Internode Length in Pisum. Three Further Loci, lh. ls and lk

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Abstract
Allelism tests indicate that at least three new internode length mutations, lh, k and ls occur in peas (Pisumsativum L.). All three mutations are recessive and cause a substantial reduction in internode length. Genes lh and ls result in plants within the dwarf/nana phenotypic range while Ik causes the erectoides phenotypewhich is characterized by short internodes, reduced yield, dark green foliage (also seen in nana types), brittlestems of increased diameter, very short peduncles and petioles and increased apical dominance. Gene lk is shown to be largely epistatic to the slender and crypto gene combinations la cry8 and la cryc,unlike the previously examined internode length genes le and na. However, erectoides-dwarf (le Ik La and/or Cryc), erectoides-slender (le Ik la cry8) and erectoides-cryptodwarf (le Ik la cryc) plants could be distinguished using characters such as leaflet area and internode length. Gene Ik also virtually obscures the phenotypic effects of the Le /le and Na/na gene differences. The double-recessive gene combinations na ls, na lh and ls lh all appear to be shorter than the single recessive classes, suggesting that na, ls and lh are all leaky genes. It is suggested that all three genes, lh, ls and na, may partially block steps in the gjbberellin biosynthetic pathway, while lk may influence some step leading to elongation after gibberellin reception. The problem of allocating plants to phenotypic classes is also discussed now that eight internode length genes are established in peas.