Rapid estimation of taro (Colocasia esculenta) quality by near-infrared reflectance spectroscopy

The aim of the present study is to develop a methodology for the rapid estimation of taro (Colocasia esculenta) quality. Chemical analyses were conducted on 315 accessions for major constituents (starch, total sugars, cellulose, proteins, and minerals). NIRS calibration equations, developed on a calibration set composed of 243 accessions, showed high explained variances in cross-validation (r(2)(cv)) for starch (0.89), sugars (0.90), proteins (0.89), and minerals (0.90) but poor response for amylose (0.44) and cellulose (0.61). The predictions were tested on an independent set of 58 randomly selected accessions. The r(2)(pred) values for starch, sugars, proteins, and minerals were, respectively, of 0.76, 0.74, 0.85, and 0.85 with ratios of performance to deviation (RPD) of 3.41, 4.01, 3.78, and 3.64. New calibration equations developed on 303 accessions confirmed good RPD values for starch (3.30), sugars (4.13), proteins (3.61), and minerals (3.74). NIRS could be used to predict starch, sugars, proteins, and minerals contents in taro corms with reasonably high confidence.     

Quantitative determination of NPK uptake requirements of taro (Colocasia esculenta (L.) Schott)

Taro yield in many parts of the world is stagnant mainly due to conventional blanket recommendation of fertilizers, lower nutrient use efficiency and imbalance in the use of nutrients. The Quantitative Evaluation of Fertility of Tropical Soils (QUEFTS) model was used for determining the region specific balanced NPK uptake requirements and recommendations for a target yield of taro. The constants for minimum and maximum accumulation (kg cormel kg^?1 nutrient) of N (33 and 177), P (212 and 606) and K (25 and 127) were derived as standard model parameters. The results showed that taro requires N, P and K accumulation of 12.97, 2.75 and 17.47?kg t^?1 of cormel yield, suggesting an average NPK ratio in the plant dry matter of about 4.7:1:6.4. The NPK fertilizer requirements for different potential yield situations were also calculated. The results need to be validated in major taro growing regions.     

Diversity of 21 taro (Colocasia esculenta (L.) Schott) accessions of Andaman Islands

The genetic diversity of taro (Colocasia esculenta (L.) Schott.) accessions growing naturally in Andaman Islands was analysed using morphological and DNA markers. Twenty one representative samples of C. esculenta from different parts of Islands in addition to three commercial varieties as reference genotypes were used in study. About 63% phenotypic variation was observed in C. esculenta A total number of 491 amplified fragments were obtained of which 347 showed polymorphic banding patterns. The accessions were grouped into two major clusters with both RAPD and ISSR markers with 56 and 57% diversity, respectively. The reference genotypes were grouped into one group and island population in other cluster. Both marker systems divided population into two sub clusters and showed correlation with morphological parameters. The diversity pattern observed in present study showed rich genetic diversity of C. esculenta in Andaman Islands provided simple strategy for reducing repeatability of taro germplasm in gene banks. The study also suggested pre-evaluation of germplasm using molecular and morphological markers to enhance efficiency of exploration trips.     

Identification and characterization of SSR markers in taro [Colocasia esculenta (L.) Schott] by RAD sequencing

Genetic Resources and Crop Evolution - Taro [Colocasia esculenta (L.) Schott] is an old crop with high genetic diversity. However, the breeding of taro is limited by the lack of well-developed...     

Genetic data confirms field evidence for natural breeding in a wild taro population (Colocasia esculenta) in northern Queensland, Australia

Taro (Colocasia esculenta) is a vegetatively propagated, starchy root crop cultivated in tropical to temperate regions of the world. Wild forms of taro are distributed from India to southern China, Australia and Melanesia. They are widely known wild food or fodder sources, including in Aboriginal Australia, so it is unclear to what extent wild populations have been dispersed by humans, or naturally via insect-borne pollen and seed dispersal by birds or other animals. In Australia, pollinators and seedlings of taro have not been reported, and a key question is whether or not the wild taro there can breed naturally. Here we report field observations of flowering, fruit set, and an insect pollinator (Colocasiomyia, pupal stage), in a historically significant wild taro population at Hopevale in northern Queensland. The observed pupa is congeneric with two pollinating fly species that have a highly specialised, probably coevolutionary, relationship with taro in neighbouring Papua New Guinea. The field observations suggested the possibility of natural breeding at Hopevale. By analyzing microsatellite diversity within the Hopevale taro population, we found high genetic variation overall, indicative of multiple founding individuals. Two sublocations showed low genetic diversity and strongly negative inbreeding coefficients, consistent with predominantly clonal (vegetative) reproduction. A third sublocation showed high genetic diversity and a weakly negative inbreeding coefficient, indicative of sexual reproduction. This difference between sublocations may relate to microenvironmental conditions that favour seedling establishment in some parts of the site. The data constitute the first demonstration that natural breeding and population spread occurs in Australian wild taro.     

Analysis of genetic diversity in Indian taro [Colocasia esculenta (L.) Schott] using random amplified polymorphic DNA (RAPD) markers

Taro [Colocasia esculenta (L.) Schott] germplasm accessions collected from different parts of India were subjected to RAPD (Random Amplified Polymorphic DNA) analysis to assess the genetic diversity prevalent and also to test the genetic basis of morphotypic classification. Thirteen random decamer primers out of the 22 tested were used to analyse 32 taro accessions belonging to 28 morphotypes. Three out of these thirteen primers analysed showed 100 per cent polymorphism. Per cent polymorphism varied from 60 to 100 among the polymorphic primers. High genetic diversity was revealed as the similarity coefficient values ranged from 0.50 to 0.98. No two accessions analysed in the present study showed a similarity coefficient value of one thereby indicating their distinctness and presence of high genetic diversity in Indian taro germplasm. Dendrogram obtained from UPGMA analysis grouped 32 accessions in four clusters and three accessions were placed as outliers. Clustering pattern did not show any strict relationship with geographical distribution, morphotype classification and genotypic diversity. Further, accessions classified, as belonging to the same morphotypic group did not always cluster together. Presence of a very close genepool of the wild, weedy and cultivated forms with extreme levels of phenotypic and genotypic variation is suggested as the reason for high genetic diversity reported. Usefulness of DNA markers such as RAPD in characterising and assessing the genetic diversity in Indian taro germplasm is hereby demonstrated.     

Nature of taro (Colocasia esculenta (L.) Schott) genetic diversity prevalent in a Pacific Ocean island, Vanua Lava, Vanuatu

Taro (Colocasia esculenta (L.) Schott), cultivated in Vêtuboso, a village of northern Vanuatu, Melanesia, was surveyed to: (1) assess the extent of morphological and molecular variation being maintained by growers at the village level and, (2) compare this diversity with the diversity found in the crops in Vanuatu. Ethnobotanical data were combined with AFLP analysis to elucidate possible sources of variation. Folk assessment of variation is based on: (a) morphological characteristics (11 characters), (b) names and (c) classification according to habitat, uses, origin and agronomic adaptation. This 3-fold approach allowed growers to differentiate 96 morphotypes, all of which are given distinct vernacular names. AFLP fingerprints successfully differentiated all these 96 morphotypes which do not present a significant intra-clonal variation. But genetic results showed no clear groupings according to geographic origin or habitat of morphotypes and stated that the diversity found within the village was comparable with the overall diversity found in Vanuatu. Local nomenclature and stories associated with each cultivar suggested three sources of diversity: introductions (38%), somatic mutations (15%) and sexual recombinations (48%). AFLP results confirm folk beliefs about origin at least for three pairs of mutants. The 11 so-called wild forms analysed by AFLP were suggested to be feral, escapes from domestication. A dynamic in situ conservation strategy (DISC), favouring a broadening of the national genetic base, was discussed for taro.     

Genetic diversity of taro (Colocasia esculenta (L.) Schott) in Vanuatu (Oceania): an appraisal of the distribution of allelic diversity (DAD) with SSR markers

In Vanuatu, an oceanic archipelago located in south-west Pacific, taro (Colocasia esculenta (L.) Schott) is one of the staple crops. An eco-geographical survey of its genetic resources was conducted in ten villages, each located on a different island. A sample of 344 landraces referred as the National Sample (NS) was collected. Its genetic diversity was assessed using nine microsatellites markers and then was compared with an International Core Sample (ICS) that was previously distributed in the ten villages of the study in order to test the geographical distribution of allelic diversity as an effective mean for the on-farm conservation of root crops. The ICS was composed of 41 accessions, including 23 originating from South-East Asia. The molecular dataset revealed in the NS (1) 324 distinct multilocus genotypes, (2) six genetic clusters mainly differentiated by rare alleles, (3) a geographical structure of the genetic resources of taro based, within each village, on the dominance of one or two of these clusters rather that their exclusivity, and (4) an analogy between the patterns of dominant clusters between villages and the past and present social networks. In addition, accessions from the ICS revealed 52 new alleles. Based on these findings, we formulate hypotheses regarding the processes involved in the genetic diversification of taro in Vanuatu. We also discuss the use of this set of microsatellite markers along with the molecular dataset obtained from this study as effective tools to monitor the diversity and evolution of taro in the future.     

Molecular degradation rate of rice and corn starches during acid-methanol treatment and its relation to the molecular structure of starch

The degradation rates of rice and corn starches with different contents of amylose treated in methanol containing 0.36% HCl at 25 degrees C for 1-15 days were evaluated by monitoring the weight average degree of polymerization of starch. A two-stage degradation pattern during acid-methanol treatment was found for the starches studied, which were the slow (first) and the rapid (second) degradation stages. Waxy starches showed a shorter time period of the first stage than that of nonwaxy starch. Rice starch showed a shorter time period of the first stage and a higher degradation rate of the second stage than the counterpart corn starch with similar amylose content. Despite the botanic source and amylose content of starch, the degradation rate of starch in the second stage significantly (p < 0.05) correlated to the S/L ratio (r = -0.886) and polydispersity (r = 0.859) of amylopectin branch chains of native starch.     

Discovery of an amylose-free starch mutant in cassava (Manihot esculenta Crantz)

One of the objectives of the cassava-breeding project at CIAT is the identification of clones with special root quality characteristics. A large number of self-pollinations have been made in search of useful recessive traits. During 2006 harvests an S1 plant produced roots that stained brownish-red when treated with an iodine solution, suggesting that it had lower-than-normal levels of amylose in its starch. Colorimetric and DSC measurements indicated low levels (3.4%) and an absence of amylose in the starch, respectively. SDS-PAGE demonstrated the absence of GBSS enzyme in the starch from these roots. Pasting behavior was analyzed with a rapid visco-analyzer and resulted in larger values for peak viscosity, gel breakdown, and setback in the mutant compared with normal cassava starch. Solubility was considerably reduced, while the swelling index and volume fraction of the dispersed phase were higher in the mutant. No change in starch granule size or shape was observed. This is the first report of a natural mutation in cassava that drastically reduces amylose content in root starch.     

Plantain and banana starches: granule structural characteristics explain the differences in their starch degradation patterns

Different banana cultivars were used to investigate the influences of starch granule structure and hydrolases on degradation. The highest degrees of starch degradation were observed in dessert bananas during ripening. Scanning electron microscopy images revealed smooth granule surface in the green stage in all cultivars, except for Mysore. The small and round granules were preferentially degraded in all of the cultivars. Terra demonstrated a higher degree of crystallinity and a short amylopectin chain length distribution, resulting in high starch content in the ripe stage. Amylose content and the crystallinity index were more strongly correlated than the distribution of amylopectin branch chain lengths in banana starches. α- and β-amylase activities were found in both forms, soluble in the pulp and associated with the starch granule. Starch-phosphorylase was not found in Mysore. On the basis of the profile of α-amylase in vitro digestion and the structural characteristics, it could be concluded that the starch of plantains has an arrangement of granules more resistant to enzymes than the starch of dessert bananas.     

Response of Mycorrhiza,Organic Sources,Secondary and Micro Nutrients on Soil Microbial Activities and Yield Performance of Colocasia (Colocasia esculenta L.) in Alfisols

Response of the integrated use of mycorrhiza, inorganic and organic manures on microbial variables and yield performance of colocasia (Colocasia esculenta L.) was studied in an acid Alfisol. Significantly highest mean cormel yield (14.13 t ha^?1) was recorded due to application of super optimal doses of nitrogen, phosphorus, and potassium (NPK). Integrated application of lime + farmyard manure (FYM) + ½ NPK + zinc sulfate (ZnSO₄) has recorded the highest dehydrogenase activity (2.048 µg TPF hr^?1 g^?1) and Fluorescein Diacetate Hydrolysis assay (1.855 µg g^?1 hr^?1). The highest acid and alkaline phosphatase activities (77.67 and 51.18 µg PNP g^?1 h^?1, respectively) were observed due to Vesicular Arbuscular Mycorrhiza (VAM) inoculation in combination with lime + FYM + ½ NPK. Dehydrogenase and phosphatase activities had a highly significant relationship with cormel yield and the biochemical constituents of colocasia. The study emphasized the conjunctive use of balanced inorganic fertilizers and organic manures to enhance the enzymatic activities and to realize higher crop yields of colocasia in acid Alfisols.     

Evaluation and selection of taro [Colocasia esculentra (L.) Schott] accessions under dryland conditions in South Africa

Taro [Colocasia esculenta (L.) Schott] is an important underutilised staple food crop in South Africa, with a lot of potential to address food insecurity among poor rural households. Development of high yielding stable taro cultivars is one of the most important goals of plant breeders. Twenty-nine taro accessions collected from major taro producing regions of the country were evaluated for growth performance, yield potential and stability under dryland conditions at two sites (Umbumbulu and Roodeplaat) in 2013, 2014 and 2015 cropping seasons. The experiment was laid in a randomised complete block design replicated three times. Growth and yield traits were measured. Analysis of variance and correlation analysis was done on all measured traits. The genotype by environment interaction was analysed using additive main effects and multiplicative interaction (AMMI). As a result, significant variation was observed for most of the traits except number of leaves and leaf width as well as number of suckers, while all the traits showed significant variation for location by year interaction. Number of corms showed significant variation for location by year by genotype interaction among all the traits evaluated. Genotype effect was highly significant (p?<?.01) on plant height, corm length, number of corms and significant (p?<?.05) on yield. The significant difference between genotypes for these traits proves that there was a genetic variability and there is a scope for selection. The correlation study also reveals that majority of the characters were positively correlated with each other. Total yield was positively and highly significantly (p?<?.01) correlated with all the measured traits. AMMI was effective in identifying stable genotypes. The top ranking cultivars per environment may be considered for cultivation under the specific environment, the stable cultivars may be considered for cultivation across all the taro growing regions.     

Influence of storage conditions on the structure, thermal behavior, and formation of enzyme-resistant starch in extruded starches

Starch structures from an extrusion process were stored at different temperatures to allow for molecular rearrangement (retrogradation); their thermal characteristics (DSC) and resistance to amylase digestion were measured and compared. The structure of four native and processed starches containing different amylose/amylopectin compositions (3.5, 30.8, 32, and 80% amylose content, respectively) before and after digestion was studied with small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD). Rearrangement of the amylose molecules was observed for each storage condition as measured by the DSC endotherm at around 145 degrees C. The crystalline organization of the starches after processing and storage was qualitatively different to that of the native starches. However, there was no direct correlation between the initial crystallinity and the amount of enzyme-resistant starch (ERS) measured after in vitro digestion, and only in the case of high-amylose starch did the postprocess conditioning used lead to a small increase in the amount of starch remaining after the enzymatic treatment. From the results obtained, it can be concluded that retrograded amylose is not directly correlated with ERS and alternative mechanisms must be responsible for ERS formation.     

旱地不同小麦品种产量与干物质及氮磷钾养分需求的关系

【目的】 黄土高原是我国旱地小麦主要产区,但产量普遍偏低,明确不同小麦品种的产量与干物质及氮磷钾养分需求的关系,对高产高效小麦品种选育、科学合理施肥、实现区域小麦增产有重要意义。 【方法】 于2014和2015年,在黄土高原典型旱作雨养农业区种植来自我国不同主产区和当地的123个小麦品种,采集收获期的植株样品,测定了不同小麦品种的产量、干物质及氮磷钾养分累积和需求量,分析了产量与干物质及养分需求的关系。 【结果】 不同小麦品种的籽粒产量与生物量、收获指数、养分吸收量和养分收获指数均呈显著正相关,与干物质、需氮量、需磷量呈显著负相关。从两年的平均结果来看,当小麦籽粒产量从5474 kg/hm2增至7891 kg/hm2时,生物量从12194 kg/hm2增至17032 kg/hm2,收获指数从38%增至54%,地上部氮、磷、钾吸收量分别从159 kg/hm2增至231 kg/hm2、21.3 kg/hm2增至29.5 kg/hm2、79.1 kg/hm2增至136.9 kg/hm2,氮、磷、钾收获指数分别从62%增至83%、75%增至90%、20%增至37%。干物质需求量却从2611 kg/Mg降至1873 kg/Mg,氮、磷需求量也分别从35.1 kg/Mg降至23.7 kg/Mg、4.5 kg/Mg降至3.2 kg/Mg。品种间需钾量也随产量升高而降低,从19.9 kg/Mg降至11.9 kg/Mg,但产量与需钾量间并无显著负相关关系。 【结论】 旱地条件下,高产品种具有较高的生物量、收获指数、养分吸收量和养分收获指数,而干物质及养分需求量却较低。因此,在实际生产中,不仅要选育高产高效小麦品种,提高生物量,协调籽粒产量与生物量、养分吸收量和收获指数的关系,也要根据高产品种的养分需求规律,结合区域土壤养分供应能力和气候特点,科学合理施肥,保证作物有充足的养分吸收量,并向籽粒高效转移,使高产品种的产量潜力充分发挥。      

Response of soyabean (Glycine max Mer.) to wheat straw mulching in different cropping seasons

Abstract. The favoured temperature range for soyabean seed germination is 25–30 °C and the crop is sensitive to water stress. In northern India, the crop is sown in the hot-dry months of May–June. Straw mulching can alter the soil's hydrothermal regime by lowering the temperature and reducing evaporation losses. A field experiment was conducted from 1999 to 2002 at the Research Farm of Punjab Agricultural University, Ludhiana on a loamy sand soil to evaluate the effect of wheat straw mulch on soil temperature, soyabean seed yield and crop growth. Maximum soil temperatures at sowing depth, recorded during the 1-month period after sowing (seed germination to seedling establishment stage), were high under no-mulch, ranging from 30.6 to 48.6 °C, while mulching substantially reduced these temperatures by 1.4 to 12.7 °C. Mulching increased soyabean seed yield by 4.4 to 68.3% in different cropping seasons; it also increased plant biomass by 17 to 122% and nodule mass by 8 to 220%. Leaf area index, chlorophyll content of leaves and number of pods per plant were all increased. Seed yield improvement under mulch was negatively correlated with rainfall distribution (number of rainy days) and amount during the whole cropping season. The percentage increase in seed yield with mulching was regressed against the total number of rainy days and total rainfall in millimetres in the cropping season. Thereby 93% of the variation in response to mulching in different cropping seasons was explained by the distribution and amount of rainfall.