| In order to study basic characteristic of the boll, hereditary law of the boll number in different development period, the relationship between the boll number and yield , and yield component traits, and quality properties, according to NCII mating design,using additive-dominant genetic model.11 Island Cotton parents with different ecological sources was selected for researching. The conclusion is as follows:1. The boll number is increasing gradually with the time, the developmental patterns of it are similar with the way of Logistic growth equation. The boll number of F1 is more than parents'in each period. The bolls of Island Cotton usually concentrate on the middle part of joint, the boll number has comparatively obvious middle part advantages. The result indicates that the boll number of Island Cotton reduces obviously after August 3.2. The unconditional genetic variance analysis showed that the development change of Island Cotton's boll number traits is controlled by additive and dominant effects. Additive effects express in the earlier and later stage of the boll, while dominant effects express in the middle. According to the ratio of genotype variance, the boll number is controlled mainly by dominance effects. From the the result of variance analysis, in the course of the Island Cotton's boll, the adding effects and dominant effects play a replacing role in different stage. The unconditional genetic variance and conditional genetic variance analysis are not completely the same. The conditional variance analysis is stringent and sensitive owing to reflecting the different genetic gradually effects in the different stages.3. The heritabilities analysis showed that, whether unconditional heredity rate or conditional heredity rate, the broad-sense heritabilites of boll number is reached significant or highly significant level in many stages, while the narrow sense heritablity reach prominent or extremely prominent level only in few satges. It is more difficulty to select the boll number in the course of breeding, so we should improve heredity to select the boll number. Analysising the traits of yield and quality hereditary rate, the result indicates that fiber length and fibrous should be selected in early stage, but lint percentage, boll weight, micronaire should be selected in middle stage. 4. Between the boll number and yield quality traits ,the correlation analysis showed that the boll number will help for select high yield, high-quality Island cotton varieties. There are different correlationships between the boll number and yield, and quality traits in different stage, so we can select yield and quality traits indirectly according to the boll number in different development stage. In the course of indirect selection, the positive and negative effects of the boll-part traits to the finally yields traits and qualities traits must be paied more attention in order to synchronization improve both yields and qualities traits.5. The boll number of F1and F2 has significant population heterosi in the middle and later stages in Island Cotton, the population heterosi of F2 will decline to some extent, better-parent heterosi will decline obviously in earlier stage. Different parent have different hereditary effects of yield and quality traits. Rational select the parent will help to crossbreed of Island Cotton and to use hybrid heterosi. In order to be help for boll number, breed Island Cotton of high yield and high quality, we must strengthen getting early-maturing choice, form more cotton boll early.In conclusion, the regular change of the boll number and the boll number mainly controlled by dominant effects, meanwhile controlled by significant gene adding effects some time. Select the boll number correctly will favorable to breeding high yield and high qualities of Island Cotton. According to the hereditary characteristic of the boll number in different development period, we should make the corresponding selection and use tactics to achieve the goal of improving yield and qualities.
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