K. Kaushal

Near-isogenic lines in NP 4 background carrying the genes Lr13, Lr18, Lr19 and Lr26 as locally adapted differentials for Indian pathotypes of wheat leaf rust

A backcross programme was conducted to transfer 13 of the Lr genes present in the leaf rust differentials being currently used in India viz., Lr1, Lr2a, Lr2c, Lr3a, Lr9, Lr10, Lr13, Lr15, Lr17a, Lr18, Lr19, Lr20 and Lr26 in the background of wheat variety NP 4 having desired agronomic traits. Homozygous resistant lines carrying these genes singly have been developed through six backcrosses and subsequent selection. Nine of these lines have already been reported. Present communication reports the remaining four lines carrying the genes Lr13, Lr18, Lr19 and Lr26. These lines being locally adapted and early maturing are easy to maintain under Indian conditions, and can be widely used for virulence analysis and genetic studies.

Near-isogenic lines in NP 4 background carrying the genes Lr1, Lr2a, Lr2c, Lr3a, Lr9, Lr10, Lr15, Lr17a and Lr20 as locally adapted differentials for Indian pathotypes of wheat leaf rust

Wheat leaf rust differentials being used in India include selected near-isogenic Lr lines in ‘Thatcher’ background (set A), some of the historical differentials like Malakoff, Webster, Loros etc. (set B) and IWP 94 (Lr23) out of a set of eight Indian wheat genotypes (set 0). The set A lines and most varieties in set B are late maturing as they require long photoperiod for flowering, which limits their utilization in virulence analysis and genetic studies under Indian conditions. A backcross programme was conducted to transfer those Lr genes which occur in these lines and varieties in the background of NP 4 having desired agronomic traits. Nine homozygous resistant lines carrying Lr1, Lr2a, Lr2c, Lr3a, Lr9, Lr10, Lr15, Lr17a, and Lr20 have been developed through six backcrosses and subsequent selection based on seedling tests with appropriate leaf rust pathotypes of selected BC6F3 lines having NP 4 plant type. These lines being locally adapted and early maturing are easy to maintain under Indian conditions, and can be widely used for virulence analysis and genetic studies.

Validation of race non-specific, adult plant leaf rust resistance genes Lr34 and Lr67 in some common wheat (Triticum aestivum L.) cultivars

Twelve common wheat cultivars with Lr34 postulated based on leaf tip necrosis and other observations were studied for adult plant resistance to leaf rust (Puccinia triticina) pathotype 77-5 (121R63-1), and validation of Lr34 and Lr67 through allelic tests. Line 897 and Frontana, known Lr34 carriers, served as checks. Resistance was governed by one dominant gene each in C 306, Kalyansona, Line 897, NI 5439 and WH 147; and by two dominant genes each in Frontana, GW 173, HD 2189, HI 1077, HP 1744, K 9107, PBW 175, PBW 373, and UP 2338. Allelic tests showed presence of Lr34 in Frontana, GW 173, HD 2189, HP 1744 and Line 897; and of Lr67 in C 306, NI 5439 and K 9107. Comparison is drawn with reports based on molecular markers. Our findings should be useful in multiple disease resistance breeding as Lr34 and Lr67 are associated with resistance to multiple wheat pathogens.

Genetic diversity for adult plant resistance to leaf rust in bread wheat (Triticum aestivum L.)

There is an increasing worldwide interest in adult plant resistance (APR) since most examples of durable resistance to leaf rust in wheat are this kind. Twelve bread wheat genotypes were studied for inheritance of APR to leaf rust using pathotype 77-5 (121R63-1), the most prevalent and widely virulent one on bread wheat germplasm in India. Resistance was controlled by a pair of dominant and recessive genes each in CPAN 1676 and CSP 44 and by two independent dominant genes each in CPAN 1796, Frontana, HD 2009, HD 2135, HUW 37, HW 517, Nainari 60, Pavon 76,VL 404 and WG 138. Segregation patterns observed in their intercrosses showed the presence of at least four genes, including a recessive one, among these genotypes in addition to known APR genes Lr34, Lr46, Lr48, Lr49 and Lr68. The present findings are expected to contribute toward enriching diversity for leaf rust resistance in bread wheat improvement programmes.