The inheritance and effects of leaf rust resistance in triticale

Jeffrey Paul Wilson, Purdue University

Abstract

PI 429120 possesses two dominant genes together conferring a 0;n infection type (IT) to Puccinia recondita tritici. PI 429155 possesses one dominant gene conferring a 1$\sp{+}$c IT. PIs 429121 and 429215 express 1n and 0;n ITs, each possesses one major dominant gene, and another minor gene. The minor-effect gene is recessive in PI 429121 and dominant in PI 429215. The genes in PI 429120 are independent of those in the other cultivars. PIs 429215 and 429121 have a major-effect gene in common, linked 9 map units from that in PI 429155. The cultivars possess recessive genes for long latent period (T$\sb{50}$) in addition to their resistant IT genes. The low IT and long T$\sb{50}$ genes of PI 429155 were separated into different experimental cultivars expressing no resistance (SUSC), long T$\sb{50}$ and high IT (SR), low IT and short T$\sb{50}$ (HR), or both resistances (SR+HR). All resistances reduced infection frequency. The IT, T$\sb{50}$, and uredinium areas of SUSC, SR, HR, and SR+HR were 4, 3, 2, and 1$\sp{+}$; 7.1, 13.0, 9.5, and 14.3 days; and 0.282, 0.124, 0.093, and 0.069 mm$\sp2$. The gamma distribution fit the pattern of spores produced/uredinium/day. Cumulative spores/uredinium of SR, HR, and SR+HR were 27.5, 16.4, and 13.6% of SUSC. The T$\sb{50}$ of SR provided greater resistance than the reduced sporulation and smaller uredinia of HR in observed and computer-generated epidemics. The relationships between slow-rusting PIs 434889, 429155 and 429220 were examined. Transgressive segregation in PI 429155/PI 434889 F$\sb2$ indicated these cultivars possess different T$\sb{50}$ genes. Broad sense heritability (H$\sb{\rm bs}$) was 81%. Transgression in PI 429220/PI 434889 F$\sb3$ and F$\sb4$ indicated these cultivars possess different T$\sb{50}$ genes. H$\sb{\rm bs}$ was 71.4%. Heritabilities from parent-offspring regressions (9 to 19.4%) and responses to selection (0 to 47.1%) indicate nonadditive genetic variances contributed substantially to PI 429220/PI 434889 H$\sb{\rm bs}$. F$\sb3$ family selection for T$\sb{50}$ was more effective for F$\sb3$ individual selection. The association of rye chromosomes with resistance of PIs 429120 and 429215 was determined. Mitotic chromosomes of triticale/wheat F$\sb2$ were C-banded. In both populations, rye chromosomes segregated independently of IT, indicating the resistance genes are on wheat genome chromosomes.

Degree

Ph.D.

Advisors

Shaner, Purdue University.

Subject Area

Plant pathology

COinS