| Sweet sorghum is considered to be the most promising energy crop for high glucose, high yield of stalk and food as well. In order to solve the problem of cultivation and breeding sweet sorghum in Guangxi, we investigated its yield traits, stem juices composition, sugar accumulation, correlation among traits, etc by analysis of sugar accumulation in different growth period and after harvest, different sowing date trial, test of genetic correlation of main characters of F2generation. The results are as follows:1. Law of stem brix and sugar accumulation. Stem brix of LT3grew slowly before flowering, increased most from wax mature to complete ripe and got the highest point of16.3%at complete ripe stage. Stem brix of BT3had more accumulation before flowing, increased most from packing flag to flowering and got the highest point of19.2%at complete ripen stage. Reducing sugar of LT3was low at prophase stage, then it increased at middle stage, and dropped at last. However, sucrose was contrarious. Reducing sugar of BT3got the highest point at packing flag stage and dropped with growing process, While sucrose was reversed. So the most suitable harvest time was complete ripen period.2. Stem sugar concentration changed after harvest. As storing time flied, sugar concentration dropped slowly before the12th day and dropped sharply after the12th day, so the stem of LT3should be processed before the12th day after harvest.3.The most suitable sowing time.The time from March to August was the most suitable sowing time, and April was the best sowing period. From the eye of growth period, the two cultivars could not realise high yield twice in one year. 4.Yield Traits. There were three classes of stem yield with six sowing periods of LT1and LT3. The first class, sweet sorghum with the highest yield was sowed between March and May. LT1had a yield of3956.1～4335.6kg/667m2and LT3had a yield of4644.97-5348.28kg/667m2. The second class, sweet sorghum which was sowed between middle June and middle July had a medium yield. LT1had a yield of2632.69-2827.15kg/667m2, and LT3had a yield of2996.58-3292.6kg/667m2The third class, sweet sorghum which was sowed in late August had the lowest yield between the three periods. LT1had a yield of51.66kg/667m2, and LT3had a yield of447.36kg/667m2.5.Different sowing periods had different effect on sugar brix and sugar composition. The trend of sugar brix in different sowing dates was identical, but reached the highest value in different periods. The sugar brix got the highest value in complete ripen period if sowing before July. If sowing after July, it would at its highest value at wax ripen stage. The sugar brix had the highest value in April25th. LT1had a value of21.18%, and LT3had a value of18.27%which was higher than any other sowing dates apparently. Sugar composition had no identical changing trend.6.Comparison of growth period. As sowing date delayed, the growth period got shortened. Growth period of LT1and LT3had their longest growth period, if they were sowed in March28th(139d and140d).T.Genetic variation of F2generation’s characters. The plant height, stem node number, brix and fresh stem weight coefficient of variation achieved respectively20.21%、20.59%、29.44%、50.3%. The genetic variation was rich.8.Correlation analysis. Fresh stem weight, plant height, stem diameter, stem node number, the days of seeding to flowering and sugar brix had significant correlation. The correlation value was0.73、0.70、0.75、0.72、0.58., respectively.Brix, plant height, plant node number and days from seeding to flowering had significant correlation too. The correlation value was0.63、0.61、0.75, respectively。9. Path analysis. The path coefficient between plant height, stem diameter and fresh stem weight was bigger which was up to0.3128and0.4297, respectively. The direct path coefficient between days from seeding to flowering and stem sugar brix was0.6793. These characters can be the most helpful for breeding high yield plant. |
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