INDIAN AGRICULTURAL RESEARCH INSTITUTE

Division of Genetics, New Delhi - 110 012, India.

New sources of resistance to stem, leaf, and stripe rusts from crosses of Triticum aestivum L. and T. timopheevii Zhuk.

G. Guha, J.G. Bhowal, and S.K. Dasgupta.

A large number of stocks resistant to stem (Puccinia recondita f. sp. tritici), leaf (P. graminis f. sp. tritici), and stripe (P. striiformis f. sp. tritici) rusts were derived from crosses of T. aestivum cv. `Kalyansona' and stocks CM 108-31 and CM 108-33) with T. timopheevii Zhuk. (2n = 4x = 28; AAGG). These derivatives were designated as Pusa timopheevii derivatives (PTD).

In a multilocation test (IRSN) conducted by the Directorate of Wheat Research, these derivatives scored a high degree of resistance against stem, leaf, and stripe rust pathogens (Table 1). A number of PTD lines screened against specific leaf rust races (77-1, 77-2, 104B, and 12-2) were found resistant, both in the field (adult plants) and at the seedling stage in the glasshouse.

Table 1. Rust resistance of the PTD lines in multilocation tests during 1994-95.

______________________________________________________________________________________

Rust

_______________________________________________________________________________________

Line Pedigree1 Stem Leaf Stripe

_____________ _____________________________ _________________

South North South North

HS2 ACI2 HS ACI HS ACI HS HS

_______________________________________________________________________________________

PTD45 C/T//KS*3 15S 12 0 F 0 F F F

PTD9l T/KS//KS*3 20MS 6 5MK 0 TMR 0 F 5S

PTD103 T/KS//KS*3 10S 4 10MS 3 10S 2 10S TS

PTD104 C/T//KS*2 TMR 0 TMK 0 10MK 1 10S 5S

PTD108 40MS 14 30MK 5 F 0 F F

PTD8 CB/T//C 40MS ll F 0 TR 0 F TS

PTD12 40MS 12 5MS 1 40S 7 F F

Chcck C 80S 5S 40S 20 80S 29 F 20S

KS 60S 47 80S 47 100S 43 80S 60S

______________________________________________________________________________________

1 C = CM 108-31; T = T. timopheevii; KS = Kalyansona; CB = CM 108-31 M5B;

2 HS = highest score; ACI = average coefficient of infection.

Insert Table 2 here. Page 113-Table 2.

The derivatives were predomimantly semidwarf in habit and had longer spikes, unlike the T. timopheevii parent. In a replicated trial (spaced planted) of 14 derivatives, the two bread wheat parents Kalyansona and CM 108-31 and the check HD2329 were most similar to the T. Aestivum parents and the checks for traits such as tiller number, grain number/ear, grain weight/ear, and yield/plant (Table 2).

Resistance to rust diseases is an additonal trait in these lines. These new sources of resistance to the three rust diseases of wheat, developed in an indigenous background, will be very useful in Indian wheat breeding programs.

In PTD 8 and PTD 12, resistance was monogenic and dominant to leaf rust races 77-1, 104B, and 12-1. These lines also showed both adult and seedling resistances to the most virulent race of leaf rust, 77-5.

Biochemical characterization of the PTD lines.
Biochemical characterization of the PTD lines.

The PTD lines (PTD 8, 12, 31, 45, 97-1, 106, 108, and 91) along with the three parents (CM108-31, Kalyanlsona, and T. timopheevii) were analyzed for specific protein fractions, i.e., high molecular weight glutenins, which were diagnostic markers to detect the introgression of T. timopheevii in a bread wheat background.

Ten seeds from each line were crushed in extraction buffer in a reducing condition, and electrophoresis was done using discontinuous SDS-PAGE. Gels were stained in coomassie blue and photographed.

Triticum timopheevii has three unique bands (Nos. 1, 2, and 5; RM values = 0.24, 0.35, and 0.36, respectively) in the HMW-glutenin subunit region that are absent in Kalyansona and CM 108-31; however, bands 3 and 7 (RM value = 0.32 and 0.48, respectively) present in Kalyansona and CM 103-31 are absent in T. timopheevii. Of interest is the fact that at least one single band of T. timopheevii is present in all derived lines.

This study confirms the presence of T. timopheevii genes in the new genetic stocks (PTD 8, 12, 31, 45, 91, 97, 106, and 108), which can be used as sources for resistance to all three rusts.


PUNJAB AGRICULTURAL UNIVERSITY

Biotechnology Centre, Ludhiana - 141 004, India.

Evaluation and cataloguing of wild germplasm of wheat.

H.S. Dhaliwal, Harjit Singh, Khem Singh Gill, Tajinder Singh, P.P.S. Pannu, and P.S.Bagga.

Under a recently concluded US-India Fund sponsored project, `Cataloging and Pre-breeding of Wheat Genetic Resources', studies were carried out to evaluate and catalogue the wild germplasm collection at the Punjab Agricultural University. The findings are reported here.

Different accessions of wild Triticum and Aegilops species (700 to 1,000 accessions) were evaluated in l994-95 for resisance to leaf rust (Puccinia recondita f. sp. tritici) ard stripe rust (Puccinia striiformis) under natural field conditions at the Punjab Agricultural University (PAU), Ludhiana, and at the PAU Regional Station, Gurdaspur (a hot-spot for these rusts). The observations indicated that among diploid progenitors or closely related species, Ae. speltoides (S) and T. boeoticum (Ab) are good sources of resistance to leaf rust and stripe rust. Among the relatively less closely related species, diploid Aegilops species with the C, U, and M genomes, and polyploid species carrying combinations of these genomes, are excellent sources of resistance to these two rusts. Polyploid Aegilops species with the D genome, in combination with one or more of these three genomes, had a lower proportion of accessions resistant to leaf rust, except for Ae. ventricosa (DU). The presence of a suppressor on the D genome that inhibited the expression of resistance of the other genomes is indicated.

The screening of wild Triticum and Aegilops species at three locations PAU, Ludhiana; PAU Regional Station, Gurdaspur; and the PAU farm, Keylong (a focus of infection of these rusts) since 1984 (under a previous USIF project and the present project) identified 47 outstanding accessions that consistantly have exhibited resistance to leaf rust and stripe rust. A maximum number of accessions possessing durable resistance belonged to Ae. speltoides, T. boeoticum, and Ae. triuncialis (UC), thereby further supporting the usefulness of these species as sources of rust resistance.

Cataloging variability for resistance to leaf rust and stripe rust by testing of seedlings of different accessions of wild Triticum and Aegilops species with individual isolates of rusts showed a large intraspecific diversity within these species. A study of various generations of 29 intraspecific crosses within these species by testing with single-spore isolates supported these observations. The genetics of rust resistance was worked out in various accessions of wild Triticum and Aegilops species. This information will be useful in planning strategies for the transfer of rust resistance. Comparison of seedling reaction to individual isolates of rust with that of the adult plant reaction indicated the presence of adult plant resistance gene(s) in certain accessions of Ae. squarrosa and T. boeoticum.

The screening of various accessions of wild Triticum and Aegilops species for resistance to Karnal bunt disease under artificial conditions (boot inoculation) showed that the A-genome species, T. urartu (Au) and T. boeoticum, and Ae. squarrosa (D) are good sources of resistance. Also, sources of resistance to powdery mildew (25 accessions) were identified among two wild Triticum and two Aegilops species.

Evaluation of four wild Triticum and 14 Aegilops species for resistance to a Punjab population of the cereal cyst nematode, Heterodera avenae, under artificial conditions suggested that Aegilops species with the C and U genomes are good sources of resistance to this pest. Screening of different perennial Triticeae species over 2 years at Ludhiana and Keylong (Himachal Pradesh) showed that Elytrigia pycnatha, Leymus augustus, L. secalinus, and Pascopyrum smithii are useful sources of resistance to prevalent pathotypes of stripe rust. Agropyron (three species), Elytrigia (three species), and Pascopyrum (one species) remained free of leaf rust in both the seasons at Ludhiana. Resistance of a large number of perennial Triticeae species to powdery mildew at Keylong over 2 years indicated that these species could be good sources of rust resistance to this disease in the northern hills of India. Survival of 19 lines of perennial Triticeae at Ludhiana during the summer of 1993 also showed that E. pycnatha (SHY), L. augustus (JH), Thinopyrum ponticum (JE), and Thinopyrum junceum (J-E) may be good sources of heat tolerance.

The observations indicated variability for yield components within the donor species, e.g., variation for grain size in Ae. squarrosa and for grain number in T. boeoticum. These traits can be exploited for improvement of yield potential in bread wheat.

SDS-PAGE of 169 accessions belonging to eight diploid and two tetraploid progenitor species identified new alleles of high molecular weight (HMW) glutenin subunits at Glu1 loci. Three new alleles for the x subunit and five for the y subunit have heen identified in the A-genome species. Aegilops speltoides is the most variable among the S-genome species. In these species, 10 new alleles of the x subunit and six of the y subunit have been identified. In Ae. squarrosa, 47 % of the accessions have new alleles at the Glu-D1 locus; three for the x subunit and six for the y subunit, in addition to new subunit combinations, i.e., 5+12 and 2+10. Triticum araraticum had greater variability than T. dicoccoides. In tetraploid species, seven alleles each for the x and y subunits were observed. New nomenclature to catalogue the newly identified alleles has been proposed.