Molecular and morphological differentiation between the crop and weedy types in velvetleaf (Abutilon theophrasti Medik.) using a chloroplast DNA marker: seed source of the present invasive velvetleaf in Japan

Abstract

A comparison of chloroplast DNA (cpDNA) sequences was carried out between the crop and weed types of Abutilon theophrasti to clarify the seed source of the present weedy velvetleaf in Japan. A sequencing analysis of approx. 6% of the chloroplast genome (ca 10 kbp) detected three nucleotide substitutions, one six-base-pair insertion/deletion (indel) and one 30-base pair inversion, which distinguish two haplotypes of cpDNA. A PCR-based survey of the indel and the inversion revealed that the 93 accessions of velvetleaf collected from the world could be divided into two groups. A morphological marker (capsule color) could be used to discriminate the crop type and the weed type, and hence, along with cpDNA haplotype, to distinguish three genotypes (Type I, II, and III). All Japanese cultivars and crop accessions from other countries were Type I. Weed types were divided into Type II and III. All of the samples from the USA, and the samples taken from grain imports to Japan were Type III. Since most of the weedy types distributed in Japan were of Type III, it is argued that they were introduced as seeds in the imported grain. We also found that the Type II plants sporadically occurred in Japan. It is suggested that they originated as hybrids, with indigenous cultivars as the maternal ancestor. Such hybrids must have survived since the cessation of velvetleaf cultivation about a century ago.

Estimation of the Process Invaded by Accidentally Introduced Strains of Abutilon theophrasti into Japan: Temporal Change of Chloroplast DNA Haplotype Frequencies across a Century

“…This specimen type was evenly collected in all decades of the period surveyed except for the 1890s, 1900s, and 1970s (Table 1). Since haplotype A occurs also in forage crop fields now 10 , these results suggest that voluntary strains that escaped from cultivated plants have persisted in the wild. In contrast, the first specimen of cpDNA haplotype B was collected in Tokyo in 1893.…”

“…All of the samples from the United States and the samples taken from grain imports to Japan were found to be Type III (haplotype B, ebony capsule) in contrast to all Japanese cultivars, which were Type I (haplotype A, ivory capsule) 10 . Since most of the weedy types distributed in Japan were Type III, it was argued that they were introduced as seed in imported grain, that is, the second outbreak scenario 10 . In order to understand the process of invasion by accidental introduction, it is useful to know the temporal changes in genotype frequencies over a century.…”

“…460 base pairs) containing 6 base of an insertion or deletion polymorphism 10 . For successful amplification of this polymorphic site, it was necessary to devise a primer pair for a nested PCR technique.…”

“…The contaminants detected in imported grain showed strong weedy growth, and were genetically different from crop types indigenous to Japan 8,9 . Chloroplast DNA (cpDNA) variations, which distinguish two haplotypes (A and B), were used to distinguish three genotypes (Type I, II, and III) with capsule color variations (ebony and ivory) as a morphological marker 10 . All of the samples from the United States and the samples taken from grain imports to Japan were found to be Type III (haplotype B, ebony capsule) in contrast to all Japanese cultivars, which were Type I (haplotype A, ivory capsule) 10 .…”

“…Chloroplast DNA (cpDNA) variations, which distinguish two haplotypes (A and B), were used to distinguish three genotypes (Type I, II, and III) with capsule color variations (ebony and ivory) as a morphological marker 10 . All of the samples from the United States and the samples taken from grain imports to Japan were found to be Type III (haplotype B, ebony capsule) in contrast to all Japanese cultivars, which were Type I (haplotype A, ivory capsule) 10 . Since most of the weedy types distributed in Japan were Type III, it was argued that they were introduced as seed in imported grain, that is, the second outbreak scenario 10 .…”