苹果水心病无损检测与防治研究进展

苹果水心病是一种果实生理病害,在所有苹果的栽培生长区域均有发生。品种、果实成熟度、温度、栽培条件、果实大小、矿质营养、贮藏条件等因素影响苹果水心病的发生。目前其无损检测的主要方法有光密度法、X-射线法、质量密度法和磁共振影像法。补充钙素营养、增施有机肥、适时采收、合理修剪等是防治苹果水心病的关键措施。     

Cellular compartmentation and membrane permeability to sugars in relation to early or high temperature-induced watercore in apples

Early watercore was observed in apples (Malus domestica Borkh.) from the outer canopy of ‘Orin’, an early watercore susceptible cultivar, while there was no watercore in ‘Orin’ fruit from the inner canopy and resistant ‘Fuji’. Sorbitol content was higher not only in the free space but also in the vacuole and cytoplasm in watercored ‘Orin’ than in other non-watercored fruit. Comparing watercored apples to non-watercored fruit of ‘Orin’, higher fructose and glucose in the vacuole and no significant difference in the distribution rate of sorbitol to each compartment were observed. Watercored ‘Orin’ apples showed significantly higher permeability of tonoplast to fructose, glucose, and sorbitol than those in other non-watercored apples. The permeability of plasma membrane to each sugar was much higher than that of tonoplast but no marked difference was observed among the treatments. The results suggest that metabolism of sorbitol could be active even in watercored ‘Orin’ apples and the accumulated sorbitol in the intercellular spaces might be primarily due to an active unloading from the phloem and not be brought by increased leakage from the cells.     

苹果水心病在贮藏期变化的无损检测

该研究通过自制差分仪监测了贮藏中苹果透光强度的变化,建立了贮藏中苹果透光强度和质量随时间变化的回归方程.在贮藏过程中有水心病的苹果透光强度下降较无水心病苹果快,贮藏后期发病不严重的病果症状消失,同时发现质量较大的苹果中水心病发病比率高.     

苹果贮藏中水心消失速率的研究

利用可见-近红外光谱和X射线成像技术研究了水心苹果贮藏中水心消失速率.采用PLSDA和平均灰度值法对水心判别,研究120水心苹果贮藏中的光谱及灰度图像的变化规律.结果表明:PLSDA和平均灰度值法对水心判别,判别正确率分别为96.7%和97.43%;水心消失速率在贮藏前期高于贮藏后期;水心苹果平均光谱峰面积与贮藏时间拟合方程为:y=-0.0002x3 0.0733x2-7.405x 342.06;该实验条件下,近红外平均能量谱峰面积和X射线图像平均灰度值的贮藏临界值分别为110.21,143.91.实验结果表明可见-近红外能量光谱和X射线成像技术可以快速、无损、准确鉴别苹果水心及检测贮藏变化规律.     

Relationship between early watercore development and leaf photosynthesis or partitioning of photosynthates in apple

Seasonal changes in leaf photosynthetic rate and partitioning of ¹³C taken up by leaves were compared in relation to the development of early watercore using susceptible ‘Orin’ and resistant ‘Fuji’ apples (Malus domestica Borkh.). There was no difference between the cultivars in leaf photosynthetic rate from mid-July to mid-October. The extent of watercore in ‘Orin’ increased from mid-July and peaked in late-August, followed by a decrease through mid-October, while no watercore was detected during the experimental period in ‘Fuji’. Fruit fresh weight and soluble solids content (SSC) were higher in ‘Orin’ than ‘Fuji’ during the earlier stages. Leaf dry weight of ‘Orin’ was higher than that of ‘Fuji’ throughout the experimental period. Accumulation of dry matter in the fruit increased in both cultivars and ‘Orin’ kept significantly higher level than ‘Fuji’ from mid-July to mid-October. The amount of ¹³C distributed to ‘Orin’ fruit at 5 days after labeling was significantly higher than ‘Fuji’ in mid-July just before watercore started to occur. ¹³C taken up by ‘Orin’ fruit with prevalent watercore was also higher than ‘Fuji’ in late-August but the difference was not significant. In mid-October when early watercore was gradually reducing, ¹³C recovered by ‘Orin’ fruit decreased and was significantly lower than ‘Fuji’. The difference of partitioning pattern of ¹³C between the cultivars was associated with the susceptibility to early watercore as well as the changes in fruit growth and SSC. The seasonal changes in the amount of ¹³C distributed to ‘Orin’ fruit were also related to the fluctuations in watercore severity. The results suggest that active phloem transport might be the cause of early watercore in our previous work, which might be induced by the increased partitioning of assimilates to the fruit during summer in susceptible ‘Orin’ compared to resistant ‘Fuji’ and not by the higher potential of leaf photosynthesis.     

碳水化合物、矿质元素及活性氧代谢与富士苹果水心发生的关系

以新疆阿克苏地区水心（冰糖心）富士苹果为试材,分析讨论了果实碳水化合物、矿质元素和活性氧代谢与水心发生的关系。结果表明：果实可溶性固形物（SSC）含量越高,水心指数越高,呈显著正相关（P < 0.05）;而单果质量、果实纵横径比及L、b*、h°值与水心果率和水心指数相关不显著;进一步分析发现,与正常果实和组织相比,水心果实和组织中,山梨醇和蔗糖含量均显著升高,尤其是山梨醇含量,分别是正常果实和组织的2.19倍和2.86倍,果糖和葡萄糖含量相对较低;此外,水心组织中K和B含量显著高于正常组织,而Ca、Zn及Fe含量则显著降低;同时,水心果实和组织中超氧阴离子和过氧化氢含量较正常果实和组织显著升高,分别高282.39%、68.17%和12.6%、107.62%;POD、SOD和CAT等抗氧化酶活性显著降低,MDA含量和相对电导率显著升高,膜质过氧化水平严重。     

基于电学特征的苹果水心病无损检测

为了探寻快速而准确的苹果水心病无损检测新方法,该文以‘秦冠’水心病疑似病果和好果作为试材,逐果采集11个电学指标在100 Hz~3.98 MHz间13个频率点的特征值,然后切开并统计真实发病情况。利用主成分分析结合不同分类模型进行好果与病果判别分析,结果选取方差累积贡献率大于90%的主成分15个,Fisher判别、多层感知器人工神经网络(multi-layer perceptron,MLP)对好果和病果的判断正确率均随着主成分数的增加而增大,并分别在主成分数量达到前13、10时趋于稳定水平93.3%、95.4%。径向基人工神经网络(radical basis function,RBF)结合15个主成分判别的正确率75.1%。水心病引起介电损耗系数D、复阻抗相角deg、串联等效电容Cs和并联等效电容Cp及相对介电常数(ε')、损耗因子(ε")共6个参数在低频区(100~10 000 Hz)的观测值高于好果,是电学法能够对水心病果和好果进行‘识别’的原因。同时发现,利用低频率下(100~25 100 Hz)损耗因子(ε")值结合MLP或RBF人工神经网络模型对水心病果和好果识别正确率均能达到100%,是一种简便而高效的苹果水心病无损检测方法,可为今后进一步研发苹果果实水心病在线无损检测仪器提供理论与技术依据。     

水心病菠萝果实生理指标和内源激素含量变化

为了解水心病菠萝果实生理指标和内源激素含量的变化特征,本研究以菠萝主栽品种‘巴厘’为材料,采用液质联用（LC-MS）、高效液相色谱（HPLC）等方法测定了不同发病程度的水心病菠萝果实中主要内源激素、单糖、可溶性固形物、可滴定酸和维生素C（Vc）、丙二醛（MDA）含量及超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性,并分析了水心病发病程度、内源激素和抗氧化酶活性间的相关性。结果表明,不同发病程度水心病菠萝可溶性固形物、Vc和糖含量、SOD和POD酶活性以及内源激素玉米素（ZT）、茉莉酸（JA）和脱落酸（ABA）含量均比对照显著下降,且随着发病程度的加深下降幅度增加;不同发病程度水心病菠萝CAT酶活性、MDA含量和SA含量较对照显著提高;可滴定酸含量、果糖和葡萄糖含量在轻度发病果中含量较对照明显增加,在中度发病果中含量显著降低,而1-氨基环丙烷羧酸（ACC）含量变化趋势与其刚好相反。相关分析表明,菠萝水心病病害级别与内源激素ZT、JA和ABA含量呈显著负相关,相关系数分别为-0.98、-0.98和-0.94;与SA含量呈显著正相关,相关系数为0.93。一方面水心病降低了菠萝果实糖酸比和Vc含量,导致果实品质下降;另一方面菠萝通过调节内源激素ZT、JA、ABA和SA含量,进而调控SOD、POD和CAT活性,增强对水心病的防御反应。     

苹果水心病的发病机理研究进展

苹果水心病是果实生理性内部失调现象,主要症状为果肉组织细胞间隙充满液体,呈透明状或水渍状,甜度增加,多发生在心室周围的维管束附近及梗洼处。以苹果果实中的山梨醇为关注点,通过分析果实中山梨醇的来源、运输途径、代谢路径等研究结果,总结苹果水心病产生及消失机理,讨论影响苹果水心病发生的因素,以期为苹果水心病的认知提供参考。     

基于BiSeNet的糖心苹果截面糖心特征提取方法

为解决因糖心苹果截面糖心特征分布不规则导致的种植过程中对糖心品质评估方法精度低、复杂等问题，以380个糖心苹果作为试验样本，基于BiSeNet模型对苹果糖心特征进行提取与占比计算，分别评估该方法在理论研究与实践研究两方面的多项性能指标，并与FCN、PPLiteSeg与DeepLabV3这3种网络模型进行对比。结果显示，BiSeNet无论是在训练时间还是训练准确度都优于其他3种网络模型，用时130 s，准确率98.36%，交并比85.1%。在实际占比计算中，平均占比计算误差为4.04%，低于其他3种模型，且无较大偏差值。结果表明，基于BiSeNet的糖心苹果截面糖心特征提取方法在提供具体糖心占比的同时，可为糖心苹果的糖心特征等无损检测提供更精确的评估方法和比对目标。