The invention provides an isolated gene encoding Mch4 or an isolated gene encoding Mch5 as well as functional fragments thereof. may be realized which make it possible to easily realize an arrangement which reduces a possibility of deterioration of an optical characteristic, and which is suitable for a reduction in manufacturing costs and for mass-production, an image pickup lens of the present invention satisfies the following formulas and ;1. , Candidatus Liberibacter asiaticus, Corynebacterium, Erwinia spec.