Evaluation of Cold Resistance of Wild Germplasm Resources of Hevea brasiliensis and Correlation Analysis Between Cold Resistance and Growth

In order to understand the cold resistance of rapid growing germplasm resources of Hevea brasiliensis and obtain excellent materials for breeding, annual dormancy branches of 12 wild germplasm resources of H. brasiliensis were used as experimental materials. The 5 indexes including the relative electronic conductivity, malondialdehyde, free proline, soluble protein and soluble sugar content were measured after different artificial simulated low temperature stress treatments( 4 ℃ contrast, 0 ℃, −2 ℃, −4 ℃). The cold resistance of each clone was comprehensively evaluated, and the correlation between growth and cold resistance was also analyzed. The results indicated that with decreasing temperature, the relative electronic conductivity of branches of each clone showed a different degree of upward trend, the content of malondialdehyde and free proline showed an " ascending-descending” trend, the soluble protein content of most clones also showed the same as the free proline, but few clones showed a trend of " descending-ascending-descending”. The variation trend of soluble sugar content in each clone was different, but the soluble protein content of the same clone did not fluctuate greatly at different low temperature treatments. The comprehensive evaluation of the cold resistance of H. brasiliensis germplasm resources by the membership function method could be concluded as follows: 3>5>2>8>1>11>7>9>6>4>10>12. Among them, No.3, 5 and 2, which ranked top 3 in cold resistance, corresponding growth of diameter circumference all were large. Meanwhile, the No.10 and 12 with the worst cold resistance were smaller. Most fast-growing of H. brasiliensis germplasm resources showed stronger cold resistance, and the amount of diameter circumference growth can be used as an indirect indicator in cold resistance identification of H. brasiliensis germplasm.