Effects of application of phosphorus fertilizer on brown blotch disease of cowpea

A field experiment was conducted to investigate the effects of level of phosphorus application on brown blotch disease of cowpea during the planting seasons of 2001, 2002 and 2003. Application of phosphorus from Single Super Phosphate at 30, 60, 90, and 120 kg P2O5/ha significantly increased the number of petioles, pods, nodules, seed/pod leaf area and yield. The higher the level of application of phosphorus the higher values of all the parameters. Disease incidence and severity of brown blotch were significantly reduced at higher levels of phosphorus (90 and 120 kg/ha) irrespective of the method of application. Moreover, there were also increases in the grain yield of cowpeaKeywords: Cowpea, disease phosphorus, levels, method

Evaluation of fallow and cover crops for nematode suppression in three agroecologies of south western Nigeria

A study was conducted in three agroecological zones of south-western Nigeria to evaluate the effect of siam weed (Chromolaena odorata) and mucuna (Mucuna utilis) cover/fallow crops on plant-parasitic nematode population. The natural bush regrowth was used as control. Plant-parasitic nematodes were identified and counted during the fallow periods. Eleven genera of nematodes were identified and three (Meloidogyne, Pratylenchus, and Helicotylenchus) species were predominant across the trial locations.Other important genera present were Scutellonema, Tylenchorhynchus and Rotylenchus species. Nematode population densities of pre-crop were lowest in Alagba soil (Rhodic lixisols) at Ikenne in the wet forest zone of Nigeria. The populations in Iwo soil (Rhodic haplustalf) at Ibadan, a dry forest zonewas lower than in the Temidire soil (Plinthic luvisol) at Ilora in the derived savannah of south-western Nigeria. There was significant suppression of nematode population densities under the different crops as the fallow period increased. The population reduction in the different locations depended on the nematode species and the cover crops. The natural bush re-growth had the least effect on the nematode suppression at the end of the fallow period. On the average, siam weed fallow reduced nematode population densities by 67-79%, mucuna by 64-72% and the natural bush by 30-49% across the trial locations. For effective nematode suppression with fallow cropping, proper determination of the principal nematode species predominant in an environment is essential

Food security outcomes in agricultural systems models: Current status and recommended improvements

Improvement of food security is a common objective for many agricultural systems analyses, but how food security has been conceptualized and evaluated within agricultural systems has not been systematically evaluated. We reviewed the literature on agricultural systems analyses of food security at the household- and regionallevels, finding that the primary focus is on only one dimension of food security-agricultural output as a proxy for food availability. Given that food security comprises availability, access, utilization and stability dimensions, improved practice would involve more effort to incorporate food access and stability indicators into agricultural systems models. The empirical evidence base for including food access indicators and their determinants within agricultural systems models requires further development through appropriate short and longterm investments in data collection and analysis. Assessment of the stability dimension of food security (through time) is also particularly under-represented in previous work and requires the development and application of appropriate dynamic models of agricultural systems that include food security indicators, coupled with more formalized treatment of robustness and adaptability at both the regional and household levels. We find that agricultural systems models often conflate analysis of food security covariates that have the potential to improve food security (like agricultural yields) with an assessment of food security itself. Agricultural systems modelers should exercise greater caution in referring to analyses of agricultural output and food availability as representing food security more generally

Genetic diversity of Colletotrichum gloeosporioides in Nigeria using amplified fragment length polymorphism (AFLP) markers

Colletotrichum gloeosporioides is the causal agent of yam anthracnose disease in Nigeria. Differential cultivars and amplified fragment length polymorphic DNA markers were used to assess the extent of genetic diversity among 39 isolates of the pathogen. Fourteen (14) pathotypes of the pathogen were identified based on inoculation of a differential set of Dioscorea alata genotypes of which pathotype P11 was the most virulent attacking all differential D. alata host genotypes, while pathotype P8 was the least virulent. 52% of the isolates were avirulent, 23% were slightly virulent and 25% were virulent. Amplified fragment length polymorphism (AFLP) analysis confirmed genetic variation among the C. gloeosporioides isolates and was effective in establishing genetic relationships between them. However, the grouping of the isolates based on AFLP analysis was not directly related to virulence groups or geographical origin of the isolates. The genetic variation in C. gloeosporioides is important in choosing strategies to develop durable resistanceKeywords: Anthracnose disease, pathotypes, genetic diversity, amplified fragment length polymorphism (AFLP) markers, ya