Late blight horizontal resistance in L. hirsutum.

PI 251305 L. hirsutum exhibits partial resistance to Phytophthora infestans blight as indicated by the low apparent-infection rate obtained with the material in comparison to that of 'Licato' (susceptible control). The value for the F1, between 'Licato' and PI 251305 was closer to that of the resistant parent, which suggests dominance of the resistance. Low values for apparent infection approximating that of L. hirsutum PI 251305 were also obtained with two hybrids between hirsutum and L. esculentum lines (Table 1). The above results point to the possibility of employing PI 351205 as a source of horizontal resistance to late blight.

Table 1. Late-blight apparent infection rate (r) obtained with L. hirsutum PI 251305, 'Licato' (susceptible control) and interspecific hybrids with PI 251305.

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Genotype Species r (1)
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PI 251305           L.   hirsutum      0.108  b
Licato x PI 251305  esc. x hirsutum    0.162  b
Licato              L. esculentum      0.305  a
LLS 6 x PI 251305   esc. x hirsutum    0.156  b
LLS 14 x PI 251305  esc. x hirsutum    0.154  b