Analysis of genetic diversity and population structure in upland cotton (Gossypium hirsutum L.) germplasm using simple sequence repeats

Improvement of cotton fibre yield and quality is challenging due to the narrow genetic base of modern cotton cultivars, which emphasizes the great need to effectively explore the existing germplasm resources. With major objective to assess the genetic diversity and population structure at DNA level, 302 elite upland cotton germplasm accessions (253 Chinese and 49 different exotic origins), were genotyped using 198 simple sequence repeats (SSRs) markers. Each of the 198 markers differed greatly in its ability to detect variations in the panel of cotton germplasm. The SSRs amplified 897 alleles, of which 77.7% were polymorphic. The number of alleles varied from 2 to 12 (mean 4.53). Gene diversity ranged from 0.020 to 0.492 with a mean of 0.279. The polymorphic information content (PIC) values ranged from 0.371 to 0.019 (mean 0.225). Genetic distances in the whole cotton germplasm ranged from 0.451 to 0.052 (mean 0.270), demonstrating relatively wider genetic diversity range. Chinese-origin cotton germplasm showed the highest level of SSR polymorphisms (gene diversity=0.268, PIC=0.218), whereas American-origin revealed the highest mean genetic distance (0.274). Model-based Bayesian analysis clustered the whole cotton germplasm into three subpopulations, and the highest molecular variation ws revealed between subpopulations (4%, P<0.001). The SSRs revealed moderate level of genetic diversity at DNA level, identified three structured subpopulations, suggesting a potential use of these markers for genomewide association mapping studies and for identifying and conserving useful alleles in upland cotton germplasm.

Genetic and epigenetic status of triple exotic consanguinity cotton introgression lines

Introgression lines are some of the most important germplasm for breeding applications and other research conducted on cotton crops. The DNA methylation level among 10 introgression lines of cotton (Gossypium hirsutum) and three exotic parental species (G. arboreum, G. thurberi and G. barbadense) were assessed by methylation-sensitive amplified polymorphism (MSAP) technology. The methylation level in the introgression lines ranged from 33.3 to 51.5%. However, the lines PD0111 and PD0113 had the lowest methylation level (34.6 and 33.3%, respectively) due to demethylation of most non-coding sequences. Amplified fragment length polymorphism (AFLP) was used to evaluate the genetic polymorphism in the cotton introgression lines. A high degree of polymorphism was observed in all introgression lines (mean 47.2%) based on AFLP and MSAP analyses. This confirmed the effects of genetic improvement on cotton introgression lines. The low methylation varieties, PD0111 and PD0113 (introgression lines), clustered outside of the introgression lines based on MSAP data, which was incongruent with an AFLP-based dendrogram. This phenomenon could be caused by environmental changes or introgression of exotic DNA fragments.

[A case-control study of prostate cancer]

In America and many European countries, prostate cancer is the most common cancer and the second leading cause of cancer death in men. Among 10-30% of all the men older than 50 years of age, a silent microscopic form of prostate cancer may be harbored. This high rate is similar throughout the world. However, few epidemiologic studies of prostate cancer have implicated its risk factors. A 1:1 matched case-control study looked into risk factors of prostate cancer. A total number of 102 cases of prostate cancer and 102 controls were surveyed. The results showed that high body mass index, history of urinary diseases, coitus frequency > 3 times per week, hormone drug use, and number of children > 3 are identified as risk factors of prostate cancer statistically, but physical labor, exercise, and age of first nocturnal emission > 18 are protective factors of prostate cancer.

[Analysis of population attributable risk of breast cancer in urban and mining districts inhabitants]

In order to study the risk factors associated with female breast cancer, two 1:2 matched case-control studies were conducted from 1986 to 1993 in five cities in Hubei province and from 1991 to 1994 in Pingdingshan coal mining districts in Henan province. The results of multivariate conditional logistic regression analysis showed that history of breast diseases, number of births, age of first birth were major risk factors for breast cancer in urban inhabitants. Their adjusted attributable risks (PARs) were 0.3917, 0.3564, 0.1414 respectively. The combined population attributable risks (PAR) for the three factors was 0.7419. History of breast disease, number of births, menstrual disorder, family history of breast cancer were major risk factors in the Mining districts. Their PARs were 0.1487, 0.4781, 0.1282, 0.0791 respectively. PAR for four factors was 0.6952.

[A matched case-control study on the relations between beta-carotene and lung cancer]

In order to discover the relationship between dietary nutrients intake and risk of lung cancer 1:1 matched case-control study on 156 recent histologiclly diagnosed primary lung cancer patients and 156 patients with respiratory tumour and other related diseases as controls, was conducted in Wuhan. All cases and controls were asked to participate in the nutritional assessment program and a food frequency questionnaire containing 64 food items was filled in. The findings showed that there was a statistically significant difference between dietary intake of beta-carotene between the two groups (2877.13 +/- 393.43 vs. 3445 +/- 430.98 micrograms/day). Having controled the confounding factor of cigarette smoking, a significant linear trend for lower dietary carotene intake toward higher lung cancer risk was observed.

The relation of urinary cations to blood pressure in boys aged seven to eight years

A study on the relation between urinary cations and blood pressure was conducted in Wuhan, China. A total of 148 boys aged 7-8 years entered the study from November 23, 1984, to January 13, 1985. Seven consecutive 24-hour urine specimens were collected and blood pressure was measured on the seven successive days corresponding to urine collection. The multiple regression showed that none of the sodium, potassium, calcium, and magnesium cations was statistically significantly related to blood pressure. However, the ratio of sodium/calcium or potassium/calcium in the urine was positively correlated with systolic pressure in multivariate analysis. The results suggest that there may be a complex interaction between sodium and calcium in their effects on blood pressure, and genetic background might have some influences on the sodium/calcium (or potassium/calcium)-blood pressure relation in the 7-8-year-old boys in the study.