| Pennisetum americanum × P.purpureum is a triploid perennial forage made from the cross of diploid pearl millet and tetraploid elephant grass.It has the advantages of high yield and tall strain,but it has the problems of poor digestibility and poor cold resistance.Plant polyploidy is expected to result in tall plants,more tillers and good stress resistance.In this experiment,hybrid pennisetum was treated with different concentrations at different times.Morphological measurement and cytological identification were used to analyze the ploidy of hybrid pennisetum.In order to further clarify the excellent characteristics of hybrid pennisetum mutant strains,and to analyze the yield and quality of double triploid and hexaploid,dry heat resistance and cold resistance of the two strains with optimal high yield and high quality were compared.The results were as follows:Induction of hexaploid lines:1.polyploidy treatment with 0.0%,0.1%,0.2%,0.3% colchicine concentrations at 24 h,36h and 48 h.The results showed that the induction rate of 18 lines was relatively higher at the treatment concentration with low survival rate,among which the best induction mode of colchicine treatment was 0.3 h and 48 h,and the induction rate of 0.1% concentration was the lowest.2.Identification of hexaploid lines: Five lines with higher growth,larger and stronger,more long and wider leaves and more tillers were selected in pot experiment than the control lines.It was found that the length and width of stomata in these five strains increased significantly.Stomatal size is inversely proportional to stomatal density,and stomatal density decreases.Chromosome technology showed that the five lines had 42 chromosomes,which were double successful hexaploid plants,and were named AN2021-1,AN2021-2,AN2021-8,AN2021-9 and AN2021-10,respectively.3.Comparison of morphology and yield: Morphological and yield comparisons were conducted between the five screened pot plants and the control.The results showed that hexaploid plants were significantly superior to triploid plants in leaf length,leaf width,stem diameter and tillering number(p<0.05).AN2021-10 had the longest leaf length(72.63cm),45.99% longer than triploid plants,and the widest leaf width.It was 2.09 times that of triploid,and the stem diameter was the largest,1.33 times that of triploid.AN2021-1 had the highest plant height(1.59 times of triploid)and the highest tiller number(26 times of triploid).AN2021-1 had the highest stem-leaf ratio(5.1:1),and AN2021-10 had the lowest ratio(1:2.8).Hay yield of AN2021-1 and AN2021-10 was the highest,which was 2.58 and 2.32 times of that of triploid,and the difference was significant(p<0.05).4.Comparison of quality: The crude protein,crude fat,ash,neutral detergent fiber and acid detergent fiber of the six strains were determined.The results showed that the contents of crude protein,crude fat and ash of the hexaploid strains were significantly higher than those of the control(p<0.05),and the contents of AN2021-10 were 2.23 times,2.12 times and 2.29 times of the triploid strains,respectively.There was a significant difference(p<0.005),followed by AN2021-1.The acid detergent fiber,neutral detergent fiber and lignin of hexaploid were significantly lower than that of triploid,and the lowest of AN2021-10 were 36.94% and 39.65% lower than that of triploid hybrid pennisetum,respectively(p<0.005),followed by AN2021-1.The relative feeding value of AN2021-10 was the highest(113.64),followed by AN2021-1(102.64),which was 1.64 times and 1.48 times of triploid,respectively.In summary,among the six strains,AN2021-1 has the highest yield,followed by AN2021-10,and AN2021-10 has the best quality,followed by AN2021-10.Both the yield and quality of these two strains are the best,so the two strains are selected for further study on stress resistance.5.The results of drought stress,high temperature stress and combined drought and high temperature stress showed that:With the increase of stress,the relative water content of AN2021-1 and AN2021-10 was significantly higher than three times,and the conductivity and MDA were continuously increased,but the hexaploid was significantly lower than the triploid,the enzyme activities of SOD,POD and CAT were first increased and then decreased,and the enzyme activities of the two hexaploid strains were significantly higher than the control.(p<0.05).The enzyme activity of single stress was higher than that of dry heat stress.Comprehensive analysis showed that AN2021-1>AN2021-10> triploid strain.6.Low temperature stress treatment: 25℃,4℃ and-10℃,4 h,24 h after the determination of physiological indicators.The results showed that the relative water content of AN2021-1 and AN2021-10 changed slowly,the electrical conductivity increased less,the enzyme activities of SOD,POD and CAT were higher,and the content of MDA was lower.It can be proved that AN2021-1 has the best cold resistance,followed by AN2021-10,and triploid strain has the worst cold resistance.In this thesis,the hexaploid strain of hybrid pennisetum was obtained by doubling the colchicine treatment,which improved its yield,quality and resistance to dry heat and cold.Existing studies believed that polyploidy induced by colchicine could not improve the yield.Some studies suggested that polyploid induction by colchicine could not improve the yield.In this thesis,hexaploid lines of hybrid pennisetum were obtained by treating double hybrid pennisetum with colchicine.It was found that the obtained hexaploid lines could increase the yield,significantly improve the quality and better stress resistance,which provided a new vision and method for breeding hybrid pennisetum and provided a basis for further application. |
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