RK-2

The virulence index of three Meloidogyne incognita field isolates to the resistance gene Rk in cowpea was 0%, 75%, and 120%, with the index measured as reproduction on resistant plants as a percentage of the reproduction on susceptible plants. Continuous culture of the 75% virulent isolate on susceptible tomato for more than 5 years (about 25 generations) resulted in virulence decline to about 4%. The rate of the decline in virulence was described by exponential decay, indicating the progressive loss of virulence on a susceptible host. The 120% virulent isolate declined to 90% virulence during five generations on susceptible cowpea. Following virulence decline, the two isolates were compared over 5 years in inoculated field microplots both separately and as a mixture on susceptible, gene Rk, and gene Rk(2) cowpea plants. At infestation of the plots, the two isolates were 1.2% and 92.0% virulent, respectively, to gene Rk and 0.2% and 8.1% virulent, respectively, to gene Rk(2). Virulence to gene Rk in the two isolates and in mixture increased under 5 years of continuous Rk cowpea plants to 129% to 172% and under Rk(2) cowpea plants to 113% to 139 % by year 5. Virulence to gene Rk(2) increased during continuous cropping with Rk cowpea plants to 42% to 47% and with Rk(2) cowpea plants to 22% to 48% by year 5. Selection of Rk(2)-virulence was slower in the isolate with low itt-virulence. The virulence to both genes Rk and Rk(2) in the mixed population was not different from that in the highly virulent isolate by year 5 of all cropping combinations. Selection of Rk(2)-virulence on plants with Rk, and vice versa, indicated at least partial overlap of gene specificity between Rk and Rk(2) with respect to selection of nematode virulence. This observation should be considered when resistance is used in cowpea rotations.

Defensins are endogenous antimicrobial peptides. We demonstrated recently the existence of RK-1, a defensin-like peptide in rabbit kidneys. Defining the renal-defensin system is an essential step toward understanding how the kidney responds to infection. Here, using a combination of high-performance liquid chromatography, matrix-assisted laser desorption time-of-flight mass spectrometry, amino acid compositional analysis, and microsequence analysis, we show that the rabbit kidney contains a novel alpha-defensin-like peptide, RK-2. This work establishes the existence of a new subfamily of alpha-defensins in the kidney.

Nigeria is second to South Africa with the highest reported cases of COVID-19 in sub-Saharan Africa. In this paper, we employ an SEIR-based compartmental model to study and analyze the transmission dynamics of SARS-CoV-2 outbreaks in Nigeria. The model incorporates different group of populations (that is, high- and- moderate risk populations) and is use to investigate the influence on each population on the overall transmission dynamics.The model, which is fitted well to the data, is qualitatively analyzed to evaluate the impacts of different schemes for controlstrategies. Mathematical analysis reveals that the model has two equilibria; i.e., disease-free equilibrium (DFE) which is local asymptotic stability (LAS) if the basic reproduction number ( R 0 ) is less than 1; and unstable for R 0 > 1 , and an endemic equilibrium (EE) which is globally asymptotic stability (LAS) whenever R 0 > 1 . Furthermore, we find that the model undergoes a phenomenon of backward bifurcation (BB, a coexistence of stable DFE and stable EE even if the R 0 < 1 ). We employ Partial Rank Correlation coefficients (PRCCs) for sensitivity analyses to evaluate the model's parameters. Our results highlight that proper surveillance, especially movement of individuals from high risk to moderate risk population, testing, as well as imposition of other NPIs measures are vital strategies for mitigating the COVID-19 epidemic in Nigeria. Besides, in the absence of an exact solution for the proposed model, we solve the model with the well-known ODE45 numerical solver and the effective numerical schemes such as Euler (EM), Runge-Kutta of order 2 (RK-2), and Runge-Kutta of order 4 (RK-4) in order to establish approximate solutions and to show the physical features of the model. It has been shown that these numerical schemes are very effective and efficient to establish superb approximate solutions for differential equations.