QTL mapping for resistance against cereal cyst nematode (Heterodera avenae Woll.) in wheat (Triticum aestivum L.).

The resistance to cereal cyst nematode (Heterodera avenae Woll.) in wheat (Triticum aestivum L.) was studied using 114 doubled haploid lines from a novel ITMI mapping population. These lines were screened for nematode infestation in a controlled environment for two years. QTL-mapping analyses were performed across two years (Y1 and Y2) as well as combining two years (CY) data. On the 114 lines that were screened, a total of 2,736 data points (genotype, batch or years, and replication combinations) were acquired. For QTL analysis, 12,093 markers (11,678 SNPs and 415 SSRs markers) were used, after filtering the genotypic data, for the QTL mapping. Composite interval mapping, using Haley-Knott regression (hk) method in R/QTL, was used for QTL analysis. In total, 19 QTLs were detected out of which 13 were novel and six were found to be colocalized or nearby to previously reported Cre genes, QTLs or MTAs for H. avenae or H. filipjevi. Nine QTLs were detected across all three groups (Y1, Y2 and CY) including a significant QTL "QCcn.ha-2D" on chromosome 2D that explains 23% of the variance. This QTL colocalized with a previously identified Cre3 locus. Novel QTL, QCcn.ha-2A, detected in the present study could be the possible unreported homeoloci to QCcn.ha-2D, QCcn.ha-2B.1 and QCcn.ha-2B.2. Six significant digenic epistatic interactions were also observed. In addition, 26 candidate genes were also identified including genes known for their involvement in PPNs (plant parasitic nematodes) resistance in different plant species. In-silico expression of putative candidate genes showed differential expression in roots during specific developmental stages. Results obtained in the present study are useful for wheat breeding to generate resistant genetic resources against H. avenae.

Compatibility of Predatory Nematode, Fictor composticola and Bacterial Parasite, Pasteuria penetrans for the Management of Root-Knot Nematode.

Compatibility of Fictor composticola and Pasteuria penetrans was evaluated through two experiments against Meloidogyne incognita. In vitro assay conducted in 5 cm diameter Petri plates containing 1% water agar. Two males and two females of F. composticola were released alongwith 200 P. penetrans encumbered or healthy J2 of M. incognita. Observations on prey consumed were taken after 24 and 48 h of release. P. penetrans-encumbered J2 were consumed more by the predator than healthy J2. In a pot assay, cucumber plants grown in one kg pots were inoculated with 2000 P. penetrans encumbered or healthy J2 of M. incognita and 400 individuals of F. composticola. After 45 days; numbers of galls, egg masses and final J2 population in soil were significantly less in the treatment with F. composticola + P. penetrans-encumbered J2 than F. composticola with healthy J2. The root galls and the number of Pasteuria-infected females were more in the absence of predatory nematode.