Modification of Heterosis for Protein and Yield Components by Bean Common Mosaic Virus in Phaseolus vulgaris

The effect of bean common mosaic virus on yield, yield components, and seed protein content was studied in tour bean cultivars and their F1 hybrids. The results of this experiment showed 3 significant decrease for yield in diseased plants; the 100 seed weight was also significantly reduced in one of the diseased varieties. The percentage of protein was increased m virus-diseased plants: this increase was due to non-protein nitrogen. Usually, the percentage of heterosis in virus-diseased F1 hybrid of two susceptible varieties was decreased while in F1 hybrids of “susceptible × resistant” varieties it was increased. This study shows the danger of drawing conclusions in quantitative genetic studies then dealing with both diseased and healthy plants.