Arbind K. Choudhary

Cross-genera amplification of informative microsatellite markers from common bean and lentil for the assessment of genetic diversity in pigeonpea.

A total of 24 pigeonpea (Cajanus cajan L. Millspaugh) cultivars representing different maturity groups were evaluated for genetic diversity analysis using 10 pigeonpea specific and 66 cross-genera microsatellite markers. Of the cross-genera microsatellite markers, only 12 showed amplification. A total of 45 alleles were amplified by the 22 markers. Nine markers showed 100 % polymorphism. Markers Lc 14, BMd 48 and CCB 9 amplified maximum number (5) of alleles each. One genotype specific unique band in Pusa 9 was generated by markers CCB 8. Maximum genetic diversity (74 %) was observed between cultivars MA 3 and CO 6, while the minimum diversity (12 %) was observed between NDA 1 and DA 11. The average diversity among the cultivars was estimated to be 45.6 %. SSR primers from pigeonpea were found to be more polymorphic (37 %) as compared to common bean and lentil markers. The arithmetic mean heterozygosity (Hav) and marker index (MI) were found to be 0.014 and 0.03, respectively, indicating the potential of common bean and lentil microsatellite markers for genetic mapping, diversity analysis and genotyping in Cajanus.

Genetic control of aluminium tolerance in pigeonpea (Cajanus cajan L.)

Aluminium toxicity is a major factor limiting plant growth in acid soil and more adequate genetic tolerance is needed to improve pigeonpea adaptation and production in affected areas. To study the inheritance, tolerant lines IPA7-10, T-7 were crossed with sensitive lines Pusa 9 and Bahar. The parents, F1 ,F 2 and F3 generations were grown in a nutrient solution containing 30ppm aluminium for hematoxylin staining and root re-growth measure and classified for tolerance by stainingofroottipsandrootre-growth.ThesegregationratiosobtainedforaluminiumtoleranceintheF2andF3generations were 15:1 and 7:8:1, respectively. These results indicated that aluminium tolerance is controlled by two dominant genes.

Characterization of CcSTOP1; a C2H2-type transcription factor regulates Al tolerance gene in pigeonpea

AbstractMain conclusionAl-responsive citrate-transportingCcMATE1function and its regulation byCcSTOP1were analyzed usingNtSTOP1-KD tobacco- and pigeonpea hairy roots, respectively, CcSTOP1 binding sequence ofCcMATE1showed similarity withAtALMT1promoter. The molecular mechanisms of Aluminum (Al) tolerance in pigeonpea (Cajanus cajan) were characterized to provide information for molecular breeding. Al-inducible citrate excretion was associated with the expression of MULTIDRUGS AND TOXIC COMPOUNDS EXCLUSION (CcMATE1), which encodes a citrate transporter. Ectopic expression of CcMATE1-conferred Al tolerance to hairy roots of transgenic tobacco with the STOP1 regulation system knocked down. This gain-of-function approach clearly showed CcMATE1 was involved in Al detoxification. The expression of CcMATE1 and another Al-tolerance gene, ALUMINUM SENSITIVE 3 (CcALS3), was regulated by SENSITIVE TO PROTON RHIZOTOXICITY1 (CcSTOP1) according to loss-of-function analysis of pigeonpea hairy roots in which CcSTOP1 was suppressed. An in vitro binding assay showed that the Al-responsive CcMATE1 promoter contained the GGNVS consensus bound by CcSTOP1. Mutation of GGNVS inactivated the Al-inducible expression of CcMATE1 in pigeonpea hairy roots. This indicated that CcSTOP1 binding to the promoter is critical for CcMATE1 expression. The STOP1 binding sites of both the CcMATE1 and AtALMT1 promoters contained GGNVS and a flanking 3′ sequence. The GGNVS region was identical in both CcMATE1 and AtALMT1. By contrast, the 3′ flanking sequence with binding affinity to STOP1 did not show similarity. Putative STOP1 binding sites with similar structures were also found in Al-inducible MATE and ALMT1 promoters in other plant species. The characterized Al-responsive CcSTOP1 and CcMATE1 genes will help in pigeonpea breeding in acid soil tolerance.

Using AFLP-RGA markers to assess genetic diversity among pigeon pea (Cajanus cajan) genotypes in relation to major diseases

Resistance gene analog (RGA)-anchored amplified fragment length polymorphism (AFLP-RGA) marker system was used in order to evaluate genetic relationships among 22 pigeon pea genotypes with varied responses to Fusarium wilt and sterility mosaic disease. Five AFLP-RGA primer combinations (E-CAG/wlrk-S, M-GTG/wlrk-S, M-GTG/wlrk-AS, E-CAT/S1-INV and E-CAG/wlrk-AS) produced 173 scorable fragments, of which 157 (90.7%) were polymorphic, with an average of 31.4 fragments per primer combination. The polymorphism rates obtained with the five primers were 83.3%, 92.0%, 92.3%, 93.0% and 93.1%, respectively. Mean polymorphic information content (PIC) values ranged from 0.24 (with E-CAT/S1-INV) to 0.30 (with E-CAG/wlrk-AS), whereas resolving power (RP) values varied from 11.06 (with M-GTG/wlrk-S) to 25.51 (with E-CAG/wlrk-AS) and marker index (MI) values ranged from 5.98 (with M-GTG/wlrk-S) to 12.30 (with E-CAG/wlrk-AS). We identified a positive correlation between MI and RP (r2=0.98, p<0.05), stronger that that observed for the comparison between PIC and RP (r2=0.88, p<0.05). That implies that either MI or RP is the best parameter for selecting more informative AFLP-RGA primer combinations. The Jaccard coefficient ranged from 0.07 to 0.72, suggesting a broad genetic base in the genotypes studied. A neighbor-joining tree, based on the unweighted pair group method with arithmetic mean, distinguished cultivated species from wild species. The grouping of resistant genotypes in different clusters would help in the selection of suitable donors for resistance breeding in pigeon pea.

Breeding pigeonpea cultivars for intercropping: synthesis and strategies

Pigeonpea [Cajanus cajan (L.) Millsp.] is an ideal pulse crop of rainfed tropics and sub-tropics due to its high nutritive value and ability to survive various biotic and abiotic stresses. Thus it has continued to be cultivated on marginal land mostly under rainfed situation where the risk of crop failure is very high. To have insurance against crop failures and harvest more food in time and space, most farmers grow pigeonpea as an intercrop with short-aged cereals and other crops. Presently, intercropping system accounts for over 70% of the pigeonpea area. However, yield of pigeonpea in this system is very low (400–500 kg/ha). The non-availability of improved cultivars adapted specifically to the intercropping environments is perhaps the major constraint that accounts for low yield. Considering the food and nutritional needs of the ever increasing population, productivity enhancement of this high-protein pulse is highly indispensable. In this review, the authors critically examine the technical difficulties encountered by breeders in developing high yielding cultivars for intercropping systems and discuss the strategies to overcome these constraints.