Tall Varieties Research Articles

Wheat Breeding for Durable Rust Resistance and High Yield Potential in Historical Prospective and Current Status

Epidemics of leaf, stripe and stem rusts on wheat have induced significant losses in the past during the early nineteenth century and have destroying role in reducing product yield bringing about socio-economic variability worldwide. The old tall varieties with qualitative resistance couldn't continue for longer period because of the advancement of new virulent pathogen races. But varieties like Yaqui-50, Lyalpur-73, and Lerma Rojo-64 were released during early period of green revolution, still linked with durable resistance to stripe, leaf and stem rust. Advancement of new rust races like virulence's Yr27 and Yr9 followed by the appearance of Ug99 and its mutants lead the breeders to review their breeding plan. Breeders are presently relying upon to gather minor genes and their use in grouping with major genes to develop rust resistance in wheat varieties. The minor genes, Lr46/Yr29, Lr34/Yr18, Sr2/Yr30, are being broken in wheat breeding at CIMMYT and different region. The germplasm with this kind of resistance have shown existence stability over space and time. At Ayub Agriculture Research Institute, Faisalabad the home of green revolution in Pakistan, this approach has been established since1994-95. The durable resistance assortments were crossed in a top cross/back cross technique and the segregating populations were improved by adopting mass strategy, which brought about the advancement of material having preferred yield and rust resistance over the pre-exiting assortments (e.g., Inqlab-91, MH-97). Five varieties, Shafaq-06, Lasani-08, AARI-11, Millat-11 and Galaxy-13 from these crosses have been approved for general cultivation. Essentially, the material developed and circulated by CIMMYT, Mexico having this sort of resistance is being worldwide adopted. The simple sequence repeat markers (SSR) for above mentioned durable genes are accessible and can be used in early selection of superior varieties.

Genetic impact of Rht dwarfing genes on grain micronutrients concentration in wheat

Wheat is a major staple food crop providing about 20% of dietary energy and proteins, and food products made of whole grain wheat are a major source of micronutrients like Zinc (Zn), Iron (Fe), Manganese (Mn), Magnesium (Mg), Vitamin B and E. Wheat provides about 40% intake of essential micronutrients by humans in the developing countries relying on wheat based diets. Varieties with genetically enhanced levels of grain micronutrient concentrations can provide a cost-effective and sustainable option to resource poor wheat consumers. To determine the effects of commonly deployed dwarfing genes on wheat grain Zn, Fe, Mn and Mg concentrations, nine bread wheat (Triticum aestivum) and six durum wheat (T. turgidum) isoline pairs differing for Rht1 (=Rht-B1b) and one bread wheat pair for Rht2 (=Rht-D1b) dwarfing genes were evaluated for three crop seasons at N.E. Borlaug Research Station, Cd. Obregon, Sonora, Mexico. Presence of dwarfing genes have significantly reduced grain Zn concentration by 3.9ppm (range 1.9-10.0ppm), and Fe by 3.2ppm (range 1.0-14.4ppm). On the average, about 94ppm Mg and 6ppm Mn reductions occurred in semidwarf varieties compared to tall varieties. The thousand kernel weight (TKW) of semidwarf isolines was 2.6g (range 0.7-5.6g) lower than the tall counterparts whereas the plant height decreased by 25cm (range 16–37cm). Reductions for all traits in semidwarfs were genotype dependent and the magnitude of height reductions did not correlate with reductions in micronutrient concentrations in wheat grain. We conclude that increased grain yield potential of semidwarf wheat varieties is associated with reduced grain micronutrient concentrations; however, the magnitude of reductions in micronutrients varied depending on genetic background and their associated pleiotropic effect on yield components.

Assessment of yield and economics of vegetables as intercropping system in coconut garden for additional returns

A field experiment was conducted on assessment of yield and economics of vegetables as intercropping system in coconut garden for additional returns at different villages of Tiptur taluk, Tumkur districts of Karnataka during from 2013 to 2015 to study the influence of intercropping system on coconut yield, economics of coconut based intercropping system with vegetables and the soil fertility status of coconut garden. The experiment consisted of three different intercropping systems viz., coconut sole cropping as farmers practice (T 1 ), coconut+vegetable cowpea (T 2 ) and coconut+French bean (T 3 ) with seven replications at farmers field in a 36 year old coconut garden of Tiptur tall variety planted at 9m × 9m spacing. The average three year results of experiments were recorded. The yield of coconut was found to higher nut yield (9594 nuts/ha/year) under french bean as intercrop in coconut garden followed by cowpea as intercrop in coconut garden (9348 nuts/ha/year) during third year. Whereas lowest nut yield was recorded in coconut sole crop in farmers practice. The highest net annual income Rs. 99,720/ha and B:C 3.22 were recorded in coconut+French bean intercropping system with more additional income and market demand of beans followed by coconut+vegetable cowpea (Net annual income Rs. 84,260/ha and B:C 3.10) with less market demand of vegetable cowpea, where as lowest net annual income Rs. 43,107/ha and B:C 2.34 were recorded in coconut sole cropping with no additional income from the farmers practices. The soil fertility status viz ., NPK availability in soil were analyzed before and after the experimental period of three year. Gradually increased N, P and K content of soil in coconut intercropping with beans and cowpea on far with each other, but lowest soil fertility were recorded in coconut as sole cropping system in farmers practices due to high biomass of french bean and cowpea, which fixes atmospheric nitrogen, residue incorporated into soil and suppression of weed growth results in improvement of soil fertility status. Higher net returns and improve the soil fertility by growing the french bean as intercrops in coconut garden is more suitable cropping system to boost economy of farmers.

Kriteria planlet kelapa kopyor yang siap untuk diaklimatisasi [Criteria of kopyor coconut plantlets ready to be acclimatized

Kopyor coconut is a special coconut grown in Indonesia. Nuts of kopyor can not be used as a source of planting material due to its endosperm damage; therefore in vitro embryo rescue technique is applied to propagate kopyor coconuts. Acclimatization is a critical stage during in vitro culture of kopyor coconut. Experiments were conducted to determine the effect of plantlet initial conditions prior to acclimatization on survival and growth in ex vitro conditions. Five replications of 50 plantlets of tall variety of kopyor coconut with different shoot and root conditions were used in the acclimatization process. The coconut plantlets were planted on plastic pots containing a mixture of soil, sand and dung manure, and then placed inside a closed plastic tunnel. The tunnel was opened gradually after 3 months and the plants were transferred to the nursery after 4.5 months. Survival frequency and growth (plant height, leaf number and shoot diameter) of the plantlets were observed after 6 months of acclimatization period. Research results show that the initial plantlet height and initial root length affected significantly the survival rate and growth of the plantlets of kopyor coconut during acclimatization. Other parameters of plantlet initial conditions such as leaf number, stem diameter, primary root number, and the existence of secondary roots did not influence the survival rate and growth of the plantlets. In order to obtain high survival rate (84.7%) and good growth of plantlets during acclimatization, the plantlet height must be at least 20 cm prior to acclimatization. Differences in root length on plantlets with the height of 20 cm or more, did not affect survival percentage of the vitroplants.

Kriteria planlet kelapa kopyor yang siap untuk diaklimatisasi [Criteria of kopyor coconut plantlets ready to be acclimatized

Kopyor coconut is a special coconut grown in Indonesia. Nuts of kopyor can not be used as a source of planting material due to its endosperm damage; therefore in vitro embryo rescue technique is applied to propagate kopyor coconuts. Acclimatization is a critical stage during in vitro culture of kopyor coconut. Experiments were conducted to determine the effect of plantlet initial conditions prior to acclimatization on survival and growth in ex vitro conditions. Five replications of 50 plantlets of tall variety of kopyor coconut with different shoot and root conditions were used in the acclimatization process. The coconut plantlets were planted on plastic pots containing a mixture of soil, sand and dung manure, and then placed inside a closed plastic tunnel. The tunnel was opened gradually after 3 months and the plants were transferred to the nursery after 4.5 months. Survival frequency and growth (plant height, leaf number and shoot diameter) of the plantlets were observed after 6 months of acclimatization period. Research results show that the initial plantlet height and initial root length affected significantly the survival rate and growth of the plantlets of kopyor coconut during acclimatization. Other parameters of plantlet initial conditions such as leaf number, stem diameter, primary root number, and the existence of secondary roots did not influence the survival rate and growth of the plantlets. In order to obtain high survival rate (84.7%) and good growth of plantlets during acclimatization, the plantlet height must be at least 20 cm prior to acclimatization. Differences in root length on plantlets with the height of 20 cm or more, did not affect survival percentage of the vitroplants.

Association Mapping in Scandinavian Winter Wheat for Yield, Plant Height, and Traits Important for Second-Generation Bioethanol Production.

A collection of 100 wheat varieties representing more than 100 years of wheat-breeding history in Scandinavia was established in order to identify marker-trait associations for plant height (PH), grain yield (GY), and biomass potential for bioethanol production. The field-grown material showed variations in PH from 54 to 122 cm and in GY from 2 to 6.61 t ha-1. The release of monomeric sugars was determined by high-throughput enzymatic treatment of ligno-cellulosic material and varied between 0.169 and 0.312 g/g dm for glucose (GLU) and 0.146 and 0.283 g/g dm for xylose (XYL). As expected, PH and GY showed to be highly influenced by genetic factors with repeatability (R) equal to 0.75 and 0.53, respectively, while this was reduced for GLU and XYL (R = 0.09 for both). The study of trait correlations showed how old, low-yielding, tall varieties released higher amounts of monomeric sugars after straw enzymatic hydrolysis, showing reduced recalcitrance to bioconversion compared to modern varieties. Ninety-three lines from the collection were genotyped with the DArTseq® genotypic platform and 5525 markers were used for genome-wide association mapping. Six quantitative trait loci (QTLs) for GY, PH, and GLU released from straw were mapped. One QTL for PH was previously reported, while the remaining QTLs constituted new genomic regions linked to trait variation. This paper is one of the first studies in wheat to identify QTLs that are important for bioethanol production based on a genome-wide association approach.

Nitrate assimilation in wheat plants depending on nitrogen nutrition and environmental conditions

Under conditions of a pot experiment, the authors assessed the effect of various environmental conditions: three levels of nitrogen nutrition and temperature and light conditions on assimilation of nitrates in wheat plants differing in stem height. It is found that the need for nitrates in short-stemmed varieties is lower than in tall varieties under favorable temperature and light conditions in connection with the lower value of biomass in those plants.

Production Technology for Kopyor Coconut Seednuts and Seedlings in Indonesia

Kopyor coconut is a naturally-occurring mutant having fluffy solid endosperm in stead of the normal one. Similar type of coconut has been found in several other Asian countries, with their distinct local names, such as Macapuno (Philippines), Makhrao Kathi (Thailand), Dikiri Pol (Sri Lanka), Thairu Thengai (India). It is a delicacy coconut to Indonesian and sells as much as ten times higher than normal coconut. In nature, three types of kopyor coconut exist in Indonesia: kopyor tall, kopyor dwarf, and kopyor hybrid. There are three kopyor dwarf varieties (‘Pati Kopyor Green Dwarf’, ‘Kopyor Yellow Dwarf’ and ‘Kopyor Brown Dwarf’) officially released, and one registered tall variety (‘Puan Kalianda Kopyor Tall’). In general, kopyor fruit yield under natural conditions is only < 25% of the total harvested fruits for both the tall and the dwarf types. Traditionally, Indonesian farmers harvest kopyor fruits at ten months after pollination while normal fruits at 11 months. They use the harvested normal fruits for propagation; but cannot guarantee whether or not they would produce korpyor fruit. Adoption of kopyor seedling production through embryo culture has been done. However, the seedling production is slow, while the price is very expensive, thus unaffordable to common farmers. Indonesian Palm Research Institute and Bogor Agricultural University have collaborated to develop alternative approaches to increase kopyor fruit production through the production of seedling that would ensure to produce korpyor fruit through control pollination. Initiated since 2010, the activities successfully overcome uncertainty in kopyor seedling production. Moreover, hybridization among local superior coconut varieties and known kopyor one have been done to broaden genetic background of kopyor trait and to develop breeding population for new kopyor varieties in the future. Overview and update of research progress on korpyor in Indonesia are presented in this paper.

Gibberellic acid-insensitive semi-dwarfs of Triticum dicoccum have delayed aleurone function

Aleurone tissue is known for its function of secreting a number of hydrolytic enzymes including α-amylases, nucleases and proteases in response to gibberellic acid (GA). The effect of GA on aleurone tissue function was studied in Triticum dicoccum including a tall variety, its semi-dwarf mutant and a semi-dwarf variety carrying RhtB1b allele, using isolated aleurone layers. A comparison of the tall and semi-dwarfs revealed that there was a decrease in the amount of α-amylase secreted and also a delay in its stimulation in the two semi-dwarfs. α-Amylase secretion exhibited a peak when the amount of α-amylase activity secreted was plotted as a function of time interval. The semi-dwarfs showed a delay in the appearance of the peak indicating that there was a delay in their response to GA treatment. Presence of GA also caused increased aleurone mitochondrial activity and enhanced loss of nitrogen and dry weight. Delays were also observed in time required to attain the peaks of the mitochondrial activity of the aleurone layer, total protein secreted in the medium, total loss in nitrogen and dry weight from the aleurone layer. The pattern of aleurone function was similar in both the semi-dwarfs, however, there was a greater delay in aleurone function in the new mutant as compared to the RhtB1b semi-dwarf. The altered GA signaling due to mutation(s) in the two GA insensitive semi-dwarfs may have resulted in a delay in attaining peak activity of the aleurone layers.

High frequency occurrence of soft endosperm mutantMacapunococonuts in Andaman Islands and their embryo culture

A relatively high frequency occurrence of mutant soft endosperm coconuts called “Dahi nariyel” in the Andaman Ordinary Tall variety is reported. These coconut types are similar to the popular “macapuno” coconuts. Embryo culture is the only method to propagate such novel mutants. We generated few plantlets in Y3 media through embryo rescue. Germination of embryo commenced in a month's time and the seedlings got developed into a three leaf stage plantlet in about 9 months. The scope of these coconut types for the islands and local prosperity is presented.

Zygotic embryo in vitro culture of Cocos nucifera L. (sv. East African Tall variety) in the coastal lowlands of Kenya

In vitro embryo culture of Cocos nucifera L. was carried out with the aim of determining whether it can be applied as an alternative coconut propagation tool to address the lack of planting materials in Kenya. Zygotic embryos excised from mature healthy pyrenes of high yielding Cocos nucifera L. (sv. East African Tall, a coconut variety from Kenya) were cultured using Murashige and Skoog (MS) culture medium supplemented with plant growth regulators (PGRs) namely 6-benzyl aminopurine (BAP) (0.5 mg/l), naphthalene acetic acid (NAA) (0.5 mg/l), 2,4 dichlorophenoxyacetic acid (2,4-D) (1.7 mg/l) and indole butyric acid (IBA) (1.7 mg/l). Germination of 84 and 27% embryos were recorded in liquid and semi-solid MS medium, respectively. Embryo cultured in liquid medium and incubated in darkness during the initial four weeks resulted in a germination percentage of 80% while incubation in light resulted in only 30% germination. MS medium was also supplemented with 100, 25, 15 and 0% (v/v) coconut water (CW). Embryo germination was 60% in medium supplemented with 15% (v/v) coconut water although 0% (v/v) gave the highest germination rate at 67%. Medium supplementation by 1.7 mg/l 2,4-D PGR resulted in germination of 30% when plant growth regulator was co-autoclaved and 84% when plant growth regulator was sterilized by microfiltration. The results presented in this study indicate that in vitro micropropagation of the Kenyan variety of Cocos nucifera L. is a feasible alternative. Keywords : Cocos nucifera L., in vitro embryo culture, east African tall (EAT) Kenyan variety, zygotic embryo African Journal of Biotechnology Vol. 12(22), pp. 3435-3440

Evaluation of Variety, Cropping Pattern and Plant Density on Growth and Yield Production of Grain Sorghum -Cowpea under Limited Water Supply Condition Growth, yield and yield component characters of Sorghum

An intercropping experiment of sorghum/cowpea intercrops was carried out in summer season of 2009 and 2010 at Agricultural and Research Station, College of Food Science and Agriculture, King Saud University. The main objective of the study was to evaluate the growth and yield potential of sorghum/cowpea intercrops over sole cropping pattern. The experiments included 18 treatments three sorghum varieties, i.e., two semi dwarfs (Pioneer and S-1007) and a tall one local variety (Shahlaa), theses varieties were planted in two cropping patterns as solid culture at the densities of 200, 300 and 400 10 3 plants/hectare for semi dwarfs varieties, whereas tall variety at 160,240 and 320 10 3 plants/hectare. These densities for the three varieties are equal to 100, 150 and 200 % of the solid recommended culture .The intercropping was alternating two rows of grain sorghum with other rows of cowpea (2 & 2) pattern. The data obtained indicated that sorghum plants, when intercropped with cowpea, exhibited greater potentiality and recorded higher values of most of the studied criteria viz., plant height, number of leaves per plant, stem diameter, leaf area, dry matter accumulation and grain yield /plant .Grain yield per hectare was lower in intercropping pattern than solid pattern. The increase in grain yield per plant and plant density could not compensate the decrease of the area occupied by the crop under solid culture.

Nitrogen fertilization effects on grain quality of durum wheat (<i>Triticum turgidum</i> L. var. durum) varieties in central Ethiopia

Four released durum wheat varieties, two medium tall (Arsi-Robe and Kilinto) and two recently released semidwarfs (Ude and Yerer) were evaluated under five different N rates (0, 60, 120, 180 and 240 kg·ha-1) in 2005/06 growing season at Akaki and Debre Zeit, central Ethiopia. The quality responses of durum wheat varieties to different N-fertilizer rates and the N responses between tall and short durum wheat varieties were assessed. Protein and gluten content, vitreous kernel count, thousand kernel weight, test weight and lodging were considered. Vitreous kernel count, protein and gluten content were higher at Debre Zeit than at Akaki. Unlike Debre Zeit, there were significant relationships between response variables and fertilizer levels at Akaki. Lodging slightly affected the medium tall varieties at Debre Zeit whereas it was not a problem at Akaki. At Akaki, varieties response to each additional N rate was entirely below the quality standard set by ICC, 2000 except for thousandkernel weight. Therefore, it is unwise to promote durum wheat scaling up/out program for quality production at Akaki.

Performance of Tomato Varieties during Rainy Season under Plastic House Conditions

Plastic house technology and arrival of hybrid varieties have increased the possibility of tomato cultivation in rainy season in high hills. An experiment was conducted to assess the performance of tomato varieties under plastic house for two consecutive years from 2009 to 2010 at National Commercial Agriculture Research Program (NCARP), Pakhribas (1750m), Nepal. The experiment consisted of eight tomato varieties namely, All Rounder, Bishesh, Dalila, Manisha, Srijna, Suraksha, Trishul and US-04 laid out in a randomized complete block design with three replications. The varieties differed significantly for all observed traits. The highest marketable yield was recorded from All Rounder (86.6 t ha-1) followed by Srijana (80.8 t ha-1). Srijana took the shortest period for flowering and harvesting with an average of 37 and 77 days after transplanting respectively. This was also the tallest variety (268.7 cm) with more clusters (36.23) per plant. However, the highest average single fruit weight was recorded from Manisha (61.94g), and the largest fruit size in US-04 with a diameter of 5.78 cm. Based on yield parameter, the varieties All Rounder and Srijana are recommended for commercial cultivation under plastic house conditions.DOI: http://dx.doi.org/10.3126/njst.v12i0.6473 Nepal Journal of Science and Technology 12 (2011) 17-22

Study of the genetic variation of tall fescue varieties using AFLP markers

Peu d’informations sont disponibles sur la variabilite genetique chez les fetuques elevees ( Festuca arundinacea Schreb). Ces renseignements sont importants pour la cartographie genetique des populations pour cibler la collecte de germoplasme et son utilisation en croisement. L’objectif de cette etude etait d’evaluer la diversite genetique de sept varietes de fetuque elevee de diverses origines. L’evaluation etait basee sur l’analyse du polymorphisme de longueur des fragments amplifies (AFLP), revelee par la methode de marquage fluorescent et en utilisant des echantillons d’ADN en bulk. Sur la base des 105 marqueurs AFLP ( amplified fragment length polymorphism) obtenus par deux combinaisons d’amorces, les sept varietes testees ont ete regroupees selon leurs origines geographiques. Fraydo et Lutine sont genetiquement les plus divergentes, Tanit et Sisa presentent une grande similitude genetique ; alors que Centurion est d’une structure genetique tres proche des varietes Flecha et Flecha endophyte (E542) ; mais tres eloignee genetiquement de la variete Lutine bien que Lutine et Centurion soient des obtentions du meme institut (Institut national de la recherche agronomique [Inra]).

Overview of the Epidemiology of Coconut Lethal Yellowing Disease (LYD) in Malayan Yellow Dwarf x Vanuatu Tall (MYD x VTT) Hybrids in the Western and Central Regions of Ghana

The Ghanaian form of lethal yellowing disease (LYD) of coconut is known as the Cape Saint Paul Wilt Disease (CSPWD). The disease is caused by phytoplasmas, and has been active in the country since 1932. The study was conducted to update the disease situation among Malayan Yellow Dwarf x Vanuatu Tall (MYD x VTT) hybrids in the Western and Central Regions of Ghana. It was also to compare the level of LYD susceptibility in the local West African Tall (WAT) variety and the MYD x VTT hybrid, recommended for replanting under the Coconut Sec-tor Development Project (CSDP). Structured survey questionnaires were administered for 15 months to obtain information on every CSPD coconut farm. Categories of data included: farm identity, hydrography, topography, soil properties, agronomic and ecological condition, and dis-ease situation around each coconut farm. Losses to LYD were higher in the Central Region than in the Western Region. Overall, only 4.8 % of total hectarage of MYD x VTT coconut plantings have been affected by the disease as at December, 2009. LYD incidence was significantly higher in the WAT variety than the MYD x VTT hybrids. Mathematical calculations also showed that, the epidemic rate (r) of LYD was higher in the WAT variety than the MYD x VTT hybrids. There was variation in disease incidence and severity in MYD x VTT hybrids between the different co-conut growing areas. The susceptibility of the MYD x VTT hybrids under intense disease pres-sure calls for the screening of more coconut varieties, to identify truly resistant types to the lethal yellowing disease.

Circular neighbour-balanced designs and one-sided circular neighbour-balanced designs

In most block designs for agricultural experiments, the nature of the yield underlying treatments may reach such a stage that the treatment received by a plot may influence the response on the neighbouring plots of the same block or sometimes it may influence the response only on the following plot. As an example of the second type, the tall varieties may affect the crops grown on the neighbouring plots by their shades. Bailey (J Indian Soc Agric Stat 56(3):302–314, 2003) has developed a type of design concerned with the study of one sided neighbour effects for application under such conditions. This paper gives, introducing a lemma, constructions of new series of (i) Circular Neighbour-Balanced designs and (ii) One-sided Circular Neighbour-Balanced designs.

Inheritance and identification of molecular markers associated with a novel dwarfing gene in barley

BackgroundDwarfing genes have widely been used in barley breeding program. More than 30 types of dwarfs or semidwarfs have been reported, but a few has been exploited in barley breeding because pleiotropic effects of dwarfing genes cause some undesired traits. The plant architecture of newly discovered dwarfing germplasm "Huaai 11" consisted of desirable agronomic traits such as shortened stature and early maturity. Genetic factor controlling the plant height in dwarf line Huaai 11 was investigated.ResultsThe Huaai 11 was crossed with tall varieties Monker, Mpyt, Zhenongda 3, Zaoshu 3, Advance, Huadamai 1, Huadamai 6, Hyproly and Ris01508. All the F1 plants displayed tall trait. Both tall and dwarf plants appeared in all the F2 populations with a 3:1 segregation ratio, suggesting that dwarfism of Huaai 11 is controlled by a single recessive gene, btwd1. Allelism test indicated that this dwarfing gene in the Huaai 11 is nonallelic with the gene br, uzu, sdw1 and denso. Using a double haploid population derived from a cross of Huadamai 6 and Huaai 11 and SSR markers the novel dwarfing gene was mapped onto the long arm of chromosome 7H, and closely linked to Bmac031 and Bmac167 with genetic distance of 2.2 cM.ConclusionHuaai 11 is a new source of dwarf for broadening the genetic base of dwarfism. This dwarf source was controlled by a recessive dwarfing gene btwd1, was mapped onto the long arm of chromosome 7H.

Abscission of Control Pollinated Coconut Fruits: Preliminary Investigations into the Possible Role of Ethylene

Recent advances in the spread of the Cape St Paul Wilt disease (CSPWD) necessitate a more rapid development of tolerant coconut types. Control pollination is the main method for producing legitimate coconut seeds for such breeding purposes. However, the process of bagging causes severe nut drop or abscission. Many scientists have implicated hormones as the primary regulators of organ abscission; with ethylene being particularly implicated. Unlike other plant hormones, which are mainly produced in other parts and transported to influence target organs, the production of ethylene could be initiated within the same organ, such as the fruit. This study was therefore undertaken to investigate the possible involvement of ethylene in abscission after control pollination. Pollen from Vanuatu Tall (VTT) variety was used to cross emasculated Malayan Yellow Dwarf (MYD) inflorescence after isolation with bags. Trials were laid out in Completely Randomised and Split Plot designs, with specified replications. Two ethylene inhibitors, namely aminoethoxyvinylglycine (AVG) and silver thiosulphate (STS) were used. Five concentrations of AVG ranging from 2mg/l to 30mg/l were applied to inflorescences during and after bagging. AVG concentrations higher than 2 mg/l resulted in significant reduction in abscission. Fruit yields up to five times that of ordinarily bagged treatments without AVG were recorded. Four concentrations of STS ranging between 0.5mM – 10mM applied in similar manner, however, did not result in any significant reduction in abscission. The results from AVG application strongly suggest the involvement of ethylene in the abscission of control pollinated coconut fruits.

Nitrogen efficiency of wheat: Genotypic and environmental variation and prospects for improvement

Winter wheat ( Triticum aestivum L.) was grown for 4 years in multi-factorial field trials at Rothamsted, southern England. Thirty nine elite commercial cultivars (primarily short-straw) were grown including those released in the UK over a 25-year period, a selection of continental varieties, and three older, tall varieties. Varieties spanned the quality spectrum from ‘bread’ to ‘feed’. The crops were given ammonium nitrate at five rates in the range 0–350 kg-N/ha as a 3-way split. The aim was to quantify the genotypic variation in total nitrogen uptake by grain and straw (total-Nup), and in nitrogen utilization efficiency for grain yield (grain yield per unit of N taken up) (grain-NutE). Depending on treatment, grain yield ranged from 2.1 to 11.8 t/ha (85% DM), grain %N from 1.1% to 2.8% (in DM), total-Nup from 31 to 264 kg-N/ha, and grain-NutE from 27 to 77 kg-DM/kg-N. There were significant varietal differences in total N-uptake and grain-NutE both between ‘tall’ and ‘short’ varieties and within ‘short’ varieties. The best short varieties took up 31–38 kg/ha more N than the worst, and grain-NutE was 24–42% better, depending on N-rate. Up to 77% of the variation in grain-NutE was accounted for by yield. All interactions between the factors ‘Variety’, ‘Year’, and ‘N-rate’ were highly significant, but only ‘Year × N-rate’ made an important contribution to the variation. There was a near-functional inverse relationship between grain-NutE and grain %N; high-quality wheat (high grain %N) can be expected to have a low grain-NutE. The four key variables determining N-efficiency in a wheat crop – grain yield, grain %N, total N-uptake and nitrogen harvest index (NHI) – are ultimately constrained by the law of conservation of matter. Improving grain-NutE for fixed total-Nup and NHI can only be achieved at the expense of grain %N. To improve grain-NutE and maintain grain %N requires a simultaneous increase in NHI and grain starch yield which may be difficult to achieve in practice. The law of conservation of matter ultimately sets a limit on the physiological and agronomic processes that determine crop N requirements. A high yield of high-quality grain (high grain %N) requires a high input and uptake of nitrogen.