h²N and lower environment interaction. Interaction between genetic effect and environment for five fiber qualities were significant or mighty significant. The h²N of fiber qualities were 28.6%, and its environment interaction was about 6.9%. The average h²N for earliness of short season cotton in Anyang, Yuncheng and Shihezi were 46.0%, 10.9%, 12.3% respectively. Average h²N of cotton plant properties including earliness, yield and fiber quality: Anyang>Yuncheng > Shihezi. The results explained and developed the different views of the former about the hereditability of the first fruiting branch node and squaring. [ABSTRACT FROM AUTHOR]

An abstract of the article "Promoter Anchored Amplified Polymorphism in Cotton," by Mingxiong Pang and colleagues is presented.

An abstract of the article "Development of High Throughput DNA Marker Systems in Cotton Based on Gene and Regulatory Sequences," by Yingzhi Lu, Mingxiong Pang and Sarah Higbie is presented.

Genome sequence information and high-throughput gene expression profiling methods such as cDNA micoarray to measure gene expression abundances open the door for investigating genome-wide gene expression and regulations in plants. However, non-coding sequences especially regulatory regions also play an important role in gene regulation and plant development. In our efforts to design molecular marker systems to search polymorphism associated with higher fiber yield and better fiber qualities, we are trying to examine a methodology that could specifically target different regulatory regions of the genome in cotton. In this study we designed 10-nucleotide degenerate promoter primers based on the conserved core promoter sequences and tested their applicability in PCR amplifications in combination with 10-mer random primers. To increase the specificity of PCR amplifications, we also designed longer primers consisting of filler sequences and the conserved core promoter sequences based on TATA box, GC box, G box and CA box. The primers were combined with AFLP primers in a PCR reaction. The markers amplified using RAPD-based and AFLP-based techniques were collectively called promoter anchored amplified polymorphism (PAAP). Forty cotton germplasm with diverse genetic and geographical backgrounds were used to test the RAPDbased primers, while eight germplasm were used to test the AFLP-based primers. Based on RAPD-PAAP markers amplified from 12 primer combinations, the 40 genotypes were grouped into 5 distinctive groups (2 Upland cotton groups from China, 2 Upland cotton groups from the US and 1 from Pima cotton), consistent with their genetic and geographical origins. Based on AFLP-PAAP, the 8 genotypes were divided into three groups, congruent with their genetic backgrounds. The new PAAP marker system is being used to map PAAP markers in a backcross inbred line (BIL) population and to identify QTLs controlling fiber quality and yield. [ABSTRACT FROM AUTHOR]

Molecular markers such as RFLP, RAPD, AFLP, SSR, and SNP have been developed and used in numerous plants including cotton (Gossypium hirsutum L.) for fingerprinting, linkage map construction, gene/QTL mapping, and genetic diversity studies. However, many of the marker systems have some limitations in terms of polymorphism levels, high throughputness, and anonymousness. Markers such as cDNA-RFLP, EST-SSR, and SNPs are gene sequence specific, but the level of DNA polymorphism within certain plant species including cotton is low, limiting their utilization in the development of genome-wide linkage maps and gene discovery. Our current research focuses on the development of new DNA marker systems using array-based hybridization and PCR-based techniques. High throughput marker systems were developed based on conserved DNA sequences for promoters, cis-acting elements, disease resistant gene analogous, microRNA genes, untranslated regions, and introns. To profile start codon regions, an ATG-anchored AFLP analysis was devised and proved to be reliable. Oligonucleotide arrays, initially designed for expression analysis, were also successfully used to detect allelic variation via direct hybridization of labeled genomic DNA. Single base changes (SNP) or insertion/deletion (Indel) within oligonucleotide region in an array produce differential hybridization signals, called single-feature polymorphism (SFP). The array-based marker technology is very powerful in that numerous markers can be assayed at once that can provide genome-wide coverage. Compared with the traditional molecular markers, the modified and new marker systems are highly cost effective and gene-regions or regulatory regions targeted. They can better resolve genetic relationships between genotypes, rendering a higher discriminatory power. [ABSTRACT FROM AUTHOR]