Changes in endogenous abscisic acid,soluble sugars and proline levels during tuber dormancy inSolanum tuberosum L.

Abscisic acid (ABA), sucrose, reducing sugars and proline contents were monitored over an eleven-month period in tubers of three potato cultivars that varied in tuber dormancy. ABA and proline levels increased after top pulling the haulms and were not affected by harvest date. Proline did not change in either a storage temperature or cultivar-specific manner. The highest concentrations of ABA were found in tubers stored at 2°C while the lowest concentrations occurred in tubers stored at 20°C. At 10°C, the end of tuber dormancy in the cultivars Kennebec and Nooksack (but not Sebago) coincided with the decline in ABA content. There was no evidence of a threshold concentration of ABA below which sprouting would occur. Tuber samples of 10 different cultivars were removed from 10°C and placed in 20°C storage (in darkness). Initial ABA concentrations (i.e., at the time of removal from 10°C storage) were positively correlated with duration of dormancy and negatively correlated with subsequent rates of sprout elongation at 20°C. Sucrose content was negatively correlated with duration of dormancy. Reducing sugars responded primarily to storage temperature and did not appear to be related to dormancy or sprouting.     

马铃薯块茎生长过程中内源赤霉素和脱落酸含量的变化

以紫花白和晋薯２号两个品种为材料，研究了马铃薯同一个体植株中，处于不同生长阶段上的块茎，其内源ＧＡ３和ＡＢＡ含量的变化规律．结果表明：开始形成的块茎（块茎直径１ｃｍ左右）中ＡＢＡ和ＧＡ３含量最高，但ＧＡ３／ＡＢＡ的比值则较低；之后随着块茎的膨大，ＡＢＡ和ＧＡ３的含量均逐渐降低，但ＡＢＡ的降低速度大于ＧＡ３，从而使ＧＡ３／ＡＢＡ的比值逐渐增高，到块茎成熟时，ＡＢＡ和ＧＡ３都有所增加。而由块茎迅速膨大到成熟的过程中，ＧＡ３／ＡＢＡ的比值则又逐渐降低。两个品种在块茎生长过程中，内源ＧＡ３和ＡＢＡ的含量具有相似的变化规律．成熟期块茎平均直径较大的紫花白，当块茎直径小于５ｃｍ左右时，其中ＧＡ３的含量大于相应大小的晋薯２号，后期两个品种之间则基本无差异；而ＡＢＡ的含量在两个品种之间则始终无多大差异；因此使ＧＡ３／ＡＢＡ的比值在块茎直径小于５ｃｍ以前紫花白大于晋薯２号。因此我们认为ＧＡ３和ＡＢＡ在块茎开始形成与膨大及成熟的整个生长过程中，对块茎的形成和生长发育具有负反馈调节与协同作用．     

Effects of Foliar and Tuber Sprout Suppressants on Storage of Ware Potatoes under Tropical Conditions

Potato (Solanum tuberosum L.) is an important source of dietary carbohydrate and cash income generation for farmers in the tropical highlands of Kenya. The feasibility for cold storage at the farm level is limited due to the high costs of maintaining such a facility and there is limited data on the long-term post-harvest storage and quality of tubers of tropical-adapted cultivars. Application of sprout suppressants to control premature sprouting of ware potato is an attractive proposition. The objectives of this study were to evaluate the efficacy of pre-harvest foliar applications of paclobutrazol (PBZ) and ethephon for sprout suppression on ware potato tubers in storage. Post-harvest spray applications of Isopropyl N-(3-chlorophenyl carbamate) chloropropham (CIPC) and 1,4-dimethylnaphthalene (DMN) on tubers as fog was also evaluated. Potato cultivars had varying levels of tuber dormancy. The tubers were stored at ambient temperature (23 C) and evaluated weekly for 24 weeks for percent of tubers sprouting, length of longest sprouts, tuber weight loss and assessed for dormancy for 24 weeks. Paclobutrazol prolonged tuber dormancy by 21–31 days and reduced tuber weight loss. Ethephon treatment had no effect on dormancy and tuber weight loss. Potato tubers treated with CIPC had greater sprout control than the other treatments in storage. Tuber response to DMN treatment varied among the three potato cultivars evaluated. The findings from this study imply that PBZ is effective in prolonging potato tuber dormancy for short-term basis at 23 C, while CIPC applied on tubers was effective for long term storage. Optimization of post-harvest potato storage can improve food security in the highland tropics.     

茶树新梢生育的内源激素水平及其调控机理（第二报）茶树休眠与内源激素的关

本文研究了不同茶树品种新梢夏季生长休止、冬季休眠与内源激素水平的关系。结果表明,内源激素水平差异及激素间的比值变化与新梢生长和休止密切相关,高含量IAA及高IAA／zeatin与IAA／GA3比值,导致夏季生长休止;高含量ABA及高BAB／GA3与ABA／zeatin比值,是诱发冬季休眠的主要原因。     

The effect of ethylene and of inhibitors of protein and nucleic acid syntheses on dormancy break and subsequent sprout growth

Summary Cycloheximide inhibited dormancy break and subsequent sprout growth of potato buds in the presence or absence of ethylene. Dormancy break was relatively insensitive to treatment with actinomycin D, in marked contrast to the inhibition observed with cycloheximide; however, sprout elongation was inhibited by actinomycin D treatment. This suggests that dormancy release may depend on protein synthesis but not on nucleic acid synthesis. Total protein analysis revealed that two high molecular weight polypeptide bands appeared during dormancy break in the presence or absence of ethylene. The response was consistent in the two cultivars used in this study. Cycloheximide treatment blocked the synthesis of any new polypeptides in response to ethylene in the tuber tissue. This indicates that dormancy release of potato buds may be associated with the regulation of protein synthesis.     

Auswirkungen des wiederholten mechanischen Entkeimens auf den Substanzverlust und die Qualität von Kartoffelknollen

The influence of a continued mechanical desprouting of potato tubers on weight loss and tuber quality was investigated in comparison with tuber irradiation (Cs 137), IPC/CIPC powder application, and the untreated control. Mechanical desprouting of tubers resulted in minimum weight loss, but it caused increased sugar content, rotting and internal sprouting. To give consumers an alternative for the conventional sprout prevention methods, tubers of varieties with a natural deep dormancy, and potato storage in low temperature should be preferred.     

Auxin-induced sprout growth inhibition: Role of endogenous ethylene

The role of endogenous ethylene in auxin-mediated tuber sprout growth inhibition was determined in potato (Solanum tuberosum L. cv. Russet Burbank) minitubers. Treatment of tubers with biologically active auxins resulted in a transient, dose-dependent increase in ethylene production and inhibition of sprout growth. Biologically inactive auxin analogs elicited neither response. Continuous exposure to > 0.001 μL L^-1 exogenous ethylene inhibited sprout growth in a dose-dependent manner with complete inhibition occurring at ethylene concentrations ≥1 μL L^-1. In further studies with the active auxin α-naphthalene acetic acid (NAA), the role of ethylene in auxin-induced sprout growth inhibition was determined using ethylene biosynthesis and action inhibitors. The ethylene biosynthesis inhibitor aminoethoxyvinylglycine reduced NAA-induced ethylene biosynthesis by over 80% but had no effect on sprout growth inhibition. The non-competitive ethylene action inhibitor silver thiosulfate had no effect on NAA-induced sprout growth inhibition. Similarly, both the competitive ethylene action inhibitor 2,5-norbornadiene and the irreversible action inhibitor 1-methylcyclopropene were ineffective in reducing NAA-mediated sprout growth inhibition. Collectively, these results do not support the proposal that, in the case of potato tuber sprouts, auxininduced growth inhibition is mediated by endogenous ethylene action.     

Hormonal Mechanisms of Dormancy Induction in Developing Seeds

Summary

Primary dormancy develops in seeds during their maturation on the mother plant. In recent years, the use of hormone mutants and the manipulation of endogenous hormone levels by their biosynthetic inhibitors have led to a new approach of the hormonal regulation of the onset of dormancy. There is good evidence to show that ABA synthesis at axis level is an absolute requirement for the induction and maintenance of dormancy. This continued de novo synthesized ABA could positively control the expression of specific ABA-responsive genes. Among the set of late embryo abundant proteins, some appear to be good candidates as “dormancy proteins.” This review aims to correlate the preliminary results obtained by molecular biology with the recent advances in understanding the hormonal control of dormancy induction in developing seeds.     

Sprouting of seed tubers during cold storage and its influence on tuber formation, flowering and the duration of the life cycle in a diploid population of potato

Summary The influence of a short tuber dormancy and the subsequent sprout growth of the seed tubers during storage at 4 °C on the processes related to plant development and tuber formation was investigated in a diploid population with 238 genotypes, its crossing parents and seven tetraploid varieties. Sprout growth during storage at 4 °C was positively correlated to the duration of the dormancy period at 18–22 °C, the low temperature prolonging the dormancy period. Results show that the duration of the dormancy period and the sprouting of seed tubers during storage at low temperature did not have a determinant influence on plant development, tuber formation or the duration of the plant cycle in this large and highly diverse population of potato.     

烯效唑和三唑酮调节水稻秧苗生长的增效作用及机理

用烯效唑、三唑酮和烯效唑+ 三唑酮浸种或苗期喷施的结果表明, 烯效唑能有效地调节水稻秧苗的生长, 使苗高降低、分蘖增加。三唑酮对水稻秧苗的生长也有一定的调节作用。烯效唑和三唑酮协同调节秧苗生长, 控制苗高和促进分蘖有明显的增效作用。与此同时, 烯效唑和烯效唑+ 三唑酮协同作用使内源激素水平发生明显变化, GA_S 和IAA 含量明显降低,iPA s和ABA 含量显著增加。根据烯效唑和烯效唑+ 三唑酮协同作用调节水稻秧苗生长与内源激素水平变化的关系, 明确使内源GA_S、IAA 含量降低和iPA s、ABA 含量增加是烯效唑和烯效唑+ 三唑酮协同调节水稻秧苗生长的主要机理。     

Assessment of Dormancy and Sprouting Behavior of CIP Elite and Advanced Clones Under Different Storage Conditions in Uzbekistan

In potato breeding and selection, storability should be regarded as equally important as yield, disease resistance, and quality. A study documenting the dormancy period, sprouting behavior, and weight loss of 17 International Potato Center potato elite and advanced clones was carried out in Tashkent, Uzbekistan, under cellar and cold store conditions, during 2008 and 2009. Ninety tubers of each of 17 clones were allocated to experimental units of 30 tubers each placed in trays and randomized in three replications following a random complete block design. Therefore, there were three replications of 30 seed tubers each per entry. The dormancy period ranged from 77 to 115 days and from 100 to 186 days under cellar and cold storage, respectively. There was a relatively high positive correlation (0.69) for dormancy period between storage systems, indicating that clones demonstrating longer and shorter dormancy periods under one system will also behave similarly under the other system. A negative correlation (−0.53 and −0.88) was found between dormancy period and length of the longest sprout in cellar and cold store, respectively, meaning that clones with shorter dormancy often showed a greater length of their longest sprout. The weight loss percentage per tuber was similar in both storage systems, from 5.0% to 8.0% in the cellar and from 5.0% to 9.8% in the cold store, although for different storage periods (an average of 110 and 166 days under cellar and cold storage conditions, respectively). The study indicated that under cellar conditions, clones with a longer dormancy period and slower rate of sprout growth have less weight loss during storage and therefore better keeping quality.     

赤霉素(GA_3)与茉莉酸甲酯(MeJA)对雾培马铃薯内源激素与生长发育的影响

试验以品种为主区,激素处理为副区进行裂区设计,研究了赤霉素(GA3)与茉莉酸甲酯(MeJA)对雾培马铃薯内源激素与生长发育的影响。结果表明:外源GA3处理增加了3个马铃薯品种叶片内源IAA和JA的含量,降低了中晚熟品种高原7号的内源ABA含量。外源MeJA对马铃薯块茎均有一定诱导作用,但结合GA3处理其诱导结薯的能力会减弱。     

马铃薯生育期间内源激素的变化

以晋薯２号、紫花白为材料，分析了马铃薯整个生育期间，叶片和块茎中内源激素的含量变化．结果：整个生育期间叶片和块茎中的ＧＡ３、ＩＡＡ含量变化是单峰曲线，叶片中的峰值在块茎形成期，块茎中的峰值在块茎迅速膨大期；ＡＢＡ含量变化则随着生育的进程而增加；叶片中ＺＲ的变化比较平缓，ＩＰＡ是单峰变化，峰值也在块茎形成期，块茎中ＺＲ，ＩＰＡ和Ｚ的变化在２品种间的变化不一致．无论是叶片还是块茎，紫花白的ＧＡ３、ＩＡＡ、ＩＰＡ的含量均比晋薯２号的高，而ＡＢＡ含量则比晋薯２号的低．     

光周期对马铃薯块茎形成的影响及对激素的调节

马铃薯出苗后接受１个月的每日８小时短日照处理并与当时自然光照长度进行比较，研究光照长度对块茎形成及内源激素②的影响，探讨块茎形成与激素水平的关系。结果表明：短日照处理使块茎形成显著提早，但使结薯数减少，植株茎叶生长受抑，块茎淀粉含量降低；短日照处理使叶片中ＡＢＡ含量提早增高，ＧＡ３含量提早减少，ＧＡ３与ＡＢＡ的比值提早显著降低．     

Abscisic and gibberellic acid in growing potato tubers

Summary The content and distribution of absicisic acid (ABA) and gibberellic acid (GA) in potato tubers differing in growth rates and sizes has been determined. No significant correlation has been found between the growth rate and the concentration of ABA and GA in tuber tissue, but the phytohormone content per tuber increased proportionally with tuber size. GA was distributed fairly uniformly throughout the tissue whereas ABA tended to be concentrated in the tuber apex.     

QTL Analysis of Tuber Dormancy and Sprouting in Potato

Tuber dormancy and sprouting are important traits in commercial potato varieties. Since wild Solanum species can contribute new alleles in breeding, we combined Solanum chacoense and S. berthaultii species in a mapping population to develop a linkage map with genome wide markers and identify quantitative trait loci (QTL) for tuber dormancy and sprouting. There was genetic variation for the evaluated traits and high correlation (0.80) between dormancy and apical dominance release. QTL for tuber dormancy and sprouting traits were mapped to the same or similar positions on chromosomes 2, 3, 5, and 7, explaining from 9.5% to 16.3% of the phenotypic variance. We identified candidate genes associated with all major phytohormone regulation in close linkage with the QTL. The QTL on chromosomes 2, 3 and 7 are good candidates for marker assisted breeding, since they were associated with dormancy and apical dominance release and should be useful to delay or accelerate tuber sprouting.     

Effect of second growth on the quality of tubers as seed in the cultivar Record

Summary Seed quality in a crop harvested in 1984 was compared in tubers which either, (a) were unsprouted prior to harvest (normal), (b) had formed secondary chain tubers prior to harvest (primary), (c) secondary chain tubers. Normal and primary tubers formed substantial sprout growth during storage, while there was little sprout growth from secondary tubers. Plants derived from these seed tuber types differed, in terms of emergence, number of emerged stems, and tuber number. It is concluded that the tuber types can be considered to vary in terms of physiological age; normal and primary tubers appear to be physiologically older than the secondary tubers. This variability in seed condition can lead to variability in the performance of the subsequent crop.     

Sprout development and processing quality changes in potato tubers stored under ethylene: 1. Effects of ethylene concentration

Ethylene effectively inhibits sprouting of potatoes (Solanum tuberosum L.) during storage, but it often darkens fry color. The objective of the work described here was to determine if altering the concentration of ethylene applied would reduce the darkening while retaining adequate sprout inhibition. Trials were conducted over three consecutive years (1991–1992, 1992–1993, and 1993–1994). Tubers of cv Russet Burbank (ca 150–300 g) were stored at 9 C for 25 wk in closed chambers in a refrigerated room under continuous exposure to 0.4, 4, 40, or 400 µL L^?1 ethylene gas delivered with the ventilation airstream (ca 0.5 air exchanges per h, for 6 h each day). Untreated control and chlorpropham-treated (CIPC) check tubers were stored under the same conditions but without ethylene supplementation. Sprout number, length, and biomass, fry color, loss of tuber mass, disease, and dry matter content were evaluated at 5-wk intervals. Dose-dependent effects (400>40>4>0.4 µL L^?1) of ethylene on sprout growth and fry color were observed. The 400, 40, and 4 µL L^?1 ethylene treatments inhibited sprout growth as effectively as CIPC, whereas in 0.4 µL L^?1 ethylene sprouting was midway between CIPC and the untreated control. Sprout mass and maximum sprout length in all ethylene treatments were significantly lower (P<0.05) than in the untreated control. Compared with the initial value (57.3 Agtron reflectance units [ARu]), after 5 wk of storage fry color was up to 5 ARu darker in the ethylene treatments, but recovered steadily at the subsequent evaluation dates. At 25 wk of storage the fry color of tubers from the 40 and 4 µL L^?1 ethylene treatments were, however, still darker than tubers stored with CIPC. Inhibition of sprout growth was slightly more effective in the 400 and 40 µL L^?1 ethylene treatments than in 4 µL L^?1, although there were no significant differences (P<0.01) in fry color between these treatments. In comparison with the other ethylene treatments, fry color in 0.4 µL L^?1 ethylene was lighter, but inhibition of sprout growth was significantly (P<0.05) poorer. There were no differences in tuber disease incidence or dry matter content between the treatments. At 25 wk, the untreated tubers had ca 50% greater loss of tuber mass than any other treatment, attributable to their heavy sprouting. Loss of tuber mass in the ethylene treatments was not significantly different (P<0.001) from that in the CIPC treatment.