Tomato fruit having increased firmness
This invention relates to a tomato fruit with significantly increased firmness due to the presence of at least one genetic element (or quantitative trait loci; QTLs) in the cultivated plant producing said tomato fruit, compared to fruit from a control tomato plant which does not have said genetic element(s). A cultivated tomato plant producing tomato fruit with significantly increased fruit firmness and a method for detecting QTLs linked to significantly increased fruit firmness are also provided.
1. A method for selecting a cultivated Solanum lycopersicum plant that provides fruit with increased firmness of the inner pericarp as compared with fruit from a control Solanum lycopersicum plant, the method comprising:
a) detecting in the cultivated Solanum lycopersicum plant the presence of QTL2 on chromosome 2, and
b) selecting a cultivated Solanum lycopersicum plant that includes the presence of said QTL2, thereby selecting a cultivated Solanum lycopersicum plant that provides fruit with increased firmness of the inner pericarp as compared with fruit from a control Solanum lycopersicum plant;
wherein detecting the presence of said QTL2 in the cultivated Solanum lycopersicum plant comprises:
i) providing a sample of genomic DNA from the cultivated Solanum lycopersicum plant, and
ii) detecting in the sample of genomic DNA at least one DNA marker including HOX7A, wherein HOX7A can be detected by a forward primer of SEQ ID NO: 7 and a reverse primer of SEQ ID NO: 8; and
wherein the increased fruit firmness of the inner pericarp is from between 1.2 to 2 times greater at the harvesting stage than that of fruit from the control Solanum lycopersicum plant.
2. The method of claim 1 , wherein the harvesting stage is the mature green stage.
3. A method of introgressing a trait for increased fruit firmness from a donor Solanum lycopersicum plant, which provides fruit with increased firmness of the inner pericarp as compared with fruit from a control Solanum lycopersicum plant, into a recipient Solanum lycopersicum plant, the method comprising:
a) crossing the donor Solanum lycopersicum plant with the recipient Solanum lycopersicum plant to provide offspring Solanum lycopersicum plants,
b) detecting in offspring Solanum lycopersicum plants the presence of QTL2 on chromosome 2, and
c) selecting an offspring Solanum lycopersicum plant that includes the presence of said QTL2, thereby introgressing the trait for increased fruit firmness of the inner pericarp from the donor Solanum lycopersicum plant into the recipient Solanum lycopersicum plant;
wherein detecting in offspring Solanum lycopersicum plants the presence of said QTL2 comprises isolating a sample of genomic DNA from the offspring Solanum lycopersicum plant and detecting in the sample of genomic DNA at least one DNA marker including HOX7A, wherein HOX7A can be detected by a forward primer of SEQ ID NO: 7 and a reverse primer of SEQ ID NO: 8.
4. A method of introducing a trait for increased fruit firmness of the inner pericarp into a hybrid Solanum lycopersicum variety, the method comprising:
a) crossing a donor Solanum lycopersicum plant that provides fruit with increased firmness of the inner pericarp as compared with fruit from a control Solanum lycopersicum plant with a recipient inbred Solanum lycopersicum plant to provide F1 progeny plants,
b) selecting F1 progeny plant(s) that have increased fruit firmness of the inner pericarp,
c) backcrossing the selected progeny plant(s) of b) with the recipient inbred Solanum lycopersicum plant to produce backcross progeny plants,
d) selecting for backcross progeny plants of c) that have increased fruit firmness of the inner pericarp and morphological and physiological characteristics of the recipient inbred Solanum lycopersicum plant, wherein the selecting steps for increased fruit firmness comprises:
(i) isolating genomic DNA of the backcross progeny, and
(ii) testing the isolated genomic DNA for the presence of at least one molecular marker for QTL2 on chromosome 2, which comprises detecting in a sample of said isolated genomic DNA at least the DNA marker HOX7A, wherein HOX7A can be detected by a forward primer of SEQ ID NO: 7 and a reverse primer of SEQ ID NO: 8, and
e) repeating steps c) and d) two or more times in succession to produce selected third or higher backcross progeny,
f) optionally selfing selected backcross progeny in order to identify homozygous plants, and
g) crossing at least one of the backcross progeny or selfed plants with another inbred Solanum lycopersicum plant to generate a hybrid Solanum lycopersicum variety with increased fruit firmness of the inner pericarp and all the morphological and physiological characteristics of a control hybrid Solanum lycopersicum variety from the same two parents in the absence of the trait for increased fruit firmness of the inner pericarp when grown under the same environmental conditions.