V. K. Vikas

Evaluation of 19,460 Wheat Accessions Conserved in the Indian National Genebank to Identify New Sources of Resistance to Rust and Spot Blotch Diseases

A comprehensive germplasm evaluation study of wheat accessions conserved in the Indian National Genebank was conducted to identify sources of rust and spot blotch resistance. Genebank accessions comprising three species of wheat–Triticum aestivum, T. durum and T. dicoccum were screened sequentially at multiple disease hotspots, during the 2011–14 crop seasons, carrying only resistant accessions to the next step of evaluation. Wheat accessions which were found to be resistant in the field were then assayed for seedling resistance and profiled using molecular markers. In the primary evaluation, 19,460 accessions were screened at Wellington (Tamil Nadu), a hotspot for wheat rusts. We identified 4925 accessions to be resistant and these were further evaluated at Gurdaspur (Punjab), a hotspot for stripe rust and at Cooch Behar (West Bengal), a hotspot for spot blotch. The second round evaluation identified 498 accessions potentially resistant to multiple rusts and 868 accessions potentially resistant to spot blotch. Evaluation of rust resistant accessions for seedling resistance against seven virulent pathotypes of three rusts under artificial epiphytotic conditions identified 137 accessions potentially resistant to multiple rusts. Molecular analysis to identify different combinations of genetic loci imparting resistance to leaf rust, stem rust, stripe rust and spot blotch using linked molecular markers, identified 45 wheat accessions containing known resistance genes against all three rusts as well as a QTL for spot blotch resistance. The resistant germplasm accessions, particularly against stripe rust, identified in this study can be excellent potential candidates to be employed for breeding resistance into the background of high yielding wheat cultivars through conventional or molecular breeding approaches, and are expected to contribute toward food security at national and global levels.

A reproducible in vitro pollen germination medium for recalcitrant cereal rye pollen (Secale cereale L): Effect of tryptone

A reproducible in vitro pollen germination medium (PGM) for cereal rye is reported here using tryptone for the first time. Rye pollen is very difficult to germinate on nutrient medium being trinucleate and is classified as recalcitrant pollen. This study addresses the possibility of testing the viability of rye pollen within short time (15–20 min) using pollen germination medium (PGM). The viability of rye pollen was tested with FDA staining also. The results of both staining and in vitro pollen germination were found comparable. In this study, tryptone, a nitrogen source was used in addition to essential sugar and inorganic salts. PGM used for rye consisted of 19% maltose, 13% poly ethylene glycol 6000, 62.5 mgl−1 boric acid, 50 mgl−1 tryptone and 1% agar. During the flowering period, a pollen sterility of 3–12% was recorded. The PGM showed >93% pollen germination with intact pollen tubes at 17±1°C and pH 6–7. This tool would be useful in many pollen biotechnological aspects such as pollen transformation, overcoming crossability barriers especially in wheat x rye wide hybridization etc.

Protein marker as an easy tool to detect Secale cereal - derived linked genes Sr31, Lr26, Yr9 and Pm8 in wheat

The high yielding potential associated with IRS. IBL translocation involving the short arm of rye chromosome 1R and the long arm of wheat chromosome IB were well exploited world over for developing disease resistant and high yielding wheat varieties. This was due to the translocation of the effective disease resistance linked genes Sr31 for resistance to stem rust (P. graminis f. sp. tritici), Lr26 for resistance to leaf rust (caused by Puccinia triticinia), Yr9 for resistance to stripe rust (P. striiformis f. sp. tritici), Pm8 for resistance against powdery mildew (caused by Erisiphe graminis f. sp. tritici) along with useful agronomic traits. However now virulent pathotypes have been reported which has overcome these rust resistance genes. The Sr31 gene complex has close linkage with the genes controlling secalins (Sec-1). Thus Sec-1 acts as a marker for the identification of Sr31, Lr26, Yr9 and Pm8 genes. SDS -PAGE was used to examine the presence of IBL. IRS translocation in six Indian wheat genotypes viz., HP 1205, HD2329, HD 2285, WH 147, Lok-1 and J 24 introgressed with Sr31+ gene complex with the aim to eliminate the lines carrying these genes, since it is tightly linked to poor baking quality. The SDS - PAGE results showed that all the lines carry Sec-l band and are therefore likely to carry the IBL. IRS translocation and the linked genes Sr31, Lr26, Yr9 and Pm8. This technique could be well exploited to detect the presence of linked genes Sr31, Lr26, Yr9 and Pm8 in wheat cultivars as it is an easy, efficient, faster and economical tool to eliminate the lines with IBL. 1RS translocation and developing wheat varieties for better end use quality and reducing the risk to Ug99 stem rust race threat