Identification of alleles at two loci controlling resistance to Phomopsis stem blight in narrow-leafed lupin (Lupinus angustifolius L.)

Manisha Shankar, M.W. Sweetingham, Wallace Cowling

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20 Citations (Scopus)

Abstract

The genetics of resistance to Phomopsis stem blight caused by Diaporthe toxica Will., Highet, Gams & Sivasith. in narrow-leafed lupin ( Lupinus angustifolius L.) was studied in crosses between resistant cv. Merrit, very resistant breeding line 75A:258 and susceptible cv. Unicrop. A non-destructive glasshouse infection test was developed to assess resistance in the F-1, F-2, selected F-2-derived F-3 (F-2:3) families, and in selfed parent plants. The F-1 of Unicrop x 75A:258 (and reciprocal cross) was very resistant, and the F-2 segregated in a ratio of 3:1 (resistant: susceptible), which suggested the presence of a single dominant allele for resistance in 75A:258. In Merrit x Unicrop (and reciprocal), the F-1 was moderately resistant, and the F-2 segregated in a ratio of 3:1 (resistant: susceptible). Thus Merrit appeared to carry an incompletely dominant resistance allele for resistance. The F-1 of Merrit x 75A:258 (and reciprocal) was very resistant and the F-2 segregated in a ratio of 15: 1 (resistant: susceptible), which supported the existence of independently segregating resistance alleles for resistance in 75A:258 and Merrit. Alleles at loci for early flowering (Ku) and speckled seeds (for which we propose the symbol Spk) segregated normally and independently of the resistance alleles. Resistant F-2 plants gave rise to uniformly resistant or segregating F-2:3 families, whereas susceptible F-2 plants gave rise only to susceptible F-2:3 families. However, the variation in resistance in the F-2 and some F-2:3 families of crosses involving 75A:258, from moderately to extremely resistant, was greater than that expected by chance or environmental variation. We propose the symbols Phr1 to describe the dominant resistance allele in 75A:258, and Phr2 for the incompletely dominant resistance allele in Merrit. Phr1 appears to be epistatic to Phr2, and expression of Phr1 may be altered by independently segregating modifier allele(s).
Original languageEnglish
Pages (from-to)35-44
JournalEuphytica
Volume125
DOIs
Publication statusPublished - 2002

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