新疆厚皮甜瓜种子萌发期的抗旱生理特性研究

Drought-resistance physiological characteristics during the seed germination period of thick-skinned melon in Xinjiang

【目的】比较新疆厚皮甜瓜(Cucumis melo L.)不同品种在种子萌发期的抗旱性差异,探究甜瓜种子在萌发期的抗旱生理机制,为优化甜瓜选育和栽培技术提供技术支持。【方法】以新疆厚皮甜瓜品种黄梦脆、黄皮9818、西州蜜17号、纳斯密和风味5号为供试材料,采用不同浓度聚乙二醇6000(PEG-6000)[0%(对照)、5%、10%、15%、20%、25%]模拟干旱胁迫,对5个甜瓜品种进行种子萌发期抗旱性试验,比较不同抗旱性的甜瓜种子在干旱胁迫下丙二醛(MDA)和脯氨酸(Pro)含量、超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性及内源激素含量的差异;设不同外源激素处理并测定种子萌发率。【结果】随着PEG-6000浓度的升高,各品种甜瓜种子发芽势、发芽率、相对发芽势、相对发芽率、胚轴长、胚根长和芽苗鲜重等萌发指标降低;隶属函数分析结果表明,甜瓜种子萌发期的抗旱能力排序为纳斯密>黄梦脆>黄皮9818>风味5号>西州蜜17号;干旱胁迫促进抗旱性最强的纳斯密和抗旱性最弱的西州蜜17号种子的MDA和Pro含量显著(P<0.05,下同)或极显著(P<0.01,下同)积累,并使SOD、POD和CAT活性显著或极显著增强,纳斯密中MDA含量增幅更低,而Pro含量及SOD、CAT和POD活性的增幅更高;干旱胁迫下,纳斯密和西州蜜17号种子的脱落酸(ABA)含量显著或极显著升高,茉莉酸(JA)含量显著降低;西州蜜17号的生长素(IAA)含量极显著下降,纳斯密的水杨酸(SA)含量极显著下降。纳斯密的IAA/ABA比西州蜜17号高20%,JA和SA含量分别比西州蜜17号高55%和68%;外源激素处理结果表明,干旱胁迫下,外源ABA处理降低甜瓜种子在不同时间的萌发率,低浓度SA(0.25 mmol/L)处理在12和24 h时分别使种子萌发率提高23%和27%,与低浓度茉莉酸甲酯(MeJA,0.025μmol/L)联合处理进一步提高种子萌发率,且适宜浓度MeJA缓解高浓度SA对种子萌发的抑制作用。【结论】纳斯密在种子萌发期抗旱性最强,西州蜜17号抗旱性最弱,干旱胁迫下纳斯密较西州蜜17号具有更高的抗氧化酶活性,其抗旱能力与IAA、ABA、SA和JA水平有关。

【Objective】Evaluated the drought tolerance differences in seed germination period among thick-skinned melon varietiesplanted in Xinjiang,and explored the drought-resistant mechanism of melon varieties during seed germination,to provide technique support for optimizing melon breeding and planting.【Method】Five thick-skinned melon varieties planted in Xinjiang were used as test materials(Huangmengcui,Huangpi 9818,Xizhou Honey 17,Nasimi and Flavor 5)and evaluated their drought resistance during seed germination by treating each variety with different concentrations of PEG-6000[0%(CK),5%,10%,15%,20%,25%].The contents of malondialdehyde(MDA)and proline(Pro),the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)and the contents of endogenous hormones of melon seeds with different drought resistance were compared under drought stress.【Result】With the increase of PEG-6000 concentration,the germination potential,germination rate,relative germination potential,relative germination rate,embryonic axis length,radicle length and fresh weight of each melon variety decreased.The membership function analysis showed that the order of drought resistance was Nasimi>Huangmengcui>Huangpi 9818>Flavor 5>Xizhou Honey 17.Drought stress significantly(P<0.05,the same below)or extremely significantly(P<0.01,the same below)promoted the accumulation of MDA and Pro contents,and enhanced the activities of SOD,POD and CAT in the most drought-resistant melon Nasimi seed and the most drought-sensitive melon Xizhou Honey 17 seed.Nasimi had a lower increase in MDA but a higher increase in Pro content,SOD and POD activities.In addition,under drought stress,abscisic acid(ABA)content significantly increased in Nasimi and Xizhou Honey 17 seeds while jasmonic acid(JA)content significantly decreased.Auxin(IAA)content extremely significant decreased in Xizhou Honey 17 seeds,salicylic acid(SA)content extremely significant decreased in Nasimi seeds.Compared to Xizhou Honey 17,Nasimi variety exhibited a 20%higher rate of IAA/ABA and 55%and 68%higher contents of JA and SA respectively.The results of exogenous hormone treatment showed that,under drought stress,exogenous ABA treatment reduced the germination rate of melon seed at different time points.Low concentration SA(0.25 mmol/L)increased seed germination rates by 23%and 27%at 12 and 24 h respectively,while co-treatment with low concentration MeJA(0.025μmol/L)further increased seed germination rates.Moreover,appropriate concentration of MeJA alleviated the inhibitory effect of high concentration of SA on seed germination.【Conclusion】Nasimi has the strongest drought resistance during the seed germination period,while Xizhou Honey 17 has the weakest drought resistance.Under drought stress,Nasimi has higher antioxidant enzyme activity than Xizhou Honey 17,and its drought resistance is related to IAA,ABA,SA and JA levels.