Cotton growth and development is effected by various ecological issues like temperature fluctuations, distribution and quantity of rainfall, relative humidity and winds which are the climate change attributes. A field experiment was carried out to find out the response of cotton to weather variables in terms of total variation in yield and quality. The effect of planting times and thermal temperatures (cumulative heat units) on yield of 4 cotton cultivars viz; CIM-600, CIM-616, CIM-622 & CRIS-641 was evaluated. Plants were sown on 6 planting times during the year 2015-2016 and 2016-2017 in an experiment conducted in randomized complete block design having three replications. Cotton cultivars depicted significant variances for number of bolls plant −1 , boll weight and seed cotton yield. The cultivar CIM-616 depicted the highest seed cotton yield of 2083.60 kg•ha −1 on interpretation of highest bolls and boll weight. Maximum seed cotton yield was noted in planting time from 1 st April to 15 th April whereas early and late planting decreases the seed cotton yield on account of less accretion of cumulative heat units. Regression analysis depicted that rise of one unit (15 days) from early to optimal date (15 th March to 15 th April) enhanced the seed cotton yield by 93.76 kg•ha −1 (y = −93.764x 2 + 521.04x + 1364). Delayed planting also reduces the seed cotton yield with the same ratio. It is therefore established that cotton must be cultivated from 1 st April to 1 st May to harvest good production in this type of climate.

Genetic diversity provides the foundation for crop improvement. Genetic variation and associations among Cotton Leaf Curl Disease (CLCuD), fiber and yield related traits were investigated in exotic lines of Gossypium arboreum L.in an experimental field at the Central Cotton Research Institute (CCRI), Multan, Pakistan during the crop season 2011-12. One hundred and nineteen (119) accessions imported from USA through the Pakistan and US "Cotton Productivity Enhancement Program" (CPEP), were evaluated in this study. Various statistical approaches including descriptive statistics, correlation and principal component analysis was performed to evaluate and identify desirable genotypes. Results revealed that seed cotton yield was significantly and positively correlated with boll weight and number of bolls plant −1. Similarly, plant height was also significantly correlated with sympodial branches, lint percentage and micronaire value. Lint percentage showed a highly significant and positive correlation with plant height, sympodial branches and micronaire value. With respect to fiber traits, negative and significant relationships were observed between the micronaire value (MIC) and fiber strength. CLCuD showed no relationship with any of the studied traits, as all the G. arboreum L.lines evaluated were scored resistant to CLCuD. Principal component analysis (PCA) showed that the first four out of 11 components contributed about 65.88% of the total variation having an eigen value greater than 1. Based on PCA, the genotypes GS-4, GS-9, GS-8, GS-55 and GS-50 could be utilized successfully in a future breeding program based on having the highest positive loading factor for staple length (0.135) in PC1 and seed cotton yield (0.625), , boll weight, first sympodial nod, staple length and fiber strength in PC2 respectively.

No abstract