Identification and comprehensive evaluation of cold resistance of Gossypium hirsutum L. resource materials during germination period

Objective To utilize the germplasm resources of Gossypium hirsutum L., in the hope of selecting excellent resource materials with strong cold resistance, thus providing parent and resource materials for the genetic improvement of cold tolerance traits and the breeding of new varieties.

Methods  271 Gossypium hirsutum L. germplasm resources were taken as test materials, two environmental conditions of control (28 ℃) and low temperature stress treatment (4 ℃) were set to test the average root length, germination rate, germination potential, germination index, average germination speed, average germination days, cold tolerance coefficient of 12 traits, and correlation analysis, principal component analysis and cluster analysis were conducted to carry out comprehensive evaluation of the germination of different upland cotton germplasm resources cold tolerance.

Results Principal component analysis converted the six cold tolerance indexes into three mutually independent comprehensive indicators, reflecting 92.99% of the information content of the six indicators. Using comprehensive cold resistance value (D), 271 germplasm resources of terrestrial cotton were divided into 4 categories; Class Ⅰ belonged to strong cold resistance with 17 materials; category Ⅱ belonged to cold resistant type, in which there were 31 materials; the third category was of not cold resistant type with 201 materials; class Ⅳ was cold sensitive category with 22 materials; they covered 6.27%, 11.44%, 74.17% and 8.12% of the test materials, respectively. Using multiple regression analysis, the prediction model of cold tolerance of upland cotton was established as Y=0.14+0.129X₃ + 0.109X₄ + 0.098X₂, and three cold tolerance indexes were selected, which were the cold tolerance coefficient of germination rate, germination potential and germination index.

Conclusion 17 strong cold tolerance materials are selected by 4 ℃ low temperature treatment, and the cold tolerance coefficient of germination rate, germination potential and germination index can be used as the cold resistance index of germination period of Gossypium hirsutum L.