Response of Potato Genotypes to Bacterial Wilt Caused by Ralstonia Solanacearum (Smith)(Yabuuchi et al.) In the Tropical Highlands

Potato varietal resistance to bacterial wilt disease caused by Ralstonia solanacearum Yabuuchi et al., (Microbiology and Immunology 39:897–904, 1995) is the best management of the disease. Because the causal pathogen exhibits strong host-pathogen-environment interaction, screening the potential parents for resistance under the target growing environmental conditions is the first important step for effective resistance breeding. The objective of this study was to determine the response to bacterial wilt of selected potato genotypes currently grown by farmers in Kenya and candidate clones from the International Potato Center to identify parents that can be used in the local breeding program to develop resistant cultivars. A study was carried out at Kabete, Kenya for three consecutive seasons between November 2011 and February 2013. Thirty six potato genotypes were planted on an inoculated field at the Kenya Agricultural Research Institute (KARI), Kabete using alpha lattice experimental design with three replications. Data collected were days from planting to onset of wilting (DTOW), bacterial wilt incidence (BWI), total tuber weight (ton ha^?1) (TTW), total tuber numbers/hectare (TTN), proportion of ware sized tubers (PWTTW), proportion of symptomatic tubers based on weight (PSTTW), proportion of symptomatic tubers based on tuber numbers (PSTTN) and latent infection (LI) of the tubers. Almost, all the potato genotypes evaluated in this study were susceptible to bacerial wilt. Ranking of genotypes based on resistance differed among the three seasons. On average, the three most resistant genotypes were Kenya Karibu, Kenya Sifa and Ingabire. The study identified eight potato genotypes (Meru, Ingabire, Kenya Karibu, Sherekea, Kihoro, Tigoni, Bishop Gitonga and Cangi) to be used as promising parents for subsequent crosses. The chosen genotypes are prolific in pollen production and popularly grown by Kenyan farmers.     

The complete elimination of vicine and convicine from the faba beans by combinations of genetic selection and processing techniques

Out of sixty six faba bean (Vicia faba) cultivars and genotypes grown locally in Egypt and in Syria, the genotype 123 A/45/76 proved to be lowest in its vicine and convicine contents. Furthermore, soaking of this bean variety in 1% acetic acid at 40°C for 48 h resulted in reducing the total vicine and convicine contents of the beans by 90%. Home-made faba beans processing including soaking prior to cooking as in the case of bean cakes resulted in considerable reduction of the vicine and convicine contents by 56 and 34% respectively.     

Effect of some variables on the extractability of proteins,urease activity,free alpha-amino groups and soluble carbohydrates from soybean meals

The effect of several variables on the extraction of soybean meal protein has been investigated. Solubility studies of the meal show that globulin is the main protein component. Overnight suspension and a meal to solvent ratio 1:10 (w/v) were found to extract maximum amount of protein in distilled water adjusted to pH 6.4 (91.07%). More protein was extracted by diluted sodium hydroxide solutions (0.02 M) adjusted to various alkaline pH-values. Results with several other salts show that concentration as well as pH are very important factors in controlling the percentage of protein extracted. The optimum temperature of extraction was 70°C for 30 minutes, although over a temperature range of 60–75°C the extraction remains essentially constant. Destruction of urease activity was achieved by heating the suspended meal at 75°C for 45 Min. The kinetic inactivation of the enzyme was studied and the energy of inactivation was found to be 32.575 K cal. The level of free alpha amino groups in soybean meals ranged from 5.50 grams: 16 gram nitrogen in meal extracted with 0.1 N HCL adjusted to pH 5.0 to 1.71/100 grams protein (in meal extracted with distilled water.). Their level correlated significantly (p=0.01) upon heat treatment with the carbohydrate content of the corresponding meal. Contrary tothe protein solubility pattern, the -NH₂ groups decrease considerably upon longer exposure to temperatures between 60–75°C.     

Alfalfa cultivar responses to phosphorus and potassium deficiency: Biomass

Soil phosphorus (P) fertility needs for alfalfa (Medicago sativa L.) in the intermountain western United States have been a concern since the inception of irrigation during the late 19th century. Soil potassium (K) fertility needs have received much less attention because K deficiencies, related to long term use of high quality, low‐K irrigation water, have developed only in recent years. The objectives of this research were to compare the responses of five commercial alfalfa cultivars (CVs) to phosphorus (P) and K deficiency and to examine the interactions between CVs and P and K soil fertility. An experiment was established on a highly calcareous Redfield silt loam soil (Fine‐silty carbonatic, mesic Xeric Torrifluvents) that was low in both P and K. The CVs, planted in 1988, were studied through 1993. A 3x3 complete factorial combination of P and K fertilizer rates was established in a split plot design where CV was the whole plot. There was a significant CV x year interaction in biomass production that was not related to diseases or insects. There was also a significant CV x P interaction within and among years. Response to K fertility, though significant, was not prominent in this trial. Alfalfa CV performance trials should segregate CVs best adapted to short term (2–3 year) rotations from those best adapted to long term (4–5 year) rotations. Fertilizer effects on low‐K calcareous soils are short lived; moderate rates of K fertilizer should be applied each spring. Soil P requirements of alfalfa can be met by applying small rates annually or by applying enough for a 4‐ to 5‐year rotation. Phosphorus‐use efficiency by alfalfa may be improved by plant breeding and selection for this trait.     

Host-status and host-sensitivity of wild Cucumis species to Meloidogyne incognita race 4

Abstract

Wild watermelon (Cucumis africanus) and wild cucumber (Cucumis myriocarpus), which are highly resistant to the southern root-knot nematode (Meloidogyne incognita) race 2, have the potential for serving as seedling rootstocks for the highly nematode-susceptible watermelon (Citrullus lanatus) cultivars. In South Africa, due to high labour costs, most cotton farmers are turning to watermelon production. In these regions, there is high incidence of M. incognita race 4. A pot experiment in the greenhouse was, therefore, initiated to investigate the host-status and host-sensitivity of Cucumis africanus and Cucumis myriocarpus to M. incognita race 4, when inoculated with 0, 200, 600, 100, 1400, 1800 and 2200 eggs and second-stage juveniles (J2s). At harvest, 56 days after inoculation, the reproductive factor values at all levels of inoculation were less than one. Penetration indices on both plant species were greater than one, suggesting that the resistance was post-infectional and therefore, introgressible. Sex (male: female) ratios of M. incognita race 4 on the two Cucumis species were greater than one, suggesting that more J2s were converted into males. Infection of Cucumis species by the test nematode had no effect on yield components of the two plant species due to poor feeding sites. The two Cucumis species were, therefore, resistant to M. incognita race 4, with post-infectional resistance, where the sex ratio was skewed towards maleness. Thus, the two Cucumis species have the potential to be used as nematode-resistant rootstocks in watermelon production.     

Effect of feed intake restriction on reproductive performance and pregnancy rate in Egyptian buffalo heifers

The objective of the present experiment is to study the effect of feed intake restriction on the reproductive performance and pregnancy rate in Egyptian buffalo heifers. Thirty anestrus buffalo heifers were randomly divided into two equal groups. The low feed intake (LFI, n?=?15, 50 % restriction) group was fed a diet that consists of 3 kg concentrate, 1 kg wheat straw, and 3 kg fresh alfalfa, while the high feed intake (HFI, n?=?15) group was fed double the amount given to the LFI group for 4 months. All animals were weighed, transrectally examined, and visually checked for the signs of estrus, and blood samples were collected. Heifers in heat were mated with one fertile bull. The number of heifers showing estrus activity was 93.3 % in HFI vs. 20 % in LFI (P?<?0.01). Ovarian activity started earlier (P?=?0.03) in the HFI than LFI group. The weight at breeding, the diameter of the dominant follicle, number of heifers showing ovulations, number of services per conception, pregnancy rate, and overall mean of progesterone and estrogen concentrations were significantly higher (P?<?0.01) in the HFI than in the LFI group. The level of serum total protein, albumin, globulin, glucose, total cholesterol, and calcium were significantly higher (P?<?0.05) in the HFI group. Restriction of the daily feed intake to 50 % from NRC recommendations impair reproductive performance in terms of increasing the age at first service and reducing the pregnancy rate in buffalo heifers. In conclusion, feed intake could be effective in improvement of reproductive performance in buffalo heifers and further studies should be done on large scale of buffaloes in this point.     

Naturally occurring infections of cattle with Theileria lestoquardi and sheep with Theileria annulata in the Sudan

Theileria annulata is endemic in northern Sudan, hindering all efforts at upgrading cattle for milk production. T. lestoquardi clinical cases occur throughout the year and causes annual outbreaks that result in substantial losses in sheep. In the northern Sudan both cattle and small ruminants are frequently raised together and/or share common grazing grounds at river banks. In an attempt to evaluate field cross infectivity of Theileria lestoquardi and T. annulata in cattle and sheep respectively, a PCR analysis was carried out on samples collected from closely reared sheep and cattle using both T. annulata and T. lestoquardi specific primers. A total of 19 sheep out of 51 (37.3%) were positive for T. lestoquardi while four sheep (7.8%) showed T. annulata specific amplicons. A total of 38 out of 52 (73.1%) surveyed cattle were PCR positive for T. annulata and only two (3.8%) showed T. lestoquardi specific bands. These findings indicate complex epidemiology of both infections in areas where both parasites are transmitted by the same vector and call for further investigations of this phenomenon.     

Effect of dietary phosphorus supplementation on utilization of algae in the grow‐out diet of Nile tilapia Oreochromis niloticus

This research involved testing the replacement of corn gluten protein concentrate in the diet of 1.5 g Nile tilapia with biofuel algae‐based or algae supplemented with phosphorus diets. Experimental diets were formulated to replace 50% of the gluten meal protein in the control diet with biofuel algae protein (Alga50) or Spirulina (Spirulina50) protein. In addition, dicalcium phosphate (P) was added to the Alga50 at a concentration of 3.8% or 7.74% to mitigate aluminium (Al) toxicity and designated as Alga50 + P, and Alga50 + PP respectively. After 9 weeks of the feeding experiment, fish fed diets supplemented with P, Alga50 + P and Alga50 + PP differed significantly (P < 0.05) with respect to the feed conversion and protein deposition from the control. The mineral composition of the fish body showed a decrease in levels of Al and iron (Fe) due to the P supplements. The mineral composition of the faeces indicated that Al and Fe were excreted in the faeces and were not accumulated in the fish body. The effect of dicalcium P supplementation on the neutralization of Al in the diet resulted in improved fish growth and histological integrity of the gastrointestinal tract.     

Optimum rate of nitrogen fertilization for drip-irrigated wheat under semi-arid conditions

Limited water availability in arid and semi-arid wheat production systems increases the need of applying efficient drip irrigation systems. However, there is little information available about the optimum level of nitrogen (N) fertilization for drip-irrigated wheat. A two-years field study in the semi-arid region of Upper Egypt was carried out in a randomized complete block design to investigate the response of drip-irrigated wheat to three levels of N fertilization (N₁₂₀ = 120, N₁₈₀ = 180, and N₂₄₀ = 240 kg ha^?1). N₂₄₀ increased the uptake of N, P, and K by 66.3, 48.6, and 43.5%, respectively, as compared to N₁₂₀. The application of N₂₄₀ increased the grain yield by 28.4 and 40.4% and water use efficiency by 27.6 and 41.8% the first and second season, respectively, as compared to N₁₂₀. Based on the obtained results, it is recommended to fertilize drip-irrigated wheat by 240 kg ha^?1.     

Agro-morphological characterisation and selection of sorghum landraces

Sorghum [Sorghum bicolor (L.) Moench] grown under rain-fed conditions is frequently affected by drought stress at different stages, resulting in reduced grain and biomass yield. The aim of this study was to characterise sorghum landraces and to select farmer-preferred medium-maturing genotypes under rainfed and irrigated conditions. Hundred and ninety-six sorghum accessions were evaluated at Kobo site of the Sirinka Agricultural Research Center in 2014/2015 in Ethiopia. Data collected from 14 traits were subjected to analysis of variance, cluster analysis, Pearson’s correlation coefficient analysis, path coefficient analysis and principal component analysis (PCA). Significant genotypic differences (p?<?0.05) were observed. Medium-maturing and drought tolerant sorghum genotypes including E-72457, E-72438, E-72435, E-206214, E-72449, E-75460 and E-75458 with superior agronomic performance were recommend for large-scale production or for further breeding. The genotypes evaluated under rain-fed and irrigated conditions were grouped into five and six clusters, respectively, representing varied different heterotic groups. Grain yield had significant and positive correlation with yield-related traits assessed under the two test conditions. Further, path coefficient analysis revealed that days to maturity under rainfed condition and harvest index under irrigated condition had the highest positive direct effects on grain yield, therefore can be targets for direct selection. Overall, there was marked genetic diversity among the tested genotypes. Suitable medium-maturing farmers-preferred accessions selected from the study will be useful for effective breeding for drought tolerance and medium-maturity.