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Matus, A., A.E. Slinkard, and A. Vandenberg. 1993. The potential of zero tannin lentil. p. 279-282. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

The Potential of Zero Tannin Lentil

A. Matus, A.E. Slinkard, and A. Vandenberg

  1. METHODOLOGY
    1. Fungicide Test
    2. Agronomic Trials
  2. RESULTS
    1. Fungicide Test
    2. Agronomic Trials
  3. DISCUSSION
  4. FUTURE PROSPECTS
  5. REFERENCES
  6. Table 1
  7. Table 2
  8. Table 3
Lentil (Lens culinaris Medikus) is the fourth most important pulse crop in the world after bean (Phaseolus vulgaris L.), pea (Pisum sativum L.), and chickpea (Cicer arietinum L.). The four major lentil producing countries in decreasing order are Turkey, India, Canada, and the United States (FAO 1988). Turkey has been the leading lentil exporter in recent years except in 1990 when Canada temporarily became the leader. Slinkard et al. (1990) reviewed the history of lentil production in Canada.

Quality in lentil is based primarily on two factors: short cooking time and physical appearance or eye appeal. In most markets, the seed must be "big and bright." 'Laird' lentil (Slinkard and Bhatty 1979), the most widely grown cultivar in Canada and thus, in the world, is a yellow cotyledon type characterized by large seeds enclosed in a bright, light green seed coat. 'Laird' lentil is the preferred cultivar in many parts of the world, largely because of its appearance.

The seed coat of 'Laird' and all other lentil cultivars contains polyphenolic compounds (tannin precursors) which slowly oxidize and undergo a "tanning" reaction. Thus, if lentil seeds are exposed to air, the polyphenolic compounds in the seed coat oxidize and the seed coat slowly turns tan, eventually turning a dark reddish brown. These discolored seed coats are a down grading factor and the seed lot will be graded "Sample" because of damaged seed. This oxidation process proceeds slowly at room temperature and rapidly under conditions of high temperature and high humidity. Rain during the final stages of seed ripening in the field may discolor some of the seed coats, and the seed lot may be down graded. Lentil seed cannot be carried over from one year to the next because of discoloration of the seed coats; the only exception is when lentil seed is stored in large bulk bins with a small surface area. Even then, seed coats will be discolored in the surface layer, due to direct exposure to the air.

A large portion of the USDA Lentil Collection was grown at the Crop Development Centre, University of Saskatchewan in 1972. The seed was harvested and stored in a seed storage room. Germination started dropping after seven years and the entire collection was regrown to produce fully viable seed. Seed coats were dark reddish brown on all accessions except those with black seed coats and PI 345635 which still had bright white seed coats. PI 345635 was crossed with 'Laird' and 'Eston' and the mode of inheritance of this trait was studied. Vaillancourt (1984) found that this trait was due to the absence of polyphenolic compounds in the seed coat and that this was controlled by a single recessive gene, tan. Vaillancourt et al. (1986) reported that the zero tannin (ZT) gene had a pleiotropic effect on plant pigmentation (no anthocyanin pigment). In addition, the seed coat of the ZT lentil was thinner and more fragile than the normal seed coat, making the seed more susceptible to seed rot. Subsequently, over 100 F2-derived F4 families from the crosses PI 345635 x 'Laird' and PI 354635 x 'Eston' were selected for agronomic evaluation. The objective of this study was to determine the agronomic potential of ZT lentil, based on the performance of these 100 plus lines.

METHODOLOGY

Over 100 F4-derived F5 and F6 families of ZT lentil were evaluated in 1990 at the University of Saskatchewan. 'Laird' and 'Eston' lentil were used as commercial check cultivars in all tests. Four-row plots with rows 30 cm apart and 4 m long were used in 3-replicate tests.

Fungicide Test

A paired comparison (metalaxyl fungicide at 6 g a.i./100 kg seed vs. check) was used to evaluate the need for fungicidal seed treatment in ZT lentil lines. Two check cultivars and 14 ZT lentil lines were grown in 3-replicate tests in 1990 and evaluated for emergence (plants/m of row), days to flower, plant height, 1,000-seed weight, and seed yield.

Agronomic Trials

Two check cultivars and 34 ZT lentil lines were grown in a 6 x 6 lattice with 3 replications in 1990. Three sets of 34 ZT lines were grown at two locations (Saskatoon and Sutherland). All seed was treated with metalaxyl to minimize differences in stand emergence. Data were collected on emergence (plants/m of row), days to flower, plant height, 1,000-seed weight, and seed yield.

RESULTS

Fungicide Test

Metalaxyl fungicide seed treatment had no effect on seedling emergence of the two check cultivars, indicating that fungicide is not required for these two commercial cultivars (Table 1). Seedling emergence of the untreated ZT lentil lines was only about 63% of the check cultivars. Metalaxyl fungicide treatment of the ZT lentil seeds increased seedling emergence of the ZT lentil lines to 90% of the check cultivars, indicating that metalaxyl seed treatment is beneficial to seedling emergence of ZT lentil.

The fungicide by ZT vs check cultivar interaction was significant for yield due to the effect of metalaxyl in increasing yield of the ZT lines (expected response) and decreasing yield of the check cultivars (unexpected response) (Table 1). Metalaxyl fungicide treatment had no effect on days to flower, plant height, or 1,000-seed weight (data not presented). In addition, differences among ZT lines were significant for all traits (data not presented).

Agronomic Trials

Results were consistent over two locations and over the three 6 x 6 lattice experiments in that in nearly every instance locations, lines and the line by location interaction were significant for every trait. The significant location effect indicated that the environmental conditions were different enough to cause markedly different responses. The significant line effects indicated large genetic differences among the ZT lentil lines for the various traits. The significant line by location interaction indicated that all lines did not respond in the same manner for all traits at the two locations. A significant line by location (genotype by environment) interaction occurs frequently among unselected lines of crops with an undeterminate growth habit such as lentil, especially in the presence of large differences in maturity.

The agronomic performance of the highest yielding 10 lines out of the 36 lines in 6 x 6 lattice test 3 averaged over two locations is presented in Table 2. Similar results occurred in 6 x 6 lattice tests 1 and 2. A general comparison of means and ranges over all three tests is presented in Table 3. Data in Tables 2 and 3 indicate that selection of some of the higher yielding ZT lentil lines would result in several lines that would approach the agronomic performance of the two check cultivars in all traits except for seed weight. The low seed weight is due to the extremely low weight of the PI 345635 parent (26 g/1,000 seeds).

DISCUSSION

Zero tannin lentil shows considerable promise as a high quality premium priced product. The seed coat does not discolor with time or weathering damage and retains its bright appearance. The first cycle of crossing produced several lines that have acceptable agronomic traits. Several of them yield 80 to 90% of the yield of the commercial cultivars and would be economically viable if they would command a price premium to compensate for the lower yield. A second cycle of crosses to adapted cultivars will result in the production of ZT lentil lines that yield competitively with standard lentil cultivars and have a wide range in seed weight as required for any market.

The ZT lentil seeds have a thinner seed coat than standard lentil seeds (Vaillancourt et al. 1984), and will imbibe water and cook more rapidly than standard lentil seeds. These ZT lentil seeds are also smaller than seeds of the commercial cultivars and thus will cook faster since speed of cooking is a function of seed size, among other factors (Bhatty 1988). The rapid cooking characteristic and the bright appealing color of the ZT lentil seeds may stimulate interest in a premium quality product for a specialty market.

The ZT lentil lines require a metalaxyl fungicide seed treatment for a normal level of seedling emergence. The seed coats of the standard lentil cultivars are thicker than the seed coats of ZT lentils and contain about 6% polyphenolic compounds (condensed tannins) (Vaillancourt et al. 1986). These polyphenolic compounds are water soluble and exhibit fungistatic properties (Azaizeh and Pettit 1987). The thin seed coat of ZT lentil makes the seed more susceptible to mechanical damage which is further complicated by extremely rapid imbibition through the thin and/or cracked seed coat. During rapid imbibition intracellular substances, primarily starch grains and protein bodies, are extruded from the seed (Spaeth 1987). Then, soil-borne and seed-borne pathogens use these substances for nutrients, resulting in increased levels of seed rot, especially in ZT lentils which lack the fungistatic polyphenolic compounds in their seed coat. Thus, ZT lentil seeds must be treated with metalaxyl fungicide to reduce seed rot and maintain a normal level of seedling emergence.

FUTURE PROSPECTS

Zero tannin lentil seeds have a thin seed coat and will require metalaxyl fungicidal seed treatment for normal seedling emergence. Special precautions must also be taken during threshing and handling of the seed to minimize mechanical damage to the seeds. Otherwise, ZT lentil can be grown just like any other lentil.

The ZT lentil is a high quality product and will command a premium price in low volume specialty markets because of its attractive appearance. ZT lentil seeds also are excellent for producing lentil sprouts due to the absence of discolored seed coats. The first cycle of crossing produced some lines yield 80 to 90% of standard lentil cultivars. A second cycle of crossing to adapted cultivars should produce lines that yield competitively with standard cultivars.

REFERENCES

Table 1. Effect of metalaxyl fungicidal seed treatment on stand establishment and seed yield of the two check cultivars and 14 zero tannin (ZT) lentil lines in 1990.

Plants/m of rowz Seed yield (kg/ha)
Line No metalaxyl Metalaxyly No metalaxyl Metalaxyl
2 checks 38 40 2230 2021
14 ZT lines 24 (63)x 36 (90) 1220 (55) 1324 (66)
z36 plants/m of row is an excellent stand.
y6 g a.i./100 kg seed.
xPercent of check in parentheses.

Table 2. Agronomic performance of the check cultivars and the 10 highest yielding zero tannin (ZT) lentil lines out of 36 lines in 6 x 6 lattice test 3 averaged over two locations (Saskatoon and Sutherland) in 1990.

Line Seed yield (kg/ha) Plants/m of row Days to flower Height (cm) 1000-seed wt (g)
Laird 2,664 40 51 45 76
VLT-15 2,018 37 49 37 48
V2-95 1,888 36 47 43 40
V2-104 1,872 38 46 32 36
VLT-19 1,837 35 49 42 45
V6-93 1,720 35 46 37 35
Eston 1,696 38 44 32 37
VLT-20 1,668 36 48 37 43
V3-104 1,593 37 47 32 29
V8-91 1,580 35 50 32 28
V5-94 1,570 36 48 40 35
Standard error 85 1 1 1 1

Table 3. Summary of agronomic data for two check cultivars and 102 zero tannin (ZT) lentil lines (2 location average in 1990).

Line Seed yield (kg/ha) Plants/m of row Days to flower Height (cm) 1000-seed wt (g)
2 checks 2,111 36 47 37 57
102 ZT lines
Mean 1,272 36 47 34 34
Range (848-2,018) (30-41) (45-50) (28-43) (22-54)

Last update April 15, 1997 aw