Genotypic response of cowpea Vigna unguiculata (L.) to in vitro regeneration from cotyledon explants

Summary A plant regeneration system applicable to 17 cowpea genotypes was developed. Cotyledons were initiated on 1/3 MS medium containing 15 to 35 mg N⁶-benzyladenine (BA) per 1 (66.6 to 155.3 μM) for 5 to 15 d. For shoot regeneration, the explants were transferred to a medium containing 1 mg BA per 1 (4.4 μM). Within 1 wk, shoot formation was visible at the proximal end of the cotyledons. Regeneration percentages (1% to 11%) and the numbers of shoots (4 to 12 per explant) were significantly influenced by genotype. Culture duration and BA concentration in the initiation stage significantly affected regeneration capacity. Explants initiated on media containing 15 mg BA per 1 for 5 d resulted in the highest percentage of explants capable of regeneration. Conversely, the highest number of shoots was obtained from explants initiated on media supplemented with 35 mg BA per 1. Whole plants were obtained on a plant growth regulator-free medium. To our knowledge, this is the first report of plant regeneration from U.S. commercial cowpea cultivars and breeding lines. This system is adaptable to diverse cowpea genotypes and will facilitate cowpea genetic transformation. Published with the approval of the Director of the Arkansas Agricultural Experiment Station.     

The changing pattern of ischemic heart disease

Male and female death rates from all the major forms of cardiovascular disease were approximately equal until about 1920. Since that time the male:female ratio in fatal ischemic heart disease (IHD) has risen dramatically, but some closely related diseases such as cerebrovascular disease and uncomplicated angina pectoris have maintained sex ratios close to unity. It is difficult to reconcile this divergent trend in the sex ratio of IHD with a simple stenotic-thrombotic view of myocardial infarction (MI) and it is suggested that the modern epidemic of MI in men may be the result of a disorder of muscle metabolism (“vulnerable myocardium”) superimposed on a relatively stable background of stenotic-thrombotic arterial disease. The proposed mechanism would also help to explain the selective action of some modern “coronary risk factors” (such as cigarette smoking and physical inactivity) which increase the risk of MI but have little or no effect on the risk of developing cerebrovascular disease or uncomplicated angina pectoris.