Studies On Biological Basis For Perennial Cultivation Of Annual Upland Cotton In Southern Guangxi

The perennial cultivation of annual cotton is very important for maintaining genic male sterile lines, producing hybrid seeds, fixing heterosis and preserving special germ plasm. Meanwhile it makes cultivation simple, save labours and raise annual yield because cotton plants can grow and develop longer. However, perennial cultivation of cotton is limited in tropical area and is used to preserve germ plasm. So far, no report about cultivating perennial upland cotton in Guangxi can be seen.Random block design and orthogonal arrays were set up to investigate the perennial cultivation and the cold resistance in winter for 10 varieties of upland cotton in Nanning Guangxi from 2005 to 2007. The main results are as follows.1.Growth and development for Perennial Cultivation of Annual Upland CottonCompared with annual cotton, the plant size of perennial cultivation of annual upland cotton increased obviously, growth stages aheaded of schedule, second grwoth and development process appeared. The total numbers of fruiting branches, fruiting nodes and leaves per plant of perennial cultivation are much more than those of annual cotton significantly. The effects of perennial ages on the diameter of main stems are obvious: it becomes more as the perennial ages longer and the resistance to lodging increase as well. The dates of budding, flowering, spitting-wadding and harvesting of perennial cultivation cotton are greatly ahead of the annual cotton. The harvesting peak appears earlier and the peak value is higher. The total bolls per plant are increased obviously. The single boll weights have no significant difference for most varieties. Lint percentage changes with varieties.Two obvious growth and development processes appeared in perennial cultivation and two peaks found accordingly in a year. The peaks of the leaf number appeared in the first and second ten days of July and September. The bud peaks per plant appeared in the second ten days of June and the last ten days of August. The flower per plant appeared in the last ten days of June and the first ten days of September. The spitting-wadding peaks appeared in the last ten days of July to the second ten days of August and the second ten days of October to the first ten days of November.2. The yield and quality for Perennial Cultivation of Annual Upland CottonThe yield of perennial cultivation is very significantly higher than that of annual cotton. Case study of Zhong 928 F₁, its lint yield of the biennial cotton reached 1882.94kg/ha, increased 62.71% than that of the annual cotton; and 1781.67kg/ha of the triennial cotton, 53.95% increased. The fibre quality of the perennial cultivation has no obvious difference with that of the annual cotton. There are no significance effects of the perennial ages on the micronaire, metric number, radix, uniformity; well the strength, 2.5% span length, short fibre rate different based on the varieties.3. The contents of N/P/K and soluble sugar in functional leaves and their relationships with the yields and qualitiesCompared with annual cotton, there were no significant differences between average value of each test and value of each test for perennial cultivation.The contents of total N in different month changed from higher in prophase to lower in anaphase, higher in July, lower in November. There was obvious difference between the higher and lower. There was significantly affirmative correlation on the total N average value of triennail cotton in different months from lesves to total bolls and uniformity , significantly negative correlation to short fibre rate. There was not significant correlation on the total N average value of biennial cotton in different months from lesves to yield factors, yields and the quality index . There was bigger correlation coefficients on the total N value of triennail and biennial cotton in August and September from lesves to yields, and significantly affirmative correlation in September. There was significantly affirmative correlation on the total N average value of annual cotton in different months from lesves to yield factors, not significant correlation to the quality index, significant correlation in July,August and September to yields.The contents of total P in different month changed from higher to lower and from higher to lower, and there was obvious difference between the higher and lower. There was significantly negative correlation on the total P average value of triennail cotton in different months from lesves to seed index, significantly negative correlation in October to yieds; There was significantly affirmative correlation on the total P average value of biennial cotton in different months from lesves to radix; There was significantly negative correlation on them of annual cotton to micronaire and radix, significantly affirmative correlation to metric count.And not significantly correlation to the others.The contents of total K in functional leaves were higher in earier stage,and it changes a little with every test. There was significantly affirmative correlation on the total K average value of triennail cotton in different months from lesves to radix; There was significantly negative correlation on them of biennial to boll weight, seed index and 2.5% span length, significantly affirmative correlation to radix, short fibre rate, significantly negative correlation in August to yieds. There was significantly negative correlation on the total K average value of annual cotton in different months from lesves to total bolls, boll weight, seed index and 2.5% span length, significant affirmative correlation to uniformity, there was significantly negative correlation in August and September to yields.The contents of soluble sugar in different month changed from lower in prophase to higher in anaphase, higher in November, and there was obvious difference between the higher and lower. Only there was significantly negative correlation on them of biennial in September to yields.4. The resistance of perennial cultivation cotton to cold and over winter abilityThe effects of varieties, seedling date,Perennial ages and state of growth and developmemt on death rate of over-winter were significant. The death rate of "Zhong 928 F₁" was lowest in 10 tested varieties. Seedling properly earlier reduced the death rate significantly. The effects of perennial ages on death rate changed as varieties and times variation. The death rate of the varieties with bad perennial for annual cotton, were significant higher than those of the perennial cultivation before the low temperature in January. Status of plant growth and development affects their over-winter ability also. The plants which grew fast in prophase and plants with larger and more branch and leaf sizes decline early. The most serious decline plants were easily killed by winter cold. The death rate was higher in prophase. So was it in anaphase.The number of cultivated year had no obviously effects on relative electrical conductivity of stem and branches, injured rate of plasma membrane permeability had no significant effects. The differences of the injured rate of plasma membrane permeability between varieties were significant. Having experienced low temperature stress the relative electrical conductivity increased greatly. The higher relative electrical conductivity was, the higher the death rate was. So the relative electrical conductivity of stem and branch can be used as index of resistance to cold.As growth and development process, MDA contents increased. After October MDA contents rapidly increased and reached higher level, and the color of leaves changes light.This indicated that grow old of leaf occurred.There was significantly negative correlation on the comprehensive marks of cold resistance in October from lesves to the death rate of before low temperature and after low temperature. This indicated that the higher the comprehensive marks of cold resistance, the lower death rate of plants; On the contrary, the higher death rate of plants.