亚热带山地多年生黑麦草及选育材料生产性能的评价

在南方亚热带山地，对１２个多年生黑麦草品种和选自老草地上１１个育种材料的生长发育状况观察及生产性能进行了评价和比较，３年的试验结果表明，在该试验条件下表现优良的有来自美国的品种编号为１７－１Ｂｉｓｏｎ和选自老草地上的９１－１，Ｈ－１５和Ｂ－１等３个选育材料，它们的共同特点是返青早，产草量高，有推广前景和继续选育的价值。     

Pisatin demethylation by fungal pathogens and nonpathogens of pea: association with pisatin tolerance and virulence

Previous studies have indicated that detoxification of their hosts' phytoalexins is a tolerance mechanism for some true fungi, but not the fungus-like Oomycota, and may be involved in determining the virulence of a pathogen. In the present study, the associations between demethylation of the pea phytoalexin pisatin, tolerance to pisatin, and virulence on pea were examined for 50 fungal isolates which represent 17 species of pathogens and nonpathogens of pea. All isolates ofPythium coloratum and P. irregulare failed to metabolize and were sensitive to pisatin, consistent with previous observations that members of the Oomycota generally lack the ability to metabolize and are sensitive to their hosts' phytoalexins. Among true fungi tested, the ability to demethylate pisatin was common, regardless of whether the particular isolate was pathogenic on pea or not. However, when the rate of pisatin demethylation was compared to virulence, all but one of the moderate to highly virulent isolates rapidly demethylated pisatin. In addition, the more rapidly demethylating isolates were generally more tolerant of pisatin. These results suggest that a specialized enzyme system for quickly detoxifying pisatin might be present in most pea pathogens. In previous studies a specific cytochrome P450 enzyme for demethylating pisatin was identified in the pea pathogen Nectria haematococca mating population VI, and genes (PDA genes) encoding that enzyme have been cloned from this fungus. When DNA specific for these genes was used to probe genomic DNA from other fungi that demethylate pisatin, significant hybridization was detected with only one fungus, the pea pathogen Fusarium oxysporum f. sp. pisi. If the other pea pathogens possess a specific cytochrome P450 system for detoxification of pisatin, the genes encoding these enzymes apparently share limited nucleotide similarity with N. haematococca PDA genes.     

白三叶(Trifolium repens L)无性系植物分株间的生理整合作用

研究了白三叶无性系植物种群，在相互连接的分株之间生理上相互依存的程度。结果显示子代在生理上取决于母株资源的转移，这一依赖性随时间而下降。相互连接的分株，一部分被遮荫至１０％，而照光分株光合速率明显增加。光被限制期间，分株将重新整合，遮荫分株无性系中由其它分株提供同化物。在子代匍匐茎数目和长度上有一个权衡。当资源受限制时，产生极少较长的子代匍匐茎，结果提高了子代能够占据更有利条件的可能性。在分株之间，生理整合作用降低了子代建立所面临的危险，使同源分株在资源的可利用能力上整合到一个局部的异质环境，增加同源分株间的竞争能力，缓冲所面对的局部微生境的选择。     

国外沙棘良种引种之管见

经过对从国外引进的沙棘优良品种的生长、结实和病虫害等的调查，为从总体上准确把握我国沙棘的引种和推广，建议做好以下工作，(1)要做好引进沙棘品种的区域试验，有针对性地选择适宜品种；(2)培育适于我国自然特点的沙棘良种；(3)开展集约经营，提高经济效益，加强对引种沙棘病虫害防治的研究；(4)进行引种沙棘的生态适宜性分区，绘制我国沙棘引种的生态区图。     

采后乙醇处理对萝卜幼苗延迟衰老作用的影响

去根小萝卜幼苗，放置在０．５Ｌ的塑料盒中，用０．０５－１．０ｍｌ不同量的乙醇处理不同的时间，４ｄ后测定叶绿素损失量，氧的消耗量，二氧化碳产生量。结果发现，经乙醇气处理后的样品组，叶绿素损失均比对照组明显减少，二氧化碳生成量和氧的消耗量也比对照组显著降低，说明呼吸作用减缓并受到了抑制，延迟了衰老作用的发生。     

侧柏种源试验苗期的初步研究

在北京的3个不同海拔高度,对来自31个地区的侧柏种子进行了种源试验。对一年生苗的分析表明,种源间差异显著。一年生苗生长快的种源比生长慢的高3.6倍。通过根系调查及苗高生长量与地表温度和土壤含水量的相关分析,可以看出天然林子代比人工林子代的适应性强。初步研究结果可为北京地区选择适宜的侧柏种源和侧柏的种源区划提供参考。     

香蕉柠檬酸合酶基因MaGCS的克隆及生物信息学分析

采用RACE-PCR的方法首次在香蕉中获得一个柠檬酸合酶基因的cDNA序列。经序列测定和Blastx比对分析表明，该cDNA全长1 885bp，编码513个氨基酸残基，具有植物柠檬酸合酶基因的特征结构域，并与其他植物来源的乙醛酸循环体的柠檬酸合酶具有很高的序列相似性，将其命名为MaGCS(Musa glyoxysomal citrate synthase)，并对其进行生物信息学分析，初步预测其理化性质及功能等。     

Bulked Segregant Analysis to Detect QTL Related to Heat Tolerance in Rice （Oryza sativa L.） Using SSR Markers

The study was undertaken to assess the genetic effect of quantitative trait loci （QTLs） conferring heat tolerance at flowering stage in rice. A population consisting of 279 F2 individuals from the cross between 996, a heat tolerant cultivar and 4628, a heat-sensitive cultivar, was analyzed for their segregation pattern of the difference of seed set rate under optimal temperature condition and high temperature condition. The difference of seed set rate under optimal temperature condition and high temperature condition showed normal distribution, indicating the polygenic control over the trait. To identify main effect of QTL for heat tolerance, the parents were surveyed with 200 primer pairs of simple sequence repeats （SSR）. The parental survey revealed 30% polymorphism between parents. In order to detect the main QTL association with heat tolerance, a strategy of combining the DNA pooling from selected segregants and genotyping was adopted. The association of putative markers identified based on DNA pooling from selected segregants was established by single marker analysis （SMA）. The results of SMA revealed that SSR markers, RM3735 on chromosome 4 and RM3586 on chromosome 3 showed significant association with heat tolerance respectively, accounted for 17 and 3% of the total variation respectively. The heat tolerance during flowering stage in rice was controlled by multiple gene. The SSR markers, RM3735 on chromosome 4 and RM3586 on chromosome 3 showed significant association with heat tolerance respectively, accounted for 17 and 3% of the total variation respectively. The two genetic loci, especially for RM3735 on chromosome 4, can be used in marker-assistant-selected method in heat tolerance breeding in rice.     

Does the Sulfur Assimilation Pathway Play a Role in the Response to Fe Deficiency in Maize (Zea mays L.) Plants?

Abstract

The finding that the methionine is the sole precursor of the mugineic acid family phytosiderophores induced us to evaluate whether sulfur assimilation pathway has a role in plant response to Fe deficiency. Maize plants were grown for 10 days in nutrient solution (NS) containing 80 µM Fe in the presence (+S) or absence (?S) of sulfate. After removing the root extraplasmatic iron pool, half of the plants of each treatment (+S and ?S) were transferred to a new Fe deficient NS (0.1 µM final Fe concentration) (?Fe). The remaining plants of each pre‐culture condition (+S and ?S) were transferred to a new NS containing 80 µM Fe (+Fe). Leaves were collected 4 and 24 hours from the beginning of Fe deprivation period and used for chemical analysis and enzyme assays. Results showed that iron content in the leaves was lower in plants grown in S‐deficiency than in those grown in the presence of the macro‐nutrient. Iron deprivation produced an increase in the level of SH compounds in both nutritive conditions (+S and ?S). These observations are suggestive of some relationship between S nutrition and Fe uptake. For this reason, we next investigated the influence of Fe availability on S metabolism through the evaluation of changes in ATPs and OASs activity, the first and the last enzyme of S assimilation pathway respectively. Results showed that S‐starvation increased the activity of both enzymes, but this effect disappeared in plants upon Fe deficiency suggesting that S metabolism is sensitive to Fe availability. Taken together these evidences suggest that S metabolism is sensitive to soil Fe‐availability for plant nutrition and support the hypothesis of S involvement in plant response to Fe deprivation.     

Fruit Yield,Plant Growth and Nutrient Status in Mango

Abstract

Fruit yield and nutrient concentration of mango (Mangifera indica L.) cultivar ‘Osteen’ were studied in relation to rootstocks Gomera-1 and Gomera-3 for three years. The results indicated that the Gomera-3 root system had higher nutrient uptake and transport towards the scion. Data from grafted and ungrafted Gomera-1 and Gomera-3 trees proved similar with respect to N, P, and K utilization profile, with post-harvest accumulation and a decline during flowering, P and K concentrations significantly decreasing during fruit growth. These trends were largely the opposite for Ca and Mg. The Fe, Zn, Mn, and Cu concentrations rose during dormancy and fell at flowering. Fruit yield was higher with Gomera-1, while Gomera-3 gave fruit with greater weight and width. Tree height, trunk cross-sectional area, canopy diameter and volume were greater in grafted and ungrafted Gomera-3, this rootstock being the most vigorous. The yield efficiency was significantly greater on Gomera-1. Thus, cv. ‘Osteen’ grafted to Gomera-1 offered better yield and required a lower amount of nutrients.