R. Sai Kumar

Differential effect of immature embryo's age and genotypes on embryogenic type II callus production and whole plant regeneration in tropical maize inbred lines (Zea mays L.)

The study was undertaken to elucidate the effect of genotypes and age of immature embryo on callus induction, embryogenic type II calli production and regeneration from immature maize embryos. The immature embryos were excised from a selfed ear of ten elite Indian maize inbred lines on 6, 12 and 18 days after pollination. The mean callus induction, embryogenic type II calli production, and regeneration was highest across all the genotypes in 12 days old immature embryos and were 44.25, 26.12, and 11.20 per cent respectively. The significant differences were observed with respect to callus induction, embryogenic type II calli production and regeneration capacity between genotypes. The highest regeneration capacity was observed by immature embryo at 12 days after pollination (DAP) of genotype HKI1105 and CM300.

Rainfall trends and maize productivity in diverse agro-climatic regions of India

Historical data on climatic parameters as well as yield data on maize are important to look into past setbacks and achievements. In the present study, we have analysed the grain yield of the best entry, the best check and trial mean of full season maturity group grown during the monsoon (kharif) season in All India Coordinated Maize Improvement Project (AICMIP) trials from 1991 to 2012 in four agro-climatic zones of the country. The monthly fluctuations in rainfall during maize cropping season are high in all the zones during maize crop season and the trend was significantly increasing in the month of August in Zone V. The seasonal rainfall decreased during the month of October in all the Zones. The yield performance of best test entry was at par or higher than the best check with significant and strong correlation with each other and with trial mean. There was increasing trend for maize yields from 1991 to 2012 in all the zones. The new maize hybrids from AICMIP are superior even under the changing climatic conditions in different agro-climatic zones, however, there was a stabilization of the zonal yields (pooled over states within agro-climatic zones) of maize around year 2002 for 7 to 12 years in different zones of the country. In spite of high fluctuations in rainfall, there was continuous improvement in the new genotypes developed at AICMIP especially in past two decades. Thus, AICMIP had an important contribution in overall increase in zonal yields of the country even though the differential impact in different zones. The impact of new hybrids in zonal or state productivity and production took less time for Zone II and Zone III and this impact lasted for more years in Zone II than Zone III.