The efficacy of salting sliced sweetpotato chips prior to drying in reducing and (or) controlling damage levels of dried chips in storage by Araecerus fasciculatus Degeer (Coleoptera: Anthribidae) was investigated. Eight salt dosage rates, 0 (controls), 0.25, 0.5; 1, 2, 3, 4, and 5 g 100 g(-1) freshly sliced chips were evaluated. Artificial infestation of dried chips with adult A. fasciculatus was conducted. Gravid females were allowed to oviposit for one week and the infested chips incubated until the F-1 generation adults had all emerged under prevailing environmental temperatures of 26.29 +/- 1.19 degrees C and relative humidity 68.96 +/- 7.39%. The number, weight, and generation time of A. fasciculatus that emerged varied significantly depending on the salt dosage rates. Best results were obtained with increasing salt dosage levels. Salt application rate at 2-3% is recommended for on-farm validation.
Decoctions of Acacia nilotica, A. modesta, Dalbergia sissoo, Azadirachta indica, and Cinnamomum zeylanicum were tested for growth inhibition against Xanthomonas campestris pv. citri strains XC-93, XC-107, XC-109, XC-113, and XC-121. Acacia nilotica showed a high level of inhibition with all strains. Most of the plant extracts tested, significantly (P < 0.05) reduced the number of lesions on detached leaves of citrus compared to a control.
The effect of intercropping yam (Dioscorea rotundata) and "Egusi" melon (Colocynthis vulgaris) on vegetative vigour, crop yield, and protein yield was studied over three years intensive cropping from March 1990 to October 1992 following a two-year fallow cover with Anthonotha macrophylia at the Faculty of Agriculture Experimental Farm, University of Uyo, Nigeria. The tuber yield and other yield components of the yam plant were significantly (P < 0.05) depressed by the presence of melon at all yam densities and spatial arrangements studied. Melon seed yield (kg ha(-1)) was significantly (P < 0.05) increased with intercropping. Increasing plant population density increased yield per hectare but decreased yield components per hectare. Intercropping favoured high protein yield per hectare in yam and depressed that of melon in relation to pure cropping, although the variations in the yields were not significant (P > 0.05). The total land equivalent ratios (LER) indicated yield advantages.
This study was conducted to determine reproductive development of soya bean [Glycine max (L.) Merr.] genotypes of Maturity Groups (MG) III-VI grown under different photoperiods in Puerto Rico to establish the appropriate light regimes required for crossing. Three genotypes of each MG III-VI were planted in replicated experiments at three field environments and in growth chambers. In the field, photoperiods were natural conditions (unlighted) or 13-h, 14-h, and 15-h lighted photoperiods. In lighted treatments, genotypes were exposed to continuous light for two weeks, and appropriate photoperiods were then used until the end of flowering, after which plants grew in natural conditions. In the growth chamber, photoperiods of 12 h, 13 h, 14 h, and 15 h were used. Dates of full bloom (R2) and of full seed (R6), number of nodes at R2 and R6, and percentage of cleistogamous flowers were recorded. Environmental, photoperiod, and MG effects were significant on days and nodes at R2, but the MG x photoperiod effect was not. Under natural field conditions, all genotypes flowered approximately 30 days after planting (DAP) and had five nodes. They reached R6 56 DAP and had eight nodes. In the 14-h photoperiod, genotypes flowered 46 DAP. Genotypes of MG III flowered 37 DAP which was the shortest time. Within photoperiods, lines of each MG flowered within short periods of time from each other. Cleistogamy was at least 90% in all MGs in natural field conditions and in the 13-h photoperiod for MG III. The crossing of genotypes of MGs III-VI will require photoperiods of 14 h. A 6-day flowering difference of genotypes of MG III and VI suggests that several planting dates in the season will be needed, with the late maturing lines planted first.
Four honeybee species viz. Apis cerana indica F., A. mellifera L., A. dorsata F., and A. florea F. were examined for the presence of mites during a study conducted between 1991 and 1992. The investigation revealed the presence of Varroa Jacobsoni Oudemans in A. cerana indica F. colonies. Tropilaelaps clareae Delfinado & Baker was found associated with A. mellifera, A cerana indica, and. dorsata colonies whereas Euvarroa sinhai Delfinado & Baker occurred with A. florea only. The maximum infestation of mites was observed during March to May and August to September In all the honeybee species. Phoretic mites Neocypholaelaps indica Evans and stored product mites Tyrophagus longior (Gervais), Caloglyphus indica, and hypot were also found in hives. Population dynamics of mites varied during different seasons as well as from one bee species to another. The study further revealed that bee mite interactions were species-specific.
Low maize (Zea mays L.) yields are common in the Dedza Hills and Thiwi-Lifidzi Rural Development Projects (RDPs) of Malawi. This study was undertaken to determine If deficiencies of minor nutrients could be reducing yields. "Missing nutrients" trials conducted during the 1990-91 and 1991-92 growing seasons showed substantial yield responses to S, Zn, and B applications. Tissue analysis indicated that Zn-deficient maize ear leaves had high Fe:Zn ratios, ut not low Zn concentrations per se. In 1992, soil samples from 105 farmer sites scattered throughout the Dedza Hills and Thiwi-Lifidzi RDPs indicated widespread S, Zn, and B deficiencies. A nutrient supplement to the standard N and P fertilizers containing S, Zn, and B was applied to 79 farmer sites. The supplement improved yields by an average of more than 1160 kg ha(-1) in the region primarily in the Dedza Hills, and 390 kg ha(-1) at sites principally in the Thiwi-Lifidzi area. Poor correlation existed between yield and soil analytical results. Evidence is presented that suggests that yield improvements were due primarily to application of Zn and (or) B.
An experiment was conducted to determine the extent to which unpeeled cassava root meal could be included in diets for laying hens. Harco pullets were raised in standard battery cages in 12 groups of 17 birds each. Each of 4 diets comprising 0, 10, 20, and 30% unpeeled cassava root meal, was fed to three replicate groups for four weeks. There were no significant differences as a result of unpeeled cassava root meal inclusion in the diets on hen-day production per cent and feed conversion values. Egg quality traits showed no significant differences for both external and internal traits. It was concluded that unpeeled cassava root meal could replace maize totally as a source of energy in diets for laying hens without affecting productive performance and egg quality traits, providing it is properly processed and adequate protein and essential amino acid levels are included.
A procedure is described to regenerate shoots and plants from the shoot tips of black gram [Vigna mungo (L.) Hepper (cv. CO-5)] seedlings with 6-benzylaminopurine (BAP). The explants were dissected out from 7-day-old seedlings, aseptically germinated on MS (Murashige and Skoog) basal medium. Isolated shoot tips were cultured on MS medium containing different concentrations of BAP (1.0-5.0 mg L -1 ) in combination with 1.0 mg L -1 indoleacetic acid (IAA) or naphthaleneacetic acid (NAA) to induce multiple shoots. Increased concentrations of BAP resulted in increased shoot-bud production. A high frequency of shoot-bud differentiation was observed on MS medium supplemented with BAP (3.0 mg L -1 ) and NAA (1.0 mg L -1 ), and about 90% of the shoot tips produced up to 15 shoots per culture. Shoots were cultured on MS medium augmented with indole-3-butyric acid (IBA) to induce rooting. About 80% of the shoots with roots survived in field conditions and produced normal phenotypic plants.
The growth and yield response of banana to N fertilization through drip irrigation (fertigation) and direct soil application were studied at the Indian Institute of Horticultural Research, Bangalore, India during 1992-94. Plant height, stem girth, leaf number, and leaf area index increased with N application and with N fertigation although the increase was not significant beyond 100 g N plant -1 applied through drip. The nutrient uptake (N, P, and K) was also higher with 100 g N plant -1 applied through drip compared to direct soil application. The fruit yields were highest with 300 g N plant -1 fertigation but the differences were not significant above 100 g N. However, the yields increased with soil-applied N up to 200 g both in the plant and the ratoon crops.
Invasiveness and efficiency of six Zambian strains of Bradyrhizobium spp., with five U.S.-bred soya bean varieties were tested. Host genotype was the major determinant in symbiotic compatibility since differences in relative nodulating abilities of strains with genotypes were apparent. Contrary to the theory that African cowpea bradyrhizobia cannot efficiently nodulate soya bean, evidence was provided to indicate that some strains can be both effective and efficient nodulators of U.S. cultivars.
A field trial of the semi-intensive culture of the cascadu, Hoplosternum littorale (Hancock, 1828), was conducted. Twelve thousand hatchery produced fingerlings of mean weight 2.20 +/- 0.29 g were stocked into a 0.8-ha-conditioned earthern pond. Growth and condition of the fish were monitored. An experimental diet of 35% protein content was fed to the fish at the daily rate of 3% biomass. The fish were harvested after a period of 30 weeks and had a mean individual weight of 67.2 g. The mortality rate was 54.6% and the feed conversion ratio was 3.38:1. The fish were in good condition throughout the trial as indicated by Fulton's Condition Factor. It was concluded that the field trial and the experimental diet were successful and that the commercial culture of the cascadu is indeed a possibility. The stocking rate of 15 000 fingerlings ha-1 was considered to be below optimal.
Labile organic and inorganic P in an alkaline sandy loam and loamy sand (Typic Ustochrepts) amended with dried Sesbania aculeata and incubated for periods ranging from 10 to 100 days was investigated. A significant decrease in soil labile organic P occurred with a simultaneous increase in the labile or dissolved inorganic P soluble in 0.5M NaHCO3. The decrease in labile organic P is explained by its rapid mineralization to inorganic P. Dissolved organic P, therefore, makes a significant contribution towards the P nutrition of crops, a factor relevant to soil management.
The effect of waterlogging on the growth, physiology, and ion uptake of nine accessions or cultivars of lentil, ILL 5845, ILL 6451, ILL 6788, ILL 6793, ILL 6796, ILL 6210, ILL 6439, ILL 6778, and Local Masoor, was assessed in a pot experiment. Different cultivars or lines showed differing responses to waterlogging. Three accessions ILL 6439, ILL 6778, and ILL 6793 had higher dry biomass than the other accessions under waterlogged conditions. The reduction in percentage of chlorophyll content in the sensitive accessions ILL 6451 and Local Masoor was significant but the reduction in the waterlogging-tolerant accessions was intermediate. Higher accumulation of total sugars was found in the intolerant accessions compared with all the other cultivars or lines. The osmotic potentials of the waterlogging-tolerant accessions ILL 6439, ILL 6778, and ILL 6793 were the highest, and those of the sensitive accessions ILL 6451 and Local Masoor were the lowest. In accessions ILL 6439, ILL 6778, and ILL 6793, the uptake of K was inhibited but that of Ca remained unaffected, except ILL 6778. In accessions ILL 6439 and ILL 6793 shoot Fe and Mn contents remained unaffected but root Mn and Fe increased after waterlogging. The shoot Fe content in ILL 6778 was increased but there was no change in the root iron and root and shoot Mn contents. Low uptake of ions by roots and shoots of these three waterlogging-tolerant accessions reflects their capability of restricting the uptake of these elements. The stomatal diffusive resistance of the tolerant accessions was very low compared with the other accessions examined. In view of the existence of variation for waterlogging tolerance in a small sample of lentil accessions or cultivars examined here, screening of a large number of local and exotic cultivars or lines of lentil should be carried out to find most tolerant lines for crop improvement for waterlogging tolerance.
Pennisetum purpureum Schum. (Napier grass or elephantgrass) and hybrids of P. glaucum (L.) R. Br. (pearl millet) x P. purpureum have been evaluated for in vitro organic matter digestibility (IVOMD), neutral detergent fibre (NDF), lignin, crude protein (CP), and biochemical methane potential (BMP). Objectives of the study were to determine if the selected lines differed, and also how the plant components were different. Although Napier grass and the triploids and hexaploids derived from crosses to pearl millet have high biomass production, the quality of the feedstock is variable. To understand how plant components (leaf blades, sheaths, stems, and meristematic regions) differ in forage quality, four Pennisetum lines were harvested at four different dates. The meristematic zone (tissue above and including the most recent fully expanded leaf blade) was always the highest in IVOMD and CP (673 and 148 g kg-1), with declining IVOMD and CP values for blades, stems, and sheaths. Bottom sheaths were consistently lowest in both IVOMD and CP (354 and 29 g kg-1). Large differences in quantity of stem and leaf material and their ratios were observed between lines tested, but the quality of the various components from the triploid, tetraploid, and hexaploid lines were very similar.
The effects on sweet potato [Ipomoea batatas (L.) Lam.] yield and components of yield of planting methods, using vertical or horizontal orientation of cuttings, variable numbers of nodes (two, four, or six) placed in the soil at planting, and one or two cuttings at each planting location, were investigated in two experiments carried out in the dry lowlands of Papua New Guinea, using two cultivars ('L22' and 'L44'), and two harvest dates. Several yield components of the two cultivars were significantly different. Method of planting did not significantly affect total yield. However, in the first of the two experiments, the percentage of small nonmarketable tubers was affected by the method of planting. Planting four nodes vertically in the soil resulted in the smallest percentage of nonmarketable tubers for cultivar 'L22,' while six nodes placed horizontally was the most effective for 'L44.' Increasing the number of cuttings at a planting location from one (36 700 cuttings ha(-1)) to two did not significantly affect total yield but resulted in the production of substantially smaller tubers for 'L44' but not for 'L22,' and increased the proportion of marketable size tubers which had internal damage by the sweet potato weevil Cylas formicarius formicarius. The amount of damage during the second experiment, when weevil damage was severe, was affected by the number of cuttings at a planting location and the method of planting. Two cuttings with 'two nodes vertical,' and one cutting with 'four nodes vertical or horizontal' resulted in minimum weevil damage. Delaying the harvest from 108 to 133 days after planting resulted in significant increases in internal damage of marketable size tubers and in the percentage of small nonmarketable tubers.
Studies on morphological characters, taxonomic scoring, and chromosome numbers of 100 South Indian banana cultivars revealed that many of the cultivar names are synonymous, The cultivars Sanna Chenkadali (AA) and Eraichivazhai (AA) had some characteristics of Musa balbisiana, Diploid clones occurred more frequently than has been suggested by Simmonds. The cultivars Krishna vazhai, Vannan, Virupakshi, Sirumalai, Agniswar, Padali moongil, Kostha bontha, and Venneettu mannan were added to the genomic group AB, In the groups AAB and ABB, cultivars exhibited the characteristic traits of Musa acuminata and M. balbisiana in various degrees. The groups AB, AAB, and ABB were common in the cultivated bananas of India.
Chlorosis responses of 'Maha' carambola (Averrhoa carambola L.) scions grafted on seedling rootstocks of 'Maha,' 'Golden Star,' and M-18960 were studied under greenhouse conditions to determine rootstock effects and to evaluate the feasibility of using a bicarbonate nutrient solution system to assay for iron chlorosis. A nutrient solution with 5 mM HCO3- increased chlorosis symptoms in plants immediately after transferring them from a bicarbonate-free solution. There was a linear increase in severity of chlorosis in these plants with time up to 83 days after transfer when the study was terminated. There was no consistent difference in the degree of chlorosis among the 'Maha' scions grafted on the three rootstock groups. These results suggest that this method may be useful for studying carambola germplasm responses to calcareous conditions. The preliminary information in this study on the influence of rootstock on bicarbonate-induced chlorosis suggests that scion genotype may be more important in carambola than rootstock genotype when considering tolerance to calcareous edaphic conditions.
Peasant farmers in Ethiopia rely on labour-intensive cultural practices for weed control in wheat, limiting both cropped area and grain yields. Herbicides available for wheat production in the peasant sector decreased over the past decade as their impact on smallholders' grain yields had not been demonstrated. On-farm trials were therefore conducted during 1988 and 1989 to assess the effects of two post-emergence herbicides on weed-infested wheat fields in two regions of southeastern Ethiopia. Brittox(R) and Illoxan(R) reduced annual broadleaf and grass weed stands by 80 and 81%, respectively. Grain yield increased by 78% relative to the current farmers' practice of selective and partial hand weeding. Under high weed competition, herbicides were economically superior to hand weeding even at triple the current official herbicide prices. Thus, increased usage of herbicides by peasant farmers has the potential to raise grain yields, decrease labour requirements, and increase profitability.
