Estival

Lettuce

Variety Description

Variety used for comparison: 'Summertime'

Summary: 'Estival' has shallower, less dense incisions on the apical margin of the leaf blade than 'Summertime'. At harvest maturity, 'Estival' has a shorter stem than 'Summertime'. When cultivated during hot summer growing conditions, the leaves from the head of 'Estival' are more resistant to rib discolouration than those of 'Summertime'.

Description:

PLANT TYPE: closed head lettuce

SEEDLING: absent to very weak anthocyanin colouration, medium to large cotyledons, elliptic cotyledons

LEAF: attitude intermediate between semi-erect and semi-prostrate at the 10 to 12 leaf stage, medium in thickness to thick, semi-erect at harvest maturity, circular, bluish green, dark intensity of colour of outer leaves, no anthocyanin colouration, weak to moderate glossiness on inner side, concave profile of outer leaves, very weak blistering, medium sized blisters, lobed, weak undulation of margin, shallow and sparse to medium density incisions of margin, flabellate (fan shaped) venation

HEAD: medium degree of overlapping of upper part of leaves, dense, circular in longitudinal section, 57 days to beginning of bolting under long day conditions, 45 days to harvest maturity

SEED: black

Origin & Breeding History: 'Estival' was developed from a cross between varieties 'Valleygreen' and 'Ithaca'. The cross took place in October of 1998 in the greenhouses of the Horticultural Research and Development Center in Saint-Jean-sur-Richelieu, Québec. F1 seeds were planted in greenhouses in December of 1998 and F2 seeds were collected and bulk massed in June of 1999. From 2000 to 2002, successive generations were grown and harvested at the Sainte-Clotilde experimental station and at a muck soil farm in Napierville, Québec. The selections from each were based on good 'Vanguard' character combined with size, flatness of butt, low ribbiness, colour, short core, weight, excellent leaf configuration and lack of symptoms of rib discolouration. In 2003, F5 seedlings designated 'X300-M-186-1071-457' were transplanted and evaluated. In 2004, single plant selection continued on F6 plants. During the same year, F6 seeds were planted in single plant progeny rows in the San Joaquin Valley for seed evaluation and multiplication. Ten single plants were selected and F7 seeds were collected from individual plants, the remainder of which were bulk massed after harvest in September of that year. In March of 2005, 'X300-M-186-1071-457' was considered a new variety and became known as 'QSJ-03' and in 2006 as 'Estival'.

Tests & Trials: The tests and trials for 'Estival' were conducted at the Ferme JPL Guérin, in Sherrington, Québec during the summers of 2005 and 2006. Both the candidate and reference varieties were sown in the greenhouse and later transplanted into fields of organic soil. Each variety was planted in four randomly planted plots. The plots were composed of two rows spaced 35.5 cm and planted in mounds that were 14.6 metres long and 91 cm wide. Each plot contained 80 plants resulting in a total of 320 plants per variety. The plants were grown under normal conditions for cultivation with long days (photo period between 15 and 16 hours per day). The lettuce was harvested and evaluated at the time of optimal maturity during the last two weeks of July. All measured characteristics were based on measurements of 4 x 12 plants, for a total of 48 plants.

Comparison tables for 'Estival' with reference variety 'Summertime'

Data from 2005 and 2006 combined.

Length of stem (mm)

Plants showing symptoms of rib discolouration (%)

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Lettuce: 'Estival' (left) with reference variety 'Summertime' (right)

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Lettuce: 'Estival' (left) with reference variety 'Summertime' (right)

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Lettuce: 'Estival' (left) with reference variety 'Summertime' (right)