71 Performance of durum wheat lines for quality and rust resistance M D Oak, R M Patil, D N Bankar, J H Bagwan, A L Bipinraj, S A Tamhankar, B K Honrao 1 and S C Misra Genetics Group, Agharkar Research Institute, GG Agarkar Road, Pune 411004 Correspondence: *bkhonrao@yahoo.co.in Stem rust (Puccinia graminis Pers. f. sp. tritici) and leaf rust (Puccinia triticina Rob. ex. Desm.) are the major constraints in wheat production in the peninsular zone. A number of wheat varieties cultivated in the past, became susceptible to rust, after a few years of cultivation. Traditionally wheat improvement aims at three major aspects viz. grain yield, disease resistance and quality. The effect of disease on yield and its components in general has been adequately studied (Mundy 1973, Knott 1989). However, there is still ample scope to study its interaction with physiology and quality in wheat. Allard (1960) suggested that early generation selection should be restricted to highly heritable traits such as disease resistance and plant height and that the traits showing low heritability should be evaluated only in those lines that survive this screening. Such a pedigree breeding system involves the retention of lines of unknown grain yield potential until a degree of homozygosity is attained (F 5 or F 6 ). In view of the severeness of the rust diseases, as well as the necessity to improve the quality of wheat, an attempt has been made to combine rust resistance and quality attributes in durum wheat. A cross was made between MACS3125 and HGPC-1 (UC1114, kindly provided by Dr. J Dubkovsky, a breeding line from UC, Davis). MACS 3125 (T. durum) is the highest yielding durum variety with a grain yield of 48.4 q/ha. It has bold grains and is highly resistant to leaf rust and moderately resistance to stem rust. However, this variety has poor yellow pigment content of 4.2 ppm and protein content of 11.4%. Whereas, HGPC-1 carries a NAC transcription factor associated with high grain protein content (16 -17%) and linked with early senescence. It shows high Yellow pigment content and dough strength but is highly susceptible to stem rust. F 1 and F 2 plants were raised under high fertility and irrigated conditions. In the F 2 generation a random single spike was harvested and repeated selfng was continued up to the F 6 generation. At this stage homozygous (RILs) lines were constituted. These 196 newly constituted RILs, were analyzed for grain protein content using a scanning monochromator Infratec 1241 grain analyzer (Foss NIR Systems INC., Hoganas, Sweden). 1000 grain weight was estimated by manually counting 1000 seeds and taking their weight in gram. These lines were screened for two consecutive years (2009- 10, 2010-11) against a mixture of stem rust (11, 40A, 42, 117-6, 122) and leaf rust (12-2, 77-2, 77-5, 104-2) pathotypes. Each homozygous line was grown in a single row of 1 meter length and spaced 30 cm apart. After every 20 cultures a highly susceptible cultivar Gulab, was sown for better spread of infection. The leaf rust epidemic was initiated by inoculating spreader rows with the mixture of virulent pathotypes of stem rust and leaf rust. Inoculations were also carried out through injections and direct spraying of spores in the feld using a fne sprayer. Standard inoculation methods were practiced and measures to create optimum, conditions for maximum disease spread were taken. Rust severity was recorded 5 to 6 times according to the scale suggested by Peterson et al. (1948). Incidence and severity of leaf rust was observed during both years in disease-infected plots. The spreader rows of the highly susceptible variety Gulab coupled with spraying of spore suspensions, ensured good inoculum pressure. The observations recorded were compiled and mean values are summarized in Table 1. It was observed that out of 196 RILs, 72 lines were resistant to both leaf and stem rust. These results confrm the fndings of Sharma et al. (1986) that durum wheat may be an important source of resistance to rust. HGPC-1 was highly susceptible to stem rust and moderately resistant to leaf rust. Among the 72 lines, 10 lines were selected exhibiting high grain protein content (14-1 to 15.8%) and high 1000 grain weight (46.0 to 55.2g). All these lines resembles MACS 3125 with respect to height, erectness, bold amber colored grains which are hard, lustrous, uniformly flled, with increasing thousand grain weight. Additionally, three lines 233, 261, 365 were early in fowering and maturity than the parent MACS3125, while the others were mid-late. All these lines will be further evaluated in yield trials. It was observed that some of the added genes conferring rust resistance showed negative impacts on quality and yield under rust-free conditions (Knott 1993, Singh and Huerta-Espino 1997). On the contrary, in a study by Cox et al. (1997), Lr41 was associated with a reduced bake-mixing time and water absorption, but no serious impediments to the use of Lr41 in breeding was reported. Similar results were reported by Kumar and Raghavaiah (2004) in a study on the effect of the gene Lr28 on the yield in bread wheats. This study was conducted to improve the grain protein content of the rust resistant cultivar MACS 3125 and lines with high disease resistance and good grain protein content were obtained. Received: 18 July 2011 / Accepted : 21 August 2011 @ Society for Advancement of Wheat Research J. Wheat Res. 3(1) : 71-72 (2011)