Koshihikari BL

Follow "varieties bred from Koshihikari as a parent" through NARO's database and 207 named entries come out. Of those, 26 are lines whose names carry "Koshihikari BL" or "Koshihikari SBL".

This site does not give each of them a page of its own. Here is the reason.

Koshihikari with a single gene swapped out

Koshihikari's weakness is blast. To fix that without changing the variety, the method taken was to bring in only the blast resistance gene from another variety, and then backcross to Koshihikari again and again.

Look at the cross notations and the method can be read straight off them.

コシヒカリ/ササニシキ//5*コシヒカリ（コシヒカリ新潟BL1号） コシヒカリ/新潟早生//6*コシヒカリ（コシヒカリ新潟BL4号） コシヒカリ*3///コシヒカリ/IRBL9-W//2*コシヒカリ（コシヒカリ関東BL1号）

5*コシヒカリ means backcrossed to Koshihikari five times. Cross once with some other variety, cross that offspring with Koshihikari, cross the next offspring with Koshihikari again. Repeat this and apart from the stretch around the gene that was brought in, the contents return almost entirely to Koshihikari.

Listing them as "separate varieties" produces the wrong impression

This site follows the differences between varieties through pedigree diagrams. Line the BL lines up one by one and on the diagram it looks as though Koshihikari has gained 26 more children.

The reality is the opposite: the BLs are made with the aim of being the same thing as Koshihikari. Culm length, maturity, eating quality — they are bred so that they cannot be told apart from Koshihikari. The only difference is the blast resistance gene.

The breeding report from the Fukui Prefectural Agricultural Experiment Station states the aim outright.

Bred with the objective of introducing the true blast resistance gene Pita into "Koshihikari" In the first cross, in 1995, "Koshihikari" was used as the seed parent, and as the pollen parent "Tohoku IL No.6" (later "Sasanishiki BL6"), which carries the true blast resistance gene Pita

The objective written down is "the introduction of one gene". It does not say to make a new variety.

Niigata replaced the prefecture's entire Koshihikari at once, in 2005

Niigata Prefecture explains its reason for introducing them like this.

Because covering Koshihikari's weakness (susceptibility to blast) also leads to a reduction in the amount of pesticide used

And the timing is this.

From the Heisei 17 crop, "Koshihikari BL", which can be grown with less pesticide than conventional Koshihikari, was introduced across the prefecture all at once The simultaneous introduction was carried out in Heisei 17

From the 2005 crop, Niigata's Koshihikari switched over to BL all at once. Much of what is sold in shops as "Koshihikari from Niigata" is BL grown since that changeover.

A variety bred so that it cannot be told apart by taste or appearance replaced the mainstay of a production region outright, at the scale of a whole prefecture. On the pedigree diagram it looks like 26 rows; this is what it actually is.

We judged that writing "there are 26 of these, and this is how they work" in one place is more accurate than listing them one by one. The full set is below.

The 26 entries held here

Line name	Variety name	Cross notation
IL-a	コシヒカリ新潟BL1号	コシヒカリ/ササニシキ//5*コシヒカリ
IL-i	コシヒカリ新潟BL2号	コシヒカリ/トドロキワセ//5*コシヒカリ
IL-ta2	コシヒカリ新潟BL3号	コシヒカリ/PiNo.4//5*コシヒカリ
IL-z	コシヒカリ新潟BL4号	コシヒカリ/新潟早生//6*コシヒカリ
IL-k	コシヒカリ新潟BL5号	コシヒカリ/越みのり//5*コシヒカリ
IL-km	コシヒカリ新潟BL6号	コシヒカリ/ツユアケ//5*コシヒカリ
IL-zt	コシヒカリ新潟BL7号	コシヒカリ/とりで1号//5*コシヒカリ
IL-b	コシヒカリ新潟BL8号	コシヒカリ/BL1//5*コシヒカリ
IL-t	コシヒカリ新潟BL13号	コシヒカリ/K59//7*コシヒカリ
富山BL1号	コシヒカリ富山BL1号	コシヒカリ*2/BC-zt
富山BL2号	コシヒカリ富山BL2号	コシヒカリ*2/BC-ta2
富山BL3号	コシヒカリ富山BL3号	コシヒカリ*3/BC-b
富山BL4号	コシヒカリ富山BL4号	コシヒカリ*4/BC89
富山BL5号	コシヒカリ富山BL5号	コシヒカリ*5/BC49
富山BL6号	コシヒカリ富山BL6号	コシヒカリ*5/BC57
富山BL7号	コシヒカリ富山BL7号	コシヒカリ/96KBIL-32//2*コシヒカリ
富山80号	コシヒカリ富山APQ1号	ハバタキ/コシヒカリ//5*コシヒカリ
越南IL6号	コシヒカリBL1号	コシヒカリ/東北IL6号//4*コシヒカリ
愛知106号	コシヒカリ愛知SBL	コシヒカリ///cmsコシヒカリ*3//(cmsコシヒカリ*2/3ⅢK-84)F6
中国IL3号	コシヒカリ近中四SBL1号	コシヒカリ/中系IL10
関東IL1号	コシヒカリ関東HD1号	コシヒカリ/96KBIL-64//コシヒカリ
関東IL3号	関東HD2号	コシヒカリ/96KBIL-140//コシヒカリ///コシヒカリ
関東IL9号	コシヒカリ関東BL1号	コシヒカリ*3///コシヒカリ/IRBL9-W//2*コシヒカリ
鳥系IL1号	ゆめそらら	コシヒカリ/アキヒカリ//6*コシヒカリ
—	コシヒカリつくばSD1号	コシヒカリ*5/IR24
—	コシヒカリかずさ1号	コシヒカリ/ハバタキ//3*コシヒカリ

What has not been confirmed yet

What has been confirmed goes as far as Niigata introducing them across the prefecture from the 2005 crop and the breeding objective of Koshihikari BL No.1 being the introduction of the Pita gene.

What we have not yet gone to is when Toyama, Aichi, Kanto and Tottori each introduced theirs, what share of Niigata's Koshihikari is actually BL (the prefecture's material gives no figure), and which blast race group each BL answers to.

That the 26 above exist and that their cross notations are these rests on NARO's database. Beyond that, we will add only what can be confirmed, as it is confirmed.