White Baron: A non-browning somaclonal variant of Danshakuimo (Irish Cobbler)

White Baron is a somaclonal variant variety resulting from the protoplast propagation of Danshakuimo, the dominant variety in the Japanese tablestock market since the beginning of this century. White Baron is an improvement over the parent clone in that its tubers do not brown after peeling whereas the tubers of the original variety brown rapidly after peeling. This commercially attractive improvement makes this variety well suited for the expanding market in Japan for pre-peeled potatoes.     

Effect of time of inoculation with potato leafroll virus on development of net necrosis and stem-end browning in potato tubers

The Green Mountain cultivar was used in field tests to determine the effects of inoculating potato plants at various times with the potato leafroll virus (PLRV) on development of internal necrosis of tuber tissue. Viruliferous apterae of the green peach aphid,Myzus persicae (Sulz.), were placed on each stem in all hills to be inoculated in each 3.0 m single-row plot. Planting and inoculation dates were varied in all field experiments and, in one, several vine-killing dates were also included. All harvested tubers were stored for approximately four months at 10°C to enhance development of internal necrosis prior to examination. Similar but smaller greenhouse studies involving both apterous and alate green peach aphids were also conducted using Green Mountain, Irish Cobbler, and Russet Burbank cultivars. All results showed that as inoculation was delayed relative to plant development, more net necrosis (NN) occurred. Conversely, when plants were inoculated early, stem-end browning (SEB) rather than NN predominated. A high percentage of naturally occurring SEB tubers (cv. Russet Burbank) were found by ELISA to contain PLRV. Plants produced by these tubers only rarely developed leafroll symptoms. These findings suggest a previously unsuspected causal relationship between SEB and PLRV. Implications of this apparent relationship on the epidemiology of potato leafroll in Maine are discussed.     

Failure of metalaxyl to eradicate late blight on potatoes (cv. Green Mountain)

Eradication of potato late blight with metalaxyl was examined in field studies from 1980 to 1983. In 1980 disease outbreak and subsequent progression were late and moderate. In 1981 and 1983, they were early and moderate to severe, while in 1982 the disease became established later in the season but developed rapidly and resulted in moderate to severe damage to foliage. There were no significant differences in foliar disease severity among metalaxyl treatments. While treated plots generally showed significantly less foliar damage throughout the season than untreated plots, except in 1983, the reduction in foliar damage in September was only 30–50% in 1980, 10–20% in 1981, 20–30% in 1982, and less than 10% in 1983. Sporulation of the pathogen occurred readily on infected leaves of both treated and untreated plants. There were no significant differences in yield, but application of metalaxyl to foliage significantly reduced the incidence of late blight tuber rot.     

Effects of transitory water stress on potato tuber stem-end reducing sugar and fry color

Potatoes grown for processing in irrigated regions of the Pacific North-west sometimes develop undesirably high concentrations of reducing sugars in tuber stem ends due to hot weather and water stress during tuber development. Such tubers usually produce french fries with dark stem ends or sugar ends. In order to better quantify the relationship between water stress and stem-end sugar levels for Russet Burbank, single episodes of transitory water stress were established by delaying irrigations until soil water potentials ranging from -32 to -107 kPa were reached during early tuber bulking. To determine when the increase in reducing sugars occurred, tubers were sampled before transitory stress, at maximum stress, after stress was relieved with sprinkler irrigation, and post harvest. Reducing sugar concentrations did not increase in tuber stem ends until two weeks or longer after the plant water stress was relieved. Increased reducing sugar concentrations were positively associated with decreased soil water potential (drier soil). Tubers were sliced and fried at harvest and six weeks post-harvest. Decreasing soil water potential (drier soil) was associated with progressively darker fry colors at harvest and post harvest. Significant darkening in the average stem-end fry color light reflectance of tubers at harvest as observed at -80 kPa in 1988 and -69 kPa in 1989. The effect of imposed water stress on tuber stem-end reducing sugar concentrations was most pronounced post harvest.     

大豆蚜对溴氰菊酯和氯氰菊酯的敏感度研究

试验测定了敏感品系大豆蚜对2.5%溴氰菊酯乳油和4.5%高效氯氰菊酯乳油的敏感度.结果表明:大豆蚜对两种药剂具有较高的敏感度.接触稀释10 000倍的2.5%的溴氰菊酯乳油和4.5%的高效氯氰菊酯乳油24 h后,大豆蚜的死亡率分别达99.28%和100%.     

大豆子叶节及苗期NaCl筛选试验研究

以NaCl为筛选剂,对5个大豆品种的子叶节诱导、丛生芽生根及大豆苗期的生长情况进行研究.结果表明:不同基因型大豆对NaCl的敏感性不同,同一基因型的不同部位对NaCl的敏感性也存在差异.最终确定了NaCl对子叶节分化、丛生芽生根以及苗期生长适宜的筛选浓度.大豆子叶节分化NaCl临界筛选浓度:吉农27和吉农17为225 ...     

大豆子叶节对潮霉素敏感性研究

标记基因的利用是筛选和鉴定转基因植株的有效方法,使用潮霉素能抑制植物的生长.选用3个基因型大豆为材料,以褐化率、分化率为指标,研究了不同质量浓度潮霉素对大豆子叶节分化和丛生芽生根的影响.结果表明不同基因型大豆对潮霉素的敏感性不同,潮霉素对大豆子叶节适宜筛选浓度黑农35为6 mg·L-1、合丰35和合丰25为4 mg·L-1;丛生芽生根筛选浓度黑农35为2 mg·L-1、合丰35和合丰25为1 mg·L-1.     

甘肃武威市凉州玉米产区截形叶螨对3种杀螨剂的敏感性测定

截形叶螨(Tetranychus truncatus Ehara)是我国玉米生产上的一种重要的害螨.目前对截形叶螨的防治主要依赖化学农药.本研究通过室内浸液法测定截形叶螨成螨、若螨对3种不同作用机制的杀螨剂乙唑螨腈、联苯肼酯和螺螨酯的敏感性.结果表明,乙唑螨腈的毒力最强,对雌成螨和若螨24 h的LC50分别为0.033...     

九万山古茶树群体种试制绿茶的品质分析

以福鼎大白茶和桂绿1号两个品种为对照,对柳州九万山古茶树群体种进行绿茶产品试制,比较分析其感官品质和生化成分。研究结果表明:古茶树群体种所制绿茶产品表现出栗香高、滋味醇爽的感官品质特征,具有高水浸出物(46.78%)、高氨基酸(4.59%)、茶多酚含量适中(23.61%)的生化特点,茶氨酸含量占总氨基酸含量的37.72%,EGCG占儿茶素总量的比例(42.53%)显著低于两个对照品种。古茶树群体种所制绿茶产品综合品质优于福鼎大白茶和桂绿1号所制绿茶。     

水稻飞虱对十三种杀虫剂的抗性监测

1987～1991年选用有机磷、有机氮和拟除虫菊酯类十三种杀虫剂对白背飞虱和褐飞虱用国际统一标准毒力测定点滴法进行抗药性监测。结果表明:1)白背飞虱和褐飞虱对呋喃丹最为敏感,对马拉硫磷敏感度最低。LD_(50)值相差上百倍。因两种飞虱均属迁飞性害虫,年度间的测定结果稍有波动。2)白背飞虱抗药性发展比褐飞虱快,在测定方法和供试昆虫条件基本相同的情况下,将1990年所测几种药剂的LD_(50)与日本Nagata(1967)测定数据进行比较,浙江省白背飞虱种群对马拉硫磷的抗性差异高达110.56倍,对杀螟松为48.90倍;褐飞虱种群对马拉硫磷、杀螟松的抗性分别相差11.61倍和6.11倍。3)褐飞虱种群对药剂的敏感度与当地用药水平呈负相关。4)有机磷类不同品种杀虫剂对两种飞虱的毒力差异较大,毒力较高的久效磷的LD_(50)值与毒力较低的马拉硫磷的LD_(50)相差数十倍。     

水稻飞虱对十三种杀虫剂的抗性监测

1987～1991年选用有机磷、有机氯和拟除虫菊酯类十三种杀虫剂对白背飞虱和褐飞虱用国际统一标准毒力测定点滴法进行抗药性监涮。结果表明：1)白背飞虱和褐飞虱对呋喃丹最为敏感。对马拉硫磷敏感度最低,LD50值相差上百倍。因两种飞虱均属迁飞性害虫,年度间的测定结果稍有波动;2) 白背飞虱抗药性发展比褐飞虱快,在测定方法和供试昆虫条件基本相同的情况下, 将1990年所测几种药剂的LD50与Nagata (1967)测定的数据进行比较。浙江省白背飞虱种群对马拉硫磷的抗性差异高达1lO．56倍, 对杀螟松为48.90倍;褐飞虱种群对马拉硫磷、杀螟松的抗性分别相差11.61倍和6．11倍。3)褐飞虱种群对药剂的敏感度与当地用药水平呈负相关。4) 有机磷类不同品种杀虫剂对两种飞虱的毒力差异较大。毒力较高的久效磷的LD50值与毒力较低的马拉硫磷的LD50值相差数十倍。     

Relationships of hollow heart in Irish potatoes to carbohydrate reabsorption and growth rate of tubers

Tubers of Irish Cobbler that were hollow grew faster than non-hollow tubers on the same plant. However, tubers of varieties without hollow heart grew just as rapidly as tubers of the variety with hollow heart. Therefore tuber growth rate was related to hollow heart occurring within a variety but could not account for differences between varieties. When plant foliage was pruned the C-¹⁴ label from sucrose was translocated from the tuber to the top of the plant. Our studies suggest hollow heart can occur in small tubers under the following conditions: (i) moisture stress in the tubers resulting in conversion of starch to sugar, followed by a rapid influx of water into the tuber resulting in rapid enlargement of the perimedullary zone and a separation in the pith that later develops into hollow heart, and/or (ii), following injury to some cells in the tuber due to reabsorption of minerals and carbohydrates or depletion of food reserves followed by tuber enlargement. It seems probable however that hollow heart that is initiated in large tubers is only associated with excessively rapid tuber enlargement without the involvement of reabsorption or depletion of food reserves.