Genetic Diversity Analysis Of Goosegrass

Genetic diversity analysis

The five primer combinations amplified 13 fragments ranging in size between 50 to 400 base pairs, of which 9 (69.23%) were polymorphic (Table 5). The highest number of amplification products was obtained with the primer combination me5-em9 and the lowest with me4-em4 while the average number of bands among the five primer pairs was 2.6 (Figure 1). The number of polymorphic fragments for each primer combination varied from 0 to 4 with the average number 1.8.

(Table 5)

(Figure 1)

The goosegrass ecotypes can be divided into 6 groups at 74% genetic similarity (Figure 2). Jaccard’s genetic similarity coefficients ranged from 0.30 to 1.00 with the lowest similarity was between ecotype S5 (Group III) and S9 (Group
M1 was sampled from a vegetable farm in Malacca and known to have developed twofold resistance to herbicide ammonium-glufosinate based on the previous research by Adam et al. (2010). Likewise, K2, B2 and J1 were collected from oil palm plantations which were heavily applied with glyphosate and ammonium-glufosinate for weed control. Detection of genes involved in herbicide resistance by SRAP markers may have influenced grouping of these ecotypes. All ten ecotypes from Sabah were divided into the six groups. Since genetic differentiation in resistance gene might have affected the groupings, we supposed that these ecotypes possess variations of alleles that are suited for the management practices or they had different genetic background than when they first introduced in Sabah. Other possible reason of this high genetic variation among all ecotypes is due to the gene flow between populations of goosegrass in different areas. Dissemination of tiny goosegrass seeds over a vast area is facilitated by wind. Viability of seed is longer than of pollen making dispersal of goosegrass even more thriving. Moving equipments and human activities in and out of the fields lead to high likelihood of seed escape as well (Kausch et al. 2010). Wang et al. (2011) suggested three other possible reasons: genetic overlap between goosegrass ecotypes, exchange of germplasm resources and ploidy. Goosegrass
Muona et al. (1984) reported that resistant barley differed from the susceptible ones in heading date and plant height where the resistant type was taller and later than the susceptible families. In point of fact, goosegrass ecotypes with prolonged exposure to glyphosate and ammonium-glufosinate in the farms were grouped together in Group I. This could have impelled some changes in the phenotypic traits of goosegrass in Group I that differentiated them from the other 2 groups. Herbicide-resistant late watergrass Echinochloa phyllopogon was reported to be shorter, had narrower, shorter flag leaves, thinner culms, smaller and slender spikelets compared to the susceptible biotype (Tsuji et al. 2003). With the exception of the plant height and unstudied characters, goosegrass ecotypes in Group I had similar narrow and short flag leaves like the resistant late watergrass.

A weak insignificant correlation between the molecular and morphological distances of goosegrass (Figure 11) were rather similar to the findings of other plants, a tropical tree species Paramichelia baillonii (Li et al. 2008), barley (Lund 2002) and potato (Vetelainen et al. 2005). Molecular markers might have detected variations in parts of the genome that do not appear to influence the phenotype. Genes revealed by the molecular markers are not necessarily expressed nor reflect