The study was carried out to identify suitable white maize variety(ies) for the production in Bangladesh, to select drought tolerant varieties at the reproductive stage and to review the drought management through limited irrigation and antitranspirant technology. Six varietal trials were carried out involving eight white maize varieties in two consecutive Rabi seasons of 2015-16 and 2016-17 at three different sites. One pot experiment was carried out in a polythene shed to examine the drought tolerance of six white maize varieties under varying irrigation regimes in 2017-18. Another experiment was conducted in field to evaluate the yield improvement of two white maize varieties to reduce transpiration loss through spraying an antitranspirant Kaolin at tasseling stage on foliage during the Rabi season of 2017-18.
In the first three experiments (Expt. 1-3) of 2015-16 Rabi seasons, eight varieties of white maize were tested at three sites such as Sher-e-Bangla Agricultural University (SAU), Dhamrai and Rangpur Sadar during Rabi 2015-16. The varieties were V1 = PSC-121, V2 = KS-510, V3 = Changnuo-1, V4 = Q- Xiangnuo-1, V5 = Changnuo-6, V6 = Yangnuo-3000, V7 = Yangnuo-7, V8 = Yangnuo-30. In the second year of 2016- 17 Rabi season (Expt. 4-6), seven varieties of white maize (V1 = PSC-121, V3 = Changnuo-1, V4 = Q- Xiangnuo-1, V5 = Changnuo-6, V6 = Yangnuo-3000, V7 = Yangnuo-7, V8 = Yangnuo-30) were tested in the above mentioned three sites. In the drought imposing trial (Expt. 7 in 2017-18) six variety of white maize such as V1 = PSC-121, V3 = Changnuo-1, V5 = Changnuo-6, V6 = Yungnuo-3000, V7 = Yungnuo-7 and V8 = Yungnuo-30 were grown at different irrigation regimes (T1 =no watering from 80 DAS to harvest), T2 =(no watering from 100 DAS to harvest) and TC = control with irrigation at every day). In the antitranspirant trial (Expt. 8, 2017-18) through the application of Kaolin, two varieties (V1- PSC-121, V2=Changnuo-1) were tested under four concentrations of Kaolin (CO = 0%, C1=2%, C2=4%, C3=6%).
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Experiment 1. Yield and yield attributes of different white maize varieties at SAU during Rabi 2015-2016
At 90 days, V1 showed the highest plant height but there was no significant difference between the variety of V2 (247.33 cm), V3 (233.67 cm), V5 (233.83 cm), V6 (221.67 cm), V7 (175.17 cm) and V8 (232.33 cm). The lowest highest was in V7 (175.17 cm) which was statistically similar to V4 (184.50 cm). During harvesting, it was observed that the longest plant height showed in V2 (263.13 cm) and the lowest was in V7
(184.17 cm). The V2 (263.13 cm) showed the highest plant height that was not significantly differed with the plant height of V1 (261.33 cm).
During harvesting, significantly the maximum number of leaves plant-1 (19.08) was produced by the variety V3 which was statistically similar to V1 (18.00) and V7 variety was the lowest performer (12.16). Although the lowest leaves plant-1 was in V7
(12.16) but there was no significant difference observed among the varieties of V8
(13.00) and V5 (12.75). Likewise, V2produced medium number of leaves plant-1 (15.083) but there was no significant difference between V4 (13.75) and V6 (14.16).
The highest leaf area index was showed in V1 (3.63) and the lowest in V6 (1.84). The V1 (3.63) should the highest leaf area index but there was no significant difference with the leaf area index of V2 (3.45), V3 (3.01) and V8 (3.22). The lowest leaf area index was found in V6 (1.84) which was not significantly differed with V7 (2.44) and V5 (1.90).
Among the treatments, V8variety took significantly maximum days to tasseling (73.000 days) followed by V2 (70.33 days), V3 (70.00 days), V1 (68.67 days), V6
(68.67 days), V4 (67.33 days) and V5 (63.33 days) while V7 (59.34 days) took significantly minimum days to tasseling (62.17 days). The highest maturity date was found in V2 (143.67 days) and the lowest in V7 (108.00 days). The V2 (143.67) showed the highest days to maturity followed by V1 (132.67 days), V8 (127.67 days), V6 (120.00days), V3 (118.33 days), V5 (115.67 days), V4 (115.33 days).
The cob length was ranged from 12.63-15.80 cm depending on varieties showing the highest by V5 and the lowest by V7. Although the V5had the highest cob length but there was no significant difference with the cob length of V6 (15.40 cm), V1 (15.10
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cm), V3 (15.10 cm), V8 (14.95 cm) and V4 (14.750 cm). The lowest cob length was found in V7. Maximum cob breadth (16.97 cm) was found in V4 but there was no significant difference observed among the varieties of V5 (16.55 cm), V8 (16.47 cm), V3 (16.39 cm), V6 (16.19 cm) and V1 (16.03 cm). The minimum (12.35 cm) cob length was achieved with V7. The Number of rows cob-1 was significantly influenced by varieties. Among the varieties, the maximum number of rows cob-1 was found in V3
(14.53) which was statistically similar to V4 and V5 (13.80 and 13.77) whereas V7
(12.00) found the lowest performance (12.25).
The highest number of grains row-1was found in V3 (31.60) and the lowest was in V7
(22.90). The V3 showed the highest number of grains row-1but there was no significant difference observed between V5 (31.53), V2 (28.60) and V8 (28.57). The second highest number of grain row-1was in V4 (27.27) that statistically similar to V1
(26.73) and V6 (26.33). The highest number of grains cob-1 was found in V3 (413.00) and the lowest was in V4 (323.00). The V3 had the highest grain cob-1 but there was no significant difference observed between number of grains cob-1 of V8 (412.69).
The highest 100-grain weight was obtained with V4 (36.00 g). The second highest 100-grain weigh was found in V5 (34.00 g) which was statistically similar to V3
(32.66). The lowest 100 grain weigh was found in V6 (26.66 g) but there was no significant difference with V2 (28.00).
The highest stover weight plant-1 was found in V1 (135.43 g) and the lowest in V7
(83.83 g). The V1 showed the highest stover yield plant-1 that not significantly differed with V2 (133.67 g). The second highest stover yield plant-1 produced by V8 (123.07 g) which was statistically similar to V3 (128.73 g). Yield ranged from 6.16-8.62 t ha-1 depending on varieties showing the highest by V3 and the lowest by V7. Likewise, stover yield was in the range of 6.26 t ha-1 - 9.03 t ha-1depending on varieties showing the highest by V1 and the lowest by V7. The biological yield ranged from 12.37 t ha-1 - 17.27 t ha-1 depending on varieties showing the highest by V1 and the lowest by V7. The harvest index was varied significantly due to varieties where V5 showed the highest harvest index (49.58 %), which was statistically similar to V3 (49.43 %), V6
(49.57 %), V7 (48.53 %) and V8 (49.43 %).
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Analysis of nutritional components of the varieties showed that V1 (PSC-121) contained maximum fiber (2.92%), while V3(Changnuo-1) contained maximum carbohydrate (75.13%) and apparent amylose content (AAC) (24.41 %). The highest amount of Glycemic Index (GI) was obtained in V7 (Yangnuo-7) (71.24 %), while the other varieties showed glycemic index a bit over 60% (61-64%).Carbohydrates with a low GI value (55 or less) are more slowly digested, absorbed and metabolized and cause a lower and slower rise in blood glucose and, therefore usually, insulin levels.
The variety V1 (PSC-121) had the lowest GI (61%) indicating that this variety would be considered as low GI white maize variety.
Experiment 2. Yield and yield attributes of different white maize varieties at Dhamrai during Rabi, 2015-2016
During harvest, V1showed the height plant height that was 252.89 cm. The lowest plant height was with V7 (192.53 cm). Likewise, V2 (235.79 cm) had medium plant height but there was no significant difference between V4 (235.06 cm). The varieties showed significant difference for leaf area index where the highest leaf area index showed in V8 (3.00) which was not significantly differed with the variety of V2 (2.74) and V1 (2.60). The lowest leaf area index was in V6 (1.50) which was not significantly differed with V5 (1.63), V4 (1.74) and V3 (1.02).
Among the treatments, V8 variety took significantly maximum days to tasseling (75.45 days) followed by V2 (66.57 days), V3 (66.57 days), V1 (65 days), V6 (63.67 days) V4 (66.56 days) and V5 (62.56 days) while V7 (53.6 days) took significantly minimum days to tasseling (62.1670 days). The latest maturity was found in V2
(138.70 days) while the earliest was with V7 (103.00 days). The V2 (138.70 days) showed the highest days to maturity followed by V1 (126.98 days), V8 (122.65 days), V6 (115.00days), V3 (114.89 days), V5 (111.07 days) and V4 (110.73 days).
Although the V3 showed the highest cob length but there was no significant difference observed with the cob length of V2 (18.63 cm), V5 (18.03 cm), V8 (17.50 cm), V4
(17.33 cm) and V6 (17.53 cm). The highest cob breadth (17.07 cm) was found in V8
but there was no significant difference founds between the varieties of V1 (16.43 cm), V6 (16.13 cm), V2 (15.83 cm) and V3 (15.80 cm). Among the varieties, the highest number of rows cob-1 was found in V3 (14.53) which was statistically similar to V4