Genetic variation and nature of gene action in assam rice for grain zinc concentration and biofortification potential

Abstract

The cultivated gene pool of rice is deficient in most of the required newlinemicronutrients. Zinc is one of the most important among these to mention about. newlineTwenty (20) percent of the world population is at risk of Zn deficiency resulting from newlineinadequate dietary Zn intake that causes stunted growth (Brown et al., 2009). Genetic newlineand agronomic manipulations for biofortification to raise the concentration of the newlinenutrients in the grain are suggested to overcome the problem. The present investigation newlinewas undertaken to study genetic diversity for grain Zn in Assam rice germplasm and newlinealso to explore the possibility of bifortification potential. A set of 29 ahu genotypes newlinerandomly collected from different places along with the high yielding sali rice variety newlineShraboni, known to be rich in Zn, were evaluated in 4 different micro-environments newlinecreated by differential application of Zn fertilizer in ahu season of 2019. Among these, newline6 were randomly selected for combining ability studies through diallel mating system newlinewithout the reciprocals. Observations were taken on different morphological and quality newlinecharacters and the recorded data were subjected to different statistical analyses newlinefollowing standard procedures. Out of 30 genotypes, 9 were grouped as low (lt20 mg newline1000g-1), 12 medium (20-30 mg 1000g-1) and 9 others were grouped as high (gt30 mg newline1000g-1) grain Zn genotypes as per their grain Zn content. Grain Zn content was found newlinehighest (52.35 mg 1000g-1) in Shraboni and lowest (11.73 mg 1000g-1) in Basantabahar. newlineGCV, PCV and heritability were high for grain Zn for the genotypes. Grain Zn showed newlinea significant positive correlation with panicle length, grains per panicle and spikelet newlinefertility. Highest grain Zn was recorded in the environment which had relatively high newlineinitial soil Zn and was then further added with fertilizer Zn while the lowest grain Zn newlinewas recorded in the environment which had low initial soil Zn and no further Zn was newlineadded with Zn fertilizer. However, increase in grain Zn with the addition of fertilizer Zn newlinewas not uniform across the tested genotypes. The genotypes - Shraboni, Dehangi, newlineKopouguni, Laishanka and Negilai recorded high grain Zn content across all the newlineenvironments. Inglongkiri, Panimudi, Arpang and Ranga Ahu showed good grain Zn newlinecontent in low Zn environment while Begungutia, Kolong, Disang and Ikhajoy showed newlinegood grain Zn content in high Zn environment. The results suggest the possibility of newlineidentifying high Zn genotypes and also the possibility of agronomic biofortification as newlinemost of the genotypes showed increase in grain Zn with addition of external Zn to soil. newlineThe genotypes exhibited significant variation in the individual environments as well as newlineover environments for most of the characters studied including yield and grain Fe. newlineBased on D2 analyses the genotypes were grouped in 5 different clusters of which 4 newlinewere mono-genotypic and the rest one was with 26 genotypes. Significant variation newlineamong the genotypes as well as tested environments was also reflected in the stability newlineanalysis. Shraboni, Dikhow and Rangadaria for grain yield and Shraboni, Dehangi, newlineKopouguni, Laishanka and Negilai for grain Zn showed high mean performance with newlineaverage stability. There is significant variation among the crosses both in low and high newlineZn environments for almost all the characters. Significant positive GCA effects were newlinefound for grain yield and grain Zn for Inglongkiri and Kolong in both high and low Zn newlineenvironments. Heterosis over mid parent was seen for grain Zn in Kasalath×Inglongkiri newlineand for grain yield in Kasalath×Ikhojoy and Ikhajoy×Kolong. Heterobeltiosis was newlinerecorded for grain Zn in Kasalath×Kolong in high Zn environment. newline