Effects of Companion Planting of Two Common Buckwheat Varieties on Yield and Yield Concerning Characters

Yield of common buckwheat (Fagopyrum esculentum Moench) tends to be low and unstable. This is because common buckwheat is an allogamous crop and thus many such factors in the pollination process as meteorological conditions or behavior of pollinator affect yield. Ogasahara et al. (1993) investigated the dynamism of pollen transfer and load on stigma with special reference to the relationship between meteorological conditions and pollinator behavior. Namai and Ohsawa (1986) reported that seed-setting of common buckwheat is restricted when pollen load was very low. It is very important to remove obstacles in the process of pollination and fertilization for the enhancement of yield of common buckwheat. When pollen grains of two different species or varieties are cultured on a same medium or loaded on a same stigma, pollen grains of one species or variety may influence the growth of the others. This is known as mixture effect (lwanami 1970) or Mentor effect. In the former Russia, Mentor effect has been investigated for quite a long time. Many Russian researchers have reported the promoted pollen tube elongation by mixed pollination of different species or varieties. This experiment was conducted aiming the yield enhancement of common buckwheat after a research in Russia reporting that free inter-varietal pollination in common buckwheat resulted in a couple of tens percent ofyield increase. Materials and Methods Two common buckwheat varieties Shinano No. 1 (Japanese variety, most wide-spread in Nagano prefecture) and Nepalese landrace (collected in Jharkot) were used. The Nepalese landrace was selected from our collection of foreign buckwheat strains as that having almost the same flowering period as Shinano No. I. Experiment was carried out in the research farm of Shinshu University. Experimental plot (11 m x 28 m; shown in Fig. 1) was located where Fagopyrum plants do not exist in the neighboring filed. Seeding was carried out on July 22, 1993, in the manner of 50 cm row distance and about 3 cm hill distance. Only Shinano No.