New leaf mutation shr*-JH87, shredded leaf --Trimnell, MR, Albertsen, MC, Noble, SW In 1987 Steve Noble observed one of his F2 breeding lines segregating for a shredded leaf phenotype. This mutant does not express until after the juvenile phase of plant growth. Then, the leaf blade lamina becomes shredded between the horizontal veins of the adult-phase leaf. The cells between the veins do not undergo visible necrosis before becoming shredded. Depending upon the wind conditions, the phenotype can become very severe, with some leaves reduced to a mass of shredded strands of leaf material that is primarily composed of leaf vein. Figure 1 shows not only the extremely shredded appearance these plants can acquire, but it also shows how the wind can "tie" the shredded leaves into a tangled mass of leaf tissue. Steve gave remnant seed of this line from two different ear rows to us. We decided that the word "shredded" better described this mutant than did "slashed" (as is currently applied to a set of specific leaf mutations) and designated this mutant as shr*-JH87. It was planted in our 1990 Johnston nursery. One of the ear rows did not segregate, but the other one did. We made self- and sib-pollinations from this row and put the progeny seed in our cold room.

In 1998 we decided to again plant this mutant and to further characterize it in our Johnston nursery. We planted 2 self rows and 2 sib-pollinated rows. These were crossed with A632 and B73, reciprocally. These F1 crosses were then self-pollinated in our Hawaii winter nursery, and the resulting F2 seed was planted in our nursery this past summer. Segregation data for the previously mentioned plantings are shown:
 
Genotype Wild-type shredded leaf Corrected X2(3:1)
Original Heterozygote Selfed (F2) 12 Plants 3 Plants 0.023
shr*-JH87 Homozygote Selfed Ear #1 (F3) 0 Plants 12 Plants --
shr*-JH87 Homozygote Selfed Ear #3 (F3) 0 Plants 6 Plants --
shr*-JH87/A632 Selfed Ear #1 (F2) 19 Plants 2 Plants 1.92
shr*-JH87/A632 Selfed Ear #2 (F2) 16 Plants 1 Plant 2.38
A632/shr*-JH87 Selfed Ear #1 (F2) 13 Plants 4 Plants 0.02
A632/shr*-JH87 Selfed Ear #2 (F2) 15 Plants 0 Plants* --
shr*-JH87/B73 Selfed Ear #1 (F2) 13 Plants 2 Plants 0.56
shr*-JH87/B73 Selfed Ear #2 (F2) 18 Plants 1 Plant 2.96

*Oil yellow looking plants segregated in this row.

During the summer of 1998, we also crossed shr*-JH87 with sl1 (slashed leaf 1) even though the shr*-JH87 phenotype is very distinctively different than the slashed leaf mutant phenotype. These test-crosses were grown in our Hawaii winter nursery. A total of 71 plants were observed without any plants showing either the shredded leaf or slashed leaf phenotypes. The leaves of shr*-JH87 can shred along nearly the entire length of the leaf blade between the parallel veins, although not every interveinal area will shred. With sl1, the leaves seem to slit primarily in distinct areas on the leaves, with some areas of the leaf remaining intact both anterior and posterior to a region of slashes. This does not occur in shr*-JH87 plants. Neuffer described a mutant, sl*-N1701, as resulting from a "weakening of midvein tissue (that) results in leaves falling apart longitudinally, like sl1". The leaves are further described as slitting following necrotic streaks (Maize DB). We plan to cross our mutant with his and to finish mapping the mutant. Leaf samples were collected for chromosome arm mapping this past summer.
 
 

Figure 1
 
 

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