Study On Salt-Tolerant Variety Screening And Regulation Of Growth Period In Sweet Sorghum

Soil salinization is one of the great threats to agricultural production all over the world.The area of secondary salinization in the world is still increasing.Sweet sorghum has a long history of cultivation in China and has strong resistance to adversity.At the same time,it has attracted widespread attention as an energy and feed crop.However,there are great differences in salt tolerance among different varieties of sweet sorghum,and the sugar content of sweet sorghum stalk is easy to ferment and not easy to store.Therefore,selecting the sweet sorghum varieties with strong salt tolerance and prolonging the processing period of sweet sorghum by adjusting the growth period is of great significance for the planting and popularization of sweet sorghum in saline-alkali soil.In this thesis,with the combination of laboratory experiment and field experiment,the salt tolerance of 15 sweet sorghum varieties at germination stage and seedling stage were comprehensively identified by laboratory experiment and greenhouse experiment,and salt tolerant sweet sorghum varieties at germination stage and seedling stage were selected respectively;The field planting experiment was divided into variety experiment and growth period regulation experiment.The varieties with different growth periods,high sugar brix,high stalk yield and high content of main forage components are selected.By setting different sowing dates,plastic film mulching and spraying 6-benzylaminopurine,the growth period of sweet sorghum was regulated by combining cultivation measures with chemical regulation.The effects of different sowing dates,film mulching and spraying 6-BA on the indexes of sweet sorghum were measured.The main results are as follows:1.The relative values of seed germination and seedling growth were used as the evaluation index of salt tolerance,the root length and germination indexes under the treatment of 50 m M Na Cl and 100 m M Na Cl,and the fresh weight and length of buds under the treatment of 150 m M Na Cl have a large load in the germination factors,which can be used as the main identification indexes for salt tolerance screening of sweet sorghum during germination.The dry and fresh weight of seedlings under 150 m M Na Cl treatment and the plant height under 50 m M Na Cl treatment can be used as the main identification indexes for salt tolerance screening at seedling stage.Fifteen sweet sorghum varieties were divided into 4 categories according to their salt tolerance during germination.The first type is highly salt-tolerant,including 8 varieties including JT2-3;The second type is salt-tolerant type,including JTZ2 and JTZ5;The third type is medium salt-tolerant type,including 4 varieties including JT2-2;The fourth type is salt sensitive type,including JT1-6.Fifteen sweet sorghum varieties were divided into 4 categories according to their salt tolerance at seedling stage.The first type is highly salt-tolerant,including 6 varieties including JTZ7;The second type is salt-tolerant type,including 4 varieties including JTZ5;The third type is medium salt tolerance type,including JT1-5,JT 3-1 and JTZ2;The fourth type is salt sensitive type,including JTZ9 and JTZ6.JTZ7.Six varieties such as Jitianza 7 were salt-tolerant or highly salt-tolerant at germination and seedling stage.2.The photosynthetic capacity,photochemical quenching and actual PSII photochemical efficiency of sweet sorghum seedlings of different varieties decreased with the increase of salt concentration.Na Cl concentration of 50 m M promoted chlorophyll content in some cultivars.Under 150 m M Na Cl treatment,net photosynthetic rate and stomatal conductance decreased significantly,but intercellular CO₂ concentration increased,indicating that 150 m M Na Cl treatment destroyed the mesophyll cell activity of sweet sorghum seedlings,and non-stomatal limitation was the main reason for the decrease of photosynthesis of sweet sorghum seedlings under high salt stress.With the increase of salt concentration,photosystemⅡof most sweet sorghum varieties was not significantly damaged.3.The growth period of seven varieties such as JT2-5 is within 90-110 days,the growth period of four varieties such as JT1-5 is within 130-140 days,the growth period of four varieties such as JT3-1 is more than 140 days,there are 11 varieties with Brix above 17%,and the sugar Brix of JT1-5 is about 20%.JTZ8 was selected as the material for different sowing dates.In the control group of each sowing date,the plant height,stalk diameter,total stalk weight per mu and sugar Brix of Sweet Sorghum in the sowing dates of May 28 and June 12 grew better.Sowing too early resulted in low seedling emergence rate and low Brix of sweet sorghum.When the sowing time was too late,insufficient grain filling,plant height,stalk diameter,sugar Brix and other indicators decreased significantly.Film mulching treatment can improve soil temperature,water content,reduce soil salt content,enhance the photosynthetic capacity of sweet sorghum,increase plant height,stalk diameter,sugar Brix and other indicators,and shorten the overall growth period by 8-10 days.In the late growth stage of late sowing sweet sorghum,spraying 6-BA can significantly delay the senescence of sweet sorghum leaves,increase the green holding time,delay the degradation of chlorophyll and enhance the photosynthetic capacity.4.The contents of crude protein and crude fat were higher in sweet sorghum stalks during sowing on June 26 and July 10.The detergent fiber content of sweet sorghum sown on July 10 was the highest,which was not conducive to digestion.There was no significant difference in the content of detergent fiber in the stalk of sweet sorghum between the sowing date of June 26 and the normal sowing date.Therefore,higher forage quality can be obtained by properly delaying the sowing date.The early sowing film mulching treatment decreased the crude protein content in sweet sorghum stalk,but the fiber content was low and the digestibility was high.Spraying 6-BA treatment on June 26 increased the content of crude protein and crude ash of sweet sorghum stalk,and increased the nutritional value compared with the control,but the fiber content was high and the digestibility was low.JT 2-5,JT2-6 and other varieties have higher feeding value.