Intra-specific variation in morphological characteristics and growth habitat of newly and accidentally introduced velvetleaf (Abutilon theophrasti Medic.) into Japan

The source of the velvetleaf spreading its distribution rapidly and causing serious problems in forage fields all over Japan since the mid 1980s was thought to be a new accidental introduction of seeds from velvetleaf mingled in some imported grains from the USA and Australia. However, velvetleaf used to be cultivated as a fiber crop until the 1880s. We examined the intraspecies variations, such as morphological characteristics and growth habits, using accessions previously collected and obtained from imported grains. Using principal component analysis (PCA), the accessions were classified into crop type and weed type. The crop type capsule was mostly an ivory color, and the weed type was mostly an ebony color. The crop type showed characteristics of a fiber crop, such as an erect form, uniform flowering and a low seed dormancy rate. Conversely, the imported grains were classified into the weed type which showed a strong weedy nature, such as branched form, long flowering period, high reproductive ability and a high dormancy rate. These results suggest that the new introduction is different from the indigenous fiber crop, and may possibly be the source of the present invasive velvetleaf because of its strong weedy nature. However, further studies comparing the new introduction directly with the present velvetleaf are necessary.     

Development and comparative test of squid liver artificial bait for tuna longline

ABSTRACT:   We have been developing an artificial bait for longline tuna fishing using the liver of the Japanese common squid Todarodes pacificus , a waste product of the squid fisheries industry, as the primary component. Three control test operations using the artificial bait and natural squid were conducted during January 1998, 1999 and 2000. During these operations, we compared the angling performance of the artificial bait with that of the natural squid. Some tuna was caught using the artificial bait; however, the hooking ratio for the artificial bait was less than that for the natural baits. Despite this, there was no significant difference between the hooking ratio by artificial bait and natural squid. In addition, species selectivity in the by-catch, a characteristic particular to this artificial bait, was observed. In the present paper, we discuss the hooking ratio and the reduction in by-catch of the artificial bait compared with natural bait.     

ISSR variation in a worldwide collection of velvetleaf (Abutilon theophrasti) and the genetic background of weedy strains mingled in grains imported into Japan

Velvetleaf seeds have been found in imported grains in Japan. The plants from these seeds show a weedy growth habit, such as that seen in the noxious velvetleaf which has recently emerged in Japan and noted in our previous study. To elucidate the genetic background of the velvetleaf strains found in imported grains we evaluated the genetic variation of six strains and an additional 39 worldwide velvetleaf accessions using the intersimple sequence repeat (ISSR) polymorphism. Cluster analysis based on the ISSR polymorphism emitted two major clusters which corresponded well with classification by growth habit, that is, crop type and weed type. Five of the six strains from the imported grains formed a small cluster. All six strains united into one major cluster containing the weed type accessions, while all of the old Japanese accessions formed another major cluster containing the crop type accessions. The genetic difference between imported weedy velvetleaf and old Japanese accessions suggests that imported velvetleaves are the source of the recent outbreak of the noxious velvetleaf in Japan.