Rajkumar Zunjare

Exploration of novel opaque16 mutation as a source for high lysine and tryptophan in maize endosperm

In the present study, two F2 populations derived by crossing wild type-(CML533 and CML537) and o16-donor line (QCL3024) were raised and genotyped. The recessive o16o16 possessed nearly two-fold more lysine (0.247%) and tryptophan (0.072%) in mutants, than wild type (0.125% lysine and 0.035% tryptophan) across populations. However, o16o16 showed wide variation for both lysine (0.111–0.376%) and tryptophan (0.027–0.117%) across populations, suggesting the role of modifier loci. The study did not show any significant correlation (r=0.14) between lysine and tryptophan, however some segregants with highlysine (>0.300%) and-tryptophan (>0.090%) were identified. Some of the segregants with o16o16 possessed comparable lysine and tryptophan with o2o2 genotypes. These o16o16 segregants may serve as novel genetic resource in the QPM breeding programme, and some of them can be used for enhancement of both lysine and tryptophan in place of o2 mutant. This is the first ever report of influence of o16 on accumulation of tryptophan in maize.

Evaluation of specialty corn inbreds for responses to stored grain weevil (Sitophilus oryzae L.) infestation

Evaluation of a diverse set of 68 specialty corn inbreds (pop corn, sweet corn and QPM) against stored grain weevil (Sitophilus oryzae L.) revealed existence of wide genetic variations for grain weight loss (3.40–41.21%), number of insect progeny emerged (5.00–76.33), germination of seeds after infestation (0.00–81.33%), pericarp thickness (36.18–178.13 m) and grain hardness (62.33–600.33 Newton). Pop corn inbreds recorded lowest mean grain weight loss (8.19%) and number of insect progeny emerged (9.23) with highest mean germination (78.28%). Grain weight loss and number of insect progeny emerged were positively correlated, while both showed negative correlation with germination percentage. Pericarp thickness and grain hardness could not contribute to confer resistance. Based on cumulative resistance index (CRI), pop corn inbreds were in general more resistant (mean CRI=1.84) to weevil infestation as compared to shrunken sweet corn (mean CRI=1.51), sugary sweet corn (mean CRI=1.26) and QPM (mean CRI=0.76) inbreds. However, resistant inbreds were also identified in sweet corn and QPM types that can be utilized effectively as donors in the resistance breeding programme. The contrasting inbreds could serve as rich genetic resources for unravelling the basis of resistance.

Opaque16 , a high lysine and tryptophan mutant, does not influence the key physico-biochemical characteristics in maize kernel

The enhancement of lysine and tryptophan in maize is so far basedon opaque2(o2) mutant, that along with the endosperm-modifiersled to development of Quality Protein Maize[QPM]. Though many mutants improving the endospermic protein quality were discovered, they could not be successfully deployed. Recently discovered opaque16 (o16)mutant enhances the lysine and tryptophan content in maize endosperm. In the present study, the influence of o16 on the endosperm modification was analyzed in four F2 populations, two each segregating for o16 allele alone and in combination with o2. The recessive o16o16 seed endosperm was found to be vitreousphenotypically similar to wild-O16O16. The mutant did not influence the degree of kernel opaqueness in o2o2 genetic background as opaqueness in o2o2/O16O16 and o2o2/o16o16 was similar. Grain hardness of o16o16 was comparable with the normal and QPM maize. The pattern of microscopic organization of proteinaceous matrix and starch granules, and zein profiling of the storage protein in o16o16 were found to be similar with normal maize endosperm, but distinct from the o2o2-soft genotype. The pattern in o2o2/o16o16 was unique and different from o2o2 and o16o16 as well. Here we demonstrated the effects of o16 on physico-biochemical characteristics of endosperm and report of o16 possessing negligible influence on kernel modification and hardness, which holds a great significance in maize quality breeding programme.

Popping quality attributes of popcorn hybrids in relation to weevil (Sitophilus oryzae) infestation

A set of 21 popcorn hybrids were evaluated at multilocations to study the effects of weevil (Sitophilus oryzae) infestation on popping quality traits. Wide genetic variation for percent popping expansion (PPE) and grain popping percentage (GPP) after weevil infestation were observed. PPE and GPP varied from 6.09–85.21% and 4.33–66.67%, across locations, respectively. The mean PPE was 52.90%, while same for GPP was 23.46%. Significant effects of environment and genotype × environment interactions were observed for both PPE and GPP. Strong positive correlation (r=0.89) across locations was recorded between PPE and GPP. Despite weevil infestation, popcorn hybrids viz., PH114 (PPE: 83.18%, GPP: 54.11%), PH110 (PPE: 69.27%, GPP: 33.11%), PH103 (PPE: 65.84%, GPP: 26.78%), PH112 (PPE: 64.91%, GPP: 29.22%) and PH109 (PPE: 64.48%, GPP: 29.00%) were identified as promising with desirable popping quality traits. Many of the popcorn hybrids possessed undesirable popping characteristics (12 hybrids with <60% PPE; 18 hybrids with <30% GPP) upon infestation. Despite having a common notion that popcorn genotypes are relatively resistant than other types of maize grain, many of the popcorn hybrids were highly susceptible to weevils leading to undesirable popping quality attributes. The study emphasizes the need for breeding weevil resistant popcorn genotypes possessing desirable popping quality attributes.

Genetics of resistance to stored grain weevil (Sitophilus oryzae L.) in maize

Abstract Stored grain weevil (Sitophilus oryzae) has emerged as important storage grain pest of maize, causing substantial economic losses. Owing to high costs and environmental hazards of pesticides, host plant resistance holds promise for effective control of weevils. In the present study, a set of experimental maize hybrids generated using line × tester mating design were evaluated against S. oryzae. Significant variation for grain weight loss (GWL) (6.0–49.1%), number of insect progeny emerged (NIP) (17.8–203.3), grain hardness (GH) (263.1–495.4 N), and pericarp thickness (PT) (60.3–161.0 μm) was observed. Strong positive association was observed between GWL and NIP. GH and PT did not show any correlation with GWL and NIP. Additive and non-additive gene actions were important for both GWL and NIP. Promising inbreds and experimental crosses identified can be effectively utilized in the resistance breeding programme. In majority of promising crosses having desirable SCA effects, one of the parents had desirable GCA effects, indicating that selection of inbred parents based on per se performance for generating resistant crosses may be possible. The commercial hybrid checks were highly susceptible compared to experimental hybrids. The inbreds and experimental hybrids identified hold promise in developing weevil resistant maize cultivars offering sustainable solution to management of weevils in maize.

Marker-assisted introgression of opaque2 allele for rapid conversion of elite hybrids into quality protein maize

Maize is a valuable source of food and feed worldwide. Maize endosperm protein is, however nutritionally poor due to the reduced levels of two essential amino acids, lysine and tryptophan. In this study, recessive opaque2 (o2) allele that confers enhanced endosperm lysine and tryptophan, was introgressed using marker-assisted backcross breeding into three normal inbred lines (HKI323, HKI1105 and HKI1128). These are the parental lines of three popular medium-maturing single cross hybrids (HM4, HM8 and HM9) in India. Gene-based simple sequence repeat (SSR) markers (umc1066 and phi057) were successfully deployed for introgression of o2 allele. Background selection using genome-based SSRs helped in recovering

Development of Biofortified Maize Hybrids through Marker-Assisted Stacking of β-Carotene Hydroxylase, Lycopene-ε-Cyclase and Opaque2 Genes

>96\%

Microsatellite marker-based characterization of waxy maize inbreds for their utilization in hybrid breeding

>96% of recurrent parent genome. The newly developed quality protein maize (QPM) inbreds showed modified kernels (25–50% opaqueness) coupled with high degree of phenotypic resemblance to the respective recipient lines, including grain yield. In addition, endosperm protein quality showed increased lysine and tryptophan in the inbreds to the range of 52–95% and 47–118%, respectively. The reconstituted QPM hybrids recorded significant enhancement of endosperm lysine (48–74%) and tryptophan (55–100%) in the endosperm. The QPM hybrids exhibited high phenotypic similarity with the original hybrids for morphological and yield contributing traits along with responses to some major diseases like turcicum leaf blight and maydis leaf blight. The grain yield of QPM hybrids was at par with their original versions under multilocation testing. These elite, high-yielding QPM hybrids with improved protein quality have been released and notified for commercial cultivation, and hold significant promise for improving nutritional security.