Expression of the Narrow Leaflet Gene for Yield and Agronomic Traits in Soybean

Abstract

Genes that affect plant form and function may be used to enhance the yield of soybean [Glycine max (L.) Merr.]. Most soybean cultivars have broad (ovate) leaflets. A single gene, ln, controls inheritance for the narrow leaflet characteristic. Narrow leaflet cultivars (ln/ln) also tend to have a higher percentage of four-seeded pods than ovate (Ln/Ln) leaflet cultivars. Heterozygous (Ln/ln) plants have a leaflet shape intermediate between narrow and ovate. Determining the agronomic effects of the narrow leaflet allele (ln) in the heterozygous (Ln/ln) condition in soybean may have applications in practical plant breeding. We studied an ovate leaflet and a narrow leaflet cultivar, crosses between them in the F(1) and F(2), and backcrosses to both cultivars. The ratio of leaflet width to leaflet length accurately distinguished among narrow, ovate, and intermediate leaflet plants in the F(2) and backcross generations. In the F(2) generation, differences occurred among plants with different leaflet morphology. Narrow leaflet plants produced more seeds per pod and lower seed weight than ovate leaflet plants. Narrow and ovate leaflet plants produced comparable numbers of pods per plant and plant yield. Compared to ovate leaflet plants, intermediate leaflet plants produced similar numbers of seeds per pod and seed weight. Intermediate leaflet plants produced significantly more pods per plant and plant yield than plants with either ovate or narrow leaflets. The heterozygous condition at the locus for leaflet morphology resulted in heterosis for plant yield and may be of benefit in association with commercialization and development of hybrid soybean.

LnIs a Key Regulator of Leaflet Shape and Number of Seeds per Pod in Soybean

“…Differences in leaflet shape and pod type between Ln and ln soybean plants have been repeatedly assessed in different soybean (Takahashi, 1934;Domingo, 1945;Weiss, 1970;Bernard and Weiss, 1973;Mandl and Buss, 1981;You et al, 1995;Dinkins et al, 2002;Jeong et al, 2011). These studies have consistently shown that Ln plants tend to have broader leaflet shapes (Figures 2A and 2B) and lower NSPP than ln plants ( Figures 2C and 2D).…”

“…Previous agronomic studies on the ln locus using isogenic lines (Mandl and Buss, 1981), diverse cultivars (You et al, 1995), and broad (Ln/Ln), heterozygous (Ln/ln), and narrow (ln/ln) leaflet types (Dinkins et al, 2002) have repeatedly found that broad and narrow leaflet soybean genotypes have similar seed yields, but narrow leaflet plants consistently produce smaller seeds than those of broad leaflet plants. The fact that the narrow leaflet plants tend to produce a greater number of seeds has garnered a great deal of attention, particularly in the development of soybean cultivars for sprouts.…”

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“…Bernard and Weiss assigned a new gene symbol, ln, to the narrow leaflet trait. Similarly, Dinkins et al (2002) reported that leaflet types were genotypically marked as follows: narrow leaflet (ln/ln), intermediate leaflet (Ln/ln), and ovate leaflet (Ln/Ln).…”

“…In Japan, Sawada (1988) who studied the crossing result between broad leaflet soybean and narrow one, found that the value of LSI < 2.6 was constantly used to classify the broad leaflet while the value of LSI > 2.6 was used to classify the narrow leaflet. Porter et al (2000) classified the leaf shape into ovate and narrow leaflet, but Dinkins et al (2002) used different classification of the leaf shape, which is used in this study i.e. narrow, intermediate, and ovate leaflet.…”

“…oval, ovate, lanceolate and linear leaflets exhibited considerable range of variation in the plant height, days to flowering, days to maturity, specific leaf weight, and number of pods per plant, harvest index and 100 seed weight. Narrow leaflet plants produced more seeds per pod, but the seed apparently has a small weight, compared to those of ovate leaflet plants, which produced less seeds per pod with the large weight (Dinkins et al 2002). The availability of genetic variation through breeding program provides a basic selection.…”