Circumvention of over-excitation of PSII by maintaining electron transport rate in leaves of four cotton genotypes developed under long-term drought

We investigated the patterns of response to a long-term drought in the field in cotton cultivars (genotypes) with known differences in their drought tolerance. Four cotton genotypes with varying physiological and morphological traits, suited to different cropping conditions, were grown in the field and subjected to a long-term moderate drought. In general, cotton leaves developed under drought had significantly higher area-based leaf nitrogen content (N (area)) than those under well irrigation. Droughted plants showed a lower light-saturated net photosynthetic rate (A (sat)) with lower stomatal conductance (g (s)) and intercellular CO (2) concentration (C (i)) than irrigated ones. Based on the responses of A (sat) to g (s) and C (i), there was no decreasing trend in A (sat) at a given g (s) and C (i) in droughted leaves, suggesting that the decline in A (sat) in field-grown cotton plants under a long-term drought can be attributed mainly to stomatal closure, but not to nonstomatal limitations. There was little evidence of an increase in thermal energy dissipation as indicated by the lack of a decrease in the photochemical efficiency of open PSII (F (v)'/F (m)') in droughted plants. On the basis of electron transport (ETR) and photochemical quenching (q (P)), however, we found evidence indicating that droughted cotton plants can circumvent the risk of excessive excitation energy in photosystem (PS) II by maintaining higher electron transport rates associated with higher N (area), even while photosynthetic rates were reduced by stomatal closure.     

苹果绵蚜对不同苹果品种春梢生长期生理指标的影响

为了筛选培育对苹果绵蚜(Eriosoma lanigerum Hausmann)的抗性品种,实现持续有效治理苹果绵蚜的目的,通过测定红富士、金帅、昭锦108、秦冠、红将军等5种不同苹果品种春梢生长期被苹果绵蚜危害前后枝条内可溶性糖、蛋白质、游离氨基酸、总酚含量以及防御性酶的活性变化,探讨苹果生理指标与抗蚜性的关系。结果表明,被害后可溶性糖含量除红将军外均有所上升,其中红富士上升达13.7%;蛋白质含量除红富士外均有所降低;氨基酸含量均有所上升,其中红将军变化明显,变化率达68.8%。酚类物质是一种重要的抗蚜物质,红富士、昭锦108、秦冠被害后总酚含量均升高,其中昭锦108、秦冠中总酚含量上升率约为红富士的2倍。红富士品种正常枝条内超氧化物歧化酶(Superoxide Dismutase,SOD)、多酚氧化酶(Polyphenol Oxidase,PPO)、过氧化物酶(Peroxidase,POD)以及过氧化氢酶(Catalase,CAT)活性均显著低于昭锦108,被害后各苹果枝条SOD活性均出现上升趋势,除红将军的PPO、POD活性降低外,其他品种均升高;金帅、红富士的CAT活性上升明显,分别为110.8%、45.5%。植物的防御性酶与其抗虫性有密切关系,苹果春梢生长期对苹果绵蚜的抗性与苹果体内的可溶性糖、游离氨基酸、SOD、PPO、POD以及CAT活性均有关,而且不同苹果品种被害后生理指标的变化也与其抗蚜性有一定关系。     

Race Profiling and Molecular Diversity Analysis of Fusarium oxysporum f.sp. ciceris Causing Wilt in Chickpea

Seventy isolates of Fusarium oxysporum f.sp. ciceris (Foc) causing chickpea wilt representing 13 states and four crop cultivation zones of India were analysed for their virulence and genetic diversity. The isolates of the pathogen showed high variability in causing wilt incidence on a new set of differential cultivars of chickpea, namely C104, JG74, CPS1, BG212, WR315, KWR108, GPF2, DCP92‐3, Chaffa and JG62. New differential cultivars for each race were identified, and based on differential responses, the isolates were characterized into eight races of the pathogen. The same set of isolates was used for molecular characterization with four different molecular markers, namely random amplified polymorphic DNA, universal rice primers, simple sequence repeats and intersimple sequence repeats. All the four sets of markers gave 100% polymorphism. Unweighted paired group method with arithmetic average analysis grouped the isolates into eight categories at genetic similarities ranging from 37 to 40%. The molecular groups partially corresponded to the states of origin/chickpea‐growing region of the isolates as well as races of the pathogen characterized in this study. The majority of southern, northern and central Indian populations representing specific races of the pathogen were grouped separately into distinct clusters along with some other isolates, indicating the existence of variability in population predominated by a single race of the pathogen. The present race profiling for the Indian population of the pathogen and its distribution pattern is entirely new. The knowledge generated in this study could be utilized in resistance breeding programme. The existence of more than one race, predominated by a single one, in a chickpea cultivation zone as supported by the present molecular findings is also a new information.     

Antioxidant defense system and cadmium uptake in barley genotypes differing in cadmium tolerance

Using two barley (Hordeum vulgare) cultivars (cvs. Tokak and Hamidiye) nutrient solution experiments were conducted in order to study the genotypic variation in tolerance to Cd toxicity based on (i) development of leaf symptoms, (ii) decreases in dry matter production, (iii) Cd concentration and (iv) changes in antioxidative defense system in leaves (i.e., superoxide dismutase, ascorbate peroxidase, glutathione reductase, catalase, ascorbic acid and non-protein SH-groups). Plants were grown in nutrient solution under controlled environmental conditions, and subjected to increasing concentrations of Cd (0, 15, 30, 60 and 120 micromol/L Cd) for different time periods. Of the barley cultivars Hamidiye was particularly sensitive to Cd as judged by the severity and earlier development of Cd toxicity symptoms on leaves. Within 48 h of Cd application Hamidiye rapidly developed severe leaf Cd toxicity symptoms whereas in Tokak the leaf symptoms appeared only slightly. Hamidiye also tended to show more decrease in growth caused by Cd supply when compared to Tokak. The differences in sensitivity to Cd between Tokak and Hamidiye were not related to Cd concentrations in roots and shoots or Cd accumulation per plant. With the exception of catalase, activities of the enzymes involved in detoxification of reactive oxygen species (ROS) were markedly enhanced in Hamidiye by increasing Cd supply. By contrast, in Tokak there was either only a slight increase or no change in the activities of the antioxidative enzymes. Similarly, levels of ascorbic acid and especially non-protein SH-groups were increased in Hamidiye by Cd supply, but not affected in Tokak. The results indicate the existence of a large genotypic variation between barley cultivars for Cd tolerance. The differential Cd tolerance found in the barley cultivars was not related to uptake or accumulation of Cd in plants, indicating importance of internal mechanisms in expression of differential Cd tolerance in barley. As a response to increasing Cd supply particular increases in antioxidative mechanisms in the Cd-sensitive barley cultivar Hamidiye suggest that the high Cd sensitivity of Hamidiye is related to enhanced production and oxidative damage of ROS.     

Genetic diversity and species-specific PCR-based markers from AFLP analyses of Thai bananas

A large amount of banana genetic resource has been found in Thailand which is believed to be one of the centers of its origins. To assess genetic diversity and determine genetic relationships of edible bananas in Thailand, 110 accessions of banana species and cultivars collected from villages and natural locations were investigated. UPGMA clustering of numerical data from Amplified Fragment Length Polymorphism (AFLP) patterns showed two large groups which corresponded to genome designations of Musa acuminata (AA) and Musa balbisiana (BB), the known ancestors of most edible cultivars. The AFLP data suggested that among Thai bananas, AA and AAA cultivars were closely related to M. acuminata subsp. malaccensis, while some of ‘B’ genome contained ones closely related to wild M. balbisiana in Thailand and some may have been imported. Eight species-specific PCR-based primer pairs, generated from the AFLP results clearly identify ‘A’ and ‘B’ genomes within cultivars and hybrids. The analyses were useful to readily and easily infer progenitors of these cultivars and pronounce wide genetic diversity of the bananas in Thailand.     

Activities of enzymes of fermentation pathways in the leaves and roots of contrasting cultivars of sorghum (Sorghum Bicolor L.) during flooding

Flooding evoked a differential response in the activities of enzymes of fermentation pathway in leaves and roots of flood sensitive (S-308) and flood-tolerant (SSG-59-3) cultivars of sorghum. Activities of alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH) and alanine aminotransferase (AlaAT) enhanced in roots of SSG-59-3 during 72 h of flooding. In contrast, a transient increase in the activities was discerned in roots of S-308 up to 24 h flooding followed by a decline in activities of these enzymes. In leaves of SSG-59-3, the activities of ADH and LDH increased to about three fold during flooding stress as compared to that in the non-flooded control plants. Though elevation in activities of these enzymes was observed in leaves of S-308 up to 48 h of flooding, the magnitude of enhancement was much lower than that in SSG-59-3. Alanine aminotranferase activity depressed in leaves of both the cultivars but the level of decline was more pronounced in sensitive cultivar S-308 as compare to tolerant SSG-59-3. The amount of alcohol, lactic acid and alanine were higher in both roots and leaves of SSG-59-3 than that in S-308 during flooding stress. It is thus apparent that roots and leaves of flood tolerant variety tends to attain greater capacity to perform reactions of various fermentation pathways to sustain production of ATP under flooded conditions.     

DNA导入和系选大豆品种及其亲本遗传关系的SSR标记分析

利用现有品种的变异进行系选并培育新品种是一种重要的育种方法。利用SSR标记, 对系选大豆（Glycine max）新品种和其亲本的遗传组成进行分析, 明确二者的遗传关系, 为大豆系选育种提供依据。使用48对SSR引物对22个大豆品种及其亲本进行分析, 结果表明, 由外源DNA导入育成的3个品种与其亲本的一致性为35.42%–95.83%, 虽然供体相同, 但由于导入的外源DNA不同, 故育成的品种间差异很大。另外19个系选品种与其亲本的一致性为27.08%–89.58%, 其中有6个品种与亲本间的差异小于30%。聚类分析发现, 所有参试品种分为东北春大豆及黄淮和南方大豆2类, 其中有8个品种不能与其亲本聚在一起, 说明系选品种并不完全是由于亲本通过突变获得。此外, 农艺性状与分子标记分析结果差异较大, 说明利用有限的农艺性状评价品种间的遗传关系存在一定的局限性。通过比较系选品种和亲本之间的保守位点发现, 特定等位变异出现次数≥7的位点有14个, 分布在11个连锁群, 其中有7个位点与产量和抗病性等重要农艺性状有关, 说明DNA导入和系选品种在选择变异性状的同时, 使一些与重要农艺性状有关的等位变异得到了保留。     

银杏观赏品种遗传关系的AFLP分析

从64对EcoRⅠ／MseⅠ引物（其中MseⅠ引物为荧光标记物）中筛选出8对扩增产物多态性高、谱带清晰的引物,对来自美国、荷兰、日本、法国和我国的21个银杏观赏品种的遗传关系进行了研究。结果表明：8对引物共产生1117条谱带,229个特异位点（其中缺失带54条、单态带175条）,多态带983条,多态带的比例为88％;每对引物鉴别效率为100％。14个国外银杏观赏品种平均多态带的比例35．86％,7个国内品种平均多态带的比例31．51％。21个观赏品种之间相似系数为0．4899-0．8499。当相似系数为0．7300时,供试观赏品种可分为四类,来源地相同的品种并不单独聚成一类,中国和法国的品种分别属于其中的三类。根据对观赏品种的特异位点、相似系数、聚类结果等进行综合分析表明,‘塔形银杏’、‘垂乳银杏’、‘筒叶银杏’、‘大耳银杏’、‘斑叶银杏’、‘展冠银杏’、‘垂枝银杏’、‘沂源叶籽银杏’这8个品种是银杏观赏品种中的重要特异种质。     

Productivity and Subordinate Species Response to Dominant Grass Species and Seed Source during Restoration

Grasses can be important regulators of species diversity and ecosystem processes in prairie systems. Although C₄ grasses are usually assumed to be ecologically similar because they are in the same functional group, there may be important differences among species or between seed sources that could impact restorations. I tested whether C₄ grass species identity, seed source, or grass species richness scales to influence aboveground net primary productivity (ANPP), resistance to weed invasion, or establishment of subordinate prairie species during restoration. Plots in western Iowa, United States, were planted with equal‐sized transplants of one of five common grass species (Panicum virgatum L., Sorghastrum nutans (L.) Nash, Andropogon gerardii Vitman, Schizachyrium scoparium (Michx.) Nash, and Bouteloua curtipendula (Michx.) Torrey) either from local seed or from cultivar seed sources. These plots were compared to plots containing all five species in mixture and to nonplanted plots. Differences in ANPP were found among species but not between cultivars and noncultivars or between monocultures and mixtures. Panicum virgatum, S. nutans, and S. scoparium were more productive than A. gerardii and B. curtipendula. Weed invasion was much higher when plots were not planted with grasses. Schizachyrium scoparium allowed greater establishment of subordinant prairie species than all other focal grass species. There were two separate mechanisms by which grasses suppressed prairie species establishment either (1) by growing tall and capturing light or (2) by quickly filling in bare space by spreading horizontally through rhizome growth in short species. These results suggest that high ANPP can be found with noncultivar plantings during the first 2 years after planting and that subordinate species establishment is most likely when shorter bunchgrasses such as S. scoparium are dominant.     

Evaluating the role of root citrate exudation as a mechanism of aluminium resistance in maize genotypes

Organic anion exudation by roots as a mechanism of aluminium (Al) resistance has been intensively studied lately. In the present study, we evaluated qualitative and quantitative aspects of root exudation of organic anions in maize genotypes of distinct sensitivity to Al in response to Al exposure. Maize seedlings were grown axenically in nutrient solution and root exudates were collected along the whole seminal root axis for a short period (4 h) using a divided-root-chamber technique. In root exudates collected from 10-mm long root apices, citrate accounted for 67% of the total organic anions found, followed by malate (29%), trans-aconitate (3%), fumarate (<1%), and cis-aconitate (1%). Rates of citrate exudation from root apices of two genotypes with differential resistance to Al were consistently higher in the Al resistant one, differing by a factor of 1.7 – 3.0 across a range of external Al concentrations. Furthermore, relative Al resistance of eight maize genotypes correlated significantly well with their citrate exudation rate measured at 40 M Al. Higher exudation rates were accompanied by a less inhibited root elongation. The exudation of citrate along the longitudinal axis of fully developed seminal roots showed a particular pattern: citrate was exuded mainly in the regions of root apices, either belonging to the main root or to the lateral roots in the most basal part of the main root. The involvement of citrate in a mechanism of Al resistance is evaluated in terms of protection of the root from the effects of excess Al on root elongation and on nutrient uptake along a root axis showing distinct sites of citrate exudation.