Efficiency of Subsurface Drip Irrigation for Potato Production Under Different Dry Stress Conditions

Efficient water delivery systems such as drip irrigation can contribute towards increasing crop yield potential, improving crop water and fertilizer use efficiency. However, critical management considerations such as subsurface drip irrigation are necessary to attain improved irrigation efficiencies and production benefits particularly under arid regions. The objective of this study was to determine the effect of two irrigation methods, surface and subsurface drip irrigation combined with four irrigation levels, 100, 80, 60 and 40% of crop evapotranspiration on yield and yield components of potato grown on sandy soil. The field experiments were conducted in the years 2008 and 2009. In terms of soil water availability to plants, subsurface drip provided more favorable growth conditions for plant growth and maintained higher soil water content at the root zone, which resulted in a significant higher potato yield compared to surface drip irrigation. The difference between the two irrigation methods on yield components was concentrated on the mean tuber weight per plant, while no significant difference was found on the tuber number per plant. Reducing the amounts of applied water significantly decreased total potato yield and its components. Under subsurface drip irrigation, reducing amounts of applied water to 80% ETc gave comparable yield and yield components to surface drip at full irrigation supply, indicating that 20% irrigation water can be saved without affecting the potato yield. At all irrigation levels, subsurface drip recorded higher water use efficiency (WUE) over surface drip. Maximum value was observed at 40% ETc. Fertilizer use efficiency (FUE) was also higher under subsurface drip and reduced significantly under both irrigation methods with increasing water deficit. These results suggested that subsurface drip offers the potential of better water management with respect to saving and distribution of water in the root zone and to obtain maximum yield accompanied by highest water and FUE.     

Determination of the optimum sterilizing radiation dose for control of the red date palm weevil Rhynchophorus ferrugineus Oliv. (Coleoptera: Curculionidae)

The optimum dose of gamma radiation for sterilizing the red date palm weevil was determined using newly emerged weevils obtained from colonies established on four date palm cultivars in the laboratory. Male weevils from each date palm cultivar were treated with gamma radiation doses of 10, 15, 20, 25 or 30 Gray (Gy) and then mated with similar aged females to determine egg hatchability and male lifespan. Hatchability percent was significantly reduced at 15 Gy and above, and male lifespan was decreased at 10–15 Gy and above. Date palm cultivar significantly affected average male lifespan as well as egg hatchability, and the interaction between radiation dose and date palm cultivar was significant for both parameters. These results indicate that 15 Gy of gamma radiation to be an optimum dose for sterilizing red date palm weevil.     

Evaluation of the U.S. peanut mini core collection using a molecular marker for resistance to <Emphasis Type="Italic">Sclerotinia minor</Emphasis> Jagger

Cultivated peanut, the second most economically important legume crop throughout the United States and the third most important oilseed in the world, is consistently threatened by various diseases and pests. Sclerotinia minor Jagger (S. minor), the causal agent of Sclerotinia blight, is a major threat to peanut production in the Southwestern U.S., Virginia, and North Carolina and can reduce yield by up to 50% in severely infested fields. Although host plant resistance would provide the most effective solution to managing Sclerotinia blight, limited sources of resistance to the disease are available for use in breeding programs. Peanut germplasm collections are available for exploration and identification of new sources of resistance, but traditionally the process is lengthy, requiring years of field testing before those potential sources can be identified. Molecular markers associated with phenotypic traits can speed up the screening of germplasm accessions, but until recently none were available for Sclerotinia blight resistance in peanut. This study objective of this study was to characterize the US peanut mini-core collection with regards to a recently discovered molecular marker associated with Sclerotinia blight resistance. Ninety-six accessions from the collection were available and genotyped using the SSR marker and 39 total accessions from spanish, valencia, runner market types were identified as new potential sources of resistance and targeted for further evaluation in field tests for Sclerotinia blight resistance.     

Yield response and <Emphasis Type="Italic">Stenocarpella</Emphasis> ear rot reaction among selected maize inbred lines and top cross hybrids

Stenocarpella ear rot of maize caused by Stenocarpella maydis (Berk.) Sutton is one of the most important ear rot diseases in South Africa. The objective of this study was to identify suitable maize inbred lines and top cross hybrids with Stenocarpella ear rot resistance and high grain yield. The study was conducted using 54 inbred lines and 54 top crosses with selected standard checks under natural and artificial disease inoculations. A split-plot design was used with three replications. There were considerable variations among tested inbred lines and top crosses for Stenocarpella ear rot resistance and grain yield. Two promising inbred lines GCI-35 and GCI-50 were selected possessing resistance to Stenocarpella ear rot and increased grain yield. Inbred line GCI-35 had a grain yield of 6.31 and 6.27 t/ha under natural and artificial inoculations, respectively. Line GCI-50 yielded 5.8 and 5.7 t/ha when tested under natural and artificial disease infestations, respectively. Two top cross hybrids GCT-14 and GCT-30 were selected with greater grain yield and high level of Stenocarpella ear rot resistance. Top cross entry GCT-14 yielded 7.5 and 9.33 t/ha, respectively, whereas GCT-30 had yield of 7.65 and 9.21 t/ha, respectively. The selected inbred lines and top cross hybrids will be useful in maize improvement for Stenocarpella ear rot resistance and increased grain yield in South Africa or other similar environments.     

Pathogenicity determinants in smut fungi revealed by genome comparison

Biotrophic pathogens, such as the related maize pathogenic fungi Ustilago maydis and Sporisorium reilianum, establish an intimate relationship with their hosts by secreting protein effectors. Because secreted effectors interacting with plant proteins should rapidly evolve, we identified variable genomic regions by sequencing the genome of S. reilianum and comparing it with the U. maydis genome. We detected 43 regions of low sequence conservation in otherwise well-conserved syntenic genomes. These regions primarily encode secreted effectors and include previously identified virulence clusters. By deletion analysis in U. maydis, we demonstrate a role in virulence for four previously unknown diversity regions. This highlights the power of comparative genomics of closely related species for identification of virulence determinants.     

The phylogeographic system survey of native sheep breeds in the eastern and southern Central Asia

The genetic diversity and phylogenetic survey of native sheep breeds in the eastern and southern Central Asia were assessed in the present study. The clustering, principal components, structure and F statistics all demonstrate that the native sheep breeds in these regions be classified into two genetic groups: Mongolia‐Tibetan sheep group and South‐Southeast Asia sheep group. The Mongolia sheep group and the Tibetan sheep group had a certain degree of gene communication from the ancient times. In the present study we demonstrated that the Chinese native sheep populations belonged to Mongolia‐Tibetan sheep group. However, the relationships among the sheep populations in Mongolia sheep group in China were not closely related to the geographical distance among sheep populations.     

DNA vaccine encoding avian influenza virus H5 and Esat-6 of Mycobacterium tuberculosis improved antibody responses against AIV in chickens

The H5 gene of avian influenza virus (AIV) strain A/chicken/Malaysia/5744/2004(H5N1) was cloned into pcDNA3.1 vector, and Esat-6 gene of Mycobacterium tuberculosis was fused into downstream of the H5 gene as a genetic adjuvant for DNA vaccine candidates. The antibody level against AIV was measured using enzyme-linked immunosorbent assay (ELISA) and haemagglutination inhibition (HI) test. Sera obtained from specific-pathogen-free chickens immunized with pcDNA3.1/H5 and pcDNA3.1/H5/Esat-6 demonstrated antibody responses as early as 2 weeks after the first immunization. Furthermore, the overall HI antibody titer in chickens immunized with pcDNA3.1/H5/Esat-6 was higher compared to the chickens immunized with pcDNA3.1/H5 (p < 0.05). The results suggested that Esat-6 gene of M. tuberculosis is a potential genetic adjuvant for the development of effective H5 DNA vaccine in chickens.     

Comparison of the pathogensis of two isolates of <Emphasis Type="Italic">Besnoitia caprae</Emphasis> in inbred BALB/c mice

This study was performed to evaluate the infectivity of bradyzoites of two Besnoitia caprae isolates, BC-1 and BC-2, to inbred BALB/c mice. Each group of inbred BALB/c mice was inoculated intraperitoneally with 1 × 10³, 1 × 10⁴, 1 × 10⁵, 5 × 10⁵ and 1 × 10⁶ of one of the two isolates of B. caprae bradyzoites. The mice were monitored daily for a period of 40 days for survival. After death of each mice, several passages from its peritoneal washing and tissues were analyzed using ribosomal DNA-specific PCR assay. Marked differences in pathogenicity between the isolates were seen. All the inbred BALB/c mice infected with BC-2 survived but all the mice that were administered with 1 × 0⁵, 5 × 10⁵ and 1 × 10⁶ BC-1 bradyzoites were died within 4–9 days post-infection (DPI). Histopathological examination of the tissues of the dead mice revealed hyperemia and necrosis with presence of mononuclear and polymorphonuclear cell infiltration in myocardium, spleen and intestines together with interstitial pneumonia and peritonitis. All inbred BALB/c mice in the 1 × 10³ and 1 × 10⁴ groups of BC-1 inoculated mice survived and they were euthanized after 40 DPI. Chronic inflammation with infiltration of mononuclear cells was evident in myocardium, spleen, alveolar septa of the lungs of most of the examined tissues with hemorrhagic enteritis in the mice infected with 1x10⁶ bradyzoites. The mice infected with different doses of BC-2 were euthanized after 40 DPI and no lesion was seen in histopathological sections of their organs. All peritoneal washings and examined tissues were PCR positive in BC-1 group. This experiment is the first report to show inbred BALB/c mice as a relevant model for B. caprae and demonstrates that this strain of inbred BALB/c mice is a suitable animal model for biological studies and examination of pathogenesis for this species of Besnoitia. The present findings also provide evidence for significant differences between the two isolates of B. caprae.     

New withanolides from Mandragora officinarum: First report of withanolides from the Genus Mandragora

Two new withanolides named mandragorolide A (1) and mandragorolide B (2) were isolated from the MeOH extract of the whole plant of Mandragora officinarum of Jordanian origin, along with five known withanolides namely larnaxolide A (3), withanolide B (4), datura lactone 2 (5), withanicandrin (6) and salpichrolide C (7). Compound 3 has been reported only once before, from the leaves of Larnax glabra. This is the first report of withanolides of different biogenetic types from the genus Mandragora. Isolation of known fatty compounds, coumarins, sterols and tropane alkaloids was also achieved in this study.