No abstract

Leaf rust (Puccinia triticina Eriks.), stripe rust (Puccinia striiformis f. tritici Eriks.) and stem rust (Puccinia graminis f. sp. tritici) cause major production losses in durum wheat (Triticum turgidum L. var. durum). The objective of this research was to identify and map leaf, stripe and stem rust resistance loci from the French cultivar Sachem and Canadian cultivar Strongfield. A doubled haploid population from Sachem/Strongfield and parents were phenotyped for seedling reaction to leaf rust races BBG/BN and BBG/BP and adult plant response was determined in three field rust nurseries near El Batan, Obregon and Toluca, Mexico. Stripe rust response was recorded in 2009 and 2011 nurseries near Toluca and near Njoro, Kenya in 2010. Response to stem rust was recorded in field nurseries near Njoro, Kenya, in 2010 and 2011. Sachem was resistant to leaf, stripe and stem rust. A major leaf rust quantitative trait locus (QTL) was identified on chromosome 7B at Xgwm146 in Sachem. In the same region on 7B, a stripe rust QTL was identified in Strongfield. Leaf and stripe rust QTL around DArT marker wPt3451 were identified on chromosome 1B. On chromosome 2B, a significant leaf rust QTL was detected conferred by Strongfield, and at the same QTL, a Yr gene derived from Sachem conferred resistance. Significant stem rust resistance QTL were detected on chromosome 4B. Consistent interactions among loci for resistance to each rust type across nurseries were detected, especially for leaf rust QTL on 7B. Sachem and Strongfield offer useful sources of rust resistance genes for durum rust breeding.

Six chickpea lines resistant to Ascochyta rabiei (PASS.) LAB. were crossed to four susceptible cultivars. The hybrids were resistant in all the crosses except the crosses where resistant line BRG 8 was involved. Segregation pattern for diseases reaction in F2, BCPI, BCP2 and F3 generations in field and glasshouse conditions revealed that resistance to Ascochyta blight is under the control of a single dominant gene in EC 26446, PG 82-1, P 919, P 1252-1 and NEC 2451 while a recessive gene is responsible in BRG 8. Allelic tests indicated the presence of three independently segregating genes for resistance; one dominant gene in P 1215-1 and one in EC 26446 and PG 82-1, and a recessive one in BRG 8.

Presence of substantial heterosis and economic hybrid seed production are two most desirable components for success of any commercial hybrid breeding programme. Thermosensitive genic male sterile (TGMS) lines of rice, in this regard, have tremendous potential in realizing further quantum jump in yield and economical hybrid seed cost. Analyses for combining ability and heterosis over optimum (120N : 60P 2 O 5 : 40K 2 O kg/ha) and high (200N : 90P 2 O 5 : 60-K 2 O kg/ha) fertility environments for six traits were made in 2 years (2001 and 2002) using 120 hybrids of inter-and intra-subspecific nature derived from hybridization of 30 elite indica TGMS lines and four cultivars, viz., ÔPant Dhan 4Õ and ÔAjayaÕ (I ¼ indica), ÔTaichung 65Õ (J ¼ japonica) and ÔIR 65598-112-2Õ (TJ ¼ tropical japonica) in line · tester mating design. Predominance of non-additive genetic variance suggested good prospects of hybrid breeding. Pooled analysis revealed highly significant variances for lines, general combining ability (GCA), specific combining ability (SCA) and line x tester. TGMS line 365-8S was the best general combiner for all the six traits including grain yield. Trend of relative mid-parent heterosis for grain yield, panicle length, grain number per panicle and earliness in flowering was I/TJ > I/J > I/I. For panicle number per plant and 1000-grain weight, trends were I/TJ > I/I > I/J and I/I > I/TJ > I/J, respectively. Grain yield recorded heterosis of 49.3%, 71.9% and 92.7% for I/I, I/J and I/TJ hybrid groups respectively. Effect of environments on the hybrid performance indicated better response of hybrids at high fertilizer dose. Study suggests greater prospects of combining improved japonica and tropical japonica germplasms having wide compatible gene with indica TGMS lines for exploitation of intersubspecific heterosis.

Three lentil genotypes resistant to Fusarium oxysporum f.sp . lentis viz . Pant L 234, JL 446 and LP 286 were crossed with two susceptible ones . The hybrid plants were all resistant in the eight crosses evaluated . Segregation pattern for wilt reaction in F2, BC(P), BC(P2) and F3 generations in field and glasshouse conditions indicated that resistance to Fusarium wilt is under the control of two dominant duplicate genes in Pant L 234 and two independent dominant genes with complementary effects in JL 446 and LP 286 . A third dominant gene complementary to the dominant genes in JL 446 and LP 286 is present in two susceptible lines . Allelic tests suggest the presence of five independently segregating genes for resistance . Duplicate dominant genes in Pant L 234 are non-allelic to two dominant genes with complementary effects in LP 286 and JL 446 and the third gene complementary to the two genes in JL 446 and LP 286 in susceptible lines JL 641 and L 9-12 . Gene symbols among parental genotypes have been designated .