Effect of waterlogging yam vines on vegetative growth and tuber yield

The effect of waterlogging the vines of two yam varieties for 24, 48 and 72 hours at two stages of growth, with or without fertiliser application, was studied in the field. Waterlogging caused a progressive degeneration of the leaf starting with the development of fresh lesions on the lower leaf surface, through necrotic spots or portions, to complete leaf necrosis. The degree of leaf damage was greater with Um 680 (Dioscorea alata) than with Obiaoturugo (D. rotundata). Waterlogging also caused the breakdown of the apical buds of the vines. The degree of damage increased with the duration of waterlogging. Younger plants suffered more damage than older plants, and plants treated with fertiliser suffered more than plants without fertiliser. Waterlogging ultimately hastened the final senescence of the yam vine. Waterlogging vines for 24 h had no effect on tuber yield, while waterlogging for 48 and 72 h reduced tuber yield by 32.4% and 43.2% respectively (P< 0.01). Waterlogging vines at the early growth stage produced 47.6% (P <0.01) less yield than waterlogging at a later stage. It is suggested that short-term or long-term waterlogging of the yam vine, or parts thereof, is the main cause of reduced leaf area and low yield in unstaked compared with staked yarn crops. Waterlogging may also be a predisposing factor to disease infection of yam vines by soil-borne micro-organisms.     

Effect of staking, nitrogen and potassium on growth and development in lesser yams: Dioscorea esculenta

Dry-matter accumulation was greater in staked than in unstaked plants of the lesser yam (Dioscorea esculenta). Staking, N and K application tended to increase the proportion of dry matter diverted into the tubers. Staking was the most important factor in increasing total tuber production, which was one and a half times greater in staked than in unstaked plants. Leaf-area development was closely and positively related to vine growth, and since staking and N application encouraged vine growth these treatments therefore led to the production of plants with greater leaf area. Leaf-area duration was increased by staking and N application and was closely and positively related to tuber yield. Staking and N application increased tuber number per plant while K application increased the size of individual tubers. Staking and K application increased bulking rate and both treatments increased the period of bulking by causing earlier tuber initiation.     

Detection of sugarcane yellow leaf virus,the causal agent of yellow leaf syndrome in sugarcane by DAS-ELISA

DAS-ELISA studies were conducted on detection of sugarcane yellow leaf virus (SCYLV) causing yellow leaf syndrome (YLS) of sugarcane in leaf and juice antigens. Among the two types of antigen sources used for the virus detection, juice antigen showed high titre for the virus as compared to leaf antigen. Assay with juice samples recorded more number of varieties positive to the virus. Further DAS-ELISA studies revealed that plants raised from disease-infected planting materials recorded high titre for SCYLV as compared to those raised from symptom-free seed canes. Similarly, assaying SCYLV titre in plant and ratoon crop in the field showed that SCYLV infection was partial in plant crop and in the subsequent ratoon crop, all the samples were positive to the virus. ELISA studies also indicated that 33 of 41 cane varieties showing YLS were positive to the virus.     

Evaluation of Water Yam (Dioscorea alata L.) Germplasm for Reaction to Yam Anthracnose and Virus Diseases and their Effect on Yield

Use of genetic resistance is the most practical and economic way to manage major diseases of yams. In a search for sources of resistance, 40 water yam (Dioscorea alata L.) accessions from Benin, Ghana, Nigeria and Puerto Rico were screened under natural disease infection conditions in Ibadan, Nigeria. The accessions were evaluated at 1, 3 and 6 months after planting (MAP) for severity of yam anthracnose and viral diseases. The effect of the pathogens on yield was also evaluated at harvest 9 MAP. There were significant differences (P < 0.001) between accessions for severities of anthracnose and viral diseases. Eight (20%) of them had lower anthracnose area under disease progress curves (AUDPC) values than the resistant check while 10 (25%) had AUDPC values below the trial mean. There were significant variations (P < 0.001) in yield components among the accessions. There was significant negative correlation of anthracnose severity with fresh tuber yield (r = −0.51) and with number of tubers per plot (r = −0.40). Similarly, significant negative correlations were observed of virus disease severity with fresh tuber yield (r = −0.78) and number of tubers per plot (r = −0.65). Linear regression models also showed that the fresh yield had significant negative relationships with anthracnose (R² = 0.26) and viral (R² = 0.62) diseases. The accessions identified as resistant constitute a valuable resource for breeding of resistant germplasm.     

Uncovering the genetic diversity of yams (Dioscorea spp.) in China by combining phenotypic trait and molecular marker analyses

Yam is an important edible tuber and root plant worldwide; China as one of the native places of yams has many diverse local resources. The goal of this study was to clarify the genetic diversity of the commonly cultivated yam landraces and the genetic relationship between the main yam species in China. In this study, 26 phenotypic traits of 112 yam accessions from 21 provinces in China were evaluated, and 24 simple sequence repeat (SSR) and 29 sequence‐related amplified polymorphism (SRAP) markers were used for the genetic diversity analysis. Phenotypic traits revealed that Dioscorea opposita had the highest genetic diversity, followed by D. alata, D. persimilis, D. fordii, and D. esculenta. Among the 26 phenotypic traits, the Shannon diversity indexes of leaf shape, petiole color, and stem color were high, and the range in the variation of tuber‐related traits in the underground part was higher than that in the aboveground part. All accessions were divided into six groups by phenotypic trait clustering, which was also supported by principal component analysis (PCA). Molecular marker analysis showed that SSR and SRAP markers had good amplification effects and could effectively and accurately evaluate the genetic variation of yam. The unweighted pair‐group method with arithmetic means analysis based on SSR‐SRAP marker data showed that the 112 accessions were also divided into six groups, similar to the phenotypic trait results. The results of PCA and population structure analysis based on SSR‐SRAP data also produced similar results. In addition, the analysis of the origin and genetic relationship of yam indicated that the species D. opposita may have originated from China. These results demonstrate the genetic diversity and distinctness among the widely cultivated species of Chinese yam and provide a theoretical reference for the classification, breeding, germplasm innovation, utilization, and variety protection of Chinese yam resources.     

Alterations in carbohydrate metabolism and enhancement in tuber production in white yam (<Emphasis Type="Italic">Dioscorea rotundata</Emphasis> Poir.) under triadimefon and hexaconazole applications

The present investigation was carried out with an aim to study the effects of two important fungicides/plant growth regulators, triadimefon (TDM) and hexaconazole (HEX) on white yam (Dioscorea rotundata Poir.). Each plant was treated with 1 l of aqueous solution containing 15 mg l^-1 TDM and 10 mg l⁻¹ HEX by soil drenching on 10, 20 and 30 days after planting (DAP). Starch and sugar contents, and the activities of α, β-amylases, sucrose phosphate synthase (SPS), sucrose synthase (SS) and acid invertase (AI) enzymes were estimated from leaf and tuber samples on 45, 60, 75 and 90 DAP. Results showed that TDM and HEX treatments inhibited the α, β-amylase and increased the fresh and dry weights, starch, sugar and sucrose contents and SPS, SS and AI activities in white yam. The data suggests that, the application of triazole fungicides may be a useful tool to increase the tuber quality as well as quantity in white yam plants, apart from their fungicidal properties.     

不同遗传背景下杂交籼稻功能叶与产量构成因素的相关性

为明确水稻功能叶与产量构成因素间的相关性,以不同遗传背景下籼稻的10个不育系和16个恢复系为亲本,按照NCII设计配制两套双列杂交组合,对水稻12个功能叶性状与8个产量性状构成因素进行了相关分析,结果表明：3片功能叶叶长与叶面积、剑叶宽、倒2叶宽等性状之间均存在极显著正相关,功能叶夹角之间也存在极显著正相关,但不同遗传背景对夹角性状与9个形态性状之间的相关性则存在明显差异,在第1套组合中,其相关系数均为负值,且相关均不显著;而第2套组合则相反。8个产量构成因素中,单株穗数与平均穗长、着粒密度、穗实粒数以及穗着粒数之间存在极显著负相关,平均穗长与穗着粒数、结实率与单株产量呈显著或极显著正相关,遗传背景对产量组成上有较大影响,在第1套组合中单株产量主要由结实率、单株穗数以及穗实粒数等性状决定,而在第2套中则主要由穗实粒数和结实率等性状决定。在功能叶与产量构成因素的相关中,叶长、叶面积、剑叶宽、倒2叶宽与着粒密度、穗实粒数以及穗着粒教等3个性状之间存在显著或极显著正相关。12个水稻功能叶性状与8个产量构成因素之间的主成分分析表明,在不同的遗传背景下,产量构成因素均主要受叶面积和叶夹角影响,两种不同遗传背景中其累积贡献率分别为69．8％和84．0％。     

Detection of Potato Leaf Roll Virus in Intact Sprout Disks by Enzyme-linked Immunosorbent Assay

Potato leaf roll virus (PLRV) was detected by enzyme-linked immunosorbent assay (ELISA) when intact sprout, stem or leaf tissue disks were substituted for leaf or tuber extracts as test samples. Absorbance (A₄₀₅) values increased with increasing number of disks per plate well. Readings with sprout disks were significantly higher than those with disks cut from other plant tissues or with tuber sap. A₄₀₅ values obtained by using 7 or 5 sprout disks per well were near the maximum oneobtained with leaf sap. PLRV was slightly more efficiently detected by ELISA in light sprout disks than in etiolated sprout ones. When ten out of 34 healthy tubers were replaced by PLRV-infected ones in the tuber indexing test, the diseased samples werereliably detected with 5 etiolated sprout disks per well. The sprout disk sampling technique should be useful for qualitative evaluation of PLRV infection in sprouted potato tubers without necessity to wound them and using sprouts not long enough for maceration.     

Prediction of relative efficiency of some selection indices used in winter wheat

Separate selection indices were constructed for various combinations of selective characters, in which together with components of economic yield also four separate subcharacters, yield prerequisites were used, namely: flag leaf area, length of the flag leaf, angle of the second leaf (from the top) and length of plant at heading time. Maximum genetic advance in weight of grains per plant (yield) from selections may be expected in selection indices in which three economic yield components together with flag leaf area or angle of the second leaf were used. When as criteria for selection the flag leaf area together with yield components were used, selection indices with six different sets of economic weights for yield and weight of one grain were also computed. For the ratio of economic values 1∶1, the total expected advance was the highest, but separate advance in yield was approximately only 57% in comparing with selection made according to yield as complex character. For the ratio of economic values 1∶0·03 to 1∶0 the expected genetic advances in yield were about 22 and 24 per cent higher in comparing with selections according to yield. It may be expected that yield improvment will not be acquired by means of a great number of small, inferior grains.     

Genetic and environmental correlation and path coefficient analysis of fruit yield per bush and other traits in black currants (Ribes nigrum L.)

Twenty-five F1 hybrid families of black currants (Ribes nigrum L.) originating from diallel crosses of five cultivars were assessed. Phenotypic correlation coefficient between full-sib family means (rFS), genetic correlation coefficient between full-sib family expected values (rG) and the environmental correlation were estimated on the basis of two years of observations for 12 quantitative characteristics studied. Evident repeatability of correlations in both years was proved. A considerable consistency between the values of genetic and phenotypic correlation coefficients was also observed. Coefficients of phenotypic and environmental correlation were significant for many pairs of traits. Most of the significant environmental correlation coefficients were found for the same pairs of characteristics for which phenotypic correlation coefficients were significant. This shows that genetic and environmental factors affected similar traits. Fruit yield expressed the largest number of significant correlations with other traits. Path coefficient analysis indicated that plant and berry size were the main factors influencing directly fruit yield in both years. It was proved that the number and length of one-year-old shoots via bush size had very large indirect effects on fruit yield per plant.     

盾叶薯蓣元素组成特点及其与土壤营养元素的关系研究

盾叶薯蓣(Dioscorea zingiberensis Wright)根状茎与地上部分各元素的含量明显不同,根状茎中含镍、铁、磷、铝量远高于地上部分,镁、钙、锰量远低于地上部分;盾叶磐蓣对钾、锌、铁等元素的吸收量大于农作物;根状拳与地上部分的比值(R2／U2)较大;大量元素在根状茎中的含量(A)及地上部分含量(B)的大小排序差别较大,微量元素含量A、B值的大小排序完全一致。盾叶薯蓣根状茎的皂素平均含量为2．87％,皂素含量与土壤有机质、全氮、全磷、全钾、有效铁、有效锌含量关系密切。薯蓣皂素含量高的盾叶薯蓣集中分布在大巴山北坡东段化龙山脉一线。     

Response of potato grown under non-inductive condition paclobutrazol: shoot growth, chlorophyll content, net photosynthesis, assimilate partitioning, tuber yield, quality, and dormancy

The effect of foliar and soil applied paclobutrazol on potato were examined under non-inductive condition in a greenhouse. Single stemmed plants of the cultivar BP1 were grown at 35(±2)/20(±2) °C day/night temperatures, relative humidity of 58%, and a 16 h photoperiod. Twenty-eight days after transplanting paclobutrazol was applied as a foliar spray or soil drench at rates of 0, 45.0, 67.5, and 90.0 mg active ingredient paclobutrazol per plant. Regardless of the method of application paclobutrazol increased chlorophyll a and b contents of the leaf tissue, delayed physiological maturity, and increased tuber fresh mass, dry matter content, specific gravity, dormancy period of the tubers. Paclobutrazol reduced the number of tubers per plant. A significant interaction between rates and methods of paclobutrazol application were observed with respect to plant height and tuber crude protein content. Foliar application gave a higher rate of net photosynthesis than the soil drench. Paclobutrazol significantly reduced total leaf area and increased assimilate partitioning to the tubers. The study clearly showed that paclobutrazol is effective to suppress excessive vegetative growth, favor assimilation to the tubers, increase tuber yield, improve tuber quality and extend tuber dormancy of potato grown in high temperatures and long photoperiods.     

Genetic Allee effects on performance, plasticity and developmental stability in a clonal plant

Negative effects of small population size on fitness, so-called Allee effects, may threaten population persistence even in intact habitat remnants. We studied genotypes of 14 isolated populations of the clonal plant Ranunculus reptans, for which molecular genetic (RAPD-) variability is higher for large than for small populations. In a competition-free greenhouse environment vegetative offspring of genotypes from large populations produced more rosettes and flowers, indicating higher fitness. Within-genotype coefficients of variation in performance traits, indicating developmental instability, were lower for genotypes from populations with higher RAPD-variability. In competition with a taller grass, we found relative reduction in leaf length less pronounced for plants from large populations, suggesting higher adaptive plasticity. Our experimental study of a plant with predominantly vegetative reproduction suggests, that negative genetic effects of recent habitat fragmentation, which so far rather were expected in plants with frequent sexual reproduction, are more severe and more common than previously acknowledged.     

Genetic parameters for agronomic characteristics. I. Early and intermediate breeding populations of true potato seed

The original variation in the source population as well as the selection method may influence the genetic variation in further cycles of genetic improvement. Therefore, the objectives of this research were to determine genetic parameters (variance components and heritability) in source and intermediate stages of a true potato seed (TPS) breeding population and to calculate the genetic and phenotypic correlations in this breeding material developed by the Centro Internacional de la Papa (CIP). The intermediate stage was derived from a source population adapted to the warm lowland tropics plus introduction of exotic germplasm from North America and Europe. Non-additive genetic variation was almost nil for plant survival, tuber yield and tuber shape uniformity in both stages of the breeding population and no quantitative genetic variation for uniformity of tuber color was observed in both source and intermediate breeding materials. Heritability was higher in the intermediate stage than in the source population for plant survival (0.86 vs 0.66), tuber yield (0.30 vs 0.14) and tuber shape (0.77 vs 0.51), but it was the reverse for tuber uniformity (0.11 vs 0.72). These results suggest that potato breeders at CIP were able to keep enough genetic variation for most important characteristics for potato production from true seed in their intermediate breeding materials by adding new sources of variation to the original breeding population. Additive genetic and phenotypic correlations were significant and positive between plant vigor after transplanting and tuber yield, and tuber shape and tuber uniformity, which suggest that high yielding offspring result from early vigorous growth, and that tuber uniformity could depend on tuber shape uniformity in this breeding material.     

山药异淀粉酶基因克隆及其在淀粉代谢中的作用北大核心CSCD

为了明确异淀粉酶基因(ISA 3)在山药淀粉代谢中的作用,该研究以‘毕克齐’和‘大和长芋’山药为试验材料,测定了块茎中淀粉及组分含量和异淀粉酶活性等;采用RT-PCR技术克隆了ISA 3,并进行生物学分析及山药块茎不同膨大期和不同组织间ISA 3基因的表达等。结果表明:(1)山药‘大和长芋’的直链淀粉、支链淀粉和总淀粉含量均显著高于‘毕克齐’,且两品种的淀粉含量随生长发育的变化均呈先升高后降低的趋势,并均于种植后120 d时达到最高,但‘毕克齐’的异淀粉酶(ISA)活性在整个膨大期均高于‘大和长芋’。(2)成功克隆获得山药ISA 3开放阅读框长1584 bp,编码527个氨基酸;ISA3为亲水性蛋白。(3)不同品种块茎在膨大时期的ISA 3基因表达趋势不同,‘毕克齐’中呈先显著上调随后下调,而在‘大和长芋’中表达总体下调,且在山药的叶、茎和块茎中均有表达,存在明显的组织特异性。(4)ISA活性与山药淀粉及支链淀粉含量呈显著和极显著正相关关系,但ISA活性与ISA 3的表达量呈负相关关系。研究表明,异淀粉酶参与了山药块茎中淀粉的合成,且主要对支链淀粉的合成起关键作用,ISA 3基因的表达可能对异淀粉酶活性和淀粉的合成起负调控作用。     

Genetic variation in Solanum tuberosum group Andigena haploids

Summary A random sample of haploids, derived from 28 parental introductions from Solarium tuberosum Gp. Andigena, was used to estimate the quantitative genetic variation for six traits within this group. The six traits analyzed on a plot mean basis were: total tuber weight, fresh vine weight, total fresh weight (tuber+vine), dry vine weight, total dry matter (tuber+vine) and specific gravity. Progenies were obtained following the North Carolina mating Design I and were evaluated along with the female parental clones at two locations. Components of variance and narrow sense heritabilities were calculated by two methods: Design I and female parent-offspring regression. Heritability estimates calculated by the two procedures were in close agreement for most traits. The estimates for total tuber weight from the Design I procedure were twice that from parent offspring regression. The genetic coefficient of variation for these traits indicated a large amount of total genetic variance in this population. Genetic variability for total tuber weight was mostly additive, while both additive and dominant genetic variances were equally important for the remaining traits.     

Relationship between Tomato yellow leaf curl viruses and the whitefly vector

Tomato Yellow Leaf Curl Virus (TYLCV) and Tomato Leaf Curl Virus (ToLCV) are the currently known begomoviruses in Uganda. The relationship with their whiteflies (Bemisia tabaci) vector and its management were not known in Uganda. A direct relationship was expected between these begomoviruses and whiteflies at Buwama in Mpigi district of Uganda. Farmer practices were expected to have limited efficacy. To investigate this, a completely randomised block design was used for all trials with six treatments replicated three times. Treatments evaluated were farmer whitefly pest management practices. These included both chemical pesticide and non-pesticide applications. Data on whitefly population and tomato yellow leaf curl virus disease incidence was recorded weekly, and analysed using SAS and SPSS statistical programmes for ANOVA, and correlations. Ranked means, coefficients of variation and standard errors were noted. Virus-vector relationship field studies established that virus occurrence varied in space and time, and with management practices, crop development stage, and weather conditions. A negative relationship (R = -0.14, p 0.04) was established between number of plants infected with TYLCV (sensu lato) and percentage marketable tomato yield. Tomato maturity was inversely propotional to whitefly infestation (R = -0.5, p 0.0001). Uprooting and application of dimethoate was most effective of the six treatments. Tomato leaf curl virus diseases and whitefly management options were established in Uganda.     

Pyruvate kinase,an enzyme subject to regulation inDioscorea alata

Different species of yam tubers were examined for the presence of pyruvate kinase and phosphatase activities, Pyruvate kinase was purified 25 fold with a yield of 50 %. using ammonium sulphate precipitation and ion exchange chromatography on DEAE-Sephadex. Partially purified enzyme showed normal Michaelis-Menten kinetics. However, pyruvate kinase from crude extract of dormant yam tuber showed slight sigmoid response towards phosphoenol-pyruvate and magnesium and to a certain extent ADP. The enzyme is activated by AMP and inhibited by ATP and citrate in both crude and partially purified preparations. Further studies on the effect of energy charge on the enzyme strongly suggest that pyruvate kinase from D. alata is a regulatory enzyme. No evidence was found for the presence of more than one pyruvate kinase in germinating D. alata tuber. With the exception of D. dumentorum, all the other three species of yams studied contain very little or no detectable phosphatase activity during dormancy. However, phosphatase activity increased during germination in all the species, thus excluding the use of sprouting yam tubers for kinetic study of pyruvate kinase.     

SIVmac Gag p27 capsid protein gene expression in potato

A cDNA encoding the Simian immunodeficiency virus type (SIV(mac)) Gag capsid protein was introduced into Solanum tuberosum cells by Agrobacterium tumefaciens-mediated transformation methods. The gag gene was detected in the genomic DNA of transformed leaf tissues by PCR DNA amplification. Immunoblot analysis of transformed potato plant extracts with anti-Gag monoclonal antibody showed that biologically active Gag protein was synthesized in transformed tuber tissues. Based on ELISA results, recombinant Gag protein made up 0.006-0.014% of total soluble tuber protein. The synthesis of SIV Gag in transformed potato tubers opens the way for development of Gag-based edible plant vaccines for protection against SIV and potentially HIV-1 infection.     

The Distribution of Garlic Viruses in Leaves and Bulbs during the First Year of Infection

Garlic plants are naturally infected with a mixture of viruses. Virus‐free garlic plants, obtained by meristem culture, rapidly become reinfected when planted in the field. With the aim of understanding virus movement and fluctuations in virus concentration in leaves and cloves of garlic plants in the first year after infection, Onion yellow dwarf virus, Leek yellow stripe virus, and other viruses were analyzed by double‐antibody sandwich enzyme‐linked immunosorbent assay. Significant differences were detected in virus concentration in different leaves, but the distribution of the viruses was variable. Therefore, no one type or position of leaf is preferable for detecting virus presence. Instead, sampling any leaf at the end of the crop cycle, about 200 days after planting, is advisable because virus concentration is several times higher in older plants. The analysis of virus distribution in bulbs revealed that virus concentration was higher in early‐inoculated than in late‐inoculated plants. In 81% of the bulbs, cloves were either all positive or all negative in serological tests. Only in 6% of the cases were positive and negative cloves found in the same bulb, and in 13% of the bulbs, negative results coexisted with an uncertain status. The tests of virus concentration in relation to the layers of each bulb revealed important differences. Only the innermost layer showed differences with other layers, but this was poorly represented as it had fewer cloves.