Author : Mi Mi Khaing

Summary : Waxy corn is one of the most important economic crops in Myanmar. The development of waxy corn for food and fodder has a problem, concerning in low productivity. Information about genetic variation and diversity is essential and the first step in corn improvement program. The first activity was conducted at the Other Cereal Crops Research Section, Department of Agricultural Research (DAR), Yezin during December 2022 to April 2023 with 51 waxy corn inbred lines by using randomized completely block design (RCBD) with three replications to estimate the genetic variation among the waxy corn inbred lines and to find out similarity of waxy corn inbred lines. Significant differences among tested waxy corn inbred lines for most of the traits were noticed, indicating the presence of substantial genetic variability. Based on genetic parameters such as phenotypic coefficient of variation (PCV), genotypic coefficient of variation (GCV), heritability in broad sense (H), genetic advance as percent of mean (GAM) and clustering method, eight lines were selected. The second activity was conducted with the same 51 waxy corn inbred lines at same location of previous activity Yezin, during April to July 2023, using RCBD with three replications to select potential inbred lines based on direct effects and selection index. Row length was observed the highest positive direct effect and strongly correlated with yield. According to path coefficient analysis, row length, ear diameter and brix (%) had high direct effects and highly positive correlation with yield. Waxy corn inbred lines such as YZWC-022, YZWC-058, YZWC-007, YZWC-002, and YZWC-037 with long row length, YZWC-005, YZWC-058, YZWC-007, YZWC-037, and YZWC-022 with big ear diameter, YZWC-002, YZWC-005, YZWC-022, YZWC-019, YZWC-035, and YZWC-037 with high brix (%) would be selected. According to the index score (IDI) calculation, the waxy corn inbred lines with the minimum and medium IDI has been chosen as waxy inbred ideotypes. The waxy inbred lines YZWC-005(P1), YZWC- 007(P2), YZWC-019(P3), YZWC-022(P4), YZWC-035(P5), YZWC-037(P6), YZWC-057(P7), and YZWC-058(P8) were selected for research activity III to estimate combining ability and gene action. Eight parental lines of waxy corn were crossed in a full diallel cross to produce 28 cross hybrids, 28 reciprocals and eight selected parents. Total 64 genotypes together with two checks (waxy star and sticky white) were evaluated at the same location by using RCBD, with three replications. The results showed that the observed characters were significantly different among the 64 genotypes. General combining ability (GCA) and specific combining ability (SCA) and reciprocal effects were varied depending on characters. The ratios of GCA/SCA were less than unity for all studied traits indicating that the non-additive gene effects dominated the genetic control of all studied traits. Significance in reciprocal effects in ear traits indicates the influence of maternal effect in those traits. Combining ability analysis revealed that P6 (Kayah Pyaung) showed the highest positive GCA values in ear characters and yield. Thus, P6 exhibited the best general combiner for development of better ear characters and yield. Moreover, parent P4 (Pagu Waxy) and P7 (WXX11 x WXX10) also showed high positive GCA effect in marketable ears and thus, they could be considered as good combiners and would be used as best parents for increasing yield. The crosses (P1xP7) and (P5xP6) could be considered as good combiners to produce high yield as these crosses showed the highest positive SCA effect in yield (marketable ears).