Effect of paddy variety,milling status and aeration on the progeny emergence of Sitophilus oryzae L. (Coleoptera: Curculionidae)

In Sri Lanka, insects cause enormous losses in stored paddy; the rice weevil Sitophilus oryzae is a devastating insect. The magnitude of losses in stored paddy caused by insects varies with characteristics of paddy but has not yet been fully investigated. Due to the increased concerns on the use of synthetic chemicals, safer alternative pest management strategies for stored paddy are needed. Objectives of this study were to determine the effect of paddy variety, milling status and nature of aeration on the progeny emergence of S. oryzae. The experimental design was a three-factor factorial, completely randomized design (CRD).Freshly emerged S. oryzae adults were introduced to un-milled paddy or milled/polished rice belonging to traditional and improved varieties. The samples were maintained either open or airtight, and the progeny adults emerged was determined at monthly intervals. Progeny emergence was lower in the traditional varieties, un-milled paddy and under air-tight condition compared to improved varieties, milled/polished rice and aerated samples, respectively. Overall, the improved variety Bg 300 exhibited the maximum resistance to infestation by S. oryzae. Furthermore, white-colour and long-grain varieties produced lower progeny of S. oryzae than red-colour and short-grain varieties, respectively. It is concluded that the maximum protection in paddy/rice from insect infestation during storage can be achieved by using traditional varieties, stored as un-milled paddy (without dehusked) under airtight condition.     

Impact of Rhyzopertha dominica (F.) on quality parameters of milled rice

The impact of Rhyzopertha dominica, the lesser grain borer, on milling quality of Francis and Wells cultivars of rough rice was assessed for the 2007 and 2008 crop years by infesting 200-g rough rice samples harvested at moderate and low moisture contents with 0, 10, 25, 50, and 100 parental adult insects, which were removed after one week. The samples were incubated for seven weeks at either 27 or 32 °C and 60% relative humidity to determine progeny production and feeding damage (insect frass), and subsequently the milled rice yield (MRY) and head rice yield (HRY). Progeny production from each parental density level varied with variety and temperature. The number of progeny produced by the parental adults was positively correlated with feeding damage, and the feeding damage caused by the progeny was in turn negatively correlated with MRY and HRY. For both years, more progeny production and feeding damage occurred in Francis versus Wells for each of the harvest moisture contents. Results show differential susceptibility of Francis and Wells cultivars to R. dominica, and also provide new methodologies for evaluating effects of infestation on rice milling quality.     

Hull characteristics as related to susceptibility of different varieties of rough rice to Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

Rhyzopertha dominica (F.), an important pest of stored grains, causes economic damage to rough rice through physical damage to the kernel, resulting in reductions in grain quality. In this test, 28 varieties of commercial rough rice (10 long grain, 11 medium grain, and 7 short grain) were examined for solid, split and cracked hulls, hull thickness, and adult emergence from neonate R. dominica introduced on each individual variety. The percentage of solid hulls ranged from 55.5% on Koshihikari variety to 92.8% on Akita variety, and the percentages of cracked and split hulls were correlated with increased susceptibility. The Dobie index for progeny production showed Wells, Jupiter, and Pirogue varieties as the most tolerant to R. dominica, while Rico and Francis were the most susceptible. The hull thickness of rough rice varied among varieties, but the tolerant varieties appeared to have thicker hulls than the susceptible varieties. There was no difference among rice types (long-, medium-, or short grain) regarding tolerance or susceptibility to R. dominica. Results show that the characteristics of the rough rice hull are important for conferring susceptibility of individual varieties to R. dominica.     

Effects of germination on the activities of amylases and phenolic enzymes in sorghum varieties grouped according to food end‐use properties

Fifty sorghum varieties were screened to determine the effects of germination on levels of starch, α‐amylase, β‐amylase, phenylalanine ammonia lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO). Germination decreased starch content, with amylose being more degraded than amylopectin. In germinated grain, α‐amylase activity increased several‐fold in all varieties, whereas β‐amylase activity did not increase uniformly and even decreased in some varieties. Activity of the key enzyme in phenolic biosynthesis, PAL, was detected in only half of the varieties before germination but in all of them after germination. PPO was not activated in germinated sorghum grains, whereas POX activity increased up to tenfold in some varieties. Zymography revealed that germination induced de novo synthesis of several POX isoenzymes, among which an anionic POX isoenzyme (pI 3.1) was ubiquitously present. Amylase and phenolic enzyme activities could be correlated with grain and plant agronomic characteristics. The use of sorghum varieties for local dishes such as ‘tô’, ‘dolo’, couscous and thin porridge could be correlated with amylase and phenolic enzyme activities and the contents of their substrates. The biochemical constituents determined are useful markers for selection of varieties for food utilisation with special emphasis on infant porridges. Copyright © 2006 Society of Chemical Industry     

The laboratory assessment of the inherent susceptibility of maize varieties to post-harvest infestation by Sitophilus zeamais Motsch. (Coleoptera, Curculionidae)

A biological technique for assessing the susceptibilities of varieties of maize to post-harvest infestation by Sitophilus zeamais Motsch. has been developed. The effects of the age and population density of the parent insects upon the results obtained were investigated, and the possible effects of insect selection due to breeding upon particular maize varieties were looked at.

Twenty-five Malawi, two Colombian and three Indonesian maize varieties were tested for susceptibility, and the results obtained were summarized using an ‘Index of Susceptibility’ which took into account both the F₁ progeny developing during the tests and a measure of the average development period of these progeny.

The effects of the proportion of floury endosperm in the maize kernels, the mean kernel weight, the 70% r.h. equilibrium moisture contents of the varieties, and the amylose contents of the varieties upon susceptibility were investigated using regression techniques. It was concluded that the hardness of the kernels, as estimated by the proportion of floury endosperm was related to susceptibility, and that the hardness was closely correlated with amylose content. However amylose may have a small effect upon susceptibility in addition to that associated with hardness.

Egg plugs placed in the kernels of different varieties during standard susceptibility tests were counted, and no evidence was found that there was any relationship between the numbers of eggs laid and susceptibility. Therefore it was concluded that susceptibility was determined in these varieties by factors operating after oviposition.     

Susceptibility of Ethiopian wheat varieties to granary weevil and rice weevil infestation at optimal and sub-optimal temperatures

Integrating varietal resistance with temperature manipulation during storage may provide a better option for protection of stored grains and may decrease reliance on the use of synthetic chemicals. The current study was conducted to determine the susceptibility of different varieties of wheat seed to the infestation by the granary weevil, Sitophilus granarius (L.), and rice weevil, Sitophilus oryzae (L.), at optimal (30 °C) and sub-optimal (19 °C) temperatures. Kernels of six wheat varieties namely, Danda'a, Digalu, ET-13-A2, Kakaba, Millennium, and Pavon-76 were examined over a period of 90 d. Significant interactions were detected between wheat varieties and storage temperature for progeny emergence, percentage of insect damaged kernels, grain weight loss, and amount of powder produced per gram of wheat. Kernels of Danda'a, infested with S. oryzae at 30 °C exhibited significantly lower mean progeny counts (13.3 live insects), lower percentage of grain weight loss (4.2%) and insect-damaged kernels (6.4%), and powder production (1.5 mg/g). Kernel weight and hardness index were negatively associated with percentage of insect damaged kernels and grain weight loss. Kernel diameter was positively associated with both of percentage of insect damaged kernels and grain weight loss. Wheat varieties with high Zeleny sedimentation values had lower percentage of insect-damaged kernels and grain weight loss. These results indicated that kernel weight, hardness index, and protein content are predominant factors contributing to wheat resistance against S. granarius and S. oryzae. The varieties Millennium and Danda'a can be considered with other integrated pest management approaches to reduce stored grain losses of wheat in Ethiopia.     

Assessment of Rhyzopertha dominica (F.) progeny and feeding damage on rice dried with infrared radiation

Infrared radiation (IR) is a method of drying grains that eliminates insect and microbial pests. It is unknown if IR could cause grains to be more susceptible to insects. Thus, the effects of IR on Rhyzopertha dominica development and feeding damage using long-grain rice varieties, Clearfield XL745 (hybrid) and CL152 (pureline), were examined. Rough rice was dried with three IR intensities: 2.15, 2.83, and 10.84 kW/m². The number of progeny developed, feeding damage, and frass weight after IR-drying were compared with air-drying methods for rough rice and rice milled to brown rice after drying. Since R. dominica develop internally, X-ray technology was used to examine internal progeny and feeding damage. Progeny development and kernel damage appeared to be more affected by fraction (brown rice) than the cultivar of rice or intensity of IR used, with more progeny produced on brown rice than rough rice. An IR intensity of 10.84 kW/m² increased the number of overall progeny, the amount of adults, and frass produced on CL152 brown rice. An intensity of 10.84 kW/m² also increased the amount of larvae observed for both varieties and fractions. The intensity of 10.84 kW/m², under the conditions of this study, is not recommended for drying rice.     

Starch properties as affected by sorghum grain chemistry

To determine the relationship between sorghum grain polyphenol content, grain structure, and starch properties, starch was isolated from 10 sorghum varieties using an alkali steep and wet‐milling procedure. SV2, a tannin‐free variety with white pericarp, gave a white starch. Varieties having red or white pericarp and higher polyphenol levels gave pink starches. Hunter colour values (L, a, b) of starches were not correlated with grain polyphenol content. Grain appearance in terms of pericarp colour, or presence or absence of pigmented testa, did not relate to the intense pink colouration of sorghum starches. Starch amylose content was significantly negatively correlated (r = −0.88, p < 0.001) to grain floury endosperm texture. Sorghum starches had higher peak viscosity (PV) in pasting than commercial maize starch. The time taken to reach peak viscosity from the initial viscosity rise was less for sorghum starches than maize starch. However, sorghum starches had a higher rate of shear thinning (R_st) than maize starch. There was a significant positive correlation between grain polyphenol content and starch PV (r = 0.75, p < 0.05). Starch gel hardness was negatively correlated to pasting properties of R_st and paste breakdown (r = −0.78 and −0.77 respectively) at p < 0.01. Peak gelatinisation temperature (T_p) occurred over a narrow range from 66 to 69 °C. T_p was negatively correlated to the floury endosperm portion of the grain (r = −0.77) at p < 0.01. It is concluded that sorghum grain polyphenol content and grain characteristics influence its starch properties. © 2000 Society of Chemical Industry     

Phenolic compounds and kernel characteristics of Zimbabwean sorghums

Sixteen sorghum varieties widely cultivated in Zimbabwe were examined for levels of phenolic compounds and kernel characteristics, to help identify those with desirable properties and develop suitable processing methods. Assays for polyphenols included the chlorox test, the vanillin‐HCl, the ferric ammonium citrate and the butanol‐HCl methods. Free phenolic acids were analysed using reverse‐phase high performance liquid chromatography. Varieties DC‐75, Mutode and Chirmaugute had the highest levels of condensed tannins. The polyphenols in Chibonda were mostly unextractable in methanol. No significant levels of polyphenols were found in 13 varieties. Phenolic acid content was related to pericarp colour. Endosperm texture and pericarp thickness were evaluated using video image analysis. Katandanzara and SV1 had relatively corneous endosperms (<30% floury). Mutode, Chibonda and DC‐75 had thick pericarps (>0.060 mm). Endosperm texture was not correlated with phenolic compounds. A positive correlation, however, was observed between pericarp thickness and polyphenol content (r > 0.64). Zimbabwean sorghums lack ideal agronomic and processing physico‐chemical characteristics defined in terms of high polyphenols, plus hard endosperm and thin pericarp. Research is required to develop effective methods to process the available polyphenol‐rich sorghums. © 1999 Society of Chemical Industry     

Structural characteristics of sorghum kernel: Effects of temperature

In this study, the effect of cold water, hot water, and steam tempering on sorghum kernel physical and mechanical properties was studied. Single kernel characteristics (SKCS), abrasive hardness, structural changes, and texture of kernels were evaluated as an effect of temperature. At the same moisture level, cold water tempered sorghum had both higher SKCS hardness and abrasive hardness than hot water and steam tempered sorghum kernels. The increase in abrasive hardness, SKCS-hardness index was highly correlated with the moisture content of kernel. The abrasive hardness index, which represents the pericarp properties, did not show any correlation with moisture content but had correlation to the structural changes. The SEM images indicated the structural changes in pericarp after hot water and steam treatment. Steam tempering methods made the pericarp tougher than the cold water and hot water tempering methods and, meanwhile, softened the endosperm by adding moisture to the kernel.     

Changes in the levels of polyphenols in three pear varieties during bud development

The polyphenol content of three orchard pear varieties, Conference, Doyenne du Comice and Williams bon Chretien as determined between November 1981 and March 1982 as a preliminary part of a study to ascertain the basis of dietary self-selection by bullfinches. The varieties most susceptible to bird damage, Conference and Williams, were shown to contain higher levels of extractable phenolic material than the partly bird-resistant variety, Comice. There were no major intravarietal differences between buds of the same variety collected at different areas of the same site. The significance of these results is discussed.     

A systemic approach to qualitative changes in the stored-wheat ecosystem: Prediction of deterioration risks in unsafe storage conditions in relation to relative humidity level, infestation by Sitophilus oryzae (L.), and wheat variety

A multidimensional laboratory trial was carried out to identify the primary causes of changes in quality traits in the stored-grain ecosystem to reveal critical storage condition boundaries that may endanger grain quality retention. Qualitative criteria were followed on grain batches from 3 wheat varieties which were stored for 160 d at temperature of 22-23 °C, at two different relative humidities, and with or without infestation by the rice weevil Sitophilus oryzae, to build a multivariate data matrix. The interactions between biotic deteriorative factors and qualitative trait changes were explored through a principal component analysis (PCA). From the Pearson’s product moment correlation matrix, it was observed that the variables that correlated significantly with insect and fungal species dynamics were: moisture content, hL mass, seed viability, and fat acidity of extracted whole flour. Four factors explained the major part of the variance: storage duration, moisture content, hidden insect infestation density, and fungal contamination level. The rate of increase of the insect population was significantly different between varieties. PCA revealed that the significant difference in qualitative deterioration pattern observed between the three varieties was not related to their hardness but rather to a different relationship between the grain and relative humidity. Germination rate was the first quality factor to decline during the storage period. The technological properties of flour extracted from each variety were not affected before insect population density exceeded 1000 adult insects per kg. The rate of qualitative changes induced by the biotic deterioration factors was processed into a “biodeterioration susceptibility index” (BSI) according to the safe storage time assessed in the present study. This index may be used in IPM approaches to predict the susceptibility of a particular wheat variety to insect and fungal damage during long-term storage.     

Modulation of chelating factors,trace minerals and their estimated bioavailability in Italian and African sorghum (Sorghum bicolor (L.) Moench) porridges

Factors able to modulate chelating factors, trace minerals and their bioavailability were investigated in porridges of five sorghum (Sorghum bicolor (L.) Moench) varieties: from Nigeria, Senegal, Burkina Faso and two from Italy. Effects of variety and traditional fermentation and cooking were assessed on iron‐binding phenolic groups, phytates and iron and zinc content and bioavailability. Chelating factors, trace elements as well as the effect of processing (mainly fermentation) were modulated by variety. Fermentation decreased iron‐binding phenolic groups until 49% and phytate content until 72% as well as increased phytase activity 3.4–16.4 fold, leading to enhancement of iron and zinc estimated bioavailability. Cooking alone had almost no effect. The lowest chelating factors content and the highest trace minerals bioavailability were shown by fermented Senegal landrace, whereas the Italian varieties overall showed the worst results. The results indicate that selection of traditional varieties and appropriate processing methods can improve sorghum nutritional value.     

Resistance of selected Mozambican local and improved maize genotypes to maize weevil,Sitophilus zeamais (Motschulsky)

Maize weevil Sitophilus zeamais (Motschulsky) is one of the most important pests of on-farm stored maize in thetropics, particularly where there is no control of moisture content and application of pesticides. This study aimed todetermine the level of resistance among Mozambican maize genotypes against S. zeamais. A total of 17 genotypes,composed of seven experimental hybrids developed from S5 inbred lines from five populations, one released hybrid,two improved open pollinated varieties (OPV), three landraces from Mozambique, two resistant and two susceptiblechecks from Kenya were screened for their resistance to S. zeamais. Four hybrids were screened at their F1 and F2generations. The genotypes were evaluated in the post-harvest laboratory, Kiboko, Kenya in a completely randomizeddesign, replicated 4 times. Data was collected on the number of emerged insects, seed weight loss, seed damage,median development period; and protein, starch and oil contents. The Dobie index of susceptibility was used to groupthe genotypes. Six of the of the eight hybrids at the F1 generation were resistant while two were moderately resistant.Three of the four hybrids evaluated at the F2 generation were moderately resistant while one was susceptible. Two ofthe five OPVs evaluated (EV8430DMRSR and landrace Kandjerendjere) were resistant. Genotypes with high proteincontent showed resistance while those with high starch contents showed susceptibility. Weevils fed on the resistantgenotype produced low number of F1 progeny, had a high median developmental time, caused low seed damage andlow seed weight loss. The resistant genotypes can be either used as cultivars or as sources of resistance in a breedingprogram for weevil resistance.     

Influence of medium and physical disturbances during rearing on development and numbers of Sitophilus progeny

Four Sitophilus populations (Sitophilus zeamais Motschulsky from Mexico, S. zeamais from Arkansas, U.S.A., Sitophilus oryzae L., and Sitophilus granarius L.) were studied. Hard red winter wheat, sorghum, and maize were used to determine effects of rearing media on progeny production of insects from the four populations.Mechanically disturbing infested samples to remove newly-emerged adult weevils every 48 hr reduced numbers of progeny surviving to the adult stage, especially for Arkansas S. zeamais and S. granarius reared in any of the three grains.With one exception, reproduction for all populations in all three grains was highest when parents were reared in wheat; other differences are discussed. Also, progeny developmental periods for all four populations were shortest when parents were reared in wheat. Progeny of all four populations had the longest developmental periods when reared in maize regardless of the medium in which their parents were reared.In 250 g samples of wheat, and 125 g samples of sorghum, 50 parent S. oryzae produced statistically as many progeny as in 500 g and 625 g samples of wheat and 250, 500, and 625 g samples of sorghum, respectively. In maize, 625 g samples produced significantly more progeny than 500 g samples.Sex ratios of progeny from each grain were 1:1, except that females of S. oryzae reared in maize outnumbered males.     

Cowpea resistance and bioactivity of two diatomaceous earths against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) on three cowpea varieties

The bruchid, Callosobruchus maculatus (F.) is the most important pest of stored cowpea in tropical climates. Experiments were conducted to evaluate the susceptibility of three cowpea varieties and the bioactivity of SilicoSec® and FossilShield® against this insect pest under ambient laboratory conditions at the contents 0, 0.5, 1, 1.5 and 2 g/kg of cowpea. The Dobie susceptibility index for cowpea genotypes was estimated to compare their relative tolerance to this insect pest. Adult mortality was assessed after 1, 2, 4 and 6 days of exposure followed by the evaluation of the F₁ progeny. Population increase, percentage seed damage and weight loss were assessed after three months of storage. The results showed that the CRPS and TN5-78 varieties were highly susceptible to C. maculatus, while Lori variety was moderately susceptible to the weevil. SilicoSec® and FossilShield® caused a significant and increasing bruchid mortality according to the dose rates and periods of exposure. Malathion 5% caused complete mortality after one day exposure time. SilicoSec® was more effective than FossilShield® on the three varieties of cowpea. The greatest dose of SilicoSec® and FossilShield® (2 g/kg) caused 100% mortality on all three varieties; 4 days of exposure in the Lori variety was the shortest exposure time leading to complete mortality. Regarding LD₅₀ and LD₉₅ values, it was observed that C. maculatus adults are more susceptible to SilicoSec® than to FossilShield®.The two formulations of diatomaceous earth (1.5 g/kg) reduced the F₁ progeny by more than 70%, and produced less than 10% of seed damage and weight loss for the three varieties of cowpea. The varietal resistance and the use of diatomaceous earth against C. maculatus in storage could represent an alternative to Malagrain® for the protection of the cowpea.     

Effects of PICS bags on insect pests of sorghum during long-term storage in Burkina Faso

The PICS bags, originally developed for cowpea storage, were evaluated for sorghum (Sorghum bicolor) preservation. Batches of 25 kg of sorghum grain were stored in 50 kg PICS or polypropylene (PP) bags under ambient conditions for 12 months and assessed for the presence of insect pests and their damage, seed viability and, oxygen and carbon dioxide variations. The grain was incubated for 35 days to assess whether any insects would emerge. After six months of storage, oxygen levels decreased in the PICS bags compared to polypropylene bags. After 12 months of storage, only two pests, Rhyzopertha dominica and Sitophilus zeamais were found in the PICS bags. However, in PP bags there were additional pests including Tribolium castaneum and Oryzeaphilus mercator and Xylocoris flavipes. Grain weight loss and damage caused by these insects in the PP bags were significantly higher compared to those stored in PICS bags. Germination rates of sorghum grains stored in PP bags decreased significantly while no changes were observed in grains stored in PICS bags when compared to the initial germination. After the incubation post storage period, there was a resurgence of R. dominica in sorghum grains from PICS bags but the population levels were significantly lower compared to polypropylene bags. PICS bags preserved the quality and viability of stored sorghum grains and protected it from key insect pests. The PICS technology is effective for long-term sorghum storage but the potential resurgence of insects in low-oxygen environment calls for further research.     

Extraction,determination and fractionation of sorghum polyphenols

Interactions between variety, dehulling, milling, extraction and method of separation of sorghum polyphenols were studied. The results indicate that the sorghum variety free of red-brown coloured testa (e.g. Egyptian varieties) had a lower content of polyphenols compared with red-coloured varieties (e.g. the bird-resistant varieties). Most of the polyphenol content of the first varieties could be extracted either with methanol or 80% aqueous acetone and could be determined by Folin Ciocalteau (FC) and/or Ferric Ammonium Citrate (FAC) methods. The best solvents to extract, and the best methods to determine, the polyphenols of the bird-resistant varieties were (75%) dimethyl formamide or 80% aqueous acetone and the FAC or vanillin (V) methods, respectively. To get a good separation of sorghum polyphenols by TLC the following conditions were required: methanol as extractant, n-butanol: acetic acid: water (4:1:2 v/v/v) as a developing solvent and iodine vapour as visualizing reagent. Dehulling of sorghum grains decreased the polyphenol content while milling removed some of its fractions.     

Phenolic compounds and antioxidant capacity of Brazilian mango (Mangifera indica L.) varieties

Phenolic compounds and antioxidant activities of four mango varieties cultivated in Brazil were analyzed. The profile of flavonol-O-glycosides and xanthone-C-glycosides was characterized in pulps from Haden, Tommy Atkins, Palmer, and Ubá cultivars and in the agro-industrial residues from Ubá variety by LC–ESI–MS analysis. The first three varieties were collected from conventional production, whereas Ubá was obtained from organic production. The total phenolic content of the peels and seed kernel extracts was analyzed utilizing Folin-Ciocalteu’s reagent. The aqueous-methanolic extracts of pulp, peel and seed kernels were analyzed for antioxidant activity (AA) by free radical-scavenging and reducing power. A total of 12 flavonoids and xanthones were identified in the pulps, peels and seed kernels, with larger amounts of these compounds being present in the organically grown Ubá variety. The Ubá mango pulp presented higher AA and the peel and seed kernel extracts showed higher AA than did a commercial standard.     

小麦籽粒品质性状基因功能标记的开发及应用

小麦籽粒加工品质是一个综合性状,并与高、低分子质量亚基、多酚氧化酶活性、脂肪氧化酶活性、黄色素含量、籽粒硬度、淀粉特性和1BL/1RS易位等多个性状密切相关。本研究主要就这些小麦品质相关性状基因的功能标记开发及其在分子育种应用的研究进展进行了综述,并对其当前存在的问题和未来发展方向进行了讨论。