Unlocking basal and acquired thermotolerance potential in tropical sorghum

Season		Months
Season		Oct	Nov	Dec	Jan
2022/23	Mean minimum temperature	26.6	26.1	24.4	19.8
	Mean maximum temperature	39.9	37.4	31.9	28.1
	Total rainfall	9.6	164	75	161
Source: Lupane State University weather station.

Table 1.

Rainfall (mm) and temperature (°C) data during the study period season (2022/23) at Lupane State University.

Source of variation	DF	Basal	Acquired
Source of variation	DF	Mean squares	Mean squares
Set 1
Temperature (T)	1	3,987.4***	11,556.2***
Genotype (G)	49	586.7***	30.9***
G × T	49	282.2***	49.8***
Error	1,400	119.2	6.5
Set 2
Temperature (T)	1	13,700.5***	5,441.1***
Genotype (G)	49	50.6***	139.9***
G × T	49	32.5***	95.0***
Error	1,400	6.7	16
DF = degrees of freedom, *** significant at < 0.001.

Table 2.

Analysis of Variance for basal and acquired thermotolerance in diverse tropical sorghum accessions done in two sets.

Treatments	Basal thermotolerance		Acquired thermotolerance
Treatments	Set 1	Set 2	Set 1	Set 2
Heat shocked	20.54^b	12.91^b	3.40^b	3.45^b
Non-heat shocked	23.80^a	18.96^a	8.96^a	7.26^a
LSD (5%)	1.11	0.26	0.26	0.41
Non heat shock for acquired thermotolerance means genotypes were acclimatized through incremental temperature increase. Means with similar superscripted letters in the same column were significantly different at (p < 0.05) measured as coleoptile length in millimeters.

Table 3.

Mean comparison of coleoptile changes for heat treatments of sorghum emergents indicating basal and thermotolerance in two sets of each experiment.

Set 1			Set 2
Genotype	Heat shocked	Non-heat shocked	Genotype	Heat shocked	Non heat shocked
Top 10			Top 10
NPGRC1695	30.80^abcdef	36.06^ab	NPGRC1704	16.72^g-x	22.5^ab
IS24426	30.56^abcdefg	28.86^abcdefg	IS9567	16.57^h-z	22.13^abc
NPGRC1478	29.24^bcdefgh	33.28^abcd	IS24426	16.22^i>-z	18.48^b-n
NPGRC1592	22.77^bcdefghi	27.67^bcdefghi	NPGRC1222	15.03^l-D	18.31^c-n
NPGRC3087	22.95^bcdefghi	26.33^bcdefghi	NPGRC175*9	14.86^m-D	18.22^c-o
"MACIA"	19.11^bcdefghi	26.20^bcdefghi	NPGRC1628	14.2O^o-D	19.32^b-j
NPGRC1868	22.80^bcdefghi	24.91^bcdefghi	NPGRC1197	14.08^o-D	18.45^b-n
IS2867	20.81^bcdefghi	24.75^bcdefghi	NPGRC1868	14.07^o-D	21.0^a-f
IS26191	13.47^fghi	24.67^bcdfghi	NPGRC1178	14.07^o-D	20.24^a-i
NPGRC1704	24.57^bcdefghi	25.31^bcdefghi	NPGRC1782	13.98^p-D	14.66^n-D
Bottom 5			Bottom 5
IS9548	14.52^fghi	18.34^cdefghi	IS12391	11.56^D	17.97^c-q
IS9303	14.11^fghi	19.09^bcdefghi	NPGRC3087	11.33^D	18.63^b-n
IS6944	13.01^ghi	18.81^bcdefghi	NPGRC3127	11.20^D	15.94^j-C
IS30164	10.92^hi	17.97^cdefghi	NPGRC3092	11.13^D	19.02^b-m
NPGRC3127	9.65ⁱ	20.42^bcdefghi	SV4	11.0^D	18.66^b-m
Overall mean	22.17		15.94
LSD	7.82		1.85
Means with similar superscripted letter(s) in the same column were significantly different at p < 0.05. Genotypes appeared in the top performers or at least performers common in both sets and genotypes in bold mantained superiority in both sets.

Table 4.

Mean comparison of coleoptile changes for 50 sorghum genotypes indicating seedlings basal thermotolerance in two sets.

Set 1			Set 2
Genotype	Acclimatized	Non- acclimatized	Genotype	Acclimatized	Non -acclimatized
Top 10
IS13837	13.56^a	1.88^B-D	NPGRC3124	22.32^a	4.64^d-j
NPGRC1704	12.5^ab	3.24^s-D	IS12391	18.2^ab	7.18^c-j
NPGRC1619	12.09^a-c	1.63^CD	IS29925	18.18^ab	2.98^g-j
IS9567	11.99^a-d	2.8^v-D	IS24272	13.30^bc	2.32^g-j
NPGRC1699	11.65^a-d	2.9^t-D	NPGRC3093	10.72^cd	4.12^e-j
NPGRC1476	11.48^a-d	2.75^w-D	NPGRC1197	10.11^c-f	2.25^g-j
NPGRC3093	11.24^a-e	1.94^B-D	NPGRC1868	10.02^c-f	3.31^g-j
IS24272	11.21^a-e	2.64^y-D	NPGRC1478	8.71^c-g	2.76^g-j
NPGRC3195	11.13^a-e	4.42^o-D	NPGRC1782	8.48^c-h	5.8^d-j
IS9548	11.12^a-e	3.40^s-D	IS30164	8.42^c-i	4.98^d-j
Bottom five
NPGRC3105	6.69^g-y	1.74^CD	NPGRC3195	4.22^e-j	4.55^d-j
IS13813	6.43^i-z	5.07^m-C	NPGRC1862	3.78^e-j	2.86^g-j
NPGRC3127	5.94^k-B	3.51^s-D	NPGRC3105	3.6^f-j	1.55^j
NPGRC1593	5.08^m-C	2.89^t-D	IS9548	2.67^g-j	3.15^g-j
NPGRC1782	4.66^n-D	3.41^s-D	IS6944	2.45^g-j	3.8^e-j
Overall mean	6.18		5.35
LSD	1.83		2.87
Means with similar superscripted letters in the same column were significantly different at p < 0.05 and genotypes in bold represent top performers in both sets.

Table 5.

Mean comparison of seedlings coleoptile length changes for 50 sorghum genotypes acquired thermotolerance.